bio remediation a novel approach

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Bioremediation: anovel approach to

food wastemanagement

P.K. Thassitou andI.S. Arvanitoyannis*

Department of Agriculture Crop and AnimalProduction, School of Technological Sciences,

University of Thessaly, Nea Ionia Magnesias,Fytoko Street, 38446 Volos, Greece

(tel.:+30-421-93104; fax: +30-421-93144;e-mail: [email protected])

Bioremediation is a general concept that includes all those

processes and actions that take place in order to biotrans-

form an environment, already altered by contaminants, to

its original status. Although the processes that can be used

in order to achieve the desirable results vary, they still have

the same principles; the use of microorganisms or their

enzymes, that are either indigenous and are stimulated by

the addition of nutrients or optimization of conditions, or

are seeded into the soil. There are several advantages of the

implementation of such methods but mainly they have to

do with the lack of interference with the ecology of the

ecosystem. This article presents general bioremediationprinciples and techniques along with representative exam-

ples of their use both in the laboratory and industry and the

ways that they work and give results in the five main areas

of the food industry where bioremediation is applicable.

Although the application of bioremediation to the food

industry is not new, developments in microbiology and

genetic engineering have given a valuable instrument to

scientists to deal with contaminants in the environment.

Pesticides, herbicides, insecticides, cleaning chemicals and

chemicals used in the food chain are among the new con-

taminants which have entered the biogeochemical cycles.

Bioremediating methods transform the contaminants into

substances that can be absorbed and used by the auto-

trophic organisms with no toxic effect on them. # 2002

Elsevier Science Ltd. All rights reserved.

A few decades ago, man’s greatest challenge residedin speeding up the industrialization process. Today man

attempts to find ways to deal with the growing indus-

trialization and the associated problems. Because of this

rapid development, problems arose due to landfills and

forests and water resources. Land degradation has been

identified as a crucial and increasing environmental

problem both in Europe and the rest of the world. A

third of Europe’s 300 million hectares of drylands suffer

from desertification and the ensuing reduction in biolo-

gical and economic productivity (UNEP, 1992).

Although the extent of polluted area affected has not

been accurately determined, many contaminants are

considered responsible for this pollution. Pesticides andfertilizers are major sources of pollution followed by

industrial processes, waste and wastewater sludge dis-

posal, and accidental release (EEA, 1995). Acidification

is frequently a transboundary problem because acid

deposition is higher than critical in roughly 60% of

Europe, with central parts of Europe receiving 20 times

more acidity than the ecosystem’s critical loads (Stan-

ners & Bourdeau, 1995).

Forests cover 27% of the region west of the Urals and

35% of the FSU (former Soviet Union)—a total of 900

million ha which makes up to almost 15% of the

world’s forest biomass (FAO, 1995). Since the early1960s, Europe’s total forest area has increased by more

than 10%, mainly in the south and west (Stanners &

Bourdeau, 1995). While there is an overall increase in

growing stock and forest productivity in the region

(FAO), large-scale deforestation is currently under way

in the boreal forests of the Russian Federation. In

Europe, on the other hand, forest degradation con-

stitutes a more serious problem than deforestation.

Although crown defoliation and discoloration indicate a

general worsening in forest conditions in many parts of

Europe, no reliable correlation has been established yet

between tree growth and defoliation. The forests most

severely affected by the defoliation are located in central,

0924-2244/01/$ - see front matter Copyright# 2002 Elsevier Science Ltd. All rights reserved.P I I : S 0 9 2 4 - 2 2 4 4 ( 0 1 ) 0 0 0 8 1 - 4

Trends in Food Science & Technology 12 (2001) 185–196

* Corresponding author.

Review



north, and southeast Europe. In a 1993 transnational

survey, 22.6% of trees were found to be defoliated by

more than 25% (EC/UN-ECE, 1994). Recent research

has disclosed a great number of causative factors,

including adverse weather conditions, air pollution,

pests and pathogens, and forest fires rather than justacid rain, as previously suspected (EC/UN-ECE, 1994).

When it comes to water the situation becomes more

serious since both the quantity and the quality of fresh

water presents major problems over much of the region,

and the issue is of growing importance (UNEP, 1996).

Although there is no overall water shortage in Europe,

water availability varies considerably (Table 1) due to

water pollution. Lake Baikal, containing 20% of the

earth’s fresh water, has been affected by pollutants,

including oil, even in its most remote and open parts. In

fact, only a minor amount (15%) of effluents into the

lake are being treated satisfactorily (Ministry of Envir-onmental Protection and Natural Resources of the

Russian Federation, 1994). The need for improved and

technologically updated water treatment facilities is cri-

tical because those currently available function poorly

and are characterized by inadequate capacity to cope

with the required level of treatment. Ground water pol-

lution is expected to become increasingly widespread

and acute in coming years, particularly because of

uncontrolled waste deposits, leakage from petrochem-

ical tanks, and continuing percolation of untreated

sewage, pesticides, and other pollutants into aquifers.

As the already high proportion of Europe’s drinking

water from the source is expected to increase, groundwater quality constitutes a priority issue (Stanners &

Bourdeau). Far from drinking water, pollution affects

the coastal ecosystem too. It is estimated that in the

region west of the Urals, 86% of the coastal ecosystems

are at high or moderate risk because of irrational and

uncontrolled development. The most significant con-

taminants in the coastal zone are synthetic organic

compounds, microbial organisms, oil, nutrients, and

litter and, to a lesser extent, heavy metals and radio-nuclides.

Solid wasteSolid waste is probably of more importance not so

much because of hazard but more because of its volume.

According to some researchers the amount of solid

waste produced by European countries is around 5 bil-

lion tonnes per year. However, statistics for waste gen-

eration have proved to be notoriously unreliable over

the years. National governments have openly stated that

many figures quoted for waste generation are based on

estimates. In the United States, waste materials releaseddirectly from industry and agriculture are responsible

for substantial contamination of the soil and water.

There are 14,000 industrial sites in the US producing

about 265 tonnes of hazardous waste annually (Levin &

Gealt, 1993).

Once an area is polluted, the next step is to suggest

possible corrective actions. Over the years, many meth-

ods have been tested, used, approved or rejected. The

most common, ineffective and inexpensive way to deal

with polluted areas is to ignore deliberately their exis-

tence. When things get more severe one can either resort

to conventional methods, such as prevention and

reduction, reuse, employment of degradable materials,recycling, incineration, pyrolysis and landfill, or to

modern innovative methods which include composting,

biodegradability and bioremediation.

Table 1. Annual internal renewable water resources and water withdrawals in selected European and CIS Countries

Annual internal renewablewater resourcesa

Annual withdrawals Sectoral withdrawal(%)b

Europe and CIS Total(km3)

1995 Per capita(m3)

Year ofdata

Percentage ofwater resourcesa

Per capita(m3)

Domestic Industry Agriculture

Albania 21.3 6190 1970 1 94 6 18 76Austria 90.3 11,333 1991c 3 304 33 58 9Belgium 12.5 1236 1980 72 917 11 85 4Estonia 17.6 11,490 1989 21 2097 5 92 3Iceland 168.0 624,535 1991c trace 636 31 63 6Italy 167.0 2920 1990 34 986 14 27 59Lithuania 24.2 6541 1989 19 1190 7 90 3Romania 208.0 9,109 1994 13 1134 8 33 59Russian Federation 4498.0 30,599 1991 3 790 17 60 23Spain 11.3 2809 1991c 28 781 12 26 62Turkmenistan 72.0 17,573 1989 33 6390 1 8 91United Kingdom 71.0 1219 1991c 17 205 20 77 3

a Annual internal renewable water resources usually include river flows from other countries.b Sectoral percentages date from the year of the annual withdrawal data.

c Data are from the early 1990s (Ministry of Environmental Protection and Natural Resources of the Russian Federation, 1994; UNEP, 1996)

186 P.K. Thassitou, I.S. Arvanitoyannis / Trends in Food Science & Technology 12 (2001) 185–196



Introduction to bioremediationBioremediation is the naturally occurring process by

which microorganisms either immobilize or transform

environmental contaminants to innocuous end pro-

ducts. Bioremediation is an important soil and ground-

water remediation strategy because it:

. harnesses naturally occurring biogeological pro-

cesses;

. destroys or immobilizes contaminants rather than

transfers them from one environmental medium to

another; and

. conserves financial resources due to shortened

cleanup times and/or lower capital expenditures to

many other remediation technologies (GZA

GeoEnvironmental, 1998).

Biotreatment is well accepted by industry as it goesalong with the current popularity of maintaining nat-

ure’s harmony. Bioremediation has become a widely

accepted option for the clean up of contaminated soils

and aquifers although it does not have a fully credible

reputation within the regulatory community (NRC,

1993).

There are numerous examples of employing bior-

emediation against various pollutants. Nowadays, there

are four main biological techniques for treating soil and

groundwater: (a) stimulation of the activity of indigen-

ous microorganisms by the addition of nutrients, reg-

ulation of redox conditions, optimizing pH conditions,

etc; (b) inoculation of the site by microorganisms withspecific biotransforming abilities; (c) application of

immobilized enzymes; and (d) use of plants (phytor-

emediation) to remove and/or transform pollutants

(Bollag & Bolllag, 1995). In the specific methods used

for bioremediating contaminated soil and water, land-

farming, composting, intrinsic bioremediation and

slurry bioreactor are included (Table 2).

Landfarming was most probably introduced into the

scientific literature by an article describing disposal by

biodegradation of oily sludges in soil (Dibble & Bartha,

1979). From an engineering perspective, landfarming is

a ‘‘managed treatment and ultimate disposal processthat involves the controlled application of a waste to a

soil or soil-vegetation system’’ (Loehr, Asce, & Over-

cash, 1985). Landfarming relies on the principles

applied in agriculture and aims at controlling the bio-

cycling of natural compounds. The biodegradation

conditions by the natural indigenous microbial popula-

tions of soil are optimized by the dilution of con-

taminated soil with clean soil, tilling of the soil to reduce

initial toxicity, as well as by controlling physical para-

meters, such as aeration, pH, soil moisture content, and

temperature. Aeration is often accomplished by tilling

the soil, or, in more automated systems, by forced

aeration. When forced aeration is employed, the plots

should be covered and the exiting air cleaned through

filters. To achieve temperature control, hot air, or the

‘greenhouse effect’, can be employed in a closed system.

Composting is a biological aerobic decomposition of

organic materials in which conditions are strictly con-

trolled in order to help the thermophilic microorgan-isms to transform organic materials into a stable, soil-

like product (Miller, 1993; Rynk, 1992). A composting-

like process occurs in nature when materials are

decomposed by microorganisms present in the soil.

However, the decomposition rates are so slow that some

materials hardly show any decomposition signs. In

order to increase these rates and use composting for

industrial purposes, it is necessary to optimize microbial

growth. The composting process is initiated by meso-

philic bacteria, which are biologically active at tem-

peratures between 30 and 45C. Degradation of the

organic matter results in heat production through exo-thermic reactions. Therefore, the temperature increases

to 50–60C thus facilitating the growth of thermophilic

bacteria. The thermophilic bacteria may further increase

the temperature with their activity and, if the conditions

are not carefully controlled, the temperature may exceed

70C, thus leading to lower activity. In order to avoid

this and achieve maximum efficiency, conditions need to

be optimized. This means optimizing oxygen con-

centration, pH, moisture content, carbon to nitrogen

(C:N) ratio and particle size (Miller, 1993; Rynk, 1992).

Since composting is an obligatory aerobic process,

employed methods must allow for the maintenance of

adequate oxygen levels, as previously mentioned.Within that frame, bulking agents such as wood chips

and vermiculite have been successfully used to increase

the void space in the compost (Baker, 1994). Compost is

the product occurring from the decomposition of the

organic matter and is usually humus-like of dark color

with a crumbly texture and earthy odor and bears very

little resemblance to the product it comes from. Good

compost is stable, which means that it cannot further

decompose, and contains no microorganisms harmful to

human health. During composting, the volume of

material undergoes a substantial decrease in the order of

25–40% according to some researchers (Willow, 1992),while according to others it may even exceed 50%

(O’Leary, Walsh, & Razvi, 1989–1990). Composts con-

stitute a valuable soil amendment and may be used as a

fertilizer substitute to supplement plant nutrient needs

because of their high organic matter content.

Composting can be used as a method to stabilize and

decrease sewage sludges, industrial wastes, yard wastes,

and municipal wastes. Recently, composting has been

applied to treatment of hazardous waste such as explo-

sives (Williams, Ziegenfuss, & Sisk, 1992) and petro-

leum wastes (Fyock, Sordrum, Fogel, & Findlay, 1991;

McMillen, Kerr, Gray, & Findlay, 1992). There are

several composting types with the same general stages

P.K. Thassitou, I.S. Arvanitoyannis / Trends in Food Science & Technology 12 (2001) 185–196 187



Table 2. Bioremediation methods

Technology Principles Advantages Disadvantages Applications

Land farming Solid- phase treatmentsystem for contaminatedsoils; may be done in-situor in a constructed soiltreatment cell.

Simple procedure. Inexpensive.Currently accepted method.

Slow degradation rates.Residue contaminationoften removed. Highexposure risks. Mayrequire long incubationperiods.

Surface contaminationAerobic process. Lowto mediumcontamination levels.

Composting An anaerobic microbialdriven process thatconverts solid organicwastes into stable,sanitary, humus-like

material.

More rapid reaction rates.Inexpensive. Self-heating.

Need bulking agents.Requires aeration.Nitrogen addition oftennecessary. High exposurerisks. Residual

contamination. Incubationperiods are months toyears.

Surface contaminationAerobic process.Agricultural and humawastes. Sewage sludgeindustrial wastes, yard

wastes, municipal solidwaste.

Intrinsicbioremediation

Relies on the naturalassimilative capacityof the ground toprovide siteremediation andcontrol contaminantmigration.

Relatively inexpensive Lowexposure risks. Excavationnot required.

Low degradation rates.Less control overenvironmental parameters.Needs good hydrogeologicalsite characterization.Incubation periods aremonths to years.

Deep contamination.Aerobic or nitrate reduconditions. Low to mecontamination levels. Oand gasoline. Chlorinaaromatics. Chlorinatedhydrocarbons.

Slurry bioreactor Soil and water agitatedtogether in reactor.

Good control over parameters.Good microbe/compoundcontact. Enhance desorptionof compound from soil. Fastdegradation rates. Incubation

periods are days to weeks.

High capital outlay. Limitedby reactor size. Highexposure risks.

Surface contaminationRecalcitrant compounSoil that binds compotightly. Aerobic andanaerobic processes.



but differ in capital and operating costs and in the ways

that they use to achieve the proper conditions for bac-

terial growth and in time required for completing their

task. The methods employed may be classified into three

general categories:

1. windrow

2. aerated static pile

3. in-vessel

The characteristics of each method are given synopti-

cally in Table 3.

One of the most exciting areas of bioremediation is in-

situ treatment of soils. In-situ bioremediation is a nat-

ural process occurring ever since the first microbes and

excess organic matter were both present in the soil

(Litchfield, 1993). This method exploits natural ways of

recycling nutrients through the cycles of nitrogen andcarbon. These cycles nowadays are utilized by man to

enhance the degradation and recycling of wastes and the

same cycles are employed by in-situ bioremediation to

clean contaminated soils (Nelson, Hicks, & Andrews,

1996).

The main advantage of in-situ treatment is that no

excavation is needed and no special equipment is required.

This automatically means lower cost and disturbance of

the natural environment. Furthermore, since no exca-

vation is required the method is ideal for treating rocky

or underground water areas. The in-situ technique is

also used for the decontamination of ground water or

the treatment of shores where both the water and thearea are polluted (Hazen et al., 1996; Litchfield, 1993).

In in-situ treatment, the decomposition of the con-

taminants is carried out by the indigenous microorgan-

isms which grow on this contaminated soil and can only

survive in that environment by using the contaminating

substances as a source of energy (Aelion, Swindoll, &

Pfaender, 1987; Litchfield & Clark, 1973). These micro-

organisms have either been forced by the environmental

conditions to adapt or die or have been genetically

modified (Ellis & Gorder, 1997). Should one wish the

microbial decomposition to continue, more nutrients,

strictly selected after screening, should be added to the

soil (Litchfield, 1993).

Although this method has several advantages there

are also some limitations for its widespread application.

Since in-situ bioremediation is a slow process it may not

be a good alternative if immediate site clean up isrequired. In some cases, the metabolic process of the

degradation produces undesirable by-products, which

could be toxic. The treatability tests are supposed to

detect the hazardous materials but sometimes condi-

tions can be altered from the laboratory to the field. The

nutrient addition is performed through drills in the soil.

In some cases and when there is no adequate control in

the nutrient distribution it is not certain whether the

substances reached their target or whether other regions

have been also attained by the nutrients. This of course

implies that the remediation process will be prolonged

and the ecology of another area has been disturbed(Litchfield, 1993; Ogunseitan, Tedford, Pacia, Sirotkin,

& Sayler, 1987). Generally, in-situ bioremediation is

more difficult to keep under control than ex-situ or

engineered bioremediation because experimental con-

trols are usually unavailable in contaminated soils

(Wilson & Jawson, 1995).

In slurry bioreactor treatment systems, the con-

taminated soils are excavated and mixed with water to

form a slurry that is mechanically aerated in a reactor

vessel. The reactor contents are agitated to promote

breakdown of soil aggregates, enhance desorption of

contaminants from soil solids, increase contact between

the wastes and microorganisms, and enhance oxygena-tion of the slurry (Baker, 1994). Different substances,

such as surfactants, dispersants and materials support-

ing microbial growth, are added to the slurry to

improve the treatment of contaminated soil and increase

the biodegradation capability (United States Environ-

mental Protection Agency, 1990). Temperature is also

controlled to minimize microbial growth. The con-

centration of the biomass is equally important for the

maintenance of the degradation so microorganisms may

be added to the slurry both in the beginning and during

the process.

Table 3. Composting methodsa

Method Composting time Cost Usage Disadvantages

Windrow 2–6 months for municipalsolid waste

Low Used mainly in combinationwith in-vessel technology forcuring the compost

Difficult control of conditions,temperature, waterconcentration odour

Aerated piles 6–12 weeks Medium Used for sewage sludges,municipal solid waste, yardwastes and industrial organicwastes

Continued electrical costs

In -vessel Less than a week to2 weeks

High due toinstallation costs

All types of waste High cost, intense andskillful management

a O’Leary et al. (1989–1990); Schaub & Leonard (1996).




King, Long, and Sheldon (1992) mentioned that in

many cases the contaminated soils are pretreated before

they are introduced into the reactor. The physical grad-

ing of soil reduces the cost of mixing and agitation.

Fractionation of soils may reduce the total volume

which needs to be treated and increase the rate of bio-degradation of the contaminants (Portier, 1989). Other

researchers have suggested that additional treatment

may be necessary, such as addition of sodium hydroxide

and sodium chloride to neutralize soil acidity and dis-

persion of clay particles to trap the contaminants

(Black, Ahlert, Kosson, & Brugger, 1991). A typical

slurry can only function under the following conditions:

addition of oxygen, nutrients and supplemental bacteria

and regulation of the temperature and pH in order to

maintain the optimum of the microbial growth and

activity (Baker, 1994). Slurry bioreactors generally have

a higher cost than the in-situ systems because of the highdegree of engineering involved. Still the biodegradation

rates of the same compound are faster in slurry bior-

eactors compared to the ones obtained by the in-situ

technique (Castaldi & Ford, 1992; Stroo, 1989).

Fruit and vegetable processing industryIndustries that process fruits and vegetables are a very

important part of the food industry especially in the

Mediterranean countries where agriculture still remains

one of the main sources of income. The fruit and vege-

table canning industry, the frozen vegetable industry,

the vegetable dehydration industry, the fruit and vege-

table drying industry, fruit pulping, tomato juice con-centrate and fruit concentrate belong to this category.

These industries may operate seasonally since operation

time depends on the production of the fruits and vege-

table that they process. That means that the environ-

mental pollution from those industries’ waste will also

be seasonal. According to the processing stage, different

types of waste may be produced thus contributing with

different percentages to the formation of the final pro-

cess waste.

The wastes from fruit and vegetable processing

industries generally contain large amounts of solid sus-

pensions and a high biochemical oxygen demand

(BOD). Some other parameters usually of interest to the

waste treatment are pH, chemical oxygen demand

(COD), dissolved oxygen and total solids. Indicative

values for BOD, COD, suspended solids (SS) and pH

for the processing of some fruit and vegetables are

summarized (Table 4) (S.E. Tsiouris, personal commu-nication). As has already been described, fruit and

vegetable industry wastes consist of various by-products

with an acidic pH (Riggle, 1989), and a moisture con-

tent of 80–90% (Grobe, 1994). The chemical composi-

tion of the wastes varies and depends on the processed

fruit or vegetable. In general, the wastes consist of

hydrocarbons and relatively small amounts of proteins

and fat. The hydrocarbons are mainly sugars and

nitrogen and cellulose fibers. The water wastes contain

dissolved compounds, pesticides, herbicides and clean-

ing chemicals. These differences in the nature of the

wastes require their separate treatment.Although the solid waste is mainly treated with com-

posting, because of superior results slurry bioreactors

and landfarming may also constitute two further

options. A pretreatment is necessary to remove the

water and neutralize the pH to ensure the best condi-

tions for microbial growth and development. Bulking

agents are also added to improve the porosity of the

sludge and decrease the bulk density (Schaub & Leo-

nard, 1996). The increased porosity may help in the

drainage of water, which can be carried out either by

gravity or by exerting pressure on the sludge. In some

investigations the waste was left in open air so that the

excess water evaporated (Grobe, 1994). The bulkingagents employed include sawdust, paper, mature com-

post, straw, and coffee residuals. Of course, every

industry prefers to employ easily available and, in par-

ticular, by-products of its own production. The bulking

agents may appear more useful than just increasing the

porosity because they can also increase the C:N ratios

due to their high carbon content. Furthermore, the

addition of bulking agents can affect the pH. It has been

reported for example that the addition of pine sawdust

and coffee grounds may increase the pH of fruit sludge.

Additives that are used to raise the pH include wood

ash and lime (Verville & Seekins, 1993).

Table 4. Waste characteristicsa

Fruit or vegetable BOD mg/l COD mg/l SSb mg/l pH

Carrots 1350 2300 4120 8.7Corn 1550 2500 210 6.9Tomatoes 1025 1500 950 7.9Green peas 800 1650 260 6.9Cherries 2550 2500 400 6.5Grapefruit 1000 1900 250 7.4Apples 9600 18700 450 5.9

a S.E. Tsiouris (personal communication).b Suspended solids.




Aerated piles are more frequently used for the treat-

ment of solid waste from fruit and vegetable industries

(Nakata, 1994) because they allow the best mixing of

the sludge while it is easy to add moisture, nutrients or

more waste for processing if necessary. However, if sta-

tic piles are initially used, then later the compost has tobe moved to an aerated pile for further cure.

Olive oil industryOlive oil mills represent an important industry in

Mediterranean countries, which automatically makes

them an important source of olive oil mill wastewater. It

is estimated that during the period between November

and February $30 million m3/year wastewater is gen-

erated. The liquid waste, a dark-colored juice, contains

organic substances such as sugars, organic acids, poly-

alcohols, pectins, colloids, tannins and lipids (Table 5).

The difficulty of disposing olive oil mill wastewaters(OMW) is mainly related to its high BOD, COD and

high concentration of organic substances (Table 5); e.g.

phenols, which make degradation a difficult and expen-

sive task (Saez, Perez, & Martinez, 1992).

The biotreatment of the olive oil mill wastewater is

conducted both aerobically and anaerobically leading to

different results. The aerobic treatment is carried out as

the oxygen needed for the aerated sludge process is

provided by an external unit, which provides the sludge

with either pure oxygen or air. This process presents

many difficulties in operation as the biodegradation that

can be accomplished, proceeds very slowly and can

operate efficiently only if the concentrations of the feedare of the order of 1 g COD/l (Rozzi & Malpei, 1996).

However, this value according to the information given

from Table 5 is rather unrealistic, as the approximate

COD for the olive oil wastewater is 100 times higher.

Moreover, the aerobic process cannot efficiently remove

certain persisting pollutants, such as polyphenols and

colouring substances. To lower the polluting load it has

been suggested to mix sewage wastewaters with OMW,

which not only gives better results in biodegrading the

pollutants but has a reduced cost as well. A full-scale

sludge plant for the combined treatment of olive oil

effluents and domestic sewage has been in operationsince 1979 in Bitonto (Apulia, Italy) (Giorgio,

Andeazza, & Rotunno, 1981).

High phenol and organic acid concentrations in

OMW were shown to increase phytotoxicity under cer-

tain conditions, thus rendering biodegradability even

more difficult and the final compost non-usable. The

removal of polyphenols from waste has been extensively

studied. Fiesta Ros de Ursinos (1992) has developed aprocess with a special biomass removing polyphenols

and lipids prior to the aerobic treatment and Flouri,

Sotirchos, Ioannidou, and Balis (1996) have used spe-

cies of the fungi Pleurotus to decolourize the OMW

which gave positive results in 17–30 days.

The anaerobic decomposition of the OMW was

shown to lead to better results on the organic pollu-

tants, sugars, polyphenols, pectins, etc. Growth rates of

these microorganisms are appreciably lower than the

corresponding rates for aerobes and the metabolic

pathways require several microbial populations in ser-

ies, which makes process control more delicate than theaerobic process (Rozzi & Malpei, 1996). Several anae-

robic processes, such as anaerobic lagooning, anaerobic

contact and the upflow anaerobic sludge blanket, have

been employed.

Fermentation industryThe fermentation industry is divided into three main

categories: brewing, distilling and wine manufacture.

Each of these industries produces liquid waste with

many common characteristics, such as high BODs and

CODs, but differ in the concentration of the organic

compounds that determine the biological treatment that

will be selected. The difficulty in dealing with fermenta-tion wastewaters is in the flows and loads of the waste.

Since the fermentation industry’s wastewater contains

high concentrations of tannins, phenols and organic

acid, anaerobic treatment results in higher perfor-

mance. Mayer (1991) attempted to compare aerobic

with anaerobic treatment of the wastewaters in a Ger-

man brewery. Anaerobic treatment achieved 91% COD

reduction at loading rates up to 20 g COD/l day,

whereas the aerobic treatment resulted in a 76% reduc-

tion at a loading rate of 69 g COD/l day. In order to

optimize the conditions of anaerobic treatment, Suzuki,

Yoneyama, and Tanaka (1997) conducted severalexperiments for the optimization of acidity and tem-

perature of highly concentrated brewery wastewater by

Table 5. Chemical composition of organic fraction and quality characteristics of liquid olive oil wastea

Components Values (%) Parameters Values

Sugars 2.0–8.0 BOD 43,000 mg/lTotal nitrogen content 1.2–1.5 COD 100,000 mg/lOrganic acid 0.5–1.55 SS 65,000 mg/lPectins, colloids, tannins 1.0–1.5 TS 6.39%Lipids 1.0–1.5 pH 3–5

a S.E. Tsiouris ( personal communication ).




applying the upflow anaerobic sludge blanket. These

experiments showed that the optimal conditions for the

particular treatment were 40C and 5–6 pH.

The amount and load of distillery waste varies

according to the raw materials used. For example the

biological load for molasses is 3 times that of rai-sins (Stroo, 1989). Benito, Miranda, and de los

Santos (1997) conducted laboratory batch tests to

examine the ability of the white rot fungus Tra-

metes vercicolor to treat molasses-based distillery was-

tewater. All the conditions affecting the treatment of

waste, such as pH, nutrients and carbon source, were

tested at various concentrations to determine their rela-

tion to the reduction of COD, decolorization and

decrease of ammonium content in the wastewater.

Employment of low sucrose concentration in con-

junction with exclusive use of KH2PO4 as a nutrient

resulted in 82% decolorization, 77% COD reduction,and a 36% decrease in ammonium nitrogen concentra-

tion (Benito et al.).

In winery, the treatment methods are based on prin-

ciples similar to the previous fermentation industries.

Experiments conducted both in the laboratory and on

industrial scale showed that with the use of a full-scale,

modular, multi-stage activated sludge treatment plant, it

is possible to reduce the COD level up to 98% when the

influent COD varies between 2000 and 9000 mg/l (Fumi

et al., 1995). One of the main problems in winery waste

treatment is the presence of vinasse, which needs to be

treated biologically for 4–8 days in order to reduce by

90% the COD (Boudouropoulos & Arvanitoyannis,2000).

Dairy industryDairy industries contribute substantially to the pollu-

tion of surface water and soil. The main wastes from

these industries are chemically modified liquid wastes.

The main characteristics of dairy waste can be sum-

marized as follows:

. high organic load (fatty substances, etc.)

. large variations in waste supply

. considerable variations in pH (4.2–9.4)

. relatively large load of suspended solids (SS) (400–

2000 mg/l)

The dairy wastewater may contain proteins, salts,

fatty substances, lactose and various kinds of cleaning

chemicals (S.E. Tsiouris, personal communication).

Detergents represent the biggest portion of chemicals

used in dairies. The detergents may be alkaline or acid

and are used for different purposes. Hydroxides or

alkaline salts are responsible for the alkalinity of the

detergent. They are mainly added to dissolve and

remove proteins, but they also help to eliminate fats

through saponification. Sodium hydroxide is the most

widely applied alkaline detergent but for special appli-

cations it may be replaced or mixed with other strongbases. Acids are used to remove the inorganic deposits

or so-called milkstone. For that purpose, nitric acid or

phosphoric acid are used both alone or in combination.

Both alkaline and acid detergents often contain addi-

tives to improve their cleaning capability. These are

phosphates, sequestering agents, surfactants and some

minor components like dispersing agents, anti-foaming

agents and inhibitors (Romney, 1990).

In addition to the pollution originating directly from

cleaning chemicals, dairy wastewater contains phos-

phorous and nitrogen from product residues removed

by the cleaning process. The total of these two compo-

nents amounts to a global pollution load per annum of 850–1788 tonnes of phosphorus and 3337–5217 tonnes

of nitrogen by the cleaning and disinfection of dairy

installations. The presence of detergents and their addi-

tives in dairy waste water hardly influences the total

COD in contrast to milk, cream or whey (Table 6).

However, detergents also present difficulties in their

treatment. Wildbrertt (1990) reported that sodium car-

bonate passed a two-stage effluent treatment almost

Table 6. COD of milk, milk products, cleaning and disinfecting chemicals and their ingredientsa

Product/substance Concentration (g/l) COD (g/l)

Cream, 30% fat – 850–860Whole milk, 3.5% fat – 160–210Skim milk – 9–100Whey – 68–75Na-dodecyl benzol sulfonate 0.1 0.216Na-ethoxy alkyl sulfate 0.1 0.178Dialkyl dimethyl ammonium chloride (C18 –C20) 0.1 0.235Sodium hydroxide 10.0 0Phosphoric acid 10.0 0Detergent and disinfectant 1 (with QAC) 10.0 2.250Detergent and disinfectant 2 10.0 0.017Detergent and disinfectant 3 (with surfactant) 5.0 0.147

a Wildbrertt (1988).




unchanged and was discharged into the river. Odzuk

(1982) estimated that one-third of the sodium ortho-

phosphate produced was utilized in biological waste-

water treatment. Although sodium carbonate affects

aquatic ecosystems only at high concentrations, even a

small quantity of sodium phosphate can induce eutro-phication. It is well known that algae need nitrogen, for

example from sodium nitrate, but presence of phos-

phorous in surface water has generally proved to be the

limiting factor for algae growth. Polyphosphates, the

most important of the sequestering agents, lead to the

same problems as sodium phosphate. On the other

hand, EDTA used as a substitute for polyphosphates,

has a low biodegradability and remains in the waste-

water after treatment. Although fish are not poisoned,

EDTA at 11 mg/l can inhibit algal growth (Scho ¨ berl &

Huber, 1988). Moreover, EDTA redissolves metals in

the sewage sludge, thus increasing the heavy metal con-tent of the treated wastewater. EDTA may also redis-

solve metals in the natural sediments of receiving

waters. Surfactants are a heterogeneous group of com-

ponents from an ecological point of view. Apart from

their undesirable foam production, leading to insuffi-

cient oxygen supply in activated sludge systems, surfac-

tants were shown to affect strongly the ecosystems of

rivers (International Dairy Federation, 1993). Some of

them transform chlorophyll of the higher plants,

whereas others are toxic to aquatic animals. Even the

‘soft’ surfactants often used today can disturb fish life

when applied in high concentrations (Odzuk, 1982).

What is noteworthy is that one of the surfactants’ mostimportant properties is their biodegradability. Still not

all of them require the same treatment since some are

degradable under aerobic and some under anaerobic

conditions. On the other hand, not only biodegrad-

ability, but also toxicity has to be considered when the

polluting effects of surfactants are investigated. Gen-

erally speaking, surfactants with greater biodegrad-

ability have higher toxicity (Maltz, 1988).

An assessment of the various types of aerobic and

anaerobic treatment systems employed in dairy waste

processing was conducted (Bell, 1992). A partial deni-

trification and some uptake of phosphorus (from 40 to70%) can be achieved in the activated sludge process.

The application of chemical phosphate precipitation

also increases because it allows an elimination of 80–

90% of phosphorus (Scho ¨ berl & Huber, 1988). Dan-

forth (1992) described in detail the use of an automatic

computer control for a sequencing batch reactor (SBR)

at another facility where the monitoring of pH and dis-

solved oxygen (DO) allowed control of the system

despite wide variations in flows and loading. A bench

scale study of a fluidized-bed aerobic system yielded

COD removals of 85 and 60% at loading rates of 500–

900 g COD/ m3 h (Rusten et al., 1992). These authors

found that milk fat appeared to inhibit methanogenic

activity and suggested that milk fat concentrations

should be reduced to below 100 mg/l before anaerobic

treatment. A laboratory-scale anaerobic sequencing

batch reactor investigated by Sung and Dague (1995)

attained a 90% reduction in soluble COD with a

synthetic milk substrate. The above treatments areapplicable in dairy wastewater without the presence of

chemicals, which, in most cases, require more sophisti-

cated treatment. It is hardly feasible to formulate a

general treatment for all chemicals used since they are

almost always applied in combinations of more than

two. The use of detergents will most likely aggravate the

applied treatments, as the chemical industry will con-

tinue to develop new substances for cleaning purposes.

The environmental effects of all these chemicals will

have to be analysed. Furthermore, the exact composi-

tion of detergents and disinfectants does not have to be

declared or labelled in many countries. Therefore, end-users buy a mixed product, not being aware what sub-

stances are contained therein, and they are not in a

position to choose substances with low ecological

effects, even if they would like to. Manufactures should

be therefore requested by the end-users to disclose their

updated evaluations and findings regarding the envir-

onmental impacts of their products (International Dairy

Federation, 1993).

Meat and poultry industryMeat, poultry and fish industries produce the highest

loads of waste within the food industry. The meat

industry contains slaughterhouses and processing unitswhere meat is prepared, cut in pieces and is either fro-

zen, cooked, cured, smoked or made into sausages.

Slaughterhouses are more important than the other

units in terms of environmental pollution. The wastes

coming from these units contain various quantities of

blood, fats, residues from the intestine, paunch grass

and manure (Cournoyer, 1996). The wastes are best

separated into wastewater and solid waste. Solid waste,

like intestines, pieces of meat or bones have been used as

animal feed after further processing.

Slaughterhouse wastewater is typically high in both

moisture (90–95%) and nitrogen, has a high BOD and isodourous. Cooper and Russell (1992) published a sum-

mary of the treatment technologies and performance

data of $44 meat processing plants in New Zealand,

most of which were located in rural areas. The investi-

gation concluded that the management of nitrogen in

both land application and direct discharge to receiving

water was the critical control point.

Waste pretreatment is necessary in order to reduce the

moisture and increase the porosity. Bulking agents are

employed to make the waste sufficiently porous for

aeration and to lower the moisture content down to 60–

75% as a function of carbon source. In some cases

where high-carbon bulking agents were needed, the




compost required the addition of inorganic nitrogen to

optimize the C:N ratio. When wastes are of a high

moisture content, the use of bulking agents alone is not

adequate, as large quantities are required thus raising

the composting cost and jeopardizing the economic

feasibility of the method. Pretreatment is also necessarybecause the sludge derived from processing of waste-

water contains pathogens. Therefore proper manage-

ment is a prerequisite to ensure that potentially high

levels of pathogens are eliminated (Cournoyer, 1996).

Poultry wastes are equally problematic to meat wastes

because the main source of wastewaters is the slaugh-

tering process. Starkey (1992) reviewed the considera-

tions for selection of a treatment system for poultry

processing wastewater, including land availability, pre-

vious site history, publicly owned treatment work dis-

charge, conventional waste treatment systems, and land

application systems. The performance of anaerobictreatment systems, including lagoons, contact processes,

sludge beds, filters, packed beds, and hybrid reactors

were out lined (Ross & Valentine, 1992).

Pretreatment is also regarded as necessary for poultry

waste to reduce the moisture and increase the porosity

with the addition of bulking agents, which also increase

the aeration and carbon level in wastewater. Proper

treatment is needed to eliminate the pathogens. A

bench-scale study by Ogunseitan (1996) indicated that

the combination of ozone and ultraviolet light would

reduce the population density of Salmonella typhimur-

ium in a poultry-processing wastewater from $3.4Â108

down to 1.2Â103 per ml after 20 min exposure.

ConclusionsThe extensive land degradation has led to intensive

experimentation, aiming at identifying the most promis-

ing techniques for attaining the lowest possible pollution

level. The results obtained showed that bioremediation

in its many forms and composting, in particular, con-

stitute ‘good technique’ for solving the environmental

pollution due to food industry waste. Investigation of

several sectors of the food industry (fruit and vegetable,

olive oil, fermentation, dairy, meat and poultry), con-

firmed the usefulness and potential of biotreating foodwaste. In general, bioremediation methods convert con-

taminants such as pesticides, herbicides and cleaning

chemicals into non-toxic substances.

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