Coffee wastewater
Encyclopedia
The unpicked fruit
of the coffee tree, known as the coffee cherry, must undergo a long process to make it ready for consumption
. This process often entails the usage of massive amounts of water
and the production of considerable amounts of both solid and liquid
waste
. To determine the type of waste stemming from coffee processing
, it is important to know how the coffee cherries are processed. The conversion of the cherry to oro or green bean (the dried coffee bean which is ready to be exported) can be achieved through three different processing techniques: dry, semi-washed, and fully washed.
layer which covers the bean takes place. This is done mechanically by feeding the beans into a cylindrical device which conveys them upward. While the friction and pressure exerted on the beans by this process is enough to remove most of the mucilage, a small amount of it will still remain in the centre cut of the beans. This technique is used in Colombia and Mexico in order to reduce the water consumption from the long fermentation process and the extensive washing. While semi-washed processing requires less time than washed processing and is thus economically advantageous, the quality of the end product is regarded as inferior.
In order to reduce the contamination generated by the wet process of coffee fruits, scientists at Cenicafé developed a technology that avoids using water when is not needed and uses the right water when is needed. The technology, called Becolsub after the Spanish initials of ecological wet coffee process with by-products handling, permits controlling more than 90% of the contamination generated by its antecessor. The quality of the coffee processed by this way is the same as the one for coffee processed by natural fermentation.
The Becolsub technology basically consists in pulping without water, mechanical demucilaging and mixing of the by-products (fruit outer-skin and mucilage) in a screw conveyor. The technology also includes a hydromechanical device to remove flouting fruits and light impurities, as well as heavy and hard objects, and a cylindrical screen to remove the fruits whose skin was not separated in the pulping machine. Scientists at Cenicafé discovered that a coffee fruit with mucilage (immature and dry fruits have no mucilage) has enough water inside for the skin and seeds to be separated in conventional pulping machines without water, that the liquid was only required as a conveying means and that pulping with water absence avoids 72% of the potential contamination.
Mucilage removal has been done throughout a fermenting process, which takes between 14 to 18 hours, until the mucilage is degraded and can be easily removed with water. Washing fermented mucilage requires, in the best case, 5,0 L/kg of DPC. Scientists at Cenicafé developed a machine to remove the mucilage covering the coffee seeds. This machine, called Deslim for initials of the Spanish words mechanical demucilager, washer and cleaner, removes more than 98% of the total mucilage (same as a well conducted fermentation) by exerting shear stresses and generating collisions among beans, using only 0,7 L/kg of DPC. The resulting highly concentrated mixture of water, mucilage and impurities is as viscous that can be added to the separated fruit skin in a screw conveyor, obtaining a great retention in the solid. The screw conveyor is as well mixer that the retention is greater than 60%, which means a 20% additional control of the potential contamination.
Until now, the two by-products have been widely used as worms’ substrate to produce natural fertilizers. However, the high concentration of the mucilage obtained from the demucilager leads to the opportunity of industrializing the by-product.
After de-pulping, the beans are collected in fermentation
tanks where bacterial removal of the mucilage takes place over 12 to 36 hours. The fermentation phase is important in the development of the flavour of the coffee, which is partially due to the microbiological processes that take place. The emergence of yeasts and moulds in acidic water can lead to off-flavours like sour coffee and onion-flavour. However, wet processing is believed to yield higher quality coffee than the other processes since small amounts of off-flavors give the coffee its particular taste and "body".
When the fermentation is complete, the beans should be washed thoroughly to remove fermentation residues and any remaining mucilage. If they are not removed, these cause decolouring of the parchment and make the beans susceptible to yeasts. After washing, the beans are dried. When the drying process is not rapid enough earthy and musty taints, like Rio-flavor come up.
Wet fully washed processing of the coffee cherries requires the most fresh water, dry processing the least. Sources indicate a wide range in water use. Recycling of water in the de-pulping process can drastically reduce the amount needed. With reuse and improved washing techniques, up to 1 to 6 m³ water per tonne of fresh coffee cherry is achievable; without reuse a consumption of up to 20m³/tonne is possible.
. The main component is organic matter
, stemming from de-pulping and mucilage
removal.
The majority of organic material in the wastewater
is highly resistant and COD
values, the amount oxygen required to stabilize organic matter by using a strong oxidant, make up 80% of the pollution load, with values as high as 50 g/l. The BOD, the amount of oxygen required for the biological decomposition of organic matter under aerobic conditions at a standardized temperature and time of incubation, coming from biodegradable organic material can reach values of 20 g/l.
With a (rough) screening and removal of the pulp COD and BOD values become considerably lower. Values in the range of 3 - 5 g/l for COD and 1.5 – 3 g/l for BOD5 were found. Recorded values of 2.5 g/l for COD and 1.5 g/l for BOD5.
A large part of the organic matter, pectin
s, precipitates as mucilated solids and could be taken out of the water. When these solids are not removed and pH
values rise and an increase in COD can be observed.
In order to optimize the anaerobic processing of the wastewater pH values should be between 6.5 and 7.5, instead of the generally present values of pH = 4, which is highly acidic. This is obtained by adding calcium hydroxide
(CaOH2) to the wastewater. This resulted in a regained solubility of the pectins, raising COD from an average of 3.7 g/l to an average of 12.7 g/l.
The water is further characterised by the presence of flavonoid
compounds, coming from the skin of the cherries. Flavonoid compounds result in dark colouration of the water at a pH = 7 or higher, but they do not add to BOD or COD levels of the wastewater, nor have major environmental impacts. Lower levels of transparency, however, can have a negative impact on photosynthetic
processes and growth and nutrient transformations by (especially) rooted water plants. Many efforts in olive
and wine
processing industries, with relatively large funds for research, have been trying to find a solution for this problem. Calvert mentions research done into the removal of polyphenolic
s and flavonoid compounds by species of wood digesting fungi (Basidiomycetes) in a submerged solution with aeration
using compressed air. These complex processes seemed to be able to remove the colour compounds, but simplified, cheaper techniques using other types of fungi (i.e. Geotrichum
, Penicillium
, Aspergillus
) only thrived in highly diluted wastewaters.
Coffee wastewater is not a constant flow of water with uniform loadings of contamination. The processing of coffee cherries is a batch process and regarding water flows, two processes can be determined: de-pulping and fermentation/washing.
Pulping water can be reused during the de-pulping of the harvest of one day. This results in an increase in organic matter and a decrease in pH. Research in Nicaragua showed COD averages rising from 5,400 mg/l up to 8,400 mg/l with most of the pulp removed. The drop in pH can be attributed to the start of fermentation of the pulping water. This drop continues until fermentation is finished and pH levels of around 4 are reached. The nutrient content of the pulping water at the maximum COD load, which was considered to reflect maximum pollution, was determined during this research. Total nitrogen (TN) concentration in the samples ranged from 50 to 110 mg/l with an average over all samples of 90 mg/l. Total phosphorus (TP) concentration in the samples ranged from 8.9 to 15.2 mg/l with an average over all samples of 12.4 mg/l.
is converted in acetic acids after reaction with oxygen, lowering the pH to levels of around 4. The high acidity can negatively affect the treatment efficiency of treatment facilities treating the coffee wastewater like an anaerobic reactor or constructed wetlands and is considered to be detrimental for aquatic life when discharged directly into surface water
s.
During the washing process the research in Nicaragua showed a clear decrease in contamination of the wastewater. The COD values drop from an average of 7,200 mg/l to less than 50 mg/l. Despite the fact that wastewater with COD values below 200 mg/l is allowed to be discharged in the natural waterways in Nicaragua it is advisable to redirect all the wastewater to the treatment system. This is because COD levels cannot be determined onsite during the washing process and discharge of the wastewater into surface waters is based on visual inspection. When the water is "clear" it is considered to be clean enough but the COD values measured during the research showed that discharge generally was to soon, resulting in wastewater with higher levels of COD than permitted. Another positive effect of diverting the wastewater to a treatment system is the dilution of the wastewater which enables better treatment by anaerobic bacteria due to more favourable pH values and better post-treatment due to lower concentrations of ammonium.
TN concentration in the samples of wastewater stemming from washing ranged from 40 to 150 mg/l with an average over all samples of 110 mg/l. TP concentration in the samples ranged from 7.8 to 15.8 mg/l with an average over all samples of 10.7 mg/l.
Fruit
In broad terms, a fruit is a structure of a plant that contains its seeds.The term has different meanings dependent on context. In non-technical usage, such as food preparation, fruit normally means the fleshy seed-associated structures of certain plants that are sweet and edible in the raw state,...
of the coffee tree, known as the coffee cherry, must undergo a long process to make it ready for consumption
Ingestion
Ingestion is the consumption of a substance by an organism. In animals, it normally is accomplished by taking in the substance through the mouth into the gastrointestinal tract, such as through eating or drinking...
. This process often entails the usage of massive amounts of water
Water
Water is a chemical substance with the chemical formula H2O. A water molecule contains one oxygen and two hydrogen atoms connected by covalent bonds. Water is a liquid at ambient conditions, but it often co-exists on Earth with its solid state, ice, and gaseous state . Water also exists in a...
and the production of considerable amounts of both solid and liquid
Wastewater
Wastewater is any water that has been adversely affected in quality by anthropogenic influence. It comprises liquid waste discharged by domestic residences, commercial properties, industry, and/or agriculture and can encompass a wide range of potential contaminants and concentrations...
waste
Waste
Waste is unwanted or useless materials. In biology, waste is any of the many unwanted substances or toxins that are expelled from living organisms, metabolic waste; such as urea, sweat or feces. Litter is waste which has been disposed of improperly...
. To determine the type of waste stemming from coffee processing
Coffee processing
Processing of coffee is the method converting the raw fruit of the coffee plant into the coffee. The cherry has the fruit or pulp removed leaving the seed or bean which is then dried...
, it is important to know how the coffee cherries are processed. The conversion of the cherry to oro or green bean (the dried coffee bean which is ready to be exported) can be achieved through three different processing techniques: dry, semi-washed, and fully washed.
Dry processing
The coffee cherries are dried immediately after they are harvested through sun drying, solar drying or artificial drying. In sun drying, the coffee cherries are placed on a clean floor and left to dry in the open air. In solar drying, the cherries are placed in a closed cabinet, which has ventilation holes to let moisture out. Artificial drying is used mostly during the wet season, when the low level of sunlight extends the time needed for solar drying and the cherries are prone to mold growth. After being dried, the cherries are hulled. In this process the dried outer layer of the cherry, known as the pericarp, is removed mechanically.Semi-washed processing
In semi-washed processing, the cherries are de-pulped to remove the pericarp. After this, the removal of the slimy mucilageMucilage
Mucilage is a thick, gluey substance produced by most plants and some microorganisms. It is a polar glycoprotein and an exopolysaccharide.It occurs in various parts of nearly all classes of plant, usually in relatively small percentages, and is frequently associated with other substances, such as...
layer which covers the bean takes place. This is done mechanically by feeding the beans into a cylindrical device which conveys them upward. While the friction and pressure exerted on the beans by this process is enough to remove most of the mucilage, a small amount of it will still remain in the centre cut of the beans. This technique is used in Colombia and Mexico in order to reduce the water consumption from the long fermentation process and the extensive washing. While semi-washed processing requires less time than washed processing and is thus economically advantageous, the quality of the end product is regarded as inferior.
In order to reduce the contamination generated by the wet process of coffee fruits, scientists at Cenicafé developed a technology that avoids using water when is not needed and uses the right water when is needed. The technology, called Becolsub after the Spanish initials of ecological wet coffee process with by-products handling, permits controlling more than 90% of the contamination generated by its antecessor. The quality of the coffee processed by this way is the same as the one for coffee processed by natural fermentation.
The Becolsub technology basically consists in pulping without water, mechanical demucilaging and mixing of the by-products (fruit outer-skin and mucilage) in a screw conveyor. The technology also includes a hydromechanical device to remove flouting fruits and light impurities, as well as heavy and hard objects, and a cylindrical screen to remove the fruits whose skin was not separated in the pulping machine. Scientists at Cenicafé discovered that a coffee fruit with mucilage (immature and dry fruits have no mucilage) has enough water inside for the skin and seeds to be separated in conventional pulping machines without water, that the liquid was only required as a conveying means and that pulping with water absence avoids 72% of the potential contamination.
Mucilage removal has been done throughout a fermenting process, which takes between 14 to 18 hours, until the mucilage is degraded and can be easily removed with water. Washing fermented mucilage requires, in the best case, 5,0 L/kg of DPC. Scientists at Cenicafé developed a machine to remove the mucilage covering the coffee seeds. This machine, called Deslim for initials of the Spanish words mechanical demucilager, washer and cleaner, removes more than 98% of the total mucilage (same as a well conducted fermentation) by exerting shear stresses and generating collisions among beans, using only 0,7 L/kg of DPC. The resulting highly concentrated mixture of water, mucilage and impurities is as viscous that can be added to the separated fruit skin in a screw conveyor, obtaining a great retention in the solid. The screw conveyor is as well mixer that the retention is greater than 60%, which means a 20% additional control of the potential contamination.
Until now, the two by-products have been widely used as worms’ substrate to produce natural fertilizers. However, the high concentration of the mucilage obtained from the demucilager leads to the opportunity of industrializing the by-product.
Fully washed processing
This process is mainly used when processing Coffea arabicaCoffea arabica
Coffea arabica is a species of Coffea originally indigenous to the mountains of Yemen in the Arabian Peninsula, hence its name, and also from the southwestern highlands of Ethiopia and southeastern Sudan. It is also known as the "coffee shrub of Arabia", "mountain coffee" or "arabica coffee"...
After de-pulping, the beans are collected in fermentation
Industrial fermentation
Industrial fermentation is the intentional use of fermentation by microorganisms such as bacteria and fungi to make products useful to humans. Fermented products have applications as food as well as in general industry.- Food fermentation :...
tanks where bacterial removal of the mucilage takes place over 12 to 36 hours. The fermentation phase is important in the development of the flavour of the coffee, which is partially due to the microbiological processes that take place. The emergence of yeasts and moulds in acidic water can lead to off-flavours like sour coffee and onion-flavour. However, wet processing is believed to yield higher quality coffee than the other processes since small amounts of off-flavors give the coffee its particular taste and "body".
When the fermentation is complete, the beans should be washed thoroughly to remove fermentation residues and any remaining mucilage. If they are not removed, these cause decolouring of the parchment and make the beans susceptible to yeasts. After washing, the beans are dried. When the drying process is not rapid enough earthy and musty taints, like Rio-flavor come up.
Water usage
The amount of water used in processing depends strongly on the type of processing.Wet fully washed processing of the coffee cherries requires the most fresh water, dry processing the least. Sources indicate a wide range in water use. Recycling of water in the de-pulping process can drastically reduce the amount needed. With reuse and improved washing techniques, up to 1 to 6 m³ water per tonne of fresh coffee cherry is achievable; without reuse a consumption of up to 20m³/tonne is possible.
| Country | Process | Water use m³/tonne cherry | Source |
|---|---|---|---|
| India | Semi-washed, wet processing | 3 | Murthy et al., 2004 |
| Kenya | Fully washed, reuse of water | 4-6 | Von Enden and Calvert 2002 [2] |
| Colombia | Fully washed and environmental processing (BECOLSUB) | 1-6 | Von Enden and Calvert 2002 [2] |
| Papua New Guinea | Fully washed, recycling use of water | 4-8 | Von Enden and Calvert 2002 [2] |
| Vietnam | Semi wet and fully washed | 4-15 | Von Enden and Calvert 2002 [2] |
| Vietnam | Traditional, fully washed | 20 | Von Enden and Calvert 2002 [1] |
| India | Traditional, fully washed | 14-17 | Deepa et al. (2002) |
| Brazil | Semi-washed, mechanical demucilage | 4 | De Matos et al. (2001) |
| Mexico | Semi-washed, mechanical demucilage | 3.4 | Bello-Mendoza and Castillo-Rivera (1998) |
| Nicaragua | Traditional, fully washed | 16 | Biomat (1992) |
| Nicaragua | Fully washed, reuse of water | 11 | Grendelman (2006) |
Characteristics
When processing coffee using the fully washed principle much wastewater is generated.General
Water used in processing coffee leaves the coffee processing unit with high levels of pollutionPollution
Pollution is the introduction of contaminants into a natural environment that causes instability, disorder, harm or discomfort to the ecosystem i.e. physical systems or living organisms. Pollution can take the form of chemical substances or energy, such as noise, heat or light...
. The main component is organic matter
Organic matter
Organic matter is matter that has come from a once-living organism; is capable of decay, or the product of decay; or is composed of organic compounds...
, stemming from de-pulping and mucilage
Mucilage
Mucilage is a thick, gluey substance produced by most plants and some microorganisms. It is a polar glycoprotein and an exopolysaccharide.It occurs in various parts of nearly all classes of plant, usually in relatively small percentages, and is frequently associated with other substances, such as...
removal.
The majority of organic material in the wastewater
Wastewater
Wastewater is any water that has been adversely affected in quality by anthropogenic influence. It comprises liquid waste discharged by domestic residences, commercial properties, industry, and/or agriculture and can encompass a wide range of potential contaminants and concentrations...
is highly resistant and COD
Chemical oxygen demand
In environmental chemistry, the chemical oxygen demand test is commonly used to indirectly measure the amount of organic compounds in water. Most applications of COD determine the amount of organic pollutants found in surface water or wastewater, making COD a useful measure of water quality...
values, the amount oxygen required to stabilize organic matter by using a strong oxidant, make up 80% of the pollution load, with values as high as 50 g/l. The BOD, the amount of oxygen required for the biological decomposition of organic matter under aerobic conditions at a standardized temperature and time of incubation, coming from biodegradable organic material can reach values of 20 g/l.
With a (rough) screening and removal of the pulp COD and BOD values become considerably lower. Values in the range of 3 - 5 g/l for COD and 1.5 – 3 g/l for BOD5 were found. Recorded values of 2.5 g/l for COD and 1.5 g/l for BOD5.
A large part of the organic matter, pectin
Pectin
Pectin is a structural heteropolysaccharide contained in the primary cell walls of terrestrial plants. It was first isolated and described in 1825 by Henri Braconnot...
s, precipitates as mucilated solids and could be taken out of the water. When these solids are not removed and pH
PH
In chemistry, pH is a measure of the acidity or basicity of an aqueous solution. Pure water is said to be neutral, with a pH close to 7.0 at . Solutions with a pH less than 7 are said to be acidic and solutions with a pH greater than 7 are basic or alkaline...
values rise and an increase in COD can be observed.
In order to optimize the anaerobic processing of the wastewater pH values should be between 6.5 and 7.5, instead of the generally present values of pH = 4, which is highly acidic. This is obtained by adding calcium hydroxide
Calcium hydroxide
Calcium hydroxide, traditionally called slaked lime, is an inorganic compound with the chemical formula Ca2. It is a colourless crystal or white powder and is obtained when calcium oxide is mixed, or "slaked" with water. It has many names including hydrated lime, builders lime, slack lime, cal, or...
(CaOH2) to the wastewater. This resulted in a regained solubility of the pectins, raising COD from an average of 3.7 g/l to an average of 12.7 g/l.
The water is further characterised by the presence of flavonoid
Flavonoid
Flavonoids , are a class of plant secondary metabolites....
compounds, coming from the skin of the cherries. Flavonoid compounds result in dark colouration of the water at a pH = 7 or higher, but they do not add to BOD or COD levels of the wastewater, nor have major environmental impacts. Lower levels of transparency, however, can have a negative impact on photosynthetic
Photosynthesis
Photosynthesis is a chemical process that converts carbon dioxide into organic compounds, especially sugars, using the energy from sunlight. Photosynthesis occurs in plants, algae, and many species of bacteria, but not in archaea. Photosynthetic organisms are called photoautotrophs, since they can...
processes and growth and nutrient transformations by (especially) rooted water plants. Many efforts in olive
Olive
The olive , Olea europaea), is a species of a small tree in the family Oleaceae, native to the coastal areas of the eastern Mediterranean Basin as well as northern Iran at the south end of the Caspian Sea.Its fruit, also called the olive, is of major agricultural importance in the...
and wine
Wine
Wine is an alcoholic beverage, made of fermented fruit juice, usually from grapes. The natural chemical balance of grapes lets them ferment without the addition of sugars, acids, enzymes, or other nutrients. Grape wine is produced by fermenting crushed grapes using various types of yeast. Yeast...
processing industries, with relatively large funds for research, have been trying to find a solution for this problem. Calvert mentions research done into the removal of polyphenolic
Polyphenol
Polyphenols are a structural class of natural, synthetic, and semisynthetic organic chemicals characterized by the presence of large multiples of phenol structural units...
s and flavonoid compounds by species of wood digesting fungi (Basidiomycetes) in a submerged solution with aeration
Aeration
Aeration is the process by which air is circulated through, mixed with or dissolved in a liquid or substance.-Aeration of liquids:-Methods:Aeration of liquids is achieved by:...
using compressed air. These complex processes seemed to be able to remove the colour compounds, but simplified, cheaper techniques using other types of fungi (i.e. Geotrichum
Geotrichum
Geotrichum is a genus of fungi found worldwide in soil, water, air, and sewage, as well as in plants, cereals, and dairy products; it is also commonly found in normal human flora and is isolated from sputum and feces....
, Penicillium
Penicillium
Penicillium is a genus of ascomycetous fungi of major importance in the natural environment as well as food and drug production. Members of the genus produce penicillin, a molecule that is used as an antibiotic, which kills or stops the growth of certain kinds of bacteria inside the body...
, Aspergillus
Aspergillus
Aspergillus is a genus consisting of several hundred mold species found in various climates worldwide. Aspergillus was first catalogued in 1729 by the Italian priest and biologist Pier Antonio Micheli...
) only thrived in highly diluted wastewaters.
Coffee wastewater is not a constant flow of water with uniform loadings of contamination. The processing of coffee cherries is a batch process and regarding water flows, two processes can be determined: de-pulping and fermentation/washing.
De-pulping
The water used for de-pulping of the cherries is referred to as pulping water. It accounts for just over half of the water used in the process. According to Von Enden and Calvert, "pulping water consists of quickly fermenting sugars from both pulp and mucilage components. Pulp and mucilage consists to a large extent of proteins, sugars and the mucilage in particular of pectins, i.e. polysaccharide carbohydrates. These sugars are fermenting using the enzymes from the bacteria on the cherries. Other components in pulping water are acids and toxic chemicals like polyphenolics (tannins) or alkaloids (caffeine).Pulping water can be reused during the de-pulping of the harvest of one day. This results in an increase in organic matter and a decrease in pH. Research in Nicaragua showed COD averages rising from 5,400 mg/l up to 8,400 mg/l with most of the pulp removed. The drop in pH can be attributed to the start of fermentation of the pulping water. This drop continues until fermentation is finished and pH levels of around 4 are reached. The nutrient content of the pulping water at the maximum COD load, which was considered to reflect maximum pollution, was determined during this research. Total nitrogen (TN) concentration in the samples ranged from 50 to 110 mg/l with an average over all samples of 90 mg/l. Total phosphorus (TP) concentration in the samples ranged from 8.9 to 15.2 mg/l with an average over all samples of 12.4 mg/l.
Washing
Washing of the fermented beans leads to wastewater containing mainly pectins from the mucilage, proteins and sugars. The fermentation of the sugars (disaccharide carbohydrates) into ethanol and CO2 leads to acid conditions in the washing water. The ethanolEthanol
Ethanol, also called ethyl alcohol, pure alcohol, grain alcohol, or drinking alcohol, is a volatile, flammable, colorless liquid. It is a psychoactive drug and one of the oldest recreational drugs. Best known as the type of alcohol found in alcoholic beverages, it is also used in thermometers, as a...
is converted in acetic acids after reaction with oxygen, lowering the pH to levels of around 4. The high acidity can negatively affect the treatment efficiency of treatment facilities treating the coffee wastewater like an anaerobic reactor or constructed wetlands and is considered to be detrimental for aquatic life when discharged directly into surface water
Surface water
Surface water is water collecting on the ground or in a stream, river, lake, wetland, or ocean; it is related to water collecting as groundwater or atmospheric water....
s.
During the washing process the research in Nicaragua showed a clear decrease in contamination of the wastewater. The COD values drop from an average of 7,200 mg/l to less than 50 mg/l. Despite the fact that wastewater with COD values below 200 mg/l is allowed to be discharged in the natural waterways in Nicaragua it is advisable to redirect all the wastewater to the treatment system. This is because COD levels cannot be determined onsite during the washing process and discharge of the wastewater into surface waters is based on visual inspection. When the water is "clear" it is considered to be clean enough but the COD values measured during the research showed that discharge generally was to soon, resulting in wastewater with higher levels of COD than permitted. Another positive effect of diverting the wastewater to a treatment system is the dilution of the wastewater which enables better treatment by anaerobic bacteria due to more favourable pH values and better post-treatment due to lower concentrations of ammonium.
TN concentration in the samples of wastewater stemming from washing ranged from 40 to 150 mg/l with an average over all samples of 110 mg/l. TP concentration in the samples ranged from 7.8 to 15.8 mg/l with an average over all samples of 10.7 mg/l.