Ammonia nitrogen:
This is derived from ammonium compounds and organic compounds in wastewater by aerobic or anaerobic digestion.
Un-ionized ammonia is toxic to fish life. Free ammonia, in concentration above about 0.2 mg/l can cause fatalities to fish. Ammonia toxicity is not a problem in receiving waters with pH below 8.0. This can be estimated by distillation of wastewater at pH above 9. The ammonia liberated is neutralized in sulfuric acid. The excess sulfuric acid is back titrated with alkali. The estimation of ammonia can be done by any other methods like nesslerization or digestion.
Nitrate nitrogen:
Nitrate nitrogen in drinking water with high nitrate content often causes methemoglobinemia (blue-baby disease) in infants. The maximum concentration should not be allowed to exceed 45 mg/l. Nitrate is reduced to nitrite in digestive system which, in turn, attacks the hemoglobin in infants resulting in methemoglobinemia. Nitrate nitrogen can be estimated by measuring the optical density at 220 nm and 275 nm in spectrophotometer.
Nitrite
Nitrite can also interact with amine chemically or enzymatically to form nitrosoamines which are carcinogens. This is measured by colorimetric determination using sulfanilamide.
Sulfate
Sulfate is one of the major anions occurring in natural waters. Sulfates form hard scales in boilers and heat exchangers. Sulfate assumes significance in water and wastewater, as it is associated with odor and sewer-corrosion problems resulting from the reduction of sulfate into hydrogen sulfide under anaerobic conditions. Sulfate in water or wastewater can be estimated by precipitation with barium chloride, acidified with hydrochloric acid.
Phosphates
Most of the synthetic detergents designed for the household applications contain large amounts of polyphosphates as builders. Many of them contain 12-13% phosphorous or over 50% poly-phosphates. The organisms involved in the biological processes of wastewater treatment require phosphorous for reproduction and synthesis of new cellular material. Phosphorous in wastewater causes eutrophication, which affects transportation in sea/lakes.
The presence of phosphorous in wastewater needs to be controlled before it is discharged into the receiving water bodies. Phosphorous present in wastewater can be estimated through colorimetric technique, by adding acidified ammonium molybdate solution to form a molybdophosphate complex.
Nutrients
Wastewater often contains large amounts of the nutrients like nitrogen and phosphorus in the form of nitrate and phosphate, which promote plant growth. In severe cases, excessive nutrients in receiving waters cause algae and other plants to grow quickly depleting oxygen in the water. Deprived of oxygen, fishes and other aquatic organisms die, emitting foul odors.
Nutrients from wastewater have also been linked to ocean “red tides” that poison fishes and cause illness in humans.
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