The characteristics of industrial effluent vary according to the industry but domestic effluent is not, it always has the same characteristics so it would be foolish to compare between two.
The pollutants of domestic effluent are always same; it contains human waste, kitchen waste, laundry detergents, etc., so the pollution standards are not too high but I want to add one thing that definitely the pollution load in terms of pollutants is less than the industrial effluent but the pollution hazard is more because of its quantity. The effluent treatment process is based on effluent characterizes.
The below table is showing the daily sewage generation in India (Urban Areas). Source website “ENVIS Centre on Hygiene, Sanitation, Sewage Treatment Systems and Technology” Ministry of Environment, Forest & Climate Change.”
Domestic Effluent Characteristics:
Temperature- In practical the temperature of the raw sewage is between 15 to 350C but it varies as per the weather conditions.
pH- It is observed that the pH of fresh sewage is neutral ( 5.5-8.0). It may decreases after a few hours due to the decomposition of organic matter by natural. If fluctuation observed in pH, it means some industrial effluent is coming in sewage.
Color and Odour– Fresh sewage looks like soapy and cloudy. It becomes gray & black after a few hours of retention. Old sewage has a pungent smell of H2S gas.
Solids- Sewage contains grit, silt, sand, and other settable solids. The quantity of biodegradable solids is less than 0.5 % of the total.
Nitrogen and Phosphorus- The main nitrogen source in sewage effluent are proteins, amines, amino acids, and urea. After biodegradation of these compounds, the ammonical nitrogen generated. The nitrogen content in sewage is observed in a range between 20 to 50 mg/L. Phosphorus comes to sewage from phosphorus-containing food waste. Synthetic detergents are also a very good source of phosphorus. The concentration of PO4 in raw sewage may in the range of 5 to 10 mg/L.
Chlorides- The chloride concentration in sewage is more than the chloride concentration of water used in houses. Chlorides are the most stable compound in water it generally combines with sodium & potassium, magnesium, and calcium.
Organic Material- Sewage mainly contains 99% of water & leftover are organic & inorganic substances which are in suspension, colloidal & in dissolved form. Carbohydrates, lignin, fats, soaps, synthetic detergents, proteins, and their decomposition products are the main organic substances present in sewage. We can measure the organic material of sewage by BOD & TOC tests. The pollution strength of sewage is mentioned in the table. The parameters are not exact; it will vary according to cities.
Industrial Effluent Characteristics:
Industrial effluent characteristics are not the same it varies according to industry. It contains organic, inorganic, heavy metals, color, and oil & grease. The organic & inorganic substances found in suspended & dissolved form. The pollution strength of few important industries areas in the table: I have tried to give exact data, but the pollution load is not always the same, the fluctuation is always there.