Nitrate-nitrogen promotes excessive aquatic plant growth and may become elevated downstream of wastewater treatment plants or following storm events. The nitrates inactivate hemoglobin and into methemoglobin and in this form is unable to transport oxygen in the body. TKN is the combination of ammonia and organic nitrogen. Organic nitrogen includes such materials as proteins, peptides, nucleic acids, urea and numerous synthetic organic compounds. Organic nitrogen can be calculated by subtracting ammonia-nitrogen from total Kjeldahl nitrogen.
Orthophosphates are condensed and organically bound.
They are applied to agricultural and residential land as fertilizers and are carried into surface waters with storm runoff or may enter surface water in wastewater treatment plant effluent. Dissolved phosphates are incorporated by plants and passed to animals in the food web. Phosphorus reenters the environment directly by animal waste and by detritus decay. Sediments may release some of the phosphate needed by aquatic organisms and the rest may become buried. Phosphates are often found in laundry detergents.