chapter 3: organic pollutants: sources, pathways, and fate through

3. Organic Pollutants

64

3. Organic Pollutants: sources, pathways, and fate through urbanwastewater treatment systems

3.1 Sources and pathways of organic pollutants in UWW

There are a large number of organic pollutants from a wide range of sources which mayenter UWW. Paxéus (1996a) identified over 137 organic compounds in the influent of themunicipal wastewater plants in Stockholm. The physical and chemical properties of some ofthese organic pollutants are outlined in Appendix B. The main categories of organicpollutants detailed in this report are:

Polycyclic Aromatic Hydrocarbons: Polycyclic aromatic hydrocarbons (PAHs) arise fromincomplete combustion or pyrolysis of organic substances such as wood, carbon or mineraloil. Such combustion processes include food preparation in households and food shops;discharge of certain petroleum products (from garages, vehicle washing and maintenance,fuel stations); discharge of storm runoff with PAHs from car exhaust particles and roadrunoff; and also from incomplete combustion processes in urban landfills.

The most frequent anthropogenic sources of PAHs are: house fires, heat and energy powerstations, vehicle traffic, waste incineration and industrial plants (cement works, metalsmelting, aluminium production). Forest fires represent natural sources. PAHs concentrate insewage sludge due to their low biodegradability.

Polychlorinated Biphenyls (PCBs): There are two main sources of PCBs:• Directly manufactured PCBs (by chlorination of biphenyls), used as hydraulic liquids

(hydraulic oils), emollients for synthetic materials, lubricants, impregnating agents forwood and paper, flame protective substances, carrier substances for insecticides andin transformers and condensers. The EU1996 PCB Disposal Directive 96/59/ECrequires the phasing out of all PCBs by 2010 or by 1999 under internationalagreement by the North Sea States. Existing transformers and other electricalequipment which contain 50-500 mg.kg-1 PCB may be retained in service until theend of their useful life.

• The other main source of PCBs in the environment are combustion processes, fromwaste incineration plants, fossil fuel burning and to other incomplete combustionprocesses.

PCBs are adsorbed by solids and therefore they accumulate in sewage sludge. The highlysubstituted (high chlorine content) PCBs are the main representatives potentially present insewage sludge, while they amount to just 35% of the total technical PCBs. Recycling ofPCBs in the environment is very important and remediating historical pollution would benecessary if the background levels found are to be reduced.

Di-(2-ethyhexyl)phthalate (DEHP):DEHP is used as emollient in synthetic materials. In Germany, 90 % of DEHP is used inPVC and about 10% in laquers and paints. It is common to use DEHP as antifoaming agentin paper production, as an emulsifier for cosmetics, in perfumes and pesticides, they aid inthe production of different synthetic materials such as dielectric in condensers, andsubstitute for substances such as PCBs and pump oil. DEHP specific emissions fromvarious human activities have been identified by Bürgermann [1988] as follows:

• cellulose/paper production• DEHP production• plastisol-coating process• PVC production and processing, leaching from PVC products• leaching from waste in landfills• waste incineration and uncontrolled combustion


65

DEHP is found regularly in municipal wastewater and, because of its lipophilic properties, itconcentrates in sewage sludge.

Anionic and Non-ionic Surfactants:

Surfactants are contained as the main active agents in all washing and cleaning agents.These compounds are covered in detail in Case Study (f).

Polychlorinated Dibenzo-p-dioxins and Dibenzofurans (PCDD/PCDF):

The generic term "dioxins" represents a mixture of 219 different polychlorinated dibenzo-p-dioxins and furans. The most well known and hazardous dioxin, is the tetrachlorodibenzo-p-dioxin (TCDD). Dioxin concentrations are calculated as sum of the toxicity equivalents (TEQ)relevative to the most toxic dioxin [TCDD].

The three main sources of polychlorinated dibenzo-p-dioxins and dibenzofurans are asfollows [Mahnke, 1997, Horstmann, 1995]:

• Chemical reactions or chemical reaction processes: Dioxins arise as unwantedby-products from the production or use of many organo-chlorine compounds, such aschlorine bleaching of cellulose in paper production and chlorine alkali electrolysis. Inthese cases the formation mechanism can be explained by substitution,condensation or cyclisation reactions.

• Combustion processes or thermal processes: Dioxins arise by thermal processesand are released into the atmosphere. The dioxin formation results from a de-novosynthesis. Important thermal sources are:

o waste incineration plants and incomplete combustion processes in landfills;o combustion plants;o iron smelting;o sinter plants, non-ferrous smelting and recycling plants;o petrol and diesel engines.

• Dioxins can also arise from all incomplete combustion processes involvingchlorine. This explains the ubiquitous dioxins occurrence in the environment.Anthropic production of dioxins has predominated since the introduction oforganochlorine compounds in industrial applications (1920). With the improvement ofthe catalysts in waste incineration plants and other measures for reducing the dioxinsemission, the fraction of anthropic dioxins has been declining since 1970. Dioxinscan be formed and released into the atmosphere also by natural events, e.g. forestfires. Dioxins can also be generated by the biochemical transformation of precursorcompounds (for example during degradation of chlorophenols).

Dioxins speciation in household wastewater and laundry wastewater is similar to those in thesediments of UWW collecting systems and sewage sludge. A mass balance indicates that 2-7 times more dioxins in sewage sludge originates from households than from urban runoff.Washing machine effluent is a major source of dioxins in household wastewater. Dioxinswere also detected in shower water, and in urban run-off from various human activities[Horstmann 1993, 1995]. These results suggest that the importance of householdwastewater as a dioxin source has been underestimated [Horstmann et.al., 1993,Horstmann, 1995].

Sources of other potential organic pollutants are listed below:

Organic pollutants can originate from food and household related products, such as longchain fatty acids and their methyl and ethyl esters, originating from faeces, soaps and foodoils. Being relatively hydrophobic these compounds are attached to particles, theconcentration of fatty acids and esters in the unfiltered influent is more than 500 µg/l. Otherorganic pollutants from domestic origin are the sterols from animal foods and faeces andindol from faeces. Caffeine is also found from discharges from coffee processing.


66

Plasticisers and flame retardants are still used in many products for household andindustrial applications. Among the organic pollutants present are benzenesulphonamides,adipates (esthers of hexandioic acid), phthalates (esters of phthalic acid, among whichDEHP is the most common), and several phosphate esters. (2-chloroethanol phosphate) andTBP (tri-n-butyl phosphate) are used in flame-retardant compositions in textiles, plastics aswell as in other products.

Preservatives and antioxidants are constituents of household and industrial products, andamong the organic pollutants linked with these compounds are parabens (esters ofhydroxybenzoic acid), and also substituted phenols and quinones are among theconstituents.

Solvents both chlorinated and non-chlorinated (alcohols, ethers, ketones) are present in alarge range of products such as car shampoos and degreasing products, householdcleaners and degreasing agents from vehicle maintenance and production. Chlorinatedsolvents, such as trichloroethylene and trichloroethane, are in increasingly wide use: theamounts consumed in France per year are 24,000 and 28,000 tonnes, respectively. Theprincipal sources of diffuse pollution from chlorinated solvents are due to artisanal activitiessuch as metal finishing activities and dry cleaners. Nevertheless, domestic sources fromaerosols and other agents are not negligible. Pollution by metal cleaning activities is usuallyconsidered as diffuse discharges as they are usually from small firms with only fewemployees. Garages consumed around 15,000 tonnes of solvents in 1988, about 60% ofwhich is lost to the atmosphere and the rest as waste. Of the 6,000 tonnes, of waste solventsome will be discharged into the UWW collecting system [Agences de l'Eau, 1993]. Metalfinishing used 50,000 tonnes of solvents in 1991 and their aqueous wastes are dischargedinto UWW collecting systems, although these are usually in low levels. Dry cleaningconsumed around 19,500 tonnes of solvents in 1988 and it has been determined that0.3x10-3 kg of solvent/100 kg of clothes cleaned ended up in wastewater.

Fragrances from households, beauticians and hairdressers, generate mixtures of terpenesand synthetic musks (galaxolides), and are also found in industrial detergents. These arecovered in more detail in Case Study E, Section 6.

Pesticides and herbicides are also a common component of the urban wastewaters andthey result from road and rail weed treatment, and from gardens, parks and urban woodlandareas. They include the triazine group, the phenyl urea group (e.g. chlorotoluron, isoproturonand diuron), the phenoxy acid group (eg. Mecoprop and 2,4-D) and glyphosate [Revitt et al.,1999].

An enormous quantitiy of pharmaceutical products are prescribed every year: 100 tonnesof human drugs were prescribed in 1995 in Germany [Ternes, 1998]. Pharmaceuticals in theUrban Environment are discussed in Case Study (d), Section 6.

Triclosan (2,4,4’trichloro-2’hydroxydiphenyl ester) has been used in soaps, shampoo andfabrics, as an antimicrobial agent. While these compunds are regarded as low toxicity their2-hydroxy isomers have been shown to undergo thermal and photochemical ring closure toform polychlorinated dibenzo-p-dioxins which are highly toxic. (Okumura et al 1995).


67

3.1.1 Domestic and Commercial Sources

A study carried out in France in 1995 by ADEME, showed the sources of the main organicmicropollutants in sludge from WWTS were mainly domestic and commercially related (seeTable 3.1). Another study, by SFT (in collaboration with the wider Norwegian governmentenvironmental study programme and the A/S Sentralrenseanlegget RA-2 WWTS),investigated sources of PAH, PCB, phthalates, LAS and NPE. This study found that sewagefrom domestic sources, in this instance from an isolated housing estate with a separatesewage and stormwater drainage system, does make a significant contribution of the aboveorganic pollutants to urban wastewater [SFT report 98/43].

Table 3.1 Principal sources of organic micropollutants in urban wastewater treatmentworks [ADEME, 1995] +++ very likely, ++ likely, + less likely present

POLLUTANT ORIGIN Domesticusage

Stormrunoff

Commercialeffluent

Aliphatichydrocarbons

Fuel ++ ++ ++

Monocyclic aromatichydrocarbons

Solvents, phenols + + ++

PAHs By-products of petroltransformation and

insecticides

+ + +

Halogens Solvents, plastics,chlorination

++ + ++

Chlorophenols andChlorobenzenes

Solvents, pesticides + + ++

Chlorinated PAHs PCB, hydraulic fluids (+) + ++Pesticides + + ++

Phthalate esters Plastifier + + ++

Detergents ++ + ++

Nitrosamines Industrial by-products(rubber)

0 + ++

Soil is also a major repository of organic matter and the soluble fractions can leach/run-off into water courses, especially in upland areas where measures to remove colour andformation of trihalomethanes during drinking water treament is important.

A. PAHs and PCBs

Table 3.2 shows that the PAH concentration profiles for three Swedish WWTS varies. Thismay in part be due to differences in the catchment areas, with the sources of the pollutantscoming from different local industries. Most of these PAHs are expected to derive fromdiffuse commercial activities and traffic but PAHs such as pyrene, which is believed to bederived from at least 50% domestic sources, is present in all the samples at more consistentconcentrations than some of the other compounds.

Mattson et al (1991) referenced in Paxéus (1996a) found that PAHs from food, an oftenoverlooked source of this pollutant, from households can reach 50-60 % of the total UWWcollecting system load for pyrene and phenanthrene. This is an important observation ashousehold sources of PAHs are likely to be more difficult to control than commercialsources.

Another source of PAHs from domestic and commercial activities is the use of phenol andcreosol in products such as wood preservatives. In Finland, 430 tonnes of woodpreservatives were used in 1995 [Finnish Environmental Institute, 1997]. PAHs may enterUWW as a result of spillages or as surface runoff from rainwater.


68

Table 3.2 PAHs concentrations in urban waste waters in Sweden [Paxéus 1996a]

WWTSPAHsHSTµg/l

GRYAABµg/l

SSWµg/l

Naphthalene, dimethyl 1 0.5 <LODNaphthalene, methylpropyl 3 <LOD <LOD

1,1’- Biphenyl, dimethyl 2 0.5 <LOD1,1’- Biphenyl, ethyl 1 <LOD <LOD

Anthracene/Phenanthrene 1 <LOD 0.5Methyldibenzothiophene <LOD <LOD 0.5

2,8-Dimethyldibenzothioprene 5 <LOD <LODAnthracene/Phenanthrene methyl (different

isomers)2 <LOD 3

Anthracene/Phenanthrene dimethyl (differentisomers)

1 <LOD 1

Retene <LOD <LOD 0.5Pyrene 3 <0.5 2.5

Pyrene, methyl (different isomers) 2 <LOD 1Pyrene, methyl, methylethyl or tetramethyl 1 <LOD 1

1,1-Diphenylethane <LOD 0.5 <LOD

1, (H)- Indene, 1-phenylmethylene 0.5 <LOD <LOD9H-Flouren-9-one 0.5 <LOD <LOD

2-Anthracenaemine <LOD <LOD 9Acridine, 9-methyl-Dibenz(b,f) azepine <LOD <LOD 0.5

Octahydrophenanthrene, dimethyl-, isopropyl 0.5 <LOD <LODTotal PAH 23.5 <2 19.5

HST = Henriksdal Sewage Treatment Plant, GRYAAB = Gothenburg Regional SewageWorks, SSW = Sjölunda Sewage Works (<LOD = below limit of detection)

A study carried out in the Rhine region of France, [Commission Internationale pour laProtection du Rhin, 1999], showed that control of organic pollutants from point sources hasbeen effective at reducing levels of contamination in the Rhine. Between 1985 and 1996, thepollution from PAHs and PCBs had decreased by over 90%. In 1985, 1,075 kg of PCBs weredischarged, which was reduced to 250 kg in 1992, and to 3 kg in 1996, all of which werefrom industrial sources. For trichloromethane, 9,000 kg were discharged in 1985, 2,300 kg in1992, and 2,210 kg in 1996; of these 600 kg were from industry and 1,610 kg fromcommunal sources.


69

B. DEHP

The Danish Ministry of the Environment and Energy [Danish Report, 1999] have estimatedthe annual consumption of phthalates in Denmark to be approximately

o 10,000 tonnes in 1992 (about 90% of this used in soft PVC)o 11,000 tonnes in 1995

In Germany, the total production of DEHP in 1988 was 234,000 tonnes. Of this, 1% wasdischarged to surface and groundwater [Brüggermann, 1988].

The vast majority of phthalate emissions to the environment occur, not during themanufacture, but during the use of the finished products. While in some cases this is acommercial setting (such as vehicle washing, which will be examined subsequently), thereare also major sources in the domestic environment. Mattson et al. (1991) mentionedpreviously regarding domestic sources of PAHs, estimated the household contribution ofphthalates and adipates to the Gothenburg sewage works as 70% of the total load (thisfigure emphasises the ubiquity of compounds and difficulty of control). Two major sources ofdomestic releases to wastewater (shown in bold in Table 3.3) are floor and wall coveringsand textiles with PVC prints.

Table 3.3 DEHP emissions in Denmark[adapted from Appendix 1 Danish Ministry of Environment and Energy Report, 1999]

Product Phthalate use (t y-1) Emission to airduring production

(t y-1)

Emission to airduring use

(t y-1)

Release towastewaterduring use

(t y-1)Cars 1000 - 0.1-1 2-10

Floor and WallCoverings

2000 - 0.2 1-5

Textiles withPVC prints

5-15 - - 2-13

C Dioxins and furans (PCDD/Fs)

The Environment Agency of England and Wales [1998] estimates dioxin emissions fromindustrial Part A processes to UWW collecting systems in the UK as 4.5 µg (TEQ), whereasemissions to air from these processes was estimated to be 1.1kg. Routes of these pollutantsinto wastewater via deposition or industrial process (i.e. washing of air pollution cleaningequipment), are not discussed. Actions taken to reduce dioxin emissions continue to ensureIPC authorisations are met.

Recent research at the University of California, Berkeley, reports that deposition of dioxins tosoil is 6 to 70 times greater than estimated emissions [Eduljee 1999]. This suggests thateither not all sources of dioxin are known and/or the contributions from these sources maynot be accurately characterised.

Table 3.4 shows the dioxin emissions for the years 1994-1998 in Austria. There was little orno change in the dioxin emissions in Austria over this period, but slight reductions, wereachieved in some sectors. The main reason for the emission reduction in 1998 is due to theair hold ordinance, which limited dioxin emissions from waste combustion as well as fromsteam-boiler plants.


70

Table 3.4 Dioxin emissions in the time period 1994-1998, Austria[Federal Environmental Agency, UNECE/CLRTAP, 1999].

1994 1995 1996 1997 1998Issuer groups Dioxin emissions (tonnes per annum)

Small consumer(household, trade,

administration)16,820 18,160 18,400 16,780 16,260

Industry (burningand processes)

3,470 3,730 3,880 3,980 3,910

Industryprocesses

8,170 8,900 7,990 8,550 8,380

Waste handlingand landfills

180 180 180 180 180

Total 28,640 30,970 30,450 29,500 28,740

In Spain, concentrations of dioxins are reported for recent samples (1999) of sewage sludgeand for archived samples (from 1979 to 1987) [Eljarrat, et.al., 1999]. Results are shown inTable 3.5. It is estimated that the current concentrations of dioxin in sludge have droppedsince the 1970s-80s. This is expected to be due to the source reduction of pollutants, fromcombustion and incineration processes, and from certain pesticides contamination andemphasises the success that controls on use of compounds and trade effluent discharge inreducing pollutant levels.

Table 3.5 Concentrations of PCDD/F in sewage sludge in Spain [Eljarrat, et.al., 1999]

Type of sewagesludge

Range ofconcentrations

(pg.g-1 DW as I-TEQ)

Mean value(pg.g-1 DW as I-TEQ)

Fresh [1999] 7 to 160 55Archived [1979-1987] 29 to 8,300 620

E. Other organic compounds

Adsorbable organo-halogen compounds (AOX) resulting from bleach products and fromchlorine use, were reported in studies done in Portugal, in Ria Formosa lagooned sewage[Bebianno, 1995] and in Italy in the city of Parma [Schowanek, et.al, 1996]. The averageAOX concentration in sewage was reported as 37 µg.l-1.

Sterols were reported in sewage sludge and around discharge wastewater points inPortugal, in Faro, Tavira and Olhao [Mudge et al., 1997, 1998 and 1999]. Concentrationsranged between 0.1 to 27.8 µg.g-1 sterols of dry weight of sludge. Hospital wastewater maycontain high phenol concentrations, up to 20,000 µg.l-1, plus other compounds such as LAS,NPE, PCBs and pharmaceuticals.

F. Vehicle washing

A specific activity identified as a source of a number of organic pollutants in urbanwastewater is vehicle washing, which consists of two distinct phases:

o Actual cleaning, involving the removal of oily dirt, which, on a quantitative basiswould be expected to be similar to the type of oily dirt (asphalt and vehicle exhaustparticles) which is in road runoff. However, this would also involve the use ofdegreasing solvents and surfactants which can enter the wastewater treatmentprocess.

o Vehicle Treatment, involves the use of protective treatments, often coatings usingdifferent types of wax against corrosion, dust and dirt.


71

The effluent is usually discharged to the UWW collecting system. Several studies of theeffluents from vehicle washing facilities have been undertaken [Paxéus 1996a, 1996b,Paxéus and Schröder, 1996, Ulmgren 2000a]. In Sweden, an environmental standard for carwashing detergents was established in Göteborg in 1992 [EHPA, 1992], based on thePrecautionary Principle and Substitution Principle in the Chemical Products Act. In generalCOD values found at the effluents of vehicle washes are in the range of typical untreatedindustrial petrochemical wastewaters [Huber, 1988].

In Gothenburg, an important site for vehicle manufacture, vehicle washing was estimated tocorrespond to 0.5 % of the total wastewater at the Gothenburg WWTS, which was concludedto have a very small effect on the total load of organic pollutants at the plant. The majorcomponents of the effluents were aliphatic hydrocarbons and alkylbenzenes, originating frompetroleum base degreasing solvents and the oily dirt on the vehicles themselves (asphalt,vehicle exhaust particles). Low aromatic products reduce the potential environmentalassociated with detergent use in car washing facilities. These are produced byhydrogenation of petroleum-based solvents where substituted benzenes and naphthalenesare converted to corresponding naphthenes and decalins. The formation and discharge ofpolyaromatic compounds is negligible for detergents that come from low aromaticmicroemulsions.

Table 3.6 summarises the results of a study on washing both of light vehicles (LV) andheavy vehicles (HV) [Paxéus 1996]. As can be seen, HVs tend to contribute larger organicpollutant loads than LVs.


72

Table 3.6 Concentration of organic pollutants in car wash effluents in mg l -1

[after Paxeus, 1996]

Conventionalparameters

LV HV

Mean Median Range Mean Median RangeTotal oil 291 242 10-1750 550 460 65-1200

COD 1263 1180 120-4200 4600 4500 1700-7500

Aliphatic hydrocarbonsC8-C16 29 22 1-139 103.86 76.72 41-220C17-C30 0.6 0.4 <0.001 1.84 1.87 0.9-3.0

Aromatic hydrocarbonsBenzene 0.01 0.01 <0.01-0.2 0.02 0.02 0.02-0.03Toluene 0.08 0.05 <0.01-0.6 0.10 0.08 0.03-0.2

Naphthalene 0.17 0.13 <0.001-0.7

1.1 0.75 0.3-3

Biphenyl 0.015 0.005 <0.001-0.1

0.12 0.11 0.04-0.2

Dibenzofuran 0.001 0.002 <0.001-0.03

0.011 0.011 0.009-0.012

Phenathrene 0.005 <LOD <0.001-0.03

0.021 <LOD 0.005-0.03

Pyrene 0.003 <LOD <0.001-0.01

0.009 <LOD 0.01-0 .02

Fluoranthene 0.003 <LOD <0.001-0.01

0.004 <LOD 0.002-0.006

PlasticizersDiethyl phthalate 0.005 0.01 2E-3-0.06 0.01 0.01 0.01-0.02Dihexyl phthalate 0.05 0.03 <0.001-

0.150.3 0.21 <0.001-

0.7DEHP 0.52 0.38 0.03 - 4.1 1.50 1.30 0.4 - 3

Washing agentsp-nonylphenol 0.60 0.26 0.01-4 0.43 0.41 0.1-0.8

2-Botoxyethanol 25 15 <0.001-270

15 17 <0.001-27

It is not known if this area is representative of the Scandinavian region as a whole in terms ofthe car washing input. However, it does seem that car washing is also an important sourceof pollutants in Norway [SFT, 1998a, 1998b]. In Norway 41 businesses were reported on assources of hazardous organic pollutants, PAHs, phthalates (DBP, BBP, DEHP),nonylphenols (nonylphenol, nonylphenol mono- and di-ethoxylates). The studies found thehighest pollutant loads in the effluents from motor vehicle workshops to urban wastewatercame from petrol stations with car washes, long haul transport depots with ‘car washes’commercial laundries, paint spraying workshop and chemical businesses [SFT, 1998a,1998b].

There are two main types of washing agent available and the choice of these would result insignificant differences in wastewater quality:

• Water-based formulations (microemulsions) containing 10-30% hydrocarbons butincreased surfactants (10-30%);

• Petroleum-based degreasing formulations containing 95-99% of hydrocarbons and3% surfactants.

Plasticisers found in the effluents from vehicle cleaning included phthalates, althoughanalysis of the cleaning and washing chemicals showed that they themselves contribute verylittle to the discharge of plasticisers.


73

3.1.2 Urban runoff

A significant proportion of organic contaminants in wastewater are derived from urban runoff.These organic compounds include aliphatic and aromatic hydrocarbons, PAHs, fatty acids,ketones, phthalate esters, plasticisers and other polar compounds. Solvent extractableorganics are dominated by petroleum hydrocarbons, which arise from motor oil and tyresfrom road surfaces. Organic pollutant sources have not received the extent of researchattention that potentially toxic element pollution has. For example, in the case of PAHs whichare combustion by-products and enter wastewater principally through atmosphericdeposition and urban runoff, the sources can be stationary (industrial sources, power andheat generation, residential heating, incineration and open fires) and mobile (petrol anddiesel engine automobile) [Sharma et al.,1994]. Different PAH species are associated witheach one of these sources.

A. Road and vehicle related pollution

The main sources of road and vehicle related metals pollution have been outlined in Section2.1.3. Table 3.7, shows some of the road and vehicle related sources of organic pollutants.

Table 3.7 Qualitative classification of road related sources of organic pollutants[after Montague and Luker, 1994].

Traffic Maintenance AccidentsPetrol

(PAHs and MTBE)Tar and bitumen Petrol

Oil Oil OilGrease Grease Grease

Antifreeze Solvents SolventsHydraulic fluid PAHs

AsphaltPCBs

Pesticides andherbicides

Table 3.8 summarises the results from three experimental catchments from 1975 to 1982 onmean concentrations of PAH.

Table 3.8 Summary of pollutant concentrations in urban runoff caused by road relatedsources [after Klein, 1982]

Test catchmentsPollutant meanconcentrations (mg.l-1) Pleidelsheim Obereisesheim Ulm / West

PAH 2.61 2.97 2.51

The necessary conditions for PAH formation is the presence of benzene and a highconcentration of radical intermediates, which then form stable compounds. Multiple ringsystems are autocatalytic and promote further ring condensations. Fuel aromatic content hasbeen shown to influence particle-associated PAH emissions almost linearly [Pedersen et al.,1980; Nunnermann, 1983; Egeback and Bertilsson, 1983]. However, the relationshipbetween the aromatic content of petrol and PAH formation is not fully understood.

PAHs are produced by unburned fuel, exhaust gases and vapour, lead compounds (frompetrol additives) and hydrocarbon losses from fuel, lubrication and hydraulic systems.Volatile solids will be added to the total suspended solids loading of rainfall runoff and canalso act as carriers for both potentially toxic elements and hydrocarbons. Some road dustshave been found to contain 8.5 µg g-1 of PAHs [Colwill et al., 1984 as reported in Luker and


74

Montague, 1994]. The introduction of the catalyst technology for motor vehicles lowered theemissions of PCDD/F in Germany to about 98% [UBA, 1999].

Tyre wear releases hydrocarbons either in particulate form or in larger pieces as a result oftyre failure. A tyre loses about 10 to 20 per cent of its weight in a lifetime. Annually it isestimated an average of 140 g of tyre-derived particles are eroded per metre of road[Environment Agency of England and Wales, 1999].

Plasticisers (such as diethyl phthalate and dihexyl phthalate) are also considered animportant parameter of organic pollution load in urban runoff. Cary et al. [1989], stated thatplasticisers, especially phthalates, represent the major pollutants found in urban storm water.The concentrations found for 8 plasticisers were recorded. Of these DEHP was found in thegreater concentrations than the other seven plasticisers combined. The main sources ofplasticisers are traffic grime and dirt, associated with the degradation of plastic componentsof the vehicles.

B. Roof Runoff

Regarding roof runoff as an interface between atmospheric boundary layer and the runoffreceiving system, Förster (1993) investigated the role of roofs as source and sink of organicpollutants. The trace organics analysed included PAH, chlorinated hydrocarbons and nitrophenols. The research indicated that the insecticide HCH was primarily introduced to theroof runoff system by wet deposition, while the amount of adsorbed PAHs (pyrene;benzo[a]pyrene=BaP) in roof runoff exceeded the input by rain with events during coldertimes of the year where fossil fuel heating systems constitutes additional source for thispollutant. The concentration profiles for a number of PAHs are illustrated in Figures 3.1 and3.2 below.

Figure 3.1 PAH in runoff from zinc sheet roof [after Förster, 1993]


75

Figure 3.2 PAH in runoff from tar roof [after Förster, 1993]

As can be seen, the concentrations of PAH in roof runoff from zinc roofs was found to beabout ten-fold higher than for tar roofs. There is a difference in the pattern of distribution forPAH concentration at different precipitation flow rates. For tar roofs PAH concentration ishighest at the lower and higher precipitation flows and lower at intermediate events, whereasfor zinc roofs it tended to be higher at lower precipitation flows. Therefore, concentrations of**pollutants in roof runoff can be considered variable depending on the characteristics of theroof material itself as well as on the characteristics of the precipitation event.

A number of hydrocarbons are present in urban rainfall runoff, particularly those associatedwith motor vehicles, such as petrol, fuel oils and lubricants. In an unmodified form theseliquids are insoluble in, and lighter than, water. Typically, 70-75% of hydrocarbon oils show astrong attachment to suspended solids [Luker and Montague, 1994]. PAHs have an evengreater affinity. In contrast, Methyl-tertiary-butyl-ether (MTBEs) the new additive to unleadedfuel is significantly more soluble in water than all other hydrocarbons in rainfall runoff.Hydrocarbons, even in low concentrations, can give rise to surface sheens and thusadversely affect surface waters. Most hydrocarbons eventually degrade by a combination ofmicrobial and oxidative processes; degradation though is slow, so the increase in oxygendemand in watercourses and wastewater is likely to be marginal and not a principalenvironmental impact.

C. Urban vegetation control practices

Herbicides and pesticides are used in road maintenance operations to control weeds andpests on the roadsides and verges. The triazine group of herbicides, including atrazine andsimazine, has been used extensively for roadside weed clearance and is more soluble andmobile than their organo-chlorine predecessors. Combined levels of atrazine and simazineabove 1µg l-1 are not uncommon in watercourses near highways (Ellis, 1991). Collins andRidgeway (1980), report that half of pesticides in urban runoff are associated with particles<63 µm, although these particles are less than 6% of the total suspended solids load.In urban areas, pesticides in general, and herbicides in particular, are becoming an integralpart of the control of unwanted vegetation by local and municipal authorities, rail and airportoperators. The main herbicides used in the UK are of the triazine group, the phenyl ureagroup (e.g. chlorotoluron, isoproturon and diuron), the phenoxy acid group (e.g. Mecopropand 2,4-D) and glyphosate (Revitt et al., 1999). Of the phenyl urea compounds, only diuron


76

has been widely used in the urban environment and in 1989 this herbicide accounted for13% of the total 550 tonnes of active ingredient used in the UK (Department of theEnvironment, 1991). The comparable use of triazines was 39% but following the introductionof restrictions for the non-agricultural use of these herbicides in 1992, many users convertedto the use of diuron and glyphosate for the control of vegetation in urban environments(White and Pinkstone, 1995). The removal of herbicides by rainfall runoff is influenced byrainfall characteristics, the time interval between herbicide application, the precipitation eventand the properties of the herbicide. However, the full range of factors that influence herbiciderelease from sites of application and the mechanisms governing the transport to, and fate ofherbicides in the aquatic environment are not fully understood [Davies et al., 1995; Heatherand Carter, 1996]. The principal herbicide sources in urban catchments include [Revitt et al.,1999]:

• Urban parks and private gardens• Road maintenance (to road kerbstones and backwalls)• Railway system maintenance.

Concentrations in receiving waters, reported by Revitt et al., (1999) in the UK, wereconsistently above the drinking water limit of 0.1 µg l-1 recommended for simazine anddiuron; the mean concentrations of which reached 0.34 and 0.45 µg l-1, respectively. InFrance [Farrugia et al., 1999], the average application rates for pesticides on the mostconsuming urban land uses are reported as 900 g ha-1 for roads and streets, 4000 g ha-1 forcemeteries and 500 to 800 g ha-1 for parks and sport yards. Householders may also uselarge amounts of herbicides and other pesticides but information on the quantities applied isnot available in published literature. However, there was considerable variation in the extentof water contamination with herbicides between catchments. Farrugia et al, (1999), reportedthe average concentration of diurons in water receiving urban runoff was 5 µg l-1, andattributed this entirely to use in urban situations.

It is to be noted that the hydrological characteristics of hard urban surfaces provide the idealconditions for the efficient transport of herbicides (particularly diuron, see also Farrugia et al.,1999) into UWW collecting systems. This, combined with the existence of inert physico-chemical environments involving neutral pH, low nutrient and total organic carbon levels,absence of absorption sites and low bacterial populations, allow the application of herbicidesin urban areas (although in low use), to be an important potential source of contamination ofwaste water.

D. Wet and dry deposition

The main repository of PCBs, PAHs and PCCD/Fs is soil. Volatilisation from soil, then furtheratmospheric transport and deposition of PAHs, PCBs and PCDD/Fs is considered to be oneof the main contemporary sources of these contaminants in the environment Wild et al.,.[1995]. PAHs are difficult to control because they are a combustion product.

The Austrian Federal Environment Agency (UBA) analysed PAHs in several media (surfaceand wastewater, sediment, soil, sewage sludge, compost, plants, street dusts and ambientair) between 1989 and 1998 [Gans, et.al., 1999]. Only 10 % of samples were above thedetection limit for PAHs of between 2.6 and 20.3 ng l-1 and these were all taken during winterand spring, suggesting that PAH originates from the emissions of heating systems during thecold period.

Once released (by the sources mentioned in the previous paragraphs), airborne PAHs aretransported by the prevailing meteorology before being removed from the atmospherethrough various scavenging mechanisms. As with other airborne pollutants the majormechanisms of removal of PAHs from the atmosphere are wet deposition, such as rain,sleet, snow, hail, and dry deposition to the surface. The wet removal of gaseous compoundsis better understood than particulate PAH removal [Ligocki et al., 1985]. The extent of in-


77

cloud or below cloud scavenging, collection efficiency of falling precipitation, solubility andsize particles has been examined in the literature [McVeety, 1986 as reported in Sharma etal., 1994].

Dry removal is a function of atmospheric conditions and the surface level concentration ofPAHs. PAHs adsorbed to particles greater than 20 µm have higher settling velocities andthus will settle in the vicinity of the source. However, this mechanism will only account for aminor percentage of removal, as PAH are mostly adsorbed on particles less than 10 µm indiameter.


78

3.2 INFLUENCE OF VARIOUS TREATMENT PROCESSES ON THE FATE OF ORGANICPOLLUTANTS THROUGH WASTEWATER TREATMENT AND SEWAGE SLUDGETREATMENT

3.2.1 PARTITIONING OF ORGANIC POLLUTANTS IN WASTEWATER TREATMENTPROCESSES.

The general effect of wastewater treatment processes is to concentrate the organicpollutants in the sewage sludge and the extent of this removal depends on the properties ofthe organic species. The overall result of this process is to discharge a treated wastewaterrelatively free of organic and inorganic contaminants and a sewage sludge that containsmost of the organic contamination present in the feed wastewater. The main complication ofthis general study arises from the large number of possible organic species that could bepresent in the feed stream and the complex chemistry sorbtion mechanisms on the solids.

During the treatment cycle, some organic materials can degrade to a certain extent,especially in aerobic environments and organic material of biological origin is easy todegrade. Indeed, some common organic pollutants such as LAS, are specifically added todetergents because they are aerobically biodegradable. A considerable body of literatureexists on this aspect and a variety of oxidants have been proposed. The main aim of thistype of work has concentrated on reducing the organic pollutant content in sewage sludgeprior to land disposal. Advanced oxidation processes might be used in tertiary treatmentespecially if the final effluent is to be used for drinking water. However, use of theseprocesses; regardless of the power of the oxidant, cannot be expected, a priori, to degradeall types of organic pollutants within a reasonably short time scale. Indeed, the presence oforganics in final effluents is an obstacle in expanding the recycling of wastewater.

3.2.2 Wastewater Treatment

Traditionally, wastewater treatment is supposed to begin at the head of a WWTS at the inletscreens used to remove large objects such as wood plastics and paper. However, in realitywastewater conditioning starts in the sewer, in large conurbations the wastewater can havequite a significant residence time in a sewer. However, it is suggested that dilution ofsewage with runoff water is likely to have an adverse effect on the efficiencies of thedownstream treatment processes (Dorussen et al., 1997).

Primary treatment is installed to enable sedimentation of the feed wastewater. This processis used to settle, retain and concentrate most of the particulate material to the bottom of thetank as primary sludge. The process is affected by temperature and the solids content of thesupernatant or primary overflow is significantly higher if the temperature is low, as it is inwinter. Though simple, primary sedimentation is a widespread process in Europe, althoughnot practised in all WWTS. In some cases primary sedimentation is not installed and in otherplants flocculation, by addition of flocculants, is carried out in the primary sedimentation tank(Hahn et al., 1999).

The objective of secondary treatment is to contact the primary overflow (settled sewage) withair in the presence of aerobic bacteria and other micro-organisms, which convert the organicmatter to carbon dioxide and water to a variable extent. There are two types of plantcommonly used for this process: bio filters and activated sludge. Most WWTS use primaryand secondary processes. However some plants may have tertiary treatment which, caninvolve coagulation, flocculation and rapid gravity filtration.

A novel process for secondary treatment is the lagoon (Salter et al., 1999). This is large unitseveral meters deep and can be stirred gently and aerated. Aquatic life including fish cansurvive in some lagoons. The residence time in the lagoon is long and they can be used totreat the more contaminated municipal wastes. In addition secondary pre-treatment can becarried out using magnetic flocs. In this process the organic contaminants present are


79

loaded on to the magnetic flocs at a low pH and washed off in a high pH medium (Booker etal., 1996).

There is some concern about the use of iron coagulants, which is of direct relevance to thisstudy. Some iron reagents used in wastewater treatment are made as a by-product oftitanium oxide production. The titanium ore contains traces of vanadium and uranium. Twoother tertiary methods often cited are activated carbon and membrane filtration. Bothhowever are rather expensive. Activated carbon is a very efficient means of removal oforganic pollutants and the technique is widely used in small domestic plants used to polishdrinking water. Membrane filtration is also very effective in removing particulate materialfrom water. However, the membranes are expensive and fouling can occur.

In order to estimate organic and inorganic pollutant removal in wastewater treatmentprocesses models are required to simulate them. In such models physical properties of thepollutants are used to determine the likelihood that they will be removed by the process.More work is needed on modelling the fate of organic pollutants through WWTS and theirtransformation throughout the different treatment methods.

It is clear that the regular screening of priority organic pollutants on a day-to-day basis wouldbe complex and uneconomical. It has been suggested that determination of adsorbableorganic halogens (AOX) be used as an indicator for these priority substances (Hahn et al .,1999). AOX determination is a relatively easy technique to use (Korner, 2000). Thesesubstances are sorbed from the water on charcoal, which is subsequently pyrolysed. Thehydroxyhalides produced are sorbed and analysed by titration. Another general testmentioned in the literature (Ono et al., 1996) is the bacterial umu-test, which measuresdamage caused by organic pollutants on DNA.

3.2.3 Properties of Organic PollutantsOctanol-water partition coefficient and solubilityThe octanol- water partition coefficient is the ratio of a compound’s concentration in octanolto that in water at equilibrium.

Kow =

Kow is dimensionless and values vary over the range of at least 10-3 to 107 and are usuallyexpressed logarithmically. Large Kow values are characteristic of large hydrophobicmolecules which tend to be associated with solid organic matter while smaller hydrophilicmolecules have low Kow values. Octanol-water partition coefficients can be measured directlyby using conventional “shake flask” methods (Leo and Hansch, 1971). This experimentalapproach is restricted to compounds of low-to-medium hydrophobicity, since for compoundswith high hydrophobicity, the concentration in the aqueous phase is too low to be measuredaccurately.

Kow can also be correlated with various environmental parameters, such as solubility. Bydefinition, the partition coefficient expresses the concentration ratio at equilibrium of anorganic chemical partitioned between an organic liquid and water. This partitioning is, inessence, equivalent to partitioning the organic chemical between itself and water. One wouldexpect that a correlation would exist between the partition coefficient and solubility. Lyman etal. (1990) presented the following correlation between solubility based on 156 compounds:

978.0log339.11

log oww

KS

=

where Sw is the solubility expressed in mol l-1. This correlation was obtained empirically andthe correlation coefficient was found to be 0.874.

Concentration of compound in octanol

Concentration of compound in water


80

Organic carbon-water partition coefficient, KOC

The tendency of a compound to sorb to the organic matter such as humic substances in soil or sewage sludge particles can be assessed using the organic carbon-water partitioncoefficient. It is defined as the ratio between the concentration of the organic compound onorganic carbon (mg.g-1) and its concentration in water (mg.l-1), at equilibrium.

Koc =

The likelihood of the leaching of a compound through soil or adsorption onto soil organiccarbon can be assessed from Koc values. Generally, organic compounds with high Koc valueswill tend to adsorb onto organic carbon whilst compounds with low values have a greatertendency to be leached. Koc values can be estimated from the octanol-water coefficient orwater solubility. Karickhoff et al. (1981) found the following correlation:

Log Koc = 0.82 log Kow + 0.14

when he examined sorbtion data for a variety of aromatic hydrocarbons, chlorinatedhydrocarbons, chloro-S-triazines and phenyl ureas. The correlation coefficient was 0.93.

In this study a specific list of organic pollutants has been defined and it can be seen thattheir solubilities are very low but the Koc values are very high in the region of 105 indicatingthat the sorbtion would be very favourable. From the Koc values and the weight fraction oforganic carbon species present in the feed (f) an estimate of the removal of organic speciescan be made. The amount left in the supernatant water as a percentage left (L) is given by:

L = 100

fK oc

1

Thus if f = 10-3 and Koc = 10-5, the percentage left would be 1%. There is limited dataavailable or actual results but figures for L are generally much higher. (Pham et al., 1997)report that 30% of PCB and only 25% of the PAHs were removed from a specific treatmentplant.

3.2.4 Modelling

Understanding the processes involved in wastewater treatment is likely to provide a basis forunderstanding the pathways and partitioning of pollutants in these processes. The way to dothis is to develop models of the processes and to simulate plants using computers. Anexample of such a comprehensive model has been published (Gabaldon et al., 1998). Themodel does not specifically include large molecular weight organics.

It is of some of interest to note that there is some work on processes that occur in a sewer.One study aims to model the emissions of volatile organic compounds in cocurrent air flow inopen and closed sewers (Olsen et al., 1998). Another study measures the removal of CODand proteins within a sewer (Raunkjaer et al., 1995) and found that there were quitenoticeable losses in a sewer. In another study the sewer pipe was considered to consist of asediment above which was a bio-film and above that the water phase (Fronteau et al., 1997).

O’Brien et al. [1995] and Mann et al.[1997] present a first order model for a wastewaterplant. In the secondary section aeration for stripping, biodegradation and sorption on to aPAC (Powdered Activated Carbon) were considered. PCB, PCDD/F or PAH were notincluded but the methodology presented in this paper could be applicable to the study of thefate of these high molecular weight pollutants in secondary treatment. Work has been doneon modelling trickling filter-beds (Shandalor et al., 1997). This predicts the drop of solidsloading in the water as it trickles down the bed. On the more specific case of organic

Concentration of compound on organic carbon

Concentration of compound in water


81

pollutant removal, a detailed paper has been published on the removal of volatile organiccontaminants in a wastewater plant (Melcer et al., 1994). However, again no specificmention of PAH or similar organics was made.

3.2.5 Organic Degradation in WastewaterAmong the organic pollutants being studied in this report, LAS is somewhat unusual as it isadded to water in detergents. Studies in this subject (Holt et al., 1998 and Prats et al., 1997)report very similar LAS degradation levels of over 90%. Although the removal of LAS inWWTS is quite effective some 16% of the feed LAS is taken out in the sewage sludge (Fieldet al., 1995). In this sorbed form it is more difficult to degrade. Some studies of LAS in riversediments (Tabor et al., 1996) show that this compound is sorbed on to the solids and onlyslowly biodegradable. Thus there would be an amount of non degraded LAS in the solidresidue.

There have been a number of studies on the degradation rate of PCDD, PCDF and PCBs,which have been reported in a review article (Sinkkonen et al., 2000). The experiments wereconducted in laboratory rigs and the data reported as half-life analogous to radioactivedecay. The mean half-life quoted is given in Table 3.09.

Table 3.9: Half-lives of PCDD, PCDF and PCB in water

Substance Half life in water(years)

PCDD 2.6PCDF 5.0PCB 9.3

This study seems to indicate that these organics will not be degraded in a WWTS. Thesehalf-lives are considerably longer than the residence time in a sewage treatment plant orsewer. As the authors point out the experiments were conducted near ideal conditions and,in practice, the half lives are believed to be longer than the figures quoted in the table,especially if the temperature is low.

PAH compounds are believed to be persistent in the environment. There is some work thatpresents evidence that some of these compounds can be degraded in periods of 12-80hours (McNally et al., 1998). Compared with PCDDs this time period is rapid. However,these experiments on biological degradation of PAH were carried out under ideal conditions.There was a constant temperature (20oC), specially adapted bacteria were used andnutrients were added. In a practical case where low temperature and few nutrients arepresent, the actual degradation times would be much longer (in the region of 80-600 hours)so PAH compounds are unlikely to be degraded in a conventional wastewater treatmentplant. Research in Greece by Samara et.al. [1995] and Manoli et al. [1999], shows that thelower-molecular mass PAHs are removed effectively in Thessaloniki's WWTS, whereas thehigher molecular mass PAHs are resistant to the biological treatment. The heavy molecularmass PAHs are partially removed by adsorption, whereas the lower molecular mass PAHsare removed by volatilisation and/or biodegradation.

Work on oestrogenic compounds, analysing 17β-oestradiol equivalent concentrations, foundthat the load of oestrogenic activity in the wastewater was reduced by about 90% in thesewage plant. Less than 3% of the oestrogenic activities was found in the sludge (Korner etal 2000).


82

3.2.6 Removal of OrganicsCoagulants such as aluminium and ferric salts are used in water treatment to removeparticulate matter. However, soluble organics may also be removed by coagulation bymechanisms such as specific adsorption to floc particles and co-precipitation (Semmens andOcanas, 1977). Sridhan and Lee (1972) studied the removal of phenol, citric acid andglycine from lake waters by co-precipitation with iron. Though these results were reasonable,excessive concentrations of coagulant (300-1500 mg.l-1) were required. Other workers madesimilar findings. Semmens and Ocanas (1977) examined the removal of dihyroxybenzoicacid (DHBA) and resorcinol from distilled water by coagulation with ferric sulphate. Resultsindicated that the extent of organic removal increased as coagulant dosage increased.Maximum percentage removals were 35% for DHBA and 8% for resorcinol. Semmens andAyers (1985) examined the effectiveness of alum and ferric sulphate in removing octanoicacid, salicylic acid, phenol and benzoic acid from Mississippi river water and water samplesfree of organic matter. These compounds were generally poorly removed by coagulation andin most cases the extent of removal did not depend strongly on coagulant dosage. Removalsranged between 3-20%. Salicylic acid was most efficiently removed and benzoic acid wasmost poorly removed. Generally, better removal of the organic compounds occurred whennatural organics were not present.

The general consensus of the work done to date indicates that the use of coagulants forremoving organics is feasible. However it is impractical as the excessive addition ofcoagulants is necessary.

Humic substances account for around 50% of the dissolved organic matter in natural water(Vik and Eikebrokk, 1989). They are formed easily from waste material and there is evidencethat they will sorb organic matter by binding with them. Activated carbon is widely used as ameans of removing organic compounds from water. The presence of humic acid reduces therate of organics uptake (Kilduff et al., 1988). The capacity of activated carbon fortrichloroethylene (Summers et al., 1989, Wilmanki and Breeman, 1990), trichlorophenol(Najm et al., 1996) and lindane decreased in the presence of humic substances. Othersorption media such as organoclays (Dentel et al., 1998, Zhoa and Vance, 1998) and anorganic polymer resin (Frimmel et al., 1999) are not so badly affected by the presence ofhumic substances. Ying et al., (1988) studied the effects of iron precipitation on the removalof natural organic compounds like tannic acid and humic acid, and toxic organic compoundslike chlorendic acid (HET), polychlorobiphenyls (PCBs) and organochlorine pesticides.Freshly formed ferric hydroxide flocs were very effective in removing humic acid and tannicacid and it was found that the presence of humic acid enhanced significantly the removals ofPCBs and many of the organochlorine pesticides by ferrous and ferric hydroxideprecipitates. Removals were achieved by a combined mechanism of complexation,adsorption and co-precipitation. This evidence suggests that humic substances are capableof sorbing organic material.

A process was devised in which organic contaminants were removed by adding humic acidand a coagulant such as ferric hydroxide (Rebhun et al., 1998). This showed good recoveryfor the organics tested. The results of this work suggest that humic acid might be added in atertiary cycle. The humic acid could be made by composting grass cuttings, potato peelingand other waste feeds. Such material could be added to the final effluent of a wastewatertreatment plant followed by contact and flocculation.

3.2.7 Conclusions – removal of organics in wastewaterThe practical issue of the removal of organics in wastewater treatment is not welldocumented in the literature. Modelling work reviewed here, has shown that the work hasconcentrated on the removal and degradation of organic matter of biological origin and thatsynthetic organic pollutants have been largely neglected. Clearly modelling work forpollutants should be promoted.


83

This data in turn relies upon analysis of these organic pollutants. Present methods usingGC/MS are extremely complex and not suitable for routine plant use. Lack of easier methodsfor their analysis will hinder the development of simple processes to remove these organicmaterials. It could be argued that identification of a specific pollutant is not crucial for plantdevelopment and that a generic test would be suitable. One of the most important aspects offuture work is the development or identification of simple tests for WWTP analysis. Theproblem is not confined to treatment plants alone but rapid treatment methods could be usedto detect sources of heavy organic chemicals.

One of the results of the difficulty in doing analyses is that there is little data available onpartitioning process. There is a suggestion that around half the organics fed to a wastewatertreatment plant remain in the supernatant stream. This might well be a surprising result giventhe measured property values in the region of 105 (dimensionless) would suggest that therewould be a good binding between organic pollutants and the settled sludge. It is possiblethat there is some competition for sorbtion sites in the organic matter from the moreconcentrated organic compounds.

With more rapid analysis techniques in place, there would be the opportunity to makeprocess changes to reduce the amounts of organics present in the final effluents. It is feltthat advanced oxidative techniques such as the use of ozone would not be applicable in thepresent context as the organics have a very small concentration in solution and have a lowreactivity. One interesting possibility is in situ treatment in sewers such as adding activatedcarbon to contaminated streams. As humic substances are efficient scavengers for organicpollutants, humic acid derived from composting food waste could be added in a tertiary stageto strip organics from the final effluent. It is a matter of policy, to see if such ideas should bepromoted further but initial work could start before the rapid analysis methods had beenagreed.

Transfer and partitioning of organic contaminants to the sludge matrixThe sorption of organic contaminants onto the sludge solids is determined by physico-chemical processes and can be predicted for individual compounds by the octanol-waterpartition coefficient (Kow). During primary sedimentation, hydrophobic contaminants maypartition onto settled primary sludge solids and compounds can be grouped according totheir sorption behaviour based on the Kow value as follows (Rogers, 1996):

Log Kow < 2.5 low sorption potentialLog Kow > 2.5 and < 4.0 medium sorption potentialLog Kow > 4.0 high sorption potential

Volatilisation and thermal degradationMany sludge organics are lipophilic compounds that adsorb to the sludge matrix and thismechanism limits the potential losses in the aqueous phase in the final effluent. A proportionof the volatile organics in raw sludge including: benzene, toluene and the dichlorobenzenesmay be lost by volatilisation during wastewater and sludge treatment at thickening,particularly if the sludge is aerated or agitated, and by dewatering. Volatilisation is used todescribe the passive loss of organic compounds to the atmosphere from the surface of opentanks such as clarifiers. The majority of volatilisation, however, occurs through air stripping inaerated process vessels. As a general guide, compounds with a Henry’s Law constant >10-3

atm (mol -1 m -3) can be removed by volatilisation (Petrasek et al., 1983). The significance ofvolatilisation losses of specific organic compounds during sewage treatment can bepredicted based on Henry’s constant (Hc) and Kow (Rogers, 1996):

Hc > 1 x 10-4 and Hc/Kow > 1 x 10-9 high volatilisation potentialHc < 1 x 10-4 and Hc/Kow < 1 x 10-9 low volatilisation potential


84

However, more recent studies (Melcer et al., 1992) suggest that the stripping of volatilesmay not be as significant as was initially thought and biodegradation during secondarybiological wastewater treatment may be the main mechanism of loss of the potentiallyvolatile compound types (Table 3.10). For example, Melcer et al. (1992) reported thatbiodegradation processes removed ≥90 % of the dichoromethane, 1,1,1-trichoromethane,trichloroethylene, toluene and xylene from a municipal wastewater. Volatilisation was only asignificant mechanism of removal for 1,4-dichlorobenzene (20 %) and tetrachloroethylene(60 %). The fate and behaviour of volatile organic compounds in wastewater treatment planthave been modelled numerically by the TOXCHEM computer-based model that incorporatesfour removal mechanisms including: volatilisation, stripping, biodegradation and sorption onto solids (Melcer et al., 1992).

Table 3.10 Observed and predicted (TOXCHEM) removals of volatile organiccontaminants during wastewater treatment by stripping and biodegradation (Melcer etal., 1992)Compound Air stripping (%) Biotransformation (%)

Observed Predicted Observed Predicted

Dichloromethane 2.6 3.2 92.4 91.9Chloroform 7.4 7.8 73.6 71.91,1,1-Trichloroethane 10.5 6.0 79.7 89.1Trichloroethylene 10.7 3.1 82.7 91.3Tetrachloroethylene 58.7 64.2 15.8 0.01,4-Dichlorobenzene 19.1 17.2 54.7 54.8Toluene 1.2 0.4 98.6 98.3p- and m-Xylene 1.3 0.6 98.1 97.9

High temperature treatment of sludge by disinfection processes at 70 oC for 30 minutes canenhance the loss of volatile compounds. Mono- and two-ringed aromatic compounds(benzene, toluene, xylene, naphthalene, dichlorobenzene etc) may be partially lost underthese conditions (Wild and Jones, 1989). Other more persistent hydrophobic compounds, eglesser chlorinated PCBs, and the three-ringed PAHs, may also be susceptible tovolatilisation. Thermal drying is being introduced as an enhanced treatment process toproduce sanitised biosolids for unrestricted use and for improved handling and bulkreduction. This process is potentially the most effective at removing volatile substances fromsludge because the solids are exposed to high temperatures (400 oC) and the sludge isdried to >90 % ds. Thermal degradation may also be an important mechanism for theremoval of organic contaminants from sewage sludge during heat treatment (Wild andJones, 1989). Volatile organic compounds in sewage sludge are not regarded as a potentialrisk to human health or the environment when sludge is used in agriculture (Wilson et al.,1994).

Destruction by sludge stabilisation processesMesophilic anaerobic digestion is the principal sludge stabilisation process adopted in mostEuropean countries, where approximately 50 % of sludge production is treated by thismethods. Volatile compounds are generally lost to the atmosphere or transferred to thesupernatant during digestion, whereas PAHs and phthalate acid esters are conserved (Bridleand Webber, 1982).Many organic contaminants are biodegraded under anaerobic conditions and this isenhanced by increasing retention time and digestion temperature. Five characteristicbehaviour patterns (Figure 3.3) of decay are observed for organic contaminants in anaerobicdigestion systems based on net gas (total CH4 + CO2) production (Battersby and Wilson,1989):

• Easily degradable (eg ethylene glycol, diethylene glycol, triethylene glycol, sodiumstearate, ethanol);


85

• Degradable after a lag phase (eg phenol, 2-aminophenol, 3- and 4-cresol, catechol,sodium benzoate, 3 and 4-aminobenzoic acid, 3-chlorobenzoic acid, phthalic acid,dimethyl phthalate, di-n-butyl phthalate, pyridine and quinoline);

• No degradation or gas production (3- and 4-aminophenol, 2-chlorophenol, 2-cresol,2-nitrophenol, 2- and 4-chlorobenzoic acid, bis (2-ethylhexyl)phthalate, hexyleneglycol, neopentyl glycol, n-undecane, n-hexadecane, 2,4-D, dieldrin, cis- and trans-permethrin, tetrahydrofuran, furan, pyrrole, N-methylpyrrole, thiophene, benzene,pyrimidine, 1-naphthoic acid);

• Inhibitory in the initial phase of incubation (eg 3- and 4-chlorophenol, 2,4- and 2,6-dichlorophenol, 2,4,6-trichlorophenol, 3- and 4- nitrophenol, 2-phenylphenol, 2-, 3-and 4-nitrobenzoic acid, CTAB, MCPA, MCPP, lindane, naphthalene,anthraquinone);

• Inhibitory throughout incubation (eg 3,5-dichlorophenol, pentachlorophenol, 2,4- and2,5-dinitrophenol, 4-nonylphenol, sodium dodecylbenzene sulfonate, sodium 4-octylbenzene sulphonate, 2,4,5-T, butyltin trichloride, dibutyltin dichloride, tributyltinchloride).

Degradation is generally aided by carboxyl and hydroxyl groups, whereas chloro or nitrogroups tend to inhibit anaerobic biodegradation and gas production.

Figure 3.3 Typical patterns of net gas production (CH4 + CO2) from organic chemicalsincubated anaerobically with diluted primary digested sewage sludge.1, Easily degradable; 2, Degradable after a lag period; 3, little effect on gas production; 4,inhibitory in initial phase of incubation; 5, inhibitory throughout incubation(Battersby and Wilson, 1989).

Biodegradation during anaerobic digestion may virtually eliminate certain organiccontaminants from sewage sludge, but in general the destruction achieved is typically in therange of 15 – 35 % (WRc, 1994). Aromatic surfactants including linear alkyl benzenesulphonates (LAS) and 4-nonylphenol polyethoxylates (NPnEO) occur in sludge in largeconcentrations. These compounds are not fully degraded during sewage treatment and thereis significant accumulation in digested sludge. For example, mass balance calculationssuggest that approximately 80 % of LAS is biodegraded during the activated sludge processand 15-20 % is transferred to the raw sludge (Brunner et al., 1988). Approximately 20 % ofthe LAS in raw sludge may be destroyed by mesophilic anaerobic digestion sludge. Thecompounds, nonylphenol monoethoxylate (NP1EO) and nonylphenol diethoxylate (NP2EO)are formed during sewage treatment from the microbial degradation of NPnEO. These

Net

gas

pro

duct

ion

(% th

eore

tica

l)100

-100 5

4

}3

21

Time

Inhi

biti

on


86

metabolites are relatively lipophilic and accumulate in the sludge and are also dischargedwith the treated sewage effluent. One of the most important consequences of anaerobicdigestion, however, is the production of nonylphenol (NP), which accumulates in digestedsludge. Approximately 50 % of the NPnEO in raw sewage is transformed to NP in digestedsewage sludge. The loadings of LAS and NP to soil in sewage sludge used on farmland aresignificantly larger than for most of the other organic contaminants present in sludge andthere is concern about their potential environmental effects. This is particularly the case forNP in sludge due to its potential oestrogenic activity (UKWIR, 1997). However, in the aerobicsoil environment, these compounds provide substrates for microbial activity and are rapidlydegraded so there is minimal potential risk to the environment or transfer to the humanfoodchain. For example, LAS has a short half-life in soil in the range 7 – 22 days intemperate field conditions (Holt et al., 1989) and the half-life for NP is <10 days (UKWIR,1997). Current studies at Imperial College, funded by the Food Standards Agency in the UK,are investigating the potential for plant uptake of NP into staple food crops from sludge-treated soil.

Another class of organic chemicals, the phthalate acid esters, are also an abundant group ofcompounds present in sewage because of their extensive use as plasticising agents. Thephthalates are also suspected as being potential environmental oestrogens (UKWIR, 1997).Shelton et al. (1984) reported the complete degradation of the lower molecular weightphthalate esters, and of butyl benzyl phthalate, within 7 days in laboratory scale anaerobicdigesters operated at 35 oC. Therefore, these phthalate compounds should generally beremoved by most municipal anaerobic digesters at the normal mean retention timesoperated in practice (>12 days). The extent and rate of biodegradation during anaerobicdigestion is apparently related to the size of the alkyl side chain and compounds with largerC-8 group are much more resistant to microbial attack. Therefore, di-n-octyl and di-(2-ethylhexyl)phthalate (DEHP) are considerably more persistent to anaerobic microbialmineralisation and are generally not removed by conventional anaerobic stabilisationprocesses. However, phthalate esters are rapidly destroyed under aerobic conditions,usually achieving >90% removal in 24 h in activated sludge wastewater treatment systems.In soil, the reported half-life is <50 d (UKWIR, 1997).

Composting is a thermophilic aerobic stabilisation process and usually involves blendingdewatered sludge at approximately 25 % ds with a bulking agent, such as straw or woodchips, to increase porosity of the sludge to facilitate microbial activitiy. The biodegradation ofrelatively persistent organic compounds such has been reported for composted sludge (Wildand Jones, 1989). For example, PAHs may be partially degraded by composting sludge andaverage removals of 13 % and 50 % have been measured for benzo(a)pyrene andanthracene, respectively, although phenanthrene persisted unchanged in laboratorycomposting trials (Martens, 1982; Racke and Frink, 1989).

Thermophilic aerobic digestion processes and sludge storage for three months can achievesimilar overall removal rates for organic contaminants as those obtained with mesophilicanaerobic digestion (WRc, 1994). Thermal hydrolysis conditioning of sludge prior toconventional anaerobic stabilisation may have a significant influence on the removal oforganic contaminants from sludge, but this is a comparatively new enhanced treatmentprocess and effects on the destruction of organic contaminants have yet to be investigated.


87

3.3 Quantitative assessment of organic pollutants in untreated UWW, treated UWWand treated SS

For the main list of organic pollutants considered in this report there is little available data ofthe concentrations in the influent to the wastewater treatment plant. Paxéus and Schröder[1996] looked at over 50 organic compounds, in the influents and effluents of theGothenburg wastewater treatment plant. The high cost of testing explains the lack of data ondioxins in urban wastewater.

Most of these compounds were reduced to below the limit of detection during the treatmentprocess. Some of the organic compounds, such as caffeine were reduced from a level of37µg.l-1 to 4µg.l-1. Some of the phosphorus containing compounds were not reduced duringthe treatment process (although the influents and effluents were quite low at 1µg.l-1). Theoverall toxicity of the influent and the effluent were also measured and found to havedecreased by approximately 50% during the treatment process.

Figure 3.4 Dioxin content of archived samples of sewage sludge form Mogden WWTS,UKIt can be seen (Figure 3.4) that there has been a significant reduction in the concentration ofdioxins since the 1950s and 1960s in sludge over recent years.

The concentrations of other organic contaminants in sludge, including, PCBs and PAHs,have also declined significantly in sludge in the UK. This is due to the control of primarysources of these substances. In 1984, McIntyre and Lester (1984) measured median and99th percentile concentrations for PCBs in sludge (444 samples from UK sewage treatmentworks) of 0.14 and 2.5 mg kg-1, respectively. Ten years later, Alcock and Jones (1993)reported the total PCB content of 12 UK sludges from rural, urban and industrial sewagetreatment works ranged between 0.106 to 0.712 mg kg-1, with a mean value of 0.292 mg kg-

1. These results indicate that overall PCB concentrations in UK sludges have declinedmarkedly in response to the ban on industrial production, use and discharge of thesesubstances. Similar trends are apparent in Germany (Table 3.11). In effect, this means thatthe chemical composition of sewage sludge is already subject to stringent, albeit indirect,controls that have been effective in minimising industrial sources and inputs of persistentorganic contaminants.

Year

Dio

xin

co

nce

ntr

atio

n (

ng

TE

Qkg

-1 d

s)

0

50

100

150

200

250

300

350

400

450

1944 1949 1953 1956 1958 1960 1998

German limit =100 ng TEQ kg-1 ds


88

Table 3.11 Mean concentrations of organic contaminants in German sewage sludge in1988/89 relative to data collected until 1996 (Leschber, 1997)

Contaminant 1988/89 1991/96Adsorbable organo-halogens mg kg-1 ds 250-350 140-280Polychlorinated biphenyls(1) mg kg-1 ds <0.1 0.01-0.04

Polycyclic aromatic hydrocarbons(1) mg kg-1

ds0.25-0.75 0.1-0.6

Di(2-ethylhexyl)phthalate mg kg-1 ds 50-130 20-60Nonylphenol mg kg-1 ds 60-120 -

Dioxins and furans (ng TEQ kg-1 ds) <50 15-45(1)Single congeners

Table 3.12 Survey of organic pollutants in UWW and WWTS (µg.l-1)

WWTSCompound Country

Influent(µg.l-1)

Effluent(µg.l-1)

Reference

Austria:Total PAHs - EPA15 147-625 20-70 Gans et al.,1999

Germany:Total PAHs

Benzo(a)pyreneBenzo(k)fluoranthene

0.790.080.05

Hagenmaier et al,1986

Greece:Benzo(a)pyreneFluoroanthene

Indeno (1,2,3-cd) pyrene

0.0220.240.015

0.0050.0290.005

Manoli et al, 1999

France 0.05-0.44 0.02-0.09 ADEME, 1995Germany 33 Koch et al, 1989 &

Balzer et al 1991

PAHs

UK 51.8 (5.6 to349)

30.8 (2.4-147)

Morris et al, 1994

Austria 4.4 0.3 Hohenblum et al.,2000

DEHP

Germany 122 (7-232) 15 (5.6-184) Faltin, 1985Anionic

SurfactantsItaly 290-4800 - Braguglia et al,

2000Detergents France 1-26 0.1-2.7 ADEME, 1995

Austria 400-3500 11-55 Scharf et al., 1995Germany 5400 67 Feijtel et al 1995Greece 129 (35-

325)Kilikidis et al. 1994

Italy 4600 43 Feijtel et al 1995Netherlands 4000 9 Feijtel et al 1995

Spain 9600 140 Feijtel et al 1995

LAS

UK 15100 10 Feijtel et al 1995Austria:

Nonylphenol-monoethoxylate

Nonylphenol-diethoxylate

2,096,000

13,093,000

363,000

639,000

Hohenblum et al.,2000

Italy:NP

NPEONPEC

427145

Di Corcia et al.1994

Sweden 0.5-6.0 Paxéus 1996a

NPE

Germany 0.02 0.002 Koppe et al, 1993


89

Other organicpollutants:

ChlorophenolsChlorinated

organicsPesticides

VOCs

Iodinated X-Raycontrast

substances:iopamidoldiatrizoate

iothalamic acidiomeprol

iopromide

France

Germany

0.1-0.43001.1510

4.33.30.180.171.67.5

<0.1-0.5 ADEME, 1995

Ternes et al, 2000

Total Phenols Italy 2.5-300 Italian RegionalEnvironmental

Protection AgencyDioxins Italy: 0.024-16.9 Italian Regional

EnvironmentalProtection Agency

PAHs: wastewater from 8 different sewage treatment influents was investigated in 1996 bythe UBA [Gans, et.al., 1999]. Similar PAHs content were determined, except for the influentfrom a chemical plant, which had an approximately 1,000 times larger concentration. PAHsespecially, with a low molecular weight were found in high concentrations. Apart from thehigher PAH content of the wastewater from the chemical plant, no significant differencescould be detected between municipal and industrial influents. The PAHs content of theeffluent was about 10 times smaller than the influents [Gans et.al.1999].

The Danish regulation of the application of waste products [Ministry of the Environment andEnergy 1996] sets certain cut off values for the maximum concentrations of organiccontaminants in sludge to be distributed on agricultural land as shown in Table 3.13.Concentrations of PAHs in Danish sewage sludge are also shown in Table 3.14 The PAHconcentration of the nine selected compounds were all found to have mean concentrationsabove the concentrations permissible for use on agricultural land in Denmark.

Table 3.15 Danish standards for maximum concentrations of organic contaminants insewage sludge (Danish Ministry of the Environment and Energy, 1996)

Danish Standards 1997 - cut off valuesmg.kg-1 DS

2000 - cut off valuesmg.kg-1 DS

LAS 2,600 1,300nonylphenol (including nonylphenol

ethoxylates)50 10

PAHs* 6 3DEHP 100 50

*(total concentration of nine selected PAHs) Acenaphthylene, Fluorene, Phenanthrene, Fluoranthene,Pyrene, Benzo(b,j,k)fluoranthene, Benzo(a)pyrene, Benzo(g,h,i)perylene and Indeno(1,2,3,-cd)pyrene

The values in bold are difficult to achieve, as they are far below current sludgeconcentrations. If 50% of pyrene and phenathrene is from food sources and gives sludgeconcentrations of > 300mg.kg-1 ds, then this emphasises how difficult these standards are toachieve.

The mean concentrations of LAS, NPE and DEHP were found to be within the Danish limitsfor use on agricultural land but the range of concentrations in all cases went over the cut offlimits; therefore many of the sludges would not be allowed to be used on agricultural land.


90

The concentrations of some of the organic contaminants in the sludge were found to dependstrongly on the wastewater treatment process [Danish EPA]. The concentrations of LAS, NPand NPE were significantly lower (P<0.005) following activated sludge treatment than inmixed activated and digested sludge treatment, presumably due to extended aeration.

It can be seen that government and other institutions are trying to introduce limits for certainpollutants and that concern for wastewater pollution reduction is increasing. Nevertheless, itis noted that important discrepancies exist in analysis techniques, even within a country,hence slowing the determination of limits, particularly for PAHs and PCBs. Due to theexpected increase in sludge production and the reinforcing of the legislation in relation to theconcentration limits for potentially toxic elements and organic pollutants, it seems necessarythroughout Europe to harmonise analysis techniques and the pollutants targeted in thecontrol of wastewater and sludge quality. Discharge standards to UWW collecting systemsfor industries and possibly reformulation of certain domestic products should be determinedin order to reduce pollution entry into the systems.

Table 3.14a) Survey of organic pollutants in sewage sludge: mg kg-1 DS (a)PAHsPAHs Country Mean Median Min. Max. Year/s of

SurveyB[A]P

I[1,2,3-cd]pAustria 0.30

0.270.220.21

0.090.07

0.670.58

1994/95(24)

Σ PAHs*B[a]p

Fl.theneI[1,2,3-cd]p

B[a]p

Germany(municipal)

6.40.351.20.30.5 0.4

2.60.10.60.10.1

15.31.12.70.83.4

1996 (10)1996 (10)1996 (10)

(10)1995 (14)

B[a]pFl.thene

I[1,2,3-cd]p

Denmark 0.150.30.67

0.070.10.23

<0.01<0.01<0.01

1.43.30.63

(28)

Fl.thene Spain 3.4 1.1 6.0 (19)B[a]p

Fl.theneFrance 0.04

0.151131

1994 (6)1994 (6)

B[a]pFl.thene

I[1,2,3-cd]p

Greece 0.241.10.11

0.241.30.12

0.10.380.05

0.361.40.15

(15)

Σ PAHsFl.thene

Sweden 1.2-2.2 0.7-1.40.01 0.7

1995/98(26)(29)

Σ PAHs**B[a]p Fl.thene

UK 27.8

2.32.62.5

6.00.11.1

83.87.54

1994 (27)1989 (33)1991 (29)

Σ PAHs*** Switzerland(municipal)

0.50 0.35 0.04 1.83 (29)

B[a]pI[1,2,3-cd]p

Fl.thene

Italy <0.05<0.05<0.05

2000 (34)

Σ PAHs Poland 72.3 74.4 32.7 114.3 1999 (2)

EUB[a]p

Fl.theneUSA 13.8

9.954.7 154

1541988

(30/31)

Limits Agricultural Soils Sewage SludgeΣ PAHs**** EU 6 (proposed) (9)

Pyrene WHO 480 (5)B[a]p USEPA 21.4 (25)

B[a]p: Benzo[a]pyrene; Fl.thene: Fluoranthene I[1,2,3-cd]p: indeno(1,2,3-c,d)pyrene * sum of 16 USEPA priority list PAHs (see Appendix B) ** sum of naphthalene, acenaphthylene, acenaphthene, fluorene, phenanthrene, anthracene, fluoranthracene,pyrene, chrysene, benzo(a)anthracene *** sum of benzo(b+k)fluoranthene, benzo(ghi)perylene, benzo(a)pyrene, fluoranthene, indeno(1,2,3-c,d)pyrene


91

**** sum of acenapthene, phenapthene, fluorine, fluoranthene, pyrene, benzo(b+j+k)fluoranthene,benzo(a)pyrene, benzo(ghi)perylene, indeno(1,2,3-c,d)pyrene

Table 3.14b) Survey of organic pollutants in sewage sludge: mg kg-1 DS (b)PCBs

PCBs Country Mean Median Min. Max. Year/s ofSurvey

PCB (28,52,101,138, 153,180)

Austria 0.07 0.05 0.02 0.27 1994/95(24)

Germany 0.01-0.040.5 0.05 15

1991-96(13)

1985-87 (7)Denmark 0.05 0.03 <0.03 0.2 (28)

Spain 0.05 0.93 (20)PCB

(101,118,138)France 0.03 0.4 1994 (6)

Sweden 0.1 0.1 1995/98(26)

UK 0.34 0.01 21.5 (18)

EUUSA 1.46 1.48 14.8 1988

(30/31)

Limits Agricultural Soils Sewage SludgeEU 0.8 (proposed) (9)

WHO 30 (5)USEPA 6.6 (25)

Table 3.14c) Survey of organic pollutants in sewage sludge: mg kg-1 DS (c)DEHPDEHP Country Mean Median Min. Max. Year/s of

Survey

Austria 23.4 34.4 (11)Bis-(2ethylhexyl)-

phthalateGermany 20-60

<2.4 3201991-96

(13)(7)

Denmark 38 25 3.9 170 (28)Bis-(2ethylhexyl)-

phthalateSweden 6.7 28 (29)

EUBis-(2ethylhexyl)-

phthalateCanada 68.0 11 959 (3)

USA 110 17 891 1988(30/31)

Limits Agricultural Soils Sewage SludgeEU 100 (proposed) (9)


92

Table 3.14e) Survey of organic pollutants in sewage sludge: mg kg-1 DS (e)LAS

LAS Country Mean Median Min. Max. Year/s ofSurvey

Austria 8107 7579 2199 17955 1994/95(24)Germany 5000 50 16000 1985-87(7)Denmark 2700 530 11 16100 (28)

AerobicAnaerobic

Spain 10012100

50017800

(1)(21)

Finland 9700 (17)Italy 11500 14000 (4)UK 8700 10400 60 18800 (12)

EUAerobic Anaerobic USA 152

4680 1680 7000(16)(22)

Limits AgriculturalSoils

Sewage Sludge

EU 2600 (proposed) (9)

Table 3.14f) Survey of organic pollutants in sewage sludge: mg kg-1 DS (f)NPE

NPE Country Mean Median Min. Max. Year/s ofSurvey

Austria 24 12 69 1994/95(24)

NP1EONP2EO

Germany 60-120512010

3.85<3

96.38080

1988/89(13)1996 (10)(7)(7)

Denmark 15 8 0.3 67 (28)Sweden

13-2740010-26

26 1100 1990 (32)1995/98(26)

UK 326-638 256 824 (27)EUUSA

Limits Agricultural Soils Sewage SludgeEU 50 (proposed) (9)

Table 3.14g) Survey of organic pollutants in sewage sludge: mg kg-1 DS (g)PCDD/FDIOXINS &

FURANS (NG

TEQ/KG DS)

Country Mean Median Min. Max. Year/s ofSurvey

Germany 15-45 1991-96(13)

Spain 55620

42 729

1608300

1994-98 (8)1979-87 (8)

Sweden 24 23 25 (23)UK 40.2 7.6 192 (29)

EU

DioxinsUSA 82.7

90.437.4 0.49 2321

18201988

(30/31)

Limits Agricultural Soils Sewage Sludge

EU 100 (proposed) (9)


93

References1. Berna JL et al, 19892. Bodzek, B. et al,

1999.3. Bridle, T.R. et al 19834. Cavelli L, et al 19935. Chang, A.G. et al

1995.6. Conseil supérieur

d'hygiène publique deFrance, 1998

7. Drescher-Kaden et al1992,

8. Eljarrat. E, et al 1999.9. European Union, 200010. Hessische

Landesanstalt furUmwelt (1991-96).

11. Hohenblum, P, et al2000.

12. Holt MS et al 1992.13. Leschber, R. 199714. Litz. N, et al, 1998.15. Manoli, E. et al 1999. 16. McAvoy DC, et al

1994.17. McEvoy & Giger 198618. McIntyre. A,E, et al

198419. Moreda, JM, et al

(1998a)20. Moreda, JM, et al

(1998b)21. Prats D, et al 1993.

22. Rapaport RA, et al1990.

23. Rappe et al 198924. Scharf, S, et al. 199725. Smith, S.R. 200026. Statistika

meddelanden 199827. Sweetman 199428. Tørsløv J, et al 1997.29. UKWIR 199530. USEPA 199231. USEPA 199932. Wahlberg,.C, et al

199033. Wild. S,R, et al 1989.34. Braguglia et al 2000

Table 3.15 shows the occurrence of certain organic pollutants in sewage sludge in Germany.

Table 3.15 Occurrence of certain organic substances in sewage sludge, Germany[Priority list USEPA and 6/464/EEC of EG].

Compound Occurrencein sludge

Benzo(a)anthracene +++Benzo(a)pyrene +++

Benzo(k)fluoranthene +++Dibenzo(a,h)anthracene +++Indeno(1,2,3-cd)pyrene +++

PCB-1242 ++PCB-1254 +++PCB-1221 ++PCB-1232 ++PCB-1248 ++PCB-1260 +++PCB-1016 +

2,3,7,8-Tetrachlordibenzo-p-dioxin ++Frequency of occurrence: +++ frequent (90-100%), ++ less frequent, + low frequency

chapter 3: organic pollutants: sources, pathways, and fate through

Documents