Nitrification at low temperature for purification of used water

Abstract

Prokaryotes that can oxidize ammonia and/or nitrite are known as nitrifiers and are common in terrestrial, freshwater and marine environments. Where the temperature is commonly in the range 0-20 °C, psychrophilic strains or species can be isolated or identified using molecular techniques. It is therefore no surprise to also find psychrophilic nitrifiers in engineered systems used, for example, to remove ammonia from raw, used or wastewater or from contaminated air. In temperate regions, we have been using psychrophilic nitrifiers without most people realizing, and this chapter attempts to put their importance into context by comparing and contrasting their presence in natural and engineered systems. It concludes by describing a biofilm-based process technology, the expanded bed biofilm reactor, which the author has improved with several inventions that make this technology cost-effective for wider adoption.