Simultaneous nitrification and denitrification using immobilized microorganisms

Simultaneous nitrification and denitrification in moving bed bioreactor and other biological systems

Moving bed bioreactor (MBBR), used for treatment of municipal and industrial wastewater, is a completely mixed attached growth type system that involves microorganisms which grow as biofilm on the surface of the suspended carriers within the reactor. If the biofilm is thick enough, dissolved oxygen in the reactor would not diffuse into deeper strata and thus anoxic/anaerobic condition develops in those regions facilitating growth of heterotrophic denitrifying bacteria. Autotrophic nitrifiers colonize the outer surface of biofilm in biocarriers as usual. Thus, development of aerobic nitrifying and anoxic denitrifying microorganisms facilitates nitrification and denitrification simultaneously within different zones of the same biofilm. The present paper summarizes the feasibility of nitrogen removal in MBBR systems via autotrophic nitrification followed by heterotrophic denitrification, including various aspects of simultaneous nitrification and denitrification (SND) process in other biofilm units as well. Apart from that, the areas for further investigation are briefly narrated from studies conducted earlier.

Nitrogen removal by tubular gel containing Nitrosomonas europaea and Paracoccus denitrificans

A new bioreactor for the removal of nitrogen from wastewater is described which consists of a tubular polymeric gel containing Nitrosomonas europaea and Paracoccus denitrificans. The outer surface of the tube is in aerobic contact with wastewater containing ammonia, while the inside of the tube is in anaerobic contact with ethanol flowing through the tube. N. europaea oxidizes ammonia to nitrite in the gel, and then P. denitrificans reduces the nitrite to nitrogen gas in the same gel. This concept would be effective for simplifying nitrogen removal systems requiring aerobic and anaerobic operations.