ABSTRACT
Sewage represents the main point-source of water pollution. In the majority of the developing countries wastewater is directly discharged into the sea, lakes, wetlands, lands and rivers without receiving any treatment. This situation acquires a particular connotation in urban areas where exists the possibility of mixing the sewage with untreated industrial wastewater, which represents an important pollution load to the environment. Nitrogen in sewage usually consists of: dissolved inorganic nitrogen: ammonia nitrogen, nitrate nitrogen, dissolved organic nitrogen and particulate nitrogen. During anaerobic treatment organic compounds are converted to methane whereas the ammonium concentration increases owing to the mineralization of nitrogen containing organics such as proteins. Methanogenesis coupled to autotrophic nitrogen removal via an Anammox process is only applied for industrial wastewater and sludge reject water in sewage treatment. In this regard, the composition of industrial wastewater considerably differs from that of sewage, e.g. higher temperature, higher concentrations of nitrogen and minerals, and lower chemical oxygen demand/nitrogen ratios.
