Biological Nutrient Removal

Nitrogen and phosphorus are the principal nutrients of concern in wastewater discharges. Discharges containing nitrogen and phosphorus may accelerate the eutrophication of lakes and reservoirs and stimulate the growth of algae and rooted aquatic plants in shallow streams. Significant concentrations of nitrogen may have other adverse effects as well: depletion of dissolved oxygen in receiving waters, toxicity to aquatic life, and adverse impact on chlorine disinfection efficiency, creation of a public health hazard and wastewater that is less suitable for reuse. Nitrogen and phosphorus can be removed by physical, chemical and biological methods. Biological removal of these nutrients is described below.