In most industries, wastewater effluents result from the following water uses:
• Sanitary wastewater (from washing, drinking, etc.);
• Cooling (from disposing of excess heat to the environment);
• Process wastewater (including both water used for making and washing products and for removal and transport of waste and by-products); and
• Cleaning (including wastewater from cleaning and maintenance of industrial areas).
Excluding the large volumes of cooling water discharged by the electric power industry, the wastewater production from urban areas is about evenly divided between industrial and municipal sources. Therefore, the use of water by industry can significantly affect the water quality of receiving waters. The level of wastewater loading from industrial sources varies markedly with the water quality objectives enforced by the regulatory agencies. There are many possible in-plant changes, process modifications and water-saving measures through which industrial wastewater loads can be significantly reduced. Up to 90 % of recent wastewater reductions have been achieved by industries employing such methods as recirculation, operation modifications, effluent reuse or more efficient operation. As a rule, treatment of an industrial effluent is much more expensive without water-saving measures than the total cost of in-plant modifications and residual effluent treatment. Industrial wastewater effluents are usually highly variable, with quantity and quality variations brought about by bath discharges, operation start-ups and shut-downs, working-hour distribution and so on. A long-term detailed survey is usually necessary before a conclusion on the pollution impact from an industry can be reached. Typical pollutants and BOD range for a variety of industrial wastes are given in Table 1. The values of typical concentration parameters (BOD5, COD, suspended solids) and pH for different industrial effluents are given in Table 2.
Table (1) Wastewater characteristics for typical industries (Kiely,1996)
| Industry | Principal pollutants | BOD5 mg/l |
| Dairy, milk processing
Meat processing
Poultry processing
Bacon processing
Sugar refining
Breweries
Canning fruit etc
Tanning
Electroplating
Laundry
Chemical plant |
Carbohydrates, fats, proteins
SS, protein
SS, protein
SS, protein
SS, Carbohydrates
Carbohydrates, protein
SS, Carbohydrates
SS, protein, sulphide
heavy metals
SS, Carbohydrates, soaps, oils
SS, acidity, alkalinity |
1000 – 2500
200 – 250
100 – 2400
900 – 1800
200 – 1700
500 – 1300
500 – 1200
250 – 1700
minimal
800 – 1200
250 – 1500 |
SS : suspended solids
Table 2 Comparative strengths of wastewaters from industry
(Bond & Straub, 1974)
| Type of waste | BOD5 mg/l | COD mg/l | SS mg/l | pH |
| Apparel | ||||
| Cotton | 200 – 1000 | 400 – 1800 | 200 | 8 – 12 |
| Wool scouring | 2000 – 5000 | 2000 – 5000 (a) | 3000 – 30000 | 9 – 11 |
| Wool composite | 1 | – | 100 | 9 – 10 |
| Tannery | 1000 – 2000 | 2000 – 4000 | 2000 – 3000 | 11 – 12 |
| Laundry | 1600 | 2700 | 250 – 500 | 8 – 9 |
| Food | ||||
| Brewery | 850 | 1700 | 90 | 4 – 8 |
| Distillery | 7 | 10 | Low | – |
| Dairy | 600 – 1000 | 150 – 250 (a) | 200 – 400 | Acid |
| Cannery | ||||
| citrus | 2000 | – | 7000 | Acid |
| pea | 570 | – | 130 | Acid |
| Slaughterhouse | 1500 – 2500 | 200 – 400 (a) | 800 | 7 |
| Potato processing | 2000 | 3500 | 2500 | 11 – 13 |
| Sugar beet | 450 – 2000 | 600 – 3000 | 800 – 1500 | 7 – 8 |
| Farm | 1000 – 2000 | 500 – 1000 (a) | 1500 – 3000 | 7.5 – 8.5 |
| Poultry | 500 – 800 | 600 – 1050 | 450 – 800 | 6.5 – 9 |
| Materials | ||||
| Pulp; sulfite | 1400 – 1700 | 84 – 10000 | Variable | |
| Pulp; kraft | 100 – 350 | 170 – 600 | 75 – 300 | 7 – 9.5 |
| Paperboard | 100 – 450 | 300 – 1400 | 40 – 100 | |
| Strawboard | 950 | 850 (a) | 1350 | |
| Coke oven | 780 | 1650 (a) | 70 | 7 – 11 |
| Oil refinery | 100 – 500 | 150 – 800 | 130 – 600 | 2 – 6 |
(a) = COD Mn, mg O2/l
Ref.
1- Abdulrzzak Alturkmani, Dairy Industry Effluents Treatment, Thesis. UTCB University, Bucharest-Romania 2007
2- Califorina State University, Industrial Waste Treatment, V1&V2. USA,1999
3- Kiely, Environmental Engineering, 1996
4- R.G. Bond, C.P. Straub, Wastewater Treatment and Disposal, 1974