Bioremediation

Sewage is a very complex mixture of wastes, usually dominated by fecal materials but also containing toxic chemicals that have been dumped into the disposal system by industries and home owners. Many advanced sewage-treatment technologies utilize microbial processes to both oxidize the organic matter associated with fecal wastes and to decrease the concentrations of soluble compounds or ions of metals, pesticides, and other toxic chemicals. The latter effect, decreasing the aqueous concentrations of toxic chemicals, is accomplished by a combination of chemical adsorption as well as microbial biodegradation of complex chemicals into their simpler, inorganic constituents. Microbial processes are relied upon in many sewage treatment systems including activated sludges, aerated lagoons, anaerobic digestion, trickling filters, waste stabilization ponds, composting, and disposal on land.