natural treatment systems as sustainable ecotechnologies for the

Hindawi Publishing CorporationBioMed Research InternationalVolume 2013 Article ID 796373 19 pageshttpdxdoiorg1011552013796373

Review ArticleNatural Treatment Systems as Sustainable Ecotechnologies forthe Developing Countries

Qaisar Mahmood12 Arshid Pervez2 Bibi Saima Zeb2 Habiba Zaffar2 Hajra Yaqoob2

Muhammad Waseem3 Zahidullah3 and Sumera Afsheen4

1 Department of Plant and Soil Sciences University of Kentucky Lexington KY 40546-0091 USA2Department of Environmental Sciences COMSATS Institute of Information Technology Abbottabad 22060 Pakistan3Department of Biology Allama Iqbal Open University H-8 Islamabad 44000 Pakistan4Department of Zoology University of Gujrat Gujrat 50700 Pakistan

Correspondence should be addressed to Qaisar Mahmood mahmoodzjugmailcom

Received 5 April 2013 Revised 4 June 2013 Accepted 6 June 2013

Academic Editor Eldon R Rene

Copyright copy 2013 Qaisar Mahmood et al This is an open access article distributed under the Creative Commons AttributionLicense which permits unrestricted use distribution and reproduction in any medium provided the original work is properlycited

The purpose of natural treatment systems is the re-establishment of disturbed ecosystems and their sustainability for benefits tohuman and nature The working of natural treatment systems on ecological principles and their sustainability in terms of lowcost low energy consumption and lowmechanical technology is highly desirableThe current review presents pros and cons of thenatural treatment systems their performance and recent developments to use them in the treatment of various types of wastewatersFast population growth and economic pressure in some developing countries compel the implementation of principles of naturaltreatment to protect natural environmentThe employment of these principles for waste treatment not only helps in environmentalcleanup but also conserves biological communities The systems particularly suit developing countries of the world We reviewedinformation on constructed wetlands vermicomposting role of mangroves land treatment systems soil-aquifer treatment andfinally aquatic systems for waste treatment Economic cost and energy requirements to operate various kinds of natural treatmentsystems were also reviewed

1 Introduction

Rightly defined by Mitsch and Joslashrgensen [1] ldquothe ecologicalengineering is the design of sustainable ecosystems thatintegrate human society with its natural environment for thebenefit of bothrdquo It involves the restoration of ecosystemsthat have been substantially disturbed by human activitiessuch as environmental pollution or land disturbance and thedevelopment of new sustainable ecosystems that have bothhuman and ecological values The development of ecologicalengineering was spawned by several factors including lossof confidence in the view that all pollution problems canbe merely solved through technological means and therealization that with technological means pollutants arejust being moved from one form to another Conventionalapproaches require massive amounts of resources to solve

these problems and that in turn perpetuates carbon andnitrogen cycle problems for example [1]

Currently economic growth in developed nationshuman population explosion in certain areas of Asia andAfrica deforestation and destruction of natural habitats forthe conservation of biodiversity are the biggest challengesfor implementing the principles of ecological engineeringin most of the developing nations Currently economiccrunch in many developed as well as developing nations isforcing to implement low-cost natural treatment systemsfor the domestic and industrial wastewater treatment Incase the technological treatment facilities are installed inmany developing countries the energy input is difficult tobe supplied in view of the global energy crisis and very highoperational cost is a bottleneck to their affordability Theseall factors are compelling the employment of low cost natural

2 BioMed Research International

treatment systems for not only waste treatment but also forconserving biological communities in poor nations of theworld The conventional systems that may be appropriatein industrialized regions and densely populated areas withguaranteed power supplies easily replaceable parts and askilled labor force to ensure operation and maintenancerequirements might not be suitable for those regions withlimited resources [2] Hence natural treatment systemsparticularly suit to developing countries of the world

Sustainable sanitation systems require low cost with lowenergy consumption and low mechanical technology Betterchoices of low cost treatment systems for rural areas aredecentralized processes [3] Treatment systems with a verysmall energy input low operational cost and low surplussludge generation are anaerobic digesters and constructedwetlands [3ndash6] Other examples of low cost natural treatmentsystems include oxidation ponds anaerobic ponds facul-tative ponds terrestrial treatment systems and vermicom-posting constructed wetlands The objective of the currentreview was to describe some recent advancements in thedesign and efficiency of various natural treatment systemsand the comparison of their efficiencies Following sectionswill highlight the recent developments regarding varioustypes of natural treatment systems

2 Constructed Wetlands

Seidel [7] presented the ideas of improving inland waterssuffering from high nutrients originating from sewage andsanitation through native plant species However at thattime experts only considered physicochemical and bacterialwastewater treatment only and no attention was paid tocontrolled use of macrophytes for water purification [8]Figure 1 shows various components of a constructed wetland[9] Classification of constructed wetlands is based on twoparameters that is type of macrophytic growth and waterflow regime (surface and subsurface) [9] CW can be usedfor the treatment of different types of wastewaters that ismunicipal industrial leachate acid mine drainage surfacerunoff and so forth [10] The emerging technology for thetreatment of a variety of wastewaters is constructed wetlands(CWs) [11] The natural wetland system uses mostly naturalenergy requires low construction and operational costs andso is energetically sustainable [12ndash14] However this assump-tion is not true for constructed wetlands where some energyinput from human source is also required The constructedwetlands are classified into two type that is free water surface(FWS) and subsurface flow (SSF) systems In case of FWSsystems plants are rooted in the sediment layer and waterflow is above ground (surface flow) In SSF systems plantsare rooted in a porous media such as gravels or aggregatesthrough which water flows and treatment are accomplishedSSF systems are further divided into two types horizontalflow SSF (HSSF) and vertical flow SSF (VSSF) Comparedto HSSF the subsurface vertical flow constructed wetland(SVFCW) system is more effective for the mineralizationof biodegradable organic matter and has greater oxygentransport ability [15] For the removal of suspended solids

carbon and nitrification process vertical flow CW is moreefficient because of aerobic conditions and denitrification ispoor In VSSF CWs feeding is intermittent (discontinuous)and the flow of wastewater is vertically administered througha substrate layer which mainly consists of sand gravel or amixture of all these components [16]

Constructed wetlands can be used as an accepted eco-technology in small towns or industries that cannot affordconventional treatment systems [17ndash19] In the free watersurface (FWS) type of wetland the water is filtered through adense stand of aquatic plants as it flows over the bed surface[20ndash22] Another constructed wetland system known as thesubsurface flow wetland consists of a lined shallow basinwith a gravel media and emergent aquatic plants [23ndash28]Worldwide now thousands of constructed wetlands are inuse which are receiving and treating a variety of municipalindustrial and other wastewaters [29ndash31] Due to operationalsimplicity and cost efficiency the utilization of constructedwetlands in Taiwan is gaining greater popularity [12 22 2932 33] The constructed wetland technology is now wellestablished but its use for treating specific industrial effluentshas not been well documented [34ndash36] Various kinds ofconstructed wetlands have been shown in Figure 1

The technology which uses plants for the removal ofcontaminants from a specified area is known as greentechnology [37] and the process is known as phytoreme-diation Phytoextraction phytovolatilization rhizosphericdegradation phytodegradation and hydraulic control arethe five mechanisms involved in the phytoremediation forthe removal of pollutants Different types of pollutants canbe removed by phytoremediation such as heavy metalspesticides petroleum hydrocarbons explosives radionu-clides and CVOCs [38] Heavy metals are the chemicalsubstances whose densities are greater than 5 g cm3 [39]metals cleanup requires their immobilization and toxicityreduction or removal and they cannot be degraded likeorganic compounds [40] Sedimentationcoagulation filtra-tion plant uptakeremoval efficiency adsorption (bindingto sand particles and root) formation of solid compoundscation exchange and microbial-mediated reactions espe-cially oxidation are the different processes through whichdifferent types of metals can be removed in the constructedwet lands [41]

21TheComponents of CW Thebasic components employedin the construction of CW are containers plant speciesand sand and gravel media in certain ratios Other inver-tebrates and microbes develop naturally [42] Combinationof anaerobic reactors vegetated reactors (CW) and naturalwetlands forms ecological treatment systems In ecologicallyengineered systems different functions are performed bydifferent communities of flora fauna minerals andmicrobes[43] Another important component of ecological treatmentsystems is microbes which carry out the different importantprocesses like hydrolysis mineralization nitrification anddenitrification Plants are critical as an attachment surface formicrobes [43] For the construction of constructed wetlandthree forms of macrophytes are basically used

BioMed Research International 3

Constructedwetlands

Emergent plants

Submerged plants

Free floating plants

Floating-leaved plants

Surface flow

Downflow

Upflow

Tidal

Subsurface flow

Horizontal

Hybrid systems

Vertical

Figure 1 Various types of constructed wetlands [9]

Table 1 Typical characteristics of plant species used in constructed wetlands (modified after Crites and Tchobanoglous [170] Reed [171])

Characteristic Bulrush Cattail ReedsDistribution Worldwide Worldwide WorldwidePreferred temperature (∘C) 16ndash27 10ndash30 12ndash23Preferred pH range 4ndash9 4ndash10 2ndash8Salinity tolerance (pptlowast) 20 30 45Root penetration (m) asymp06 asymp03 asymp04Drought resistant moderate Possible highGrowth Moderate to rapid Rapid Very rapidlowastppt parts per thousand

(1) floating macrophytes (ie Lemna spp or Eichorniacrassipes)

(2) submerged macrophytes (ie Elodea canadiensis)(3) rooted emergent macrophytes (ie Phragmites aus-

tralis Typha spp)

The plant used for phytoremediation should have highbiomass high growth rate and ability to accumulate thetarget metal in the above-ground parts They should beable to tolerate high metal concentration and have tolerancefor several metals simultaneously [44] Table 1 describesdesirable features of plant species to be used in constructedwetlands

22 Removal of Organic Matter in CW In case of removingorganic compounds by wetland plants the focus is generallyon three types of compounds that is chlorinated solventspetroleumhydrocarbons and explosives But researchers alsoaddressed the potential of plant species to treat other organiccontaminants such as polycyclic aromatic hydrocarbons(PAHs) and polychlorinated biphenyls (PCB) [45ndash47] Forwastewater purification different natural systems involvingplants such as facultative ponds [48ndash50] terrestrial systems[51ndash55] and wetlands [8 56ndash58] have been used Floatingaquatic plant systems usually contain floating macrophytesThe extensive root systems of floating leaved plants have largesurface area and rhizoplane provides an excellent site for theadhesion of rhizobacteria In such treatment processes rhi-zobacteria play an important role in the pollutant degradationand uptake [8] A wealth of the literature has been publishedon the use of emergent plants [59 60] and floating plants suchas Elodea canadensis [61] Although water hyacinth is very

efficient in nutrient uptake the removal of naphthalene attoxic concentrations by Eichhornia crassipes has not yet beendetermined E crassipes is highly effective for the remediationof municipal sewage for a retention time of 2 to 5 days [62ndash64]

The natural systems containing various plant species wereregarded as very effective and inexpensive technology for thecleanup of hazardous waste sites polluted with hydrocarbonsmetals pesticides and chlorinated solvents [65ndash67] Thetreatment of organic pollutants by plants may involve fourmechanisms

(1) direct uptake accumulation and metabolism of con-taminants in plant tissues (detoxification)

(2) transpiration of volatile organic hydrocarbons fromleaves (avoidance)

(3) release of exudates from the roots that will stimulatemicrobial activity and biochemical transformations(chelation) and finally

(4) the presence of mycorrhizal fungi and microbial con-sortia associated with the root surfaces can enhancethe mineralization of pollutants in rhizosphere [68]

Photosynthetic activity and growth rate of plants are thetwo factors which render economic success of the treatmentprocess by plants Due to fast growth and large biomass pro-duction water hyacinth (Eichhornia crassipes (Mart) Solms)is largely used for the wastewater treatment [69] Waterhyacinth through uptake and accumulation can effectivelyremove inorganic contaminants such as nitrate ammoniumand soluble phosphorus [70 71] and heavy metals [72 73]Different organic pollutants such as phenols can also be


absorbed [74] but their removal mechanisms were rarelystudied to confirm that the removal of these pollutantsinvolved uptake or the enhancement of mineralization bymicrobial consortia associated with the root surface

A system comprising two parallel horizontal subsurface-flow constructed wetlands following an upflow anaerobicsludge blanket (UASB) reactor treatingmunicipal wastewaterfrom the city of Belo Horizonte Brazil served as the basisfor the evaluation of simple first-order kinetic performancemodels [75] One unit was planted (Typha latifolia) and theother was unplanted Tracer (Brminus) studies were undertakenand samples of filtered COD were collected from the inletoutlet and three intermediate points along the longitudinallength of the units The following kinetic models wereused and the related reaction coefficients were calculated(i) plug-flow model (ii) dispersed-flow model and (iii)tanks-in-series model For the three models the followingvariants were analysed without and with residual COD andwithout and with taking into account water losses due toevapotranspiration In general the dispersed-flowmodel andthe tanks-in-series model both adjusted for residual CODand incorporating water losses were able to give the bestpredictions and led to the same reaction coefficients whichwere also likely to best represent the actual first-order kineticcoefficients [75]

23 Removal of Inorganics and Metals by CW Since 1990sCWs have been used for the treatment of wastewater toremove solids N P heavy metals and organic pollutants[76ndash79] CW have also been used for the removal of col-iforms from storm water municipal sewage and agriculturalrunoff [80ndash83] The presence of angiospermic plants in awetland ecosystem improves treatment efficiencies [84ndash86]The unique wetlands along the coastline of tropical andsubtropical regions are mangroves Mangroves could be usedin CWs for wastewater treatment as shown by differentstudies [81 87 88]

The rapid increase of shortages in resources of chem-ical elements (and ores) used for an increasing industrialproduction raises the question of alternative strategies fortheir acquisition [89] Simultaneously the elemental loadin aquatic ecosystems increases by anthropogenic activitiesPolluted waters are purged actively by technical treatmentplants or passively by wetlands Wetlands are known toeliminatefix pollutants with a potentially high efficiencyRegarding this eliminationfixation potential less is knownabout different types of wetlands for elemental recoveryThis paucity of information prompted to us to assess theimpact of main processes in different types of wetlands onthe recovery potential of chemical elements showing advan-tages and disadvantages of autochthonous and allochthonouswetlands and possible solutionsWe show that autochthonousas well as allochthonous wetlands are able to accumulatehigh amounts of elements but it is suggested that combiningautochthonousallochthonous processes should result in ahigher efficiency [90]

The recent applications and trend of CWs in Chinawere reviewed by Hench et al [81] and presented the status

quo prospect and influencing factors in CWs constructiontechnology application and operationmanagement in Chinabased on the available data The results of the systematicsurvey showed that CWs technology achieved gradual per-fection under the pushes of national policiesmarket demandand technical feasibility with the capacity of wastewatertreatment increasing year by year However there were stillsome problems concerning engineering operation and man-agement Moreover the results demonstrated that limitedby the economic level the degree of industrialization andurbanization climatic conditions and land availability CWswere distributing predominately in the region of 20∘131015840Nndash35∘201015840N in China which covered the central areas with asubtropical monsoon climate and southern or central areasat province level In these areas there were more than 40plant species which accounted for 5714 of the total numberof common wetland plants Most of the CWs compostedseries or parallel combination forms of the vertical flow andfree water surface flow CWs units and they were suitable totreat more than 20 different types of wastewaters For theseCWs the effluent COD biological oxygen demand BOD TNand total phosphorous (TP) reached in the ranges of 20ndash60mgL 4ndash20mgL 1ndash20mgL and 02ndash1mgL respectivelyThe effluents fromCWswere reused inmore than eight wayssuch as for agricultural irrigation supplying surface waterand green belt sprinkling [81]

Galvao and Matos [91] evaluated the buffering capacityof constructed wetlands by analyzing the response to suddenorganic load changes Nine horizontal flow experimentalbeds were divided into three equal groups and monitored ina three-phase experiment Influent COD mass loads duringPhase I were 114 53 and 0 gm2day for Groups AndashCrespectively During Phase II there was a rise in COD massload and Phase III restored initial conditions Group Ashowed a reduction in COD removal efficiencies with massload increase despite more intense microbiological activityIn Group B planted beds there was a reduction of themass load removal which could have been due to a biofilmdisturbance caused by an invasive millipede species Whenmass loadwas lowered removal efficiencies improved GroupC showed residual effluent COD during Phase I but providedadequate removal efficiencies (75ndash84) when supplied with17 gm2day during Phase IIThe results of this study suggestthat the buffering capacity of constructed wetlands may notbe enough to maintain COD removal efficiencies during asudden organic load increase [91]

Three free water surface constructed wetlands (FW-SCWs) were built in the border of the Lake LrsquoAlbufera deValencia (Valencia Spain) [92] The lake is the emblematicelement of one of the most important wetlands in SpainLrsquoAlbufera de Valencia Natural Park and it is highly eutroph-icated The function of the set of CWs (9 ha) is treatingthe eutrophic water from the lake with the objective ofreducing the phytoplankton population and nutrients Thetreatment wetlands named as FG and fp are comprised ofthree basins in a series while the last F4 consists of a singlecell During the first 2 years of operation the inflow fromlake was gradually increased from 001m3s (April 2009)


to 013m3s (December 2010) with the goal of establishingthe maximum hydraulic loading rate (HLR) and finding thehighest removal efficiency Input concentrations of differentwater quality variables studied showed a high variability Theinflow contained 880ndash94mgL TSS 016ndash113mgL TP 1ndash1730mgL TN 013ndash1310mg NL DIN 010ndash1150mg NO

3-

NL and 334ndash25703 120583gL Chl a The best removal resultsfor these parameters were obtained in the FG wetlandwhere the average mass removal efficiencies were 75 TSS65 TP 52 TN 61 DIN 58 NO

3-N and 46 Chl

a In the set of constructed wetlands the removal ratesincreased with the hydraulic load rate for TSS and TP butneither for nitrogen species nor Chl a for these variablesthe input concentrations are a key factor in removal Forinstance mean removal rate for nitrate is 101mgNmminus2 dminus1but values higher than 400mgNm2 d were obtained wheninput concentrations were about 7mgNO

3-NL Values of

first-order constant aerial rate (119896119860) have been obtained for

all variables The corresponding values for nitrogen speciesand total phosphorus are higher than obtained in previousstudies but the 119896

119860value for TSS is low (949myear) owing

to the eutrophic characteristics of water and a 119896119860

valuefor phytoplankton-Chl a of 651myear is introduced Themanagement of CWs implies the harvest of vegetation notfor removing nitrogen because nitrification-denitrificationprocesses reduce the 833 of TN that enters but for thephosphorus limiting nutrient in the Lake LrsquoAlbufera that nowis accumulated in plants and soils but could be sent back inseveral years [92]

In 2008 concentrations of iron andmanganese in the sed-iments of seven constructed wetlands (CWs) with horizontalsubsurface flow in the Czech Republic were evaluated [93]The surveyed constructed wetlands varied in the length ofoperation between 2 and 16 years at the time of samplingIn each constructed wetland three samples of sediment weretaken in the inflow middle and outflow zones to the depthof 06m The sample was divided into top (0ndash20 cm) andbottom (20ndash60 cm) sections resulting in a total number of18 samples in each system In each sample the amount ofsediment on drymass basis was evaluated and concentrationsof Fe and Mn in the sediment were determined using ICP-MS The survey revealed that the amount of sediments inthe filtration bed increases with the length of operationIn general greater sediments were located at the bottomlayers due to the wastewater distribution near the bottomConcentrations of manganese in the sediment were highestin the new systems and decreased with length of operationWith the exception of one CW in all other constructedwetlands Mn concentration in the sediment was significantlyhigher within the top layer Mn concentrations in sedimentsfound in that study were found within the concentrationrange commonly occurring in natural unpolluted wetlandsIron concentration in the sediment also decreased with theincreasing length of operation but the dependence on theoperation time was not as clear as for manganese Theconcentration of ironwas comparablewith other studies fromconstructedwetlands treating sewage but higher as comparedto polluted sediments which are usually highly anaerobic

The results clearly demonstrated that in order to evaluatethe amount of iron and manganese in the filtration beds itis necessary to take into consideration both concentrationof the elements and the amount of sediment accumulatedin the filtration bed Despite the lowest concentrations inthe sediment the highest accumulated amount of both ironand manganese was found in the oldest CW Spalene Porıcıbecause of the highest concentration of sediment in thefiltration bed [94]

In another investigation by Paulo et al [93] the black-water fraction was treated in an evapotranspiration tank(TEvap) system whereas the greywater fraction was treatedby a compact setup including a grease trap sedimentationtank and two constructed wetlands Results of both systemsobtained during a 400-day trial in a 9-person householdin Campo Grande-MS Brazil showed that ecological sys-tem could be an economical alternative to conventionalseptic tank solutions The treatment system managed bothgreywater and blackwater at household level enabling thedevelopment of green areas improving microclimate andallowing for the reuse of grey water and the nutrients presentin blackwaterTheTEvap systemwas essentiallymaintenancefree but the constructed wetlands did require attention toprevent clogging of subsystems [93]

24 Role of Rhizosphere in Pollutant Uptake The term ldquorhi-zosphererdquo was introduced by the German scientist Hiltner[95] Rhizosphere is a border line between soil and plantswhich plays an important role in the agroenvironmentalstructure [96] where physiochemical and biological charac-teristics of soil biomass activity and community structureof microorganisms are significantly affecting each other [97]The rhizosphere is an environment around plants wherepathogenic and beneficial microorganisms create a potentialstrength on plant growth and health [98] The rhizosphereis usually occupied by microbial groups like bacteria funginematodes protozoa algae and microarthropods [98 99]Proper understanding of the ecosystem is necessary for thewaste treatment through beneficial integration of microor-ganisms and suitable selection of microbes [100]

It has been proved that plant roots attract soil microor-ganisms through their exudates which ultimately results invariations of the rates of metabolic activity of the rhizospheremicrobial communities and those of the nonrhizosphere soil[101] Generally the plants associated bacteria migrate fromthe soil to the rhizosphere of living plant and ultimatelycolonize the rhizosphere and roots of plants [102] These rhi-zobacteria are symbiotic partners of plants and are consideredas plants growth promoting microbes [103] Due to naturalactivities of colonizing bacterial species along the surface ofthe roots of the inoculated plants enhance the growth rate ofplants [104]

The exudates released by plant roots and associatedmicrobes may significantly mobilize heavy metals and ulti-mately increase their bioavailability [105] Bacteria are themost common type of soil microorganisms due to their rapidgrowth and utilization ofwide range of substances like carbonor nitrogen sources Rhizospheric microbes may play a dual


role in soil ecological potential both constructively as well asdestructively The number and variety of harmful and usefulmicroorganisms are related to the quality and quantity ofrhizodeposits and the effect of the microbial relations thatoccurs in the rhizosphere [106]

An alternate way for the remediation of heavy metalstoxicity is the use of rhizospheric microorganisms [107]A variety of useful free-living soil bacteria are usuallyreferred to as plant growth-promoting rhizobacteria and arefound in association with the roots of diverse plants species[108] Plants and microbes possess a strong and valuablerelationship but may have strong competition for resourcesincluding nutrients and water [109] In both natural andmanmade ecosystems plant associated bacteria play a keyrole in host adaptation to a changing environment Thesemicroorganisms can modify plant metabolism so that uponexposure to heavy metal stress the plants are able to toleratetheir high concentrations [110] Several authors have pointedout bacterial biosorption or bioaccumulationmechanism andother plant growth promoting factors the production of ACCdeaminase and phytohormones were regarded as key forbetter plant growth in heavy metals contaminated soils [111ndash113] Sedum alfredii a terrestrial ZnCd hyperaccumuluatorof Zn Cd Cu and Pb from contaminated water evidentlyimproved the phytoremediation in the presence of naturallyoccurring rhizospheric bacteria also by using antibioticampicillin [114]

25 Vermicomposting and Constructed Wetlands Vermi-composting principally employs earthworms to ingestorganic matter and consequently egests a nutrient-rich castthat can be used as a soil conditioner After fragmentationand ingestion the microbial activity for the decompositionprocess is enhanced [115] The process was also studied inrelation to the changes in the composition properties ofthe wastes [116] The advantages of this technology includespeeding up and assisting the composting process as well asthe quality of the endproducts In addition vermicompostingis considered to be odor-free because earthworms releasecoelomic fluids in the decaying waste biomass which haveantibacterial properties [117] Pathogens are also killedaccording to this effect Many workers have highlightedthe great reduction of pathogenic microorganisms byvermicomposting [118ndash120] Among vermicompostersearthworms are the most important invertebrates whichplay a significant role in the degradation of organic mattersto humus Earthworms can be classified as detritivores andgeophages according to their feeding habit [121] Detritivoresfeed on plant litter or dead roots and other plant debris as wellas on mammalian dung These earthworms are called humusformers and they include the epigeic and anecic earthwormslike Perionyx excavatus Eisenia fetida Eudrilus euginae andPolypheretima elongate [122] Geophagous worms mostlyinfluence the aeration and mixing of subsoil that is whythey are called endogeic earthworms Both types have theirrole either as composters of detritivores or fieldworkers forgeophages [123]

For using earthworms in constructed wetlands it isimperative to understand their growth conditions Speciessuch as Perionyx excavatus and Eudrilus eugeniae are morecommon inwarmer climatesTheywould bemore suitable forthe vermicomposting process in those regions For instancein Africa it is recommended to use Eudrilus eugeniae whichcan reach sexual maturity in as little as five weeks comparedwith E fetida which requires 6ndash8 weeks [124] and Perionyxexcavatus in Asia as they are widely distributed Both of thesespecies are most productive at 25∘C which is higher than theoptimal temperature quoted for other species in temperateregions [125] In Thailand the species commonly used isPheretima peguana The tolerance under different temper-atures varies considerably for each species whereas theiroptimum moisture requirements C N ratio and ammoniacontent do not vary greatly [119] The temperature tolerancefor some species as well as their distribution is described andcompared in Table 2

In principle earthworms prefer an aerobic condition[119] Therefore this should be applicable for the VSFCWsdue to intermittent feeding rather than the anaerobically-operated HSFCWs VSFCWs could offer a viable habi-tat for earthworm populations because of their ability totransfer oxygen to the root zone This ability creates theaerobic micro-sites within the largely anoxic environment[126] Under anoxic conditions the earthworms will dieEdwards [119] has described some optimal conditions forbreeding earthworms (E fetida) in animal and vegetablewastes However future researches should be focused onthe performance of earthworm based vermicomposting CWwhich are fed by various kinds of wastewaters like domes-tic municipal and some selected industrial wastewaterscontaining inorganic toxic pollutants like ammonia heavymetals and low DO Nuengjamnong et al [127] treatedswinewastewater by integrating earthworms into constructedwetlands They investigated the application of integratingearthworms (Pheretima peguana) into two-stage pilot-scalesubsurface-flow constructed wetlands (SFCWs) receivingswine wastewater in terms of their treatment performancenamely organic content total Kjeldahl nitrogen (TKN) andsolid reduction as well as the quantity of sludge productionThere was a minor difference in terms of removal efficiencyaccording to each parameter when comparing the unit withearthworms to the one without earthworms Both achievedthe TKN BOD COD total volatile suspended solids (TVSS)suspended solids (SS) and total solids (TS) removal bymore than 90 The earthworms helped in reducing thesludge production on the surface of constructed wetlands40 by volume which resulted in lowering operational costsrequired to empty and treat the sludge The plant biomassproduction was higher in the wetlands without earthwormsFurther research could be undertaken in order to effectivelyapply earthworms inside the wetlands [127]

Enhancement of rural domestic sewage treatment per-formance and assessment of microbial community diversityand structure using tower vermifiltration was investigated byWang et al [128] The performance of a novel three-stagevermifiltration (VF) system using the earthworm Eiseniafetida for rural domestic wastewater treatment was studied


Table 2 Comparison of some vermicomposting earthworm species in terms of the optimal and tolerable temperature ranges [119 124 172]

Species Temperature ranges (∘C) DistributionTolerated Optimum

Eisenia fetida 0ndash35 20ndash25 Temperate regionsEudrilus eugeniae 9ndash30 20ndash28 Africa India North and South AmericaPerionyx excavatus 9ndash30 15ndash30 Asia and AustraliaEisenia veneta 3ndash33 15ndash25 Europe

during a 131-day period The average removal efficiencies ofthe tower VF planted with Penstemon campanulatus were asfollows COD 813 ammonium 98 total nitrogen 602total phosphorus 984 total nitrogen mainly in the formof nitrate Soils played an important role in removing theorganic matter The three-sectional design with increasingoxygen demand concentration in the effluents and the distri-bution of certain oxides in the padding were likely beneficialfor ammonium and phosphorus removal respectively Themicrobial community profiles revealed that band patternsvaried more or less in various matrices of each stage atdifferent sampling times while the presence of earthwormsintensified the bacterial diversity in soils Retrieved sequencesrecovered from the media in VF primarily belonged tounknown bacterium and Bacilli of Firmicutes [128] Wang etal [129] investigated the impact of fly ash and phosphaticrock on metal stabilization and bioavailability during sewagesludge vermicomposting Sewage sludge (SS) was mixedwith different proportions of fly ash (FA) and phosphoricrock (PR) as passivators and earthworms Eisenia fetidawere introduced to allow vermicomposting The earthwormgrowth rates reproduction rates and metal (except Zn andCd) concentrations were significantly higher in the vermire-actors containing FA and PR than in the treatments withoutpassivators The total organic carbon (TOC) and total metalconcentrations in the mixtures decreased and the mixtureswere brought to approximately pH 7 during vermicompost-ing There were significant differences in the decreases in themetal bioavailability factors (BFs) between the passivator andcontrol treatments and adding 20 FA (for Cu and Zn) or20 PR (for Pb Cd and As) to the vermicompost were themost effective treatments formitigatingmetal toxicityTheBFappeared to be dependent on TOC in the all treatments butwas not closely dependent on pH in the different vermibeds[129]

26 Role of Mangroves Mangroves are sole wetlands alongthe coastline of tropical and subtropical areas They haveunique adaptations to stressed environments and a massiverequirement for nutrients because of fast growth high pri-mary productivity metabolism and yield Studies suggestedthat mangroves could be used in CWs for wastewater treat-ment [81 88 130] Studies were focused on the treatmentefficiency of the mangrove species Kandelia candel Littlework has been done on the assessment of nutrient removalefficiency of different mangrove species [131] They have spe-cial adaptations to stressful saline environments and a hugedemand for nutrients because of rapid growth high primaryproductivity metabolism and turnover Many studies have

demonstrated that mangroves could be used in CWs forwastewater treatment [81 88 130] Plants can affect theirgrowth medium by excreting exogenous enzymes and canalso affect microbial species composition and diversity byreleasing oxygen into the rhizosphere that in turn indi-rectly influences enzyme activity [132 133] Nevertheless therelationship between plant species composition and enzymeactivities in CW systems is poorly understood The subsur-face vertical flow constructed wetland (SVFCW) system withunsaturated flow possesses greater oxygen transport abilitythan the horizontal subsurface flow beds and ismore effectivefor the mineralization of biodegradable organic matter

The use of a mangrove plantation as a constructedwetland for municipal wastewater treatment was studied byBoonsong et al [89] The study evaluated the possibility ofusing mangrove plantation to treat municipal wastewaterTwo types of pilot scale (100 times 150m2) free water surfaceconstructed wetlands were set up at the Royal Laem PhakBia Environmental Research and Development Project incentral Thailand One system is a natural Avicennia marinadominated forest systemThe other system is a newmangroveplantation system in which seedlings of Rhizophora spp Amarina Bruguiera cylindrical and Ceriops tagal were plantedat 15 times 15 mintervals making up 4 strips of 375 times 100m2each Wastewater from municipal and nearby areas wascollected and pumped into the systems then retained withinthe systems for 7 and 3 days respectively before dischargingThe results indicated that the average removal percentageof TSS BOD NO

3-N NH

4-N TN PO

4-P and TP in the

new-plantation systems were 276ndash771 439ndash539 376ndash475811ndash859 448ndash544 247ndash768 and 226ndash653 respectivelywhereas the removal percentage of those parameters in thenatural forest system were 171ndash659 495ndash511 440ndash609511ndash835 434ndash504 287ndash589 and 283ndash480 respectivelyGenerally the removal percentage within the new-plantationsystem and the natural forest system was not significantlydifferent However when the removal percentages withdetention time were compared TSS PO

4-P and TP removed

percentages were significantly higher in the 7-day detentiontime treatment Even with the highly varied and temporallydependent percentage removal of TSS BOD and nutrientsthe overall results showed that a mangrove plantation couldbe used as a constructed wetland for municipal wastewatertreatment in a similar way to the natural mangrove systemTherefore the use of mangrove plantations for municipalwastewater treatment is applicable [89]

A pilot-scale mangrove wetland was constructed inFutian (China) for municipal sewage treatment by Yanget al [134] Three identical belts (length 33m width 3m


and depth 05m) were filled with stone (bottom) gravel andmangrove sand (surface) Seedlings of two native mangrovespecies (Kandelia candel Aegiceras corniculatum) and oneexotic species (Sonneratia caseolaris) were transplanted tothe belts with one species for each belt The hydraulicloading was 5m3dminus1 and hydraulic retention time 3 d Highlevels of removal of COD BOD(5) TN TP and NH

3-N

were obtained The treatment efficiency of S caseolaris andA corniculatum was higher than that of K candel Fasterplant growth was obtained for S caseolaris The substrate inthe S caseolaris belt also showed higher enzyme activitiesincluding dehydrogenase cellulase phosphatase urease andbeta-glucosidase The removal rates of organic matter andnutrients were positively correlated with plant growth Theresults indicated that mangroves could be used in a con-structed wetland for municipal sewage treatment providingthat posttreatment to remove coliforms was also included[134] Saline municipal wastewater treatment was investi-gated in constructed mangrove wetland by Li et al [135]The feasibility of using constructed mangrove wetlands totreat saline municipal wastewater was evaluated in the studyConstructed wetland acting as an ecological engineeringalternative is capable of reducing NH

4

+-N TN TP and CODfrom saline wastewater During the 10 monthsrsquo operatingperiod the constructed wetland was operated with salinityincreasing from 10 to 50 parts per thousands (ppt) When thesalinity of wastewater was below 30 ppt the removal rates ofNH4

+-Ngt TNgt TP and COD were 716 798 755ndash896827ndash974 and 666ndash853 respectively The removal rate ofCOD decreased to about 40 when the salinity increased to50 ppt A good performance of COD removal was obtainedwhen the constructed mangrove wetland was operated atloading rate between 126ndash189 gmminus2 dminus1 The preliminaryresult showed that constructed mangrove wetland for salinemunicipal wastewater treatment had a broad future [135]

3 Land Treatment Systems

Terrestrial or land treatment systems utilize land to treatwastewater The land is generally allowed to flood withwastewater to be treated the extent and treatment conditionsusually depend on many factors like soil characteristics thecharacteristics of wastewater topography the presence ofadditional media in soil and so forth When these systemsare used large buffer areas and fencing may be required toensureminimal human exposure [136] Also given the natureof these systems all requirements include disinfection andsignificant pretreatment before application In wet and coldareas an additional basin for storage or a larger dosing tankis necessary to eliminate possible runoff from the applicationareaThemost used variation of these systems is the spray irri-gation system Spray irrigation systems distribute wastewaterevenly on a vegetated plot for final treatment and dischargeSpray irrigation can be useful in areas where conventionalonsite wastewater systems are unsuitable due to low soilpermeability shallowwater depth table or impermeable layeror complex site topography Spray irrigation is not oftenused for residential onsite systems because of its large areal

demands the need to discontinue spraying during extendedperiods of cold weather and the high potential for humancontact with the wastewater during spraying Spray irrigationsystems are among the most land-intensive disposal systemsBuffer zones for residential systems must often be as large asor even larger than the spray field itself tominimize problems[137]

In spray irrigation system pretreatment of thewastewateris normally provided by a septic tank (primary clarifier) andaerobic unit as well as a sand (media) filter and disinfectionunit The pretreated wastewater in spray irrigation systems isapplied at low rates to grassy or wooded areas Vegetation andsoil microorganisms metabolize most nutrients and organiccompounds in thewastewater during percolation through thefirst several inches of soilThe cleaned water is then absorbedby deep-rooted vegetation or it passes through the soil to theground water [136]

Rapid infiltration (RI) is a soil-based treatment methodin which pretreated (clarified) wastewater is applied inter-mittently to a shallow earthen basin with exposed soilsurfaces It is only used where permeable soils are availableBecause loading rates are highmost wastewater infiltrates thesubsoil withminimal losses to evaporation Treatment occurswithin the soil before the wastewater reaches the groundwater The RI alternative is rarely used for onsite wastewatermanagement It is more widely used as a small-communitywastewater treatment system in the United States and aroundthe world [136]

The third and last type of land surface treatment isthe overland flow (OF) process In this system pretreatedwastewater is spread along a contour at the top of a gentlysloping site that has minimum permeability The wastewaterthen flows down the slope and is treated by microorganismsattached to vegetation as it travels by sheet flow over veryimpermeable soils until it is collected at the bottom of theslope for dischargeThis system requires land areas similar tothe spray irrigation system However surface water dischargerequirements (eg disinfection) from the OF system muststill be met Overland flow like rapid infiltration is rarelyused for onsite wastewater management [136]

Land treatment systems comprise a possible alternativesolution for wastewater management in cases where theconstruction of conventional (mechanical) wastewater treat-ment plants (WWTPs) are not afforded or other disposaloption are not accessible They have established to be anideal technology for small rural communities homes andsmall industrial units due to low energy low operationaland maintenance costs [137] They depend upon physicalchemical and biological reactions on and within the soilSlow rate OF systems require vegetation both to take upnutrients and other contaminants and to slow the passage ofthe effluent across the land surface to ensure the maximumcontact times between the effluents and the plantssoils Slowrate subsurface infiltration systems and RI systems are ldquozerodischargerdquo systems that rarely discharge effluents directly tostreams or other surface waters Each system has differentconstraints regarding soil permeability Slow rate OF systemsare the most expensive among all the natural systems to putinto practice


The OF systems are a land application treatment tech-nique in which treated effluents are ultimately discharged tosurface waterThemajor profits of these systems are their lowmaintenance and technical manpower requirements Subsur-face infiltration systems are designed formunicipalities of lessthan 2500 people They are usually designed for individualhomes (septic tanks) but they can be designed for clustersof homes Although they do require specific site conditionsthey can be low-cost methods of wastewater disposal

The use of subsurface infiltration systems has beenexpanded to treat various types of wastewater includinglandfill leachates [138] dairy effluents [139] meat processingwastewater [140] olive oil mill wastewater [141] agricul-tural drainage [142] and contaminated groundwater [143]Recognizing the importance of wastewater management inmeeting future water demands preventing environmentaldegradation and ensuring sustainable growth the use ofsubsurface infiltration systems in wastewater management isexpected to increase

31 Fundamental Processes Slow rate systems purify theapplied wastewater through physical chemical and biolog-ical mechanisms that occur concurrently in the soil waterand atmosphere environment These mechanisms includefiltration transformation degradation predation natural dieoff soil adsorption chemical precipitation denitrificationvolatilization and plant uptake Detailed knowledge of thefactors regulating these fundamental processes as well asthe complex interactions among them is prerequisite forachieving a reliable treatment particularly in terms of organicmatter degradation pathogen elimination and nutrientremoval Moreover the long-term treatment performanceand the sustainability of the land remain equally importantissues Plant selection is among the most critical compo-nents mediating the successful performance of SRS [144]Vegetation may dramatically affect the performance of landtreatment systems through its effects on hydraulic loadingnutrient uptake biomass production microbial community(structure and activity) and other particular functions suchas trace elements uptakeinactivation and toxic organicsdegradationinactivation

32 Vegetation of Terrestrial Systems Theprimary criteria forvegetation selection are (a)water requirements (b) the poten-tial for nutrient uptake (c) salt tolerance (d) trace elementsuptake andor tolerance and (e) biomass production

Table 3 shows some examples of popular plant speciesfor wastewater treatment Further features that should betaken into consideration include climate (frosts temperaturephotoperiod and length of growing season) soil properties(pH salt and nutrient concentration) plant availabilitylength of vegetation cycle and production direction (egpulp wood biofuels and other products) Currently a varietyof annual crops perennial grasses and forest trees are usedin slow rate systems (SRS) worldwide Comparative accountsof various design features of all terrestrial treatment systemshave been demonstrated in Table 4

33 Soil-Aquifer Treatment (SAT) The soil layers in an SATsystem allow the recycled water to undergo further physicalbiological and chemical purification as it passes through thesoil Physical treatment takes place by the soil acting as afilter removing particles that may still be in the water Thebiological treatment takes place as the microorganisms thatnaturally live in the soil consume or break down the organicmatter that may still be in the recycled water Chemicaltreatment occurs in the soil through such natural processesas neutralization reduction and oxidation during which onesubstance or compound in the recycled water is removedbroken down or transformed into another Changes alsotake place as the recycled water reaches the groundwateraquifer and mixes with the water already there and movesthrough the aquifer to extraction wells [145] There are twozones where physical chemical and biological purificationprocesses take place undergroundThefirst is inwhat is calledthe unsaturated zone The second is the saturated zone

The unsaturated zone consists of the upper layers of thesoil unconsolidated sediments and bedrock where spacesbetween soil particles are not completely filled with water likea kitchen sponge that is damp (ie not saturated) Scientistsmay also call this area the vadose zone or soil percolationzone The top few inches of the soil are called the infiltrationinterface where the recycled water is in contact with the soilsfor only a few minutes It is a very active zone of treatmentThe rest of the unsaturated or soil percolation zone is typically10 to 100 ft deep where the recycled water is in contact withthe soils ranging from several hours to days where additionalpurification occurs [145]

The saturated zone consists of lower layers of the soiland sediment and rock formations where all the spaces arefilled with water like a kitchen sponge that is completely wet(eg saturated) The thickness of the saturated zone is thevertical depth or extent of an aquiferThe upper surface of thesaturated zone is called the water table After the SAT waterreaches the saturated zone or aquifer it mixes together withthe underground water and then moves slowly to extractionwells During this contact time with the aquifer material andmixing with the native groundwater further purification ofthe recycled water occurs [145]

A pilot study was carried out in Sabarmati River bed atAhmedabad India for renovation of primary treated munic-ipal wastewater through soil aquifer treatment (SAT) system[146] The infrastructure for the pilot SAT system comprisedof twoprimary settling basins two infiltration basins and twoproduction wells located in the centre of infiltration basinsfor pumping out renovatedwastewaterTheperformance dataindicated that SAT has a very good potential for removalof organic pollutants and nutrients as well as bacteria andviruses The SAT system was found to be more efficient andeconomical than the conventional wastewater treatment sys-tems and hence recommended for adoption A salient featureof the study was the introduction of biomat concept andits contribution in the overall treatment process [146] SATproved to be efficient economical and feasible method forwastewater treatment [147] SAT system achieved an excellentreduction of BOD suspended solids and fecal coliformAbout 90 of water applied to SAT site was returned to


Table 3 Various plants species involved in wastewater treatment

Plant species Nature of waste ReferencesArundo donax (reeds)Eucalyptus botryoides (Southern mahogany)

Primary effluentslowastMeat processing effluent [173 174]

Eucalyptus camaldulensis (red gum)Eucalyptus ovata (swamp gum)Eucalyptus grandis (rose gum)

Primary effluentslowast stormwater pondMeat processing effluent

[173ndash175]

Eucalyptus globulus (Tasmanian bluegum)Eucalyptus cyanophylla (blue leaved mallee) Secondary effluentlowastlowast storm water pond [175ndash177]

Chloris gayana (Rhodes grass) Secondary effluentlowastlowastenriched with nitrogen [178]

Eucalyptus robusta (swamp mahogany) Secondary effluentlowastlowastenriched with nitrogen [178]

lowastThe liquid portion of wastewater leaving primary treatment like sedimentation but not biological oxidationlowastlowastThe liquid portion of wastewater leaving secondary treatment facility involving biological processes

Table 4 Design features of terrestrial treatment system

Feature Slow rate Rapid infiltration Infiltration Overland flowSoil texture Sandy loam Sand and sandy Sand to clayey silty loam and clay loam Clayey loamDepth to 3 ft 3 ft 3 ft Not critical GroundwaterVegetation Required Optional Not applicable RequiredClimatic restrictions Growing season None None Growing seasonSlope lt20 Not critical Not applicable 2ndash8 slopes cultivated land lt40 uncultivated land[179]

watershed A case study was made to increase the efficiencyof the system [148] A water quality model for water reusewas made by mathematics induction [148] The relationshipamong the reuse rate of treated wastewater (119877) pollutantconcentration of reused water (119862

119904) pollutant concentration

of influent (1198620) removal efficiency of pollutant in wastewater

(119864) and the standard of reuse water were discussed inthis study According to the experiment result of a toiletwastewater treatment and reuse with membrane bioreactors119877 would be set at less than 40 on which all the concernedparameters could meet with the reuse water standards Toraise 119877 of reuse water in the toilet an important way was toimprove color removal of the wastewater [148]

Through the use of innovative analytical tools theremovaltransformation of wastewater effluent organic mat-ter (EfOM) has been tracked through soil aquifer treatment(SAT) [149] While the total amount of EfOM is signifi-cantly reduced by SAT there are trends of shorter termversus longer term removals of specific EfOM fractionsThe preferential removal of nonhumic components (egproteins polysaccharides) of EfOM occurs over shortertravel timesdistances while humic components (ie humicsubstances) are removed over longer travel timesdistanceswith the removal of both by sustainable biodegradationDissolved organic nitrogen (DON) a surrogate for protein-like EfOM is also effectively removed over shorter term SATThere is some background humic-like natural organic matter(NOM) associated with the drinking water source within thewatershed that persists through SAT While most effluent-derived trace organic compounds are removed to varying

degrees as a function of travel time and redox conditions afew persist even through longer term SAT [149]

The design of a proper soil-aquifer treatment (SAT)groundwater recharge system is proposed after studying thegeological and hydrogeological regime of the coastal aquifersystem at Nea Peramos NE Greece [150] The investigationof the qualitative problem of the study area included ground-water level measurements and groundwater sampling andchemical analyses respectively The paper also includes thedesign of necessary maps such as geological piezometricand distribution of specific qualitative parametersThe inves-tigation concluded to further research and managerial usefulproposals [150]

4 Aquatic Systems

Any watery environment from small to large from pondto ocean in which plants and animals interact with thechemical and physical features of the environment is called anaquatic system Since ages the usual practice of wastewaterdisposal was its release into natural aquatic water bodiesGroundwater and surface water systems should be protectedfrom organic matter pathogens and nutrients coming fromnatural and anthropogenic resources Both grey and blackwater coming from any residential units should be treatedprior to its discharge to surface waters for reclamation andsecondary uses so that it may not make hazards to humanbeings and to the environment [151] Natural aquatic systemswork on the natural ecological principals where aquaticplants algae and other microbes absorb pollutants found in


the wastewater to accomplish treatment Wastewater pondsare one of the convenient options for the effective pollutantremoval [152] The proceeding section has been reserved forrecent advancements on the use of various ponds to treatwastewaters

41 Design of Wastewater Pond Systems Wastewater pondsare natural systems whose biochemical and hydrodynamicprocesses are influenced by meteorological factors such assunshine wind temperature rainfall and evaporation [153]Sun is the driving force in the purification process ofpond systems as is in any natural water body Wastewaterponds however differ greatly from natural water bodiesfor example lakes and oceans in nutrient loading oxygendemand depth size water residence time material residencetime and flow pattern [154] Variations in meteorologicalfactors often trigger fluctuations in water quality parameterssuch as temperature pH and dissolved oxygen (DO) bothseasonally and diurnally Photosynthetic oxygenation whichis essential for aerobic oxidation of the waste organics variesdiurnally with light intensities with peaks occurring between1300 and 1500 h in the tropics [155] It is not uncommonto find dissolved oxygen supersaturation between 300 and400 on the top water layers of algal ponds on warmsunny afternoons in the tropics [50 155ndash157] The pH ofalgal ponds increases with photosynthesis as algae continueconsuming carbon dioxide faster than it can be produced bybacterial respiration As CO

2diffusion from the atmosphere

is minimal primarily due to elevated surface water temper-atures the CO

2deficit during peak photosynthesis is met

from the dissociation of bicarbonate ions This bicarbonatedissociation with concomitant consumption of CO

2by algae

increases the concentration of hydroxyl ions in the watercolumn causing the pH to rise to well over 10 [158ndash160]

Temperature has a pronounced effect on both biochemi-cal and hydrodynamic processes of pond systems During thedaylight hours solar radiation heats up the top water layerthus causing thermal stratification with a consequence of thewarmer and lighter water overlaying the cooler and denserdeeper water Such density stratification reduces the perfor-mances of pond systems by increasing short-circuiting anddisrupting the internal diffusive and advective mass transfermechanisms Thermal stratification also localizes algae intobands of 10ndash15 cm width that move up and down throughthe water column in response to changes in light intensity[161] Seasonal and diurnal variations of temperature pH anddissolved oxygen in advanced integrated wastewater pondsystem treating tannery effluent were studied by Tadesse etal [161] Seasonal and diurnal fluctuations of pH dissolvedoxygen (DO) and temperature were investigated in a pilot-scale advanced integrated wastewater pond system (AIWPS)treating tannery effluent The AIWPS was comprised ofadvanced facultative pond (AFP) secondary facultative pond(SFP) and maturation pond (MP) all arranged in seriesThe variations of pH DO and temperature in the SFPand MP followed the diurnal cycle of sunlight intensityAlgal photosynthesis being dependent on sunlight radiationits activity reached climax at early afternoons with DO

saturation in the SFP and MP in excess of over 300 andpH in the range of 86ndash94 The SFP and MP were thermallystratified with gradients of 3ndash5∘Cm especially during thetime of peak photosynthesis The thermal gradient in theAFP was moderated by convective internal currents set inmotion as a result of water temperature differences betweenthe influent wastewater and contents of the reactor Inconclusion theAFP possessed remarkable ability to attenuateprocess variability with better removal efficiencies than SFPand MP Hence its use as a lead treatment unit in a trainof ponds treating tannery wastewaters should always beconsidered [161]

To improve the hydraulic characteristics of the pondsystem various innovations and modifications have beenmade in basic designs of the pond systems in the last twodecades along with the advances of efficient aeration toolsThere is a wide range of the pond systems depending uponthe processes characteristics design methods and operatingprocedures that is complete mix ponds complete reten-tion pond facultative ponds partial-mix ponds anaerobicponds high-performance aerated pond systems (complexdesigns) controlled discharge pond hydrograph controlledrelease proprietary in pond systems for nitrogen removal fornitrification and denitrification high-performancemodifiedaerated pond systems phosphorus removal ponds pondscoupled with wetlands and gravel beds system for nitrogenremoval nitrification filters and settling basins for control ofalgae and hydraulic control of ponds

42 Overview of Pond Systems for Wastewater Treatment Ifinexpensive ground is available then stabilization pond isone of the frequent wastewater treatment methodologiesUsually waste stabilization ponds (WSPs) are huge man-madewater ponds [151]Thewaste stabilization pond involvesthe construction of an artificial pond or the setting asideof a suitable natural pond or lagoon The liquid sewagereleased into the pond either before or after preliminarytreatment is held there to permit desired microbiologicaltransformations to take place [162] These ponds are firstlyoverflowed with wastewater and then treated by means ofnatural processes Separately or connected in a series forimproved wastewater treatment ponds can be usedThere arethree types of stabilization ponds that is (1) anaerobic ponds(2) facultative ponds and (3) aerobic (maturation) ponds Allof these have different action and design distinctiveness [152]For effective performance WSPs should be connected in asequence of three ormore with waste matter to be transferredfrom the anaerobic to the facultative pond and finally to theaerobic pond As a pretreatment phase the anaerobic pondminimizes the suspended solids (SS) and biological oxygendemand (BOD) [163] Where the entire deepness of the pondis anaerobic the pond is a man-made deep lake Anaerobicponds are built for a depth of 2 to 5m for little detention timeof 1 to 7 days A complete design manual must be consultedfor all kinds of WSPs and the actual design will depend onthe wastewater characterization and the loading rates [152]Organic carbon is converted intomethane through anaerobicbacteria and it also removes about 60 to 65 of the BOD


To offer a high level of pathogen removal numerous aerobicponds can be built in series Away from residential areasand public spaces they are particularly suitable for ruralcommunity that has open unused landsThey are not suitablefor very dense or urban areas WSPs are mainly competentin warm sunny climate and work in most climates Forefficient treatment the retention times and loading rates canbe adjusted in case of cold climates [151]

The primary costs associated with constructing an anaer-obic pond are the cost of the land building earthwork appur-tenances constructing the required service facilities andexcavation Costs for forming the embankment compactinglining service road and fencing and piping and pumps mustalso be considered Operating costs and energy requirementsare minimal [164]

To examine and assess the possible alternatives inmodernsocieties environmental management programs use modelsof systems [151]Waste stabilization ponds are commonlywellthought-out as being efficient for intestinal parasites removal[165] Rectangular and cross baffle shapes are popularlycapable to improve water quality To maintain the pondsformation of scum surplus solids and compost and garbageshould be avoided to enter in the ponds To make sure thatanimals and people stay away from the area a fence shouldbe installed and surplus trash should not enter in the ponds[166]

Aerated pond is a huge outside diverse aerobic reactorMechanical aerators are installed to give oxygen (O

2) and to

sustain the aerobic microorganisms mixed and suspended inthe water body for high rate nutrient removal and organicdegradation [151] To reduce the interferencewith the aeratorsinfluent must be subjected to screening and pretreatmentto remove trash fine and coarse particles [152] Increasedmixing along aeration through mechanical components inaerated ponds ensures high organic loading in the pondsThis results the increased organic matter degradation andpathogen removal In colder climates aerated ponds cansustain because of the continuous supply of oxygen by themechanical units besides the light-induced photosynthesis[163] A settling tank is necessary to separate the effluent fromthe solids since the exposure to air causes turbulence Theyare mainly suitable for the areas of reasonably priced landsthat are away from residences settlements and businessescommunities [151]

The advantages include reliable BOD5removal signifi-

cant nitrification of NH3possible with sufficient mean cell

resident time treatment of influent with higher BOD5in less

space and reduced potential for unpleasant odors Aeratedponds are more complicated to design and construct whichincreases capital and OampM costs A larger staff is needed forwhom training must be provided on a regular basis Finallysludge removal is more frequent and requires secondarytreatment for disposal off-site [164]

Construction costs associated with partially mixed aero-bic ponds include cost of the land excavation and inlet andoutlet structures If the soil where the system is constructedis permeable there will be an additional cost for liningExcavation costs vary depending on whether soil must beadded or removed Operating costs of partial mix ponds

include operation and maintenance of surface or diffusedaeration equipment [164]

Facultative ponds have been in use for more than 100years in USA [164] These ponds are usually 12ndash24m indepth and are not mechanically mixed or aerated Thelayer of water near the surface contains sufficient DO fromatmospheric reaeration and photosynthetic oxygenation bymicroalgae growing in the photic zone to support the growthof aerobic and facultative bacteria that oxidize and stabilizewastewater organics The bottom layer of a conventionalfacultative pond includes sludge deposits that are decom-posed by anaerobic bacteria These shallow ponds tend tointegrate carbon and primary solids undergoing acetogenicfermentation but only intermittent methane fermentationThe intermediate anoxic layer called the facultative zoneranges from aerobic near the top to anaerobic at the bottomThese three strata or layers may remain stable for monthsdue to temperature-induced water density differentials butnormally twice a year during the spring and fall seasons con-ventional facultative ponds will overturn and the three stratawill mix bottom to top top to bottomThis dimictic overturninhibits CH

4fermentation by O

2intrusion into the bottom

anaerobic stratum and as a result C is integrated ratherthan being converted into biogas [167]The presence of algaewhich release O

2as they disassociate water molecules photo-

chemically to assimilate hydrogen during photosynthesis isessential to the successful performance of conventional aswell as advanced facultative ponds [164]

The advantages of facultative ponds include infrequentneed for sludge removal effective removal of settle-ablesolids BOD

5 pathogens fecal coliform and to a limited

extent NH3 They are easy to operate and require little

energy particularly if designed to operate with gravity flowThe disadvantages include higher sludge accumulation inshallow ponds or in cold climates and variable seasonal NH

3

levels in the effluent Emergent vegetation must be controlledto avoid creating breeding areas for mosquitoes and othervectors Shallow ponds require relatively large areas Duringspring and fall dimictic turnover odors can be an intermittentproblem [164]

43 Energy Requirements for Various Natural TreatmentSystems The available cost data for different types of nat-ural treatments systems are difficult to interpret given thenumber of design constraints placed on the various systemsThe size required and resulting costs will vary dependingupon whether the systems are designed to remove BOD

5

TSS NH3 or total N Various reports by different authors

have highlighted the costs involved in the construction andoperation of these systems which include EPA [164] Critesand Fehrmann [168] and Shilton [169] Energy consumptionis a major factor in the operation of wastewater treatmentfacilities As wastewater treatment facilities are built to incor-porate current treatment technology and to meet regulatoryperformance standards the cost of the energy to run theprocesses must be consideredmore carefully in the designingand planning of the facilities Planners and designers shouldseek out themost recent information on energy requirements


Table 5 Total annual energy for typical 1mgd system including electrical plus fuel expressed as 1000 kwhyr [180]

Treatment system Energy (1000KwHyr)Rapid infiltration (facultative pond) 150Slow rate ridge and furrow (facultative pond) 181Overland flow (facultative pond) 226Facultative pond + intermittent sand filter 241Facultative pond + microscreens 281Aerated pond + intermittent sand filter 506Extended aeration + sludge drying 683Extended aeration + intermittent sand filter 708Trickling filter + anaerobic digestion 783RBC + anaerobic digestion 794Trickling filter + gravity filtration 805Trickling filter + N removal + filter 838Activated sludge + anaerobic digestion 889Activated sludge + anaerobic digestion + filter 911Activated sludge + nitrification + filter 1051Activated sludge + sludge incineration 1440Activated sludge + AWT 3809Physical chemical advanced secondary 4464These energy requirements were reported for meeting the four effluent quality standards that is BOD5 TSS P and N

so as to develop a system that incorporates the most efficientand affordable type and use of energy to treat wastewaterto meet regulatory requirements consistently and reliably[164] Expected energy requirements for various wastewatertreatment processes are shown in Table 5 Facultative pondsand land application processes can produce excellent qualityeffluent with smaller energy budgets

5 Conclusions

Currently economic crunch in many developed as well asdeveloping nations is forcing to implement low-cost naturaltreatment systems for the domestic and industrial wastewatertreatment In case the technological treatment facilities areinstalled in many developing countries the energy input isdifficult to be supplied in view of the global energy crisisand its affordability due to very high operational cost Theseall factors are compelling the employment of principles ofecological engineering for not only waste treatment but alsofor conserving biological communities in poor nations of theworld

The performance of various wetlands land and aquatictreatment were reviewed Constructed wetlands are designedbased on principles of natural wetlands employing differentaquatic plants like floating submerged and rooted macro-phytes The prominent feature of these treatment systems isextensive root system which helps to absorb various pollu-tants from their growth medium The presence of variousplanktonic forms also aids in treatability of constructedwetlands The constructed wetlands have been found usefulin metals absorption nutrients uptake (especially nitrogenand phosphorus) and reduction of BOD Vermicompostingconstructed wetlands have been found as useful in organic

matter removal and it is a recent trend to include earthwormsin wetlands for assisting the composting process as well asthe quality of the endproducts In addition vermicompostingproduces to be odor-free end products

The unique adaptations of mangroves to stressed envi-ronments and a massive requirement for nutrients due tofast growth and high primary productivity metabolism andyield which can be exploited for environmental remediationThe mangrove plants can modify their growth medium byexcreting exogenous enzymes and can also affect microbialspecies composition and diversity by releasing oxygen intothe rhizosphere that in turn indirectly influences enzymeactivity and thus treatment process

Land treatment systems comprise a possible alternativesolution for wastewater management in cases where theconstructions of conventional wastewater treatment plantsare not afforded or other disposal option are not accessibleThe terrestrial treatment systems present many variationsin their treatability and composition These systems relyon soil characteristics the characteristics of wastewatertopography the presence of additional media in soil andso forth This system comprises spray irrigation systemrapid infiltration and overland flows Soil aquifer treatmentsystem uses soil as a filter removing particles found in theapplied water Biological processes also take place duringsoil aquifer treatment by microorganisms in the soil whilechemical treatment is accomplished by natural processes asneutralization reduction and oxidation during which onesubstance or compound in the recycled water is removedbroken down or transformed into another

Natural aquatic systems work on the natural ecologicalprincipals where aquatic plants algae and other microbesabsorb pollutants found in the wastewater to accomplishtreatment Aerobic anaerobic and facultative wastewater


treatment ponds along their design characteristics werereviewed in current review Stabilization pond is one of thefrequent wastewater treatment methodologies where inex-pensive land is available Facultative ponds and land appli-cation processes can produce excellent quality effluent withsmaller energy budgets

Conflict of Interests

It is declared that the authors neither have any conflict ofinterests nor financial gain for this paper

Acknowledgment

Qaisar Mohmood is highly grateful to Fulbright ScholarshipProgram of USA for providing financial support for stayingin USA to accomplish this piece of work

References

[1] W JMitsch and S E Joslashrgensen ldquoEcological engineering a fieldwhose time has comerdquo Ecological Engineering vol 20 no 5 pp363ndash377 2003

[2] P Denny ldquoImplementation of constructed wetlands in develop-ing countriesrdquoWater Science and Technology vol 35 no 5 pp27ndash34 1997

[3] P Lens G Zeeman and G Lettinga Decentralised Sanitationand Reuse Concepts Systems and Implementation IWA Lon-don UK 2001

[4] M Von Sperling ldquoComparison among the most frequentlyused systems for wastewater treatment in developing countriesrdquoWater Science and Technology vol 33 no 3 pp 59ndash62 1996

[5] R H Kadlec R L Knight J Vymazal H Brix P Cooper and RHaberl ldquoConstructed wetlands for pollution control processesperformance design and operation IWA specialist group onise of macrophytes in water pollution controlrdquo Scientific andTechnical Report 8 IWA London UK 2000

[6] H Hoffmann C Platzer D Heppeler M Barjenbrunch JTranckner and P Belli ldquoCombination of anaerobic treatmentand nutrient removal of wastewater in Brazilrdquo in Proceedings ofthe 3rdWaterWorld CongressMelbourne Australia April 2002

[7] K Seidel ldquoPflanzungen zwischen gewassern und landrdquo Mit-teilungen Max-Planck Gesselschaft pp 17ndash20 1953

[8] J Vymazal ldquoConstructed wetlands for wastewater treatmentrdquoEcological Engineering vol 25 no 5 pp 475ndash477 2005

[9] V Nikolic D Milicevic S Milenkovic and A MilivojevicldquoConstructed wetland application in waste water treatmentprocesses in Serbia BALWOIS 2010mdashOhridrdquo Republic ofMacedonia pp 3 May 2010

[10] T Zhang D Xu F He Y Zhang and Z Wu ldquoApplication ofconstructedwetland forwater pollution control inChina during1990ndash2010rdquo Ecological Engineering vol 47 pp 189ndash197 2012

[11] J L Faulwetter V Gagnon C Sundberg et al ldquoMicrobialprocesses influencing performance of treatment wetlands areviewrdquo Ecological Engineering vol 35 no 6 pp 987ndash10042009

[12] Y-F Lin S-R Jing D-Y Lee and T-W Wang ldquoNutrientremoval from aquaculture wastewater using a constructedwetlands systemrdquo Aquaculture vol 209 no 1-4 pp 169ndash1842002

[13] J R Lloyd D A Klessa D L Parry P Buck and N L BrownldquoStimulation of microbial sulphate reduction in a constructedwetland microbiological and geochemical analysisrdquo WaterResearch vol 38 no 7 pp 1822ndash1830 2004

[14] N Ran M Agami and G Oron ldquoA pilot study of constructedwetlands using duckweed (Lemna gibba L) for treatment ofdomestic primary effluent in IsraelrdquoWater Research vol 38 no9 pp 2240ndash2247 2004

[15] S Kantawanichkul S Kladprasert and H Brix ldquoTreatment ofhigh-strength wastewater in tropical vertical flow constructedwetlands planted with Typha angustifolia and Cyperus involu-cratusrdquo Ecological Engineering vol 35 no 2 pp 238ndash247 2009

[16] N Chiarawatchai Implementation of earthworm-assisted con-structed wetlands to treat wastewater and possibility of usingalternative plants in constructed wetlands [PhD thesis] Techni-cal University of Hamburg-Harburg Hamburg Germany 2010

[17] S-R Jing Y-F Lin D-Y Lee and T-W Wang ldquoNutrientremoval from polluted river water by using constructed wet-landsrdquo Bioresource Technology vol 76 no 2 pp 131ndash135 2001

[18] A D Karathanasis C L Potter and M S Coyne ldquoVegetationeffects on fecal bacteria BOD and suspended solid removal inconstructed wetlands treating domestic wastewaterrdquo EcologicalEngineering vol 20 no 2 pp 157ndash169 2003

[19] M R Karim F D Manshadi M M Karpiscak and C PGerba ldquoThe persistence and removal of enteric pathogens inconstructed wetlandsrdquo Water Research vol 38 no 7 pp 1831ndash1837 2004

[20] L Xianfa and J Chuncai ldquoConstructed wetland systems forwater pollution control in North Chinardquo Water Science andTechnology vol 32 no 3 pp 349ndash356 1995

[21] P Cooper P Griffin S Humphries and A Pound ldquoDesignof a hybrid reed bed system to achieve complete nitrificationand denitrification of domestic sewagerdquo Water Science andTechnology vol 40 no 3 pp 283ndash289 1999

[22] S R Jing Y F Lin TWWang and D Y Lee ldquoMicrocosm wet-lands for wastewater treatment with different hydraulic loadingrates and macrophytesrdquo Journal of Environmental Quality vol31 no 2 pp 690ndash696 2002

[23] B Gopal ldquoNatural and constructed wetlands for wastewatertreatment potentials and problemsrdquo Water Science and Tech-nology vol 40 no 3 pp 27ndash35 1999

[24] P A M Bachand and A J Horne ldquoDenitrification in con-structed free-water surface wetlands II Effects of vegetationand temperaturerdquo Ecological Engineering vol 14 no 1-2 pp 17ndash32 1999

[25] D A Mashauri D M M Mulungu and B S AbdulhusseinldquoConstructedwetland at theUniversity ofDar es SalaamrdquoWaterResearch vol 34 no 4 pp 1135ndash1144 2000

[26] CM Kao J YWang K F Chen H Y Lee andM JWu ldquoNon-point source pesticide removal by a mountainous wetlandrdquoWater Science and Technology vol 46 no 6-7 pp 199ndash2062002

[27] J Garcıa E Ojeda E Sales et al ldquoSpatial variations oftemperature redox potential and contaminants in horizontalflow reed bedsrdquo Ecological Engineering vol 21 no 2-3 pp 129ndash142 2003

[28] M E Kaseva ldquoPerformance of a sub-surface flow constructedwetland in polishing pre-treated wastewatermdasha tropical casestudyrdquoWater Research vol 38 no 3 pp 681ndash687 2004

[29] M BGreen P Griffin J K Seabridge andDDhobie ldquoRemovalof bacteria in subsurface flow wetlandsrdquo Water Science andTechnology vol 35 no 5 pp 109ndash116 1997


[30] K Cameron C Madramootoo A Crolla and C KinsleyldquoPollutant removal from municipal sewage lagoon effluentswith a free-surface wetlandrdquoWater Research vol 37 no 12 pp2803ndash2812 2003

[31] M L Solano P Soriano andM P Ciria ldquoConstructed wetlandsas a sustainable solution for wastewater treatment in smallvillagesrdquoBiosystems Engineering vol 87 no 1 pp 109ndash118 2004

[32] CM Kao andM JWu ldquoControl of non-point source pollutionby a natural wetlandrdquoWater Science and Technology vol 43 no5 pp 169ndash174 2001

[33] C Y Lee C C Lee F Y Lee S K Tseng and C J Liao ldquoPerfor-mance of subsurface flow constructedwetland taking pretreatedswine effluent under heavy loadsrdquo Bioresource Technology vol92 no 2 pp 173ndash179 2004

[34] P Worrall K J Peberdy and M C Millett ldquoConstructed wet-lands and nature conservationrdquo Water Science and Technologyvol 35 no 5 pp 205ndash213 1997


[36] J Garcıa P Aguirre R Mujeriego Y Huang L Ortiz and JM Bayona ldquoInitial contaminant removal performance factorsin horizontal flow reed beds used for treating urbanwastewaterrdquoWater Research vol 38 no 7 pp 1669ndash1678 2004

[37] V Mudgal N Madaan and A Mudgal ldquoHeavy metals inplants phytoremediation plants used to remediate heavy metalpollutionrdquo Agriculture and Biology Journal of North Americavol 1 pp 40ndash46 2010

[38] S McCutcheon and J Schnoor Eds Phytoremediation Trans-formation and Control of Contaminants John Wiley amp SonsHoboken NJ USA 2003

[39] D C Adriano Trace Elements in Terrestrial EnvironmentsBiochemistry Bioavailability and Risks of Metals Springer NewYork NY USA 2001

[40] C D Jadia and M H Fulekar ldquoPhytoremediation the applica-tion of vermicompost to remove zinc cadmium copper nickeland lead by sunflower plantrdquo Environmental Engineering andManagement Journal vol 7 no 5 pp 547ndash558 2008

[41] D G A Ganjo and A I Khwakaram ldquoPhytoremediation ofwastewater using some of aquatic macrophytes as biologicalpurifiers for irrigation purposes removal efficiency and heavymetals FeMn Zn andCurdquoWorld Academy of Science Engineer-ing and Technology vol 66 pp 565ndash572 2010

[42] APHA (American Public Health Association) AWWA (Amer-ican Water Works Association) and WPFC (Water PollutionControl Federation) Standard Methods for the Examination ofWater and Waste Water American Public Health AssociationWash USA 19th edition 1998

[43] J Todd and B Josephson ldquoThe design of living technologies forwaste treatmentrdquo Ecological Engineering vol 6 no 1ndash3 pp 109ndash136 1996

[44] E Pilon-Smits andM Pilon ldquoPhytoremediation ofmetals usingtransgenic plantsrdquo Critical Reviews in Plant Sciences vol 21 no5 pp 439ndash456 2002

[45] J Fismes C Perrin-Ganier P Empereur-Bissonnet and J LMorel ldquoSoil-to-root transfer and translocation of polycyclicaromatic hydrocarbons by vegetables grown on industrial con-taminated soilsrdquo Journal of Environmental Quality vol 31 no 5pp 1649ndash1656 2002

[46] T Spriggs M K Banks and P Schwab ldquoPhytoremediation ofpolycyclic aromatic hydrocarbons in manufactured gas plant-impacted soilrdquo Journal of Environmental Quality vol 34 no 5pp 1755ndash1762 2005

[47] C Collins M Fryer and A Grosso ldquoPlant uptake of non-ionicorganic chemicalsrdquo Environmental Science and Technology vol40 no 1 pp 45ndash52 2006

[48] A Pano and E JMiddlebrooks ldquoAmmonia nitrogen removal infacultative wastewater stabilization pondsrdquo Journal of the WaterPollution Control Federation vol 54 no 4 pp 344ndash351 1982

[49] S C Reed RW Crites and E JMiddlebrooksNatural SystemsforWasteManagement andTreatmentMcGraw-Hill NewYorkNY USA 2nd edition 1995

[50] B Picot A Bahlaoui S Moersidik B Baleux and J BontouxldquoComparison of the purifying efficiency of high rate algal pondwith stabilization pondrdquoWater Science and Technology vol 25no 12 pp 197ndash206 1992

[51] H Bouwer and R L Chaney ldquoLand Treatment of WastewaterrdquoAdvances in Agronomy vol 26 no C pp 133ndash176 1974

[52] H Bouwer ldquoRenovation of wastewater with rapid infiltrationland treatment systemsrdquo in Artificial Recharge of GroundwaterT Aslano Ed pp 249ndash282 Butterworth Boston Mass USA1985

[53] W H Fuller and A W Warrick Soils in Waste Treatment andUtilization Land Treatment CRC Press Boca Raton Fla USA1985

[54] A Yediler P Grill T Sun and A Kettrup ldquoFate of heavy metalsin a land treatment system irrigatedwithmunicipal wastewaterrdquoChemosphere vol 28 no 2 pp 375ndash381 1994

[55] Q-X Zhou Q-R Zhang and T-H Sun ldquoTechnical innovationof land treatment systems for municipal wastewater in North-east Chinardquo Pedosphere vol 16 no 3 pp 297ndash303 2006

[56] R H Kadlec and R L Knight Treatment Wetlands CRC PressBoca Raton Fla USA 1995

[57] C R Gomez M L Suarez and M R Vidal-Abarca ldquoTheperformance of a multi-stage system of constructed wetlandsfor urban wastewater treatment in a semiarid region of SESpainrdquo Ecological Engineering vol 16 no 4 pp 501ndash517 2001

[58] J Vymazal ldquoThe use of sub-surface constructed wetlands forwastewater treatment in the Czech Republic 10 years experi-encerdquo Ecological Engineering vol 18 no 5 pp 633ndash646 2002

[59] K Maillacheruvu and S Safaai ldquoNaphthalene removal fromaqueous systems by Sagittarius sprdquo Journal of EnvironmentalScience and Health A vol 37 no 5 pp 845ndash861 2002

[60] ZWang X-Q Shan and S Zhang ldquoComparison between frac-tionation and bioavailability of trace elements in rhizosphereand bulk soilsrdquo Chemosphere vol 46 no 8 pp 1163ndash1171 2002

[61] I A TumaikinaOV Turkovskaya andVV Ignatov ldquoDegrada-tion of hydrocarbons and their derivatives by amicrobial associ-ation on the base of Canadian pondweedrdquoApplied Biochemistryand Microbiology vol 44 no 4 pp 382ndash388 2008

[62] Y Zimmels F Kirzhner and A Malkovskaja ldquoApplication ofEichhornia crassipes and Pistia stratiotes for treatment of urbansewage in Israelrdquo Journal of EnvironmentalManagement vol 81no 4 pp 420ndash428 2006

[63] Y Zimmels F Kirzhner and A Malkovskaja ldquoAdvancedextraction and lower bounds for removal of pollutants fromwastewater by water plantsrdquo Water Environment Research vol79 no 3 pp 287ndash296 2007

[64] Y Zimmels F Kirzhner and A Malkovskaja ldquoApplication andfeatures of cascade aquatic plants system for sewage treatmentrdquoEcological Engineering vol 34 no 2 pp 147ndash161 2008


[65] T Macek M Mackova and J Kas ldquoExploitation of plantsfor the removal of organics in environmental remediationrdquoBiotechnology Advances vol 18 no 1 pp 23ndash34 2000

[66] S Susarla V FMedina and S CMcCutcheon ldquoPhytoremedia-tion an ecological solution to organic chemical contaminationrdquoEcological Engineering vol 18 no 5 pp 647ndash658 2002

[67] H Xia L Wu and Q Tao ldquoA review on phytoremediation oforganic contaminantsrdquo Chinese Journal of Applied Ecology vol14 no 3 pp 457ndash460 2003

[68] J L Schnoor L A Licht S C McCutcheon N L Wolfeand L H Carreira ldquoPhytoremediation of organic and nutrientcontaminantsrdquo Environmental Science and Technology vol 29no 7 pp 318ndash323 1995

[69] V Singhal and J P N Rai ldquoBiogas production from waterhyacinth and channel grass used for phytoremediation ofindustrial effluentsrdquo Bioresource Technology vol 86 no 3 pp221ndash225 2003

[70] K R Reddy ldquoFate of nitrogen and phosphorus in a waste-waterretention reservoirant containing aquaticmacrophytesrdquo Journalof Environmental Quality vol 12 no 1 pp 137ndash141 1983

[71] K R Reddy K L Campbell D A Graetz and K M PortierldquoUse of biological filters for treating agricultural drainageeffluentsrdquo Journal of Environmental Quality vol 11 no 4 pp591ndash595 1982

[72] S Muramoto and Y Oki ldquoRemoval of some heavy metalsfrom polluted water by water hyacinth (Eichhornia crassipes)rdquoBulletin of Environmental Contamination and Toxicology vol30 no 2 pp 170ndash177 1983

[73] Y L Zhu A M Zayed J-H Qian M De Souza and N TerryldquoPhytoaccumulation of trace elements by wetland plants IIWater hyacinthrdquo Journal of Environmental Quality vol 28 no1 pp 339ndash344 1999

[74] M Q Nora and R O Jesus ldquoWater hyacinth [Eichhorniacrassipes(Mart) Solms-Laub] an alternative for the removal ofphenol inwastewaterrdquoActa BiologicaVenezuelica vol 17 pp 57ndash64 1997

[75] M von Sperling and A C de Paoli ldquoFirst-order COD decaycoefficients associated with different hydraulic models appliedto planted and unplanted horizontal subsurface-flow con-structed wetlandsrdquo Ecological Engineering vol 57 pp 205ndash2092013

[76] W H Zachritz L L Lundie and H Wang ldquoBenzoic aciddegradation by small pilot-scale artificial wetlands filter (AWF)systemsrdquo Ecological Engineering vol 7 no 2 pp 105ndash116 1996

[77] S Wallace ldquoAdvanced designs for constructed wetlandsrdquo Bio-Cycle vol 42 no 6 pp 40ndash43 2001

[78] Q Yang Z-H Chen J-G Zhao and B-H Gu ldquoContaminantremoval of domestic wastewater by constructed wetlandseffects of plant speciesrdquo Journal of Integrative Plant Biology vol49 no 4 pp 437ndash446 2007

[79] C-B Zhang W-L Liu J Wang et al ldquoPlant functional grouprichness-affected microbial community structure and functionin a full-scale constructed wetlandrdquo Ecological Engineering vol37 no 9 pp 1360ndash1368 2011

[80] G Lakatos M K Kiss M Kiss and P Juhasz ldquoApplicationof constructed wetlands for wastewater treatment in HungaryrdquoWater Science and Technology vol 35 no 5 pp 331ndash336 1997

[81] K R Hench G K Bissonnette A J Sexstone J G ColemanK Garbutt and J G Skousen ldquoFate of physical chemicaland microbial contaminants in domestic wastewater followingtreatment by small constructed wetlandsrdquo Water Research vol37 no 4 pp 921ndash927 2003


[83] K Sleytr A Tietz G Langergraber and R Haberl ldquoInves-tigation of bacterial removal during the filtration process inconstructed wetlandsrdquo Science of the Total Environment vol380 no 1ndash3 pp 173ndash180 2007

[84] R A Orson R L Simpson and R E Good ldquoA mechanismfor the accumulation and retention of heavy metals in tidalfreshwater marshes of the upper Delaware River estuaryrdquoEstuarine Coastal and Shelf Science vol 34 no 2 pp 171ndash1861992

[85] U N Rai S Sinha R D Tripathi and P Chandra ldquoWastewatertreatability potential of some aquatic macrophytes removal ofheavymetalsrdquoEcological Engineering vol 5 no 1 pp 5ndash12 1995

[86] D O Huett S GMorris G Smith andN Hunt ldquoNitrogen andphosphorus removal fromplant nursery runoff in vegetated andunvegetated subsurface flow wetlandsrdquoWater Research vol 39no 14 pp 3259ndash3272 2005

[87] Y S Wong N F Y Tam and C Y Lan ldquoMangrove wetlands aswastewater treatment facility a field trialrdquo Hydrobiologia vol352 no 1ndash3 pp 49ndash59 1997

[88] Y Ye N F Tam and Y S Wong ldquoLivestock wastewatertreatment by a mangrove pot-cultivation system and the effectof salinity on the nutrient removal efficiencyrdquoMarine PollutionBulletin vol 42 no 6 pp 513ndash521 2001

[89] K Boonsong S Piyatiratitivorakul and P PatanaponpaiboonldquoPotential use of mangrove plantation as constructed wetlandfor municipal wastewater treatmentrdquo Water Science and Tech-nology vol 48 no 5 pp 257ndash266 2003

[90] J Schaller J Vymazal and C Brackhage ldquoRetention ofresources (metals metalloids and rare earth elements) byautochthonouslyallochthonously dominated wetlands areviewrdquo Ecological Engineering vol 53 pp 106ndash114

[91] A Galvao and J Matos ldquoResponse of horizontal sub-surfaceflow constructed wetlands to sudden organic load changesrdquoEcological Engineering vol 49 pp 123ndash129 2012

[92] MMartın NOliver CHernandez-Crespo S Gargallo andMC Regidor ldquoThe use of free water surface constructed wetlandto treat the eutrophicated waters of lake LrsquoAlbufera de Valencia(Spain)rdquo Ecological Engineering vol 50 pp 52ndash61 2013

[93] P L Paulo C Azevedo L Begosso A F Galbiati and M ABoncz ldquoNatural systems treating greywater and blackwater on-site integrating treatment reuse and landscapingrdquo EcologicalEngineering vol 50 pp 95ndash100 2013

[94] J Vymazal and J Svehla ldquoIron and manganese in sediments ofconstructed wetlands with horizontal subsurface flow treatingmunicipal sewagerdquo Ecological Engineering vol 50 pp 69ndash752013

[95] L Hiltner ldquoUber neuere erfahrungen und probleme auf demgebiet der berucksichtigung der grundungung und bracherdquoArbeiten der Deutschen Landwirtschaftlichen Gesellschaft vol98 pp 59ndash78 1904

[96] H Wand P Kuschk U Soltmann and U StottmeisterldquoEnhanced removal of xenobiotics by halophytesrdquoActa Biotech-nologica vol 22 pp 175ndash181 2002

[97] J Sorensen ldquoThe rhizosphere as a habitat for soil microorgan-ismsrdquo inModern Soil Microbiology J D van Elsas J T Trevorsand E M H Wellington Eds pp 21ndash45 Marcel Dekker NewYork NY USA 1997


[98] J LynchThe Rhizosphere Wiley London UK 1990[99] J M Raaijmakers ldquoRhizosphere and rhizosphere competencerdquo

in Encyclopedia of Plant Pathology O C Maloy and T DMurray Eds pp 859ndash860 Wiley New York NY USA 2001

[100] G Dıaz C Azcon-Aguilar and M Honrubia ldquoInfluence ofarbuscularmycorrhizae on heavymetal (Zn and Pb) uptake andgrowth of Lygeum spartum and Anthyllis cytisoidesrdquo Plant andSoil vol 180 no 2 pp 241ndash249 1996

[101] M J Brimecombe F A De Lelj and J M Lynch ldquoThe rhi-zosphere the effect of root exudates on rhizosphere microbialpopulationsrdquo in The Rhizosphere Biochemistry and OrganicSubstances at the Soil-Plant Interface R Pinton Z Varanini andP Nannipieri Eds pp 95ndash140 Marcel Dekker New York NYUSA 2001

[102] JWKloepper andMN Schroth ldquoPlant growth promoting rhi-zobacteria on radishesrdquo in Proceedings of the 4th InternationalConference on Plant Pathogenic Bacteria vol 2 pp 879ndash882Angers France 1978

[103] Y Kapulnik ldquoPlant growth promotion by rhizosphere bacteriardquoin Plant RootsmdashThe Hidden Half Y Waisel A Eshel and UKafkafi Eds pp 769ndash781 Dekker New York NY USA 1996

[104] P K Mishra S Mishra G Selvakumar et al ldquoCharacterisationof a psychrotolerant plant growth promoting Pseudomonas spstrain PGERs17 (MTCC 9000) isolated from North WesternIndian Himalayasrdquo Annals of Microbiology vol 58 no 4 pp561ndash568 2008

[105] W W Wenzel D C Adriano D Salt and R Smith ldquoPhy-toremediation a plant-microbe-based remediation systemrdquo inAgronomy Monograph D C Adriano J-M Bollag W TFrankenberger and R C Sims Eds vol 37 pp 457ndash508Madison Wis USA 1999

[106] E Somers J Vanderleyden and M Srinivasan ldquoRhizospherebacterial signalling a love parade beneath our feetrdquo CriticalReviews in Microbiology vol 30 no 4 pp 205ndash240 2004

[107] G I Burd D G Dixon and B R Glick ldquoPlant growth-promoting bacteria that decrease heavymetal toxicity in plantsrdquoCanadian Journal of Microbiology vol 46 no 3 pp 237ndash2452000

[108] B R Glick C L Patten G Holguin and D M PenroseBiochemical and Genetic Mechanisms Used by Plant Growthpro-moting Bacteria Imperial College Press London UK 1999

[109] J P Kaye and S C Hart ldquoCompetition for nitrogen betweenplants and soil microorganismsrdquo Trends in Ecology and Evolu-tion vol 12 no 4 pp 139ndash143 1997

[110] G E Welbaum A V Sturz Z Dong and J Nowak ldquoMan-aging soil microorganisms to improve productivity of agro-ecosystemsrdquo Critical Reviews in Plant Sciences vol 23 no 2 pp175ndash193 2004

[111] S Zaidi S Usmani B R Singh and J Musarrat ldquoSignificanceof Bacillus subtilis strain SJ-101 as a bioinoculant for concurrentplant growth promotion and nickel accumulation in Brassicajunceardquo Chemosphere vol 64 no 6 pp 991ndash997 2006

[112] M Madhaiyan S Poonguzhali and T Sa ldquoMetal toleratingmethylotrophic bacteria reduces nickel and cadmium toxicityand promotes plant growth of tomato (Lycopersicon esculentumL)rdquo Chemosphere vol 69 no 2 pp 220ndash228 2007

[113] K V Kumar S Srivastava N Singh and H M Behl ldquoRole ofmetal resistant plant growth promoting bacteria in amelioratingfly ash to the growth of Brassica junceardquo Journal of HazardousMaterials vol 170 no 1 pp 51ndash57 2009

[114] J Xiong Z He D Liu Q Mahmood and X Yang ldquoThe roleof bacteria in the heavy metals removal and growth of Sedumalfredii Hance in an aqueous mediumrdquo Chemosphere vol 70no 3 pp 489ndash494 2008

[115] R M Atiyeh S Subler C A Edwards G Bachman JD Metzger and W Shuster ldquoEffects of vermicomposts andcomposts on plant growth in horticultural container media andsoilrdquo Pedobiologia vol 44 no 5 pp 579ndash590 2000

[116] O Y Kalinina O G Chertov and A I Popova ldquoChanges in thecomposition and agroecological properties of livestock wasteduring vermicomposting with Eisenia foetidardquo Eurasian SoilScience vol 35 no 9 pp 951ndash958 2002

[117] R K Sinha S Herat S Agarwal R Asadi and E CarreteroldquoVermiculture and waste management study of action of earth-worms Elsinia foetida Eudrilus euginae and Perionyx excavatuson biodegradation of some community wastes in India andAustraliardquo Environmentalist vol 22 no 3 pp 261ndash268 2002

[118] J Domınguez and C A Edwards ldquoEffects of stocking rateand moisture content on the growth and maturation of Eiseniaandrei (Oligochaeta) in pig manurerdquo Soil Biology and Biochem-istry vol 29 no 3-4 pp 743ndash746 1997

[119] C A EdwardsEarthwormEcology CRCPress Boca Raton FlaUSA 2nd edition 2004

[120] L C Vigueros and E R Camperos ldquoVermicomposting ofsewage sludge a new technology forMexicordquoWater Science andTechnology vol 46 no 10 pp 153ndash158 2002

[121] K E Lee EarthwormsTheir Ecology and Relationships with Soiland Land Use Academic Press Sydney Australia 1985

[122] S A Ismail Vermicology the Biology of Earthworms OrientLongman Chennai India 1997

[123] J C Buckerfield ldquoAppropriate earthworms for agriculture andvermiculturerdquo Tech Rep 21994 Division of Soils CSIROAustralia Adelaide Australia 1994

[124] C A Edwards and I Burrows ldquoThe potential of earthwormcomposts as plant growth mediardquo in Earthworms in Waste andEnvironmental Management C A Edwards and E NeuhauserEds pp 21ndash32 SPB Academic Press The Hague The Nether-lands 1988

[125] J Dominguez C A Edwards and J Dominguez ldquoThe biol-ogy and population dynamics of Eudrilus eugeniae (Kinberg)(Oligochaeta) in cattle waste solidsrdquo Pedobiologia vol 45 no 4pp 341ndash353 2001

[126] H Brix ldquoDo macrophytes play a role in constructed treatmentwetlandsrdquoWater Science andTechnology vol 35 no 5 pp 11ndash171997

[127] C Nuengjamnong N Chiarawatchai C Polprasert and ROtterpohl ldquoTreating swine wastewater by integrating earth-worms into constructed wetlandsrdquo Journal of EnvironmentalScience and Health A vol 46 no 7 pp 800ndash804 2011

[128] LWang F Guo Z Zheng X Luo and J Zhang ldquoEnhancementof rural domestic sewage treatment performance and assess-ment of microbial community diversity and structure usingtower vermifiltrationrdquo Bioresource Technology vol 102 no 20pp 9462ndash9470 2011

[129] Y J Wang S P Liu and X R Chen ldquoA survey on winter birdsin Shenzhen Futian Mangroverdquo Ecological Science vol 12 pp74ndash84 1993

[130] P E Lim T FWong andD V Lim ldquoOxygen demand nitrogenand copper removal by free-water-surface and subsurface-flowconstructed wetlands under tropical conditionsrdquo EnvironmentInternational vol 26 no 5-6 pp 425ndash431 2001


[131] V J Shackle C Freeman and B Reynolds ldquoCarbon supply andthe regulation of enzyme activity in constructed wetlandsrdquo SoilBiology and Biochemistry vol 32 no 13 pp 1935ndash1940 2000

[132] F Caravaca M M Alguacil P Torres and A Roldan ldquoPlanttype mediates rhizospheric microbial activities and soil aggre-gation in a semiarid Mediterranean salt marshrdquo Geoderma vol124 no 3-4 pp 375ndash382 2005

[133] D K Singh and S Kumar ldquoNitrate reductase arginine deami-nase urease and dehydrogenase activities in natural soil (ridgeswith forest) and in cotton soil after acetamiprid treatmentsrdquoChemosphere vol 71 no 3 pp 412ndash418 2008

[134] Q Yang N F Y Tam Y S Wong et al ldquoPotential use of man-groves as constructed wetland for municipal sewage treatmentin Futian Shenzhen Chinardquo Marine Pollution Bulletin vol 57no 6-12 pp 735ndash743 2008

[135] C Li F Gao W-H Jin and Z-S Chen ldquoSaline municipalwastewater treatment by constructed mangrove wetlandrdquo inProceedings of the 2011 International Conference on ElectronicsCommunications and Control (ICECC rsquo11) pp 2825ndash2828 Zhe-jiang China September 2011

[136] EPA ldquoOnsite wastewater treatment systems technologyrdquo FactSheet 12 Land Treatment Systems httpwwwadwwaorgtech fs 12pdf

[137] N V Paranychianakis A N Angelakis H Leverenz andG Tchobanoglous ldquoTreatment of wastewater with slow ratesystems a review of treatment processes and plant functionsrdquoCritical Reviews in Environmental Science and Technology vol36 no 3 pp 187ndash259 2006

[138] K Hasselgren ldquoUse of municipal waste products in energyforestry highlights from 15 years of experiencerdquo Biomass andBioenergy vol 15 no 1 pp 71ndash74 1998

[139] G P Sparling L A Schipper and J M Russell ldquoChanges insoil properties after application of dairy factory effluent to NewZealand volcanic ash and pumice soilsrdquo Australian Journal ofSoil Research vol 39 no 3 pp 505ndash518 2001

[140] L B Guo and R E H Sims ldquoSoil response to eucalypt treeplanting and meatworks effluent irrigation in a short rotationforest regime in New Zealandrdquo Bioresource Technology vol 87no 3 pp 341ndash347 2003

[141] F Cabrera R Lopez A Martinez-Bordiu E De Dupuy Lomeand J M Murillo ldquoTreatment of olive oil mill wastewaterrdquoInternational Biodeterioration and Biodegradation vol 38 no3-4 pp 215ndash225 1996

[142] J D Rhoades ldquoIntercepting isolating and reusing drainagewaters for irrigation to conserve water and protect waterqualityrdquoAgriculturalWaterManagement vol 16 no 1-2 pp 37ndash52 1989

[143] M C Negri E G Gatliff J J Quinn and R R HinchmanldquoRoot development and rooting at depthsrdquo inPhytoremediationTransformation andControl of Contaminants S CMcCutcheonand J L Schnoor Eds pp 233ndash262Wiley NewYork NY USA2003

[144] R W Crites and E J Middlebrooks Natural Wastewater Treat-ment Systems CRC Taylor and Francis Group Boca Raton FlaUSA 2006

[145] ldquoSoil aquifer treatmentrdquo 2013 httpwwwwatersmartprojectorgwatersmartsatsat satasp

[146] P Nema C S P Ojha A Kumar and P Khanna ldquoTechno-economic evaluation of soil-aquifer treatment using primaryeffluent at Ahmedabad Indiardquo Water Research vol 35 no 9pp 2179ndash2190 2001

[147] S Kaur and M Singh ldquoSoil Aquifer Treatment (SAT) System acase studyrdquo Indian Journal of Environmental Health vol 44 no3 pp 244ndash246 2002

[148] Y B Fan W B Yang G Li L L Wu and Y S Wei ldquoReuserate of treated wastewater in water reuse systemrdquo Journal ofEnvironmental Sciences vol 17 no 5 pp 842ndash845 2005

[149] GAmy and JDrewes ldquoSoil aquifer treatment (SAT) as a naturaland sustainable wastewater reclamationreuse technology fateof wastewater effluent organic Matter (EfoM) and trace organiccompoundsrdquo Environmental Monitoring and Assessment vol129 no 1ndash3 pp 19ndash26 2007

[150] F Pliakas A Kallioras I Diamantis andM Stergiou ldquoGround-water recharge using a Soil Aquifer Treatment (SAT) system inNEGreecerdquo inAdvances in the Research of Aquatic EnvironmentEnvironmental Earth Sciences L N Nicolaos G Stournarasand K Katsanou Eds pp 291ndash298 2011

[151] H Abbas R Nasr and H Seif ldquoStudy of waste stabilizationpond geometry for the wastewater treatment efficiencyrdquo Ecolog-ical Engineering vol 28 no 1 pp 25ndash34 2006

[152] A Jail F Boukhoubza A Nejmeddine S Sayadi and LHassani ldquoCo-treatment of olive-mill and urban wastewatersby experimental stabilization pondsrdquo Journal of HazardousMaterials vol 176 no 1ndash3 pp 893ndash900 2010

[153] WHO ldquoWastewater stabilization ponds principles of planningand practicerdquo WHO-EMRO Technical Publication no 10WHO-EMRO Alexandria Egypt 1987

[154] R Gu and H G Stefan ldquoStratification dynamics in wastewaterstabilization pondsrdquo Water Research vol 29 no 8 pp 1909ndash1923 1995

[155] M B Pescod and D D Mara ldquoDesign operation and mainte-nance of wastewater stabilization pondsrdquo in Treatment and Useof Sewage Effluent For Irrigation M B Pescod andA Arar Edspp 93ndash115 Butterworths UK 1988

[156] A Vonshak A Abeliovich S Boussiba S Arad and ARichmond ldquoProduction of spirulina biomass effects of environ-mental factors and population densityrdquoBiomass vol 2 no 3 pp175ndash185 1982

[157] A Richmond ldquoOutdoor mass cultures of microalgaerdquo inHand-book of Microalgal Mass Culture A Richmond Ed pp 285ndash330 CRC Press Boca Raton Fla USA 1986

[158] Y Azov ldquoEffect of pH on inorganic carbon uptake in algalculturesrdquo Applied and Environmental Microbiology vol 43 no6 pp 1300ndash1306 1982

[159] H O Buhr and S B Miller ldquoA dynamic model of the high-ratealgal-bacterial wastewater treatment pondrdquoWater Research vol17 no 1 pp 29ndash37 1983

[160] D D Mara and H W Pearson in Design Manual for WasteStabilization Ponds in Mediterranean Countries Lagoon Tech-nology Leeds UK 1998

[161] I Tadesse F B Green and J A Puhakka ldquoSeasonal anddiurnal variations of temperature pH and dissolved oxygen inadvanced integrated wastewater pond system treating tanneryeffluentrdquoWater Research vol 38 no 3 pp 645ndash654 2004

[162] R Porges and K M Mackenthun ldquoWaste stabilization pondsuse function and biotardquo Biotechnology and Bioengineering vol5 pp 255ndash273 1963

[163] D D Mara and H Pearson ldquoArtificial freshwater environmentwaste stabilisation pondsrdquo in Biotechnology H J Rehm andG Reeds Eds VCH Verlagsgesellschaft Weinheim Germany1986


[164] EPA Principles of Design and Operations of Wastewater Treat-ment Pond Systems For Plant Operators Engineers and Man-agers US Environmental Protection Agency Cincinnati OhioUSA 2011

[165] OAmahmid S Asmama andK Bouhoum ldquoUrbanwastewatertreatment in stabilization ponds Occurrence and removal ofpathogensrdquo Urban Water vol 4 no 3 pp 255ndash262 2002

[166] E Tilley C Luthi A Morel C Zurbrugg and R Scherten-leib Compendium of Sanitation Systems and Technologies TheWater Supply and Sanitation Collaborative Council (WSSCC)Geneva Switzerland 2008

[167] W J Oswald F Bailey Green and T J Lundquist ldquoPerformanceof methane fermentation pits in advanced integrated wastewa-ter pond systemsrdquoWater Science and Technology vol 30 no 12pp 287ndash295 1994

[168] R W Crites and R C Fehrmann ldquoLand application of winerystillage wastesrdquo in Proceedings of the 3rd Annual MadisonConference on Applied Research in Municipal Industrial Wastep 12 1980

[169] A Shilton Ed Pond Treatment Technology IWA London UK2005

[170] R Crites and G Tchobanoglous Small and DecentralizedWastewater Management Systems McGraw-Hill Press Singa-pore 1998

[171] S C Reed ldquoNitrogen removal in wastewater stabilizationpondsrdquo Journal of the Water Pollution Control Federation vol57 no 1 pp 39ndash45 1985

[172] R J Blakemore ldquoVermicology Imdashecological considerations ofthe earthworm species used in vermiculturerdquo in Proceedings ofthe International Conference on Vermiculture and Vermicom-posting Kalamazoo Mich USA September 2000

[173] V A Tzanakakis N V Paranychianakis S Kyritsis and A NAngelakis ldquoWastewater treatment and biomass production byslow rate systems using different plant speciesrdquo Water Scienceand Technology Water Supply vol 3 no 4 pp 185ndash192 2003

[174] T Manios E Gaki S Banou A Klimathianou N Abramakisand N Sakkas ldquoClosed wastewater cycle in a meat producingand processing industryrdquo Resources Conservation and Recy-cling vol 38 no 4 pp 335ndash345 2003

[175] D L Rockwood S M Pisano R R Sprinkle and A LeavellldquoStormwater remediation by tree crops in Floridardquo in Pro-ceedings of the 4th Biennial Stormwater Research ConferenceSouthwest FloridaWaterManagement District Clearwater FlaUSA October 1995

[176] R A Falkiner and C J Smith ldquoChanges in soil chemistry ineffluent-irrigated Pinus radiata and Eucalyptus grandis planta-tionsrdquo Australian Journal of Soil Research vol 35 no 1 pp 131ndash147 1997

[177] M J Duncan G Baker and G C Wall ldquoWastewater irrigatedtree plantations productivity and sustainabilityrdquo in Proceedingsof the 61st Annual Water Industry Engineers and OperatorsrsquoConference Shepparton Australia 1998

[178] M EdrakiH B So andEAGardner ldquoWater balance of swampmahogany and Rhodes grass irrigated with treated sewageeffluentrdquoAgriculturalWaterManagement vol 67 no 3 pp 157ndash171 2004

[179] USEPA ldquoWastewater treatmentdisposal for small communi-tiesrdquo (EPA-625R-92-005) Cincinnati Ohio USA 1992

[180] E JMiddlebrooks CHMiddlebrooks and SC Reed ldquoEnergyrequirement for small wastewater treatment systemsrdquo Journal ofthe Water Pollution Control Federation vol 53 no 7 pp 1172ndash1198 1981

Submit your manuscripts athttpwwwhindawicom

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

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International Journal of

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Zoology


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treatment systems for not only waste treatment but also forconserving biological communities in poor nations of theworld The conventional systems that may be appropriatein industrialized regions and densely populated areas withguaranteed power supplies easily replaceable parts and askilled labor force to ensure operation and maintenancerequirements might not be suitable for those regions withlimited resources [2] Hence natural treatment systemsparticularly suit to developing countries of the world

Sustainable sanitation systems require low cost with lowenergy consumption and low mechanical technology Betterchoices of low cost treatment systems for rural areas aredecentralized processes [3] Treatment systems with a verysmall energy input low operational cost and low surplussludge generation are anaerobic digesters and constructedwetlands [3ndash6] Other examples of low cost natural treatmentsystems include oxidation ponds anaerobic ponds facul-tative ponds terrestrial treatment systems and vermicom-posting constructed wetlands The objective of the currentreview was to describe some recent advancements in thedesign and efficiency of various natural treatment systemsand the comparison of their efficiencies Following sectionswill highlight the recent developments regarding varioustypes of natural treatment systems

2 Constructed Wetlands

Seidel [7] presented the ideas of improving inland waterssuffering from high nutrients originating from sewage andsanitation through native plant species However at thattime experts only considered physicochemical and bacterialwastewater treatment only and no attention was paid tocontrolled use of macrophytes for water purification [8]Figure 1 shows various components of a constructed wetland[9] Classification of constructed wetlands is based on twoparameters that is type of macrophytic growth and waterflow regime (surface and subsurface) [9] CW can be usedfor the treatment of different types of wastewaters that ismunicipal industrial leachate acid mine drainage surfacerunoff and so forth [10] The emerging technology for thetreatment of a variety of wastewaters is constructed wetlands(CWs) [11] The natural wetland system uses mostly naturalenergy requires low construction and operational costs andso is energetically sustainable [12ndash14] However this assump-tion is not true for constructed wetlands where some energyinput from human source is also required The constructedwetlands are classified into two type that is free water surface(FWS) and subsurface flow (SSF) systems In case of FWSsystems plants are rooted in the sediment layer and waterflow is above ground (surface flow) In SSF systems plantsare rooted in a porous media such as gravels or aggregatesthrough which water flows and treatment are accomplishedSSF systems are further divided into two types horizontalflow SSF (HSSF) and vertical flow SSF (VSSF) Comparedto HSSF the subsurface vertical flow constructed wetland(SVFCW) system is more effective for the mineralizationof biodegradable organic matter and has greater oxygentransport ability [15] For the removal of suspended solids

carbon and nitrification process vertical flow CW is moreefficient because of aerobic conditions and denitrification ispoor In VSSF CWs feeding is intermittent (discontinuous)and the flow of wastewater is vertically administered througha substrate layer which mainly consists of sand gravel or amixture of all these components [16]

Constructed wetlands can be used as an accepted eco-technology in small towns or industries that cannot affordconventional treatment systems [17ndash19] In the free watersurface (FWS) type of wetland the water is filtered through adense stand of aquatic plants as it flows over the bed surface[20ndash22] Another constructed wetland system known as thesubsurface flow wetland consists of a lined shallow basinwith a gravel media and emergent aquatic plants [23ndash28]Worldwide now thousands of constructed wetlands are inuse which are receiving and treating a variety of municipalindustrial and other wastewaters [29ndash31] Due to operationalsimplicity and cost efficiency the utilization of constructedwetlands in Taiwan is gaining greater popularity [12 22 2932 33] The constructed wetland technology is now wellestablished but its use for treating specific industrial effluentshas not been well documented [34ndash36] Various kinds ofconstructed wetlands have been shown in Figure 1

The technology which uses plants for the removal ofcontaminants from a specified area is known as greentechnology [37] and the process is known as phytoreme-diation Phytoextraction phytovolatilization rhizosphericdegradation phytodegradation and hydraulic control arethe five mechanisms involved in the phytoremediation forthe removal of pollutants Different types of pollutants canbe removed by phytoremediation such as heavy metalspesticides petroleum hydrocarbons explosives radionu-clides and CVOCs [38] Heavy metals are the chemicalsubstances whose densities are greater than 5 g cm3 [39]metals cleanup requires their immobilization and toxicityreduction or removal and they cannot be degraded likeorganic compounds [40] Sedimentationcoagulation filtra-tion plant uptakeremoval efficiency adsorption (bindingto sand particles and root) formation of solid compoundscation exchange and microbial-mediated reactions espe-cially oxidation are the different processes through whichdifferent types of metals can be removed in the constructedwet lands [41]

21TheComponents of CW Thebasic components employedin the construction of CW are containers plant speciesand sand and gravel media in certain ratios Other inver-tebrates and microbes develop naturally [42] Combinationof anaerobic reactors vegetated reactors (CW) and naturalwetlands forms ecological treatment systems In ecologicallyengineered systems different functions are performed bydifferent communities of flora fauna minerals andmicrobes[43] Another important component of ecological treatmentsystems is microbes which carry out the different importantprocesses like hydrolysis mineralization nitrification anddenitrification Plants are critical as an attachment surface formicrobes [43] For the construction of constructed wetlandthree forms of macrophytes are basically used


Constructedwetlands

Emergent plants

Submerged plants



Surface flow

Downflow

Upflow

Tidal

Subsurface flow

Horizontal

Hybrid systems

Vertical






tralis Typha spp)





















3-


3-N and 46 Chl


3-NL Values of



























3-N NH

4-N TN PO

4-P and TP in the


4-P and TP removed





3-N


4


























[173ndash175]














4 Aquatic Systems









2by algae











2) and to









4fermentation by O









3



5







5 Conclusions











Acknowledgment


References

































































































































































































Volume 2014

Zoology






















Advances in

Virolog y



Volume 2014




Enzyme Research



Microbiology


Constructedwetlands

Emergent plants

Submerged plants



Surface flow

Downflow

Upflow

Tidal

Subsurface flow

Horizontal

Hybrid systems

Vertical






tralis Typha spp)





















3-


3-N and 46 Chl


3-NL Values of



























3-N NH

4-N TN PO

4-P and TP in the


4-P and TP removed





3-N


4


























[173ndash175]














4 Aquatic Systems









2by algae











2) and to









4fermentation by O









3



5







5 Conclusions











Acknowledgment


References

































































































































































































Volume 2014

Zoology






















Advances in

Virolog y



Volume 2014




Enzyme Research



Microbiology












3-


3-N and 46 Chl


3-NL Values of



























3-N NH

4-N TN PO

4-P and TP in the


4-P and TP removed





3-N


4


























[173ndash175]














4 Aquatic Systems









2by algae











2) and to









4fermentation by O









3



5







5 Conclusions











Acknowledgment


References

































































































































































































Volume 2014

Zoology






















Advances in

Virolog y



Volume 2014




Enzyme Research



Microbiology
















3-N NH

4-N TN PO

4-P and TP in the


4-P and TP removed





3-N


4


























[173ndash175]














4 Aquatic Systems









2by algae











2) and to









4fermentation by O









3



5







5 Conclusions











Acknowledgment


References

































































































































































































Volume 2014

Zoology






















Advances in

Virolog y



Volume 2014




Enzyme Research



Microbiology



3-N


4


























[173ndash175]














4 Aquatic Systems









2by algae











2) and to









4fermentation by O









3



5







5 Conclusions











Acknowledgment


References

































































































































































































Volume 2014

Zoology






















Advances in

Virolog y



Volume 2014




Enzyme Research



Microbiology

















[173ndash175]














4 Aquatic Systems









2by algae











2) and to









4fermentation by O









3



5







5 Conclusions











Acknowledgment


References

































































































































































































Volume 2014

Zoology






















Advances in

Virolog y



Volume 2014




Enzyme Research



Microbiology








2by algae











2) and to









4fermentation by O









3



5







5 Conclusions











Acknowledgment


References

































































































































































































Volume 2014

Zoology






















Advances in

Virolog y



Volume 2014




Enzyme Research



Microbiology






2) and to









4fermentation by O









3



5







5 Conclusions











Acknowledgment


References

































































































































































































Volume 2014

Zoology






















Advances in

Virolog y



Volume 2014




Enzyme Research



Microbiology





5 Conclusions











Acknowledgment


References

































































































































































































Volume 2014

Zoology






















Advances in

Virolog y



Volume 2014




Enzyme Research



Microbiology





Acknowledgment


References

































































































































































































Volume 2014

Zoology






















Advances in

Virolog y



Volume 2014




Enzyme Research



Microbiology




































































































































































Volume 2014

Zoology






















Advances in

Virolog y



Volume 2014




Enzyme Research



Microbiology

natural treatment systems as sustainable ecotechnologies for the

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