Nitrogen removal reactor using packed gel envelopes containing Nitrosomonas europaea and Paracoccus denitrificans

Packed gel envelopes were constructed as simple, compact reactors for remov ing nitrogen from wastewater. Each packed gel envelope consisted of two pla te gels with a spacer in between. Nitrosomonas europaea and Paracoccus deni trificans were co-immobilized in the plate gels, and ethanol, serving as an electron donor for denitrification, was injected into the internal spaces of the envelopes. The external surfaces of the envelopes were in contact wi th ammonia-containing wastewater; the N. europaea present in the gels oxidi zed the ammonia to nitrite aerobically. On the other hand, the internal sur faces of the envelopes were in contact with the ethanol solution, which P. denitrificans used to reduce the nitrite to nitrogen gas anaerobically. In this way, the reactor using the packed gel envelopes removed ammonia from w astewater in a single step. When artificial wastewater containing 200 mg-N/ L was treated using the reactor using eight envelopes, the ammonia was remo ved by the reactor without accumulating nitrite or ethanol. This simple sys tem exhibited high rates of nitrification (ammonia to nitrite; 1.9 kg-N/day for 1m(3) of reader volume) and nitrogen removal (ammonia to nitrogen gas; 1.6 kg-N/day). It is presumed that these high rates were achieved as a con sequence of cooperation between the N, europaea and P. denitrificans presen t in the gels and the efficient uptake and exhaust of gases leading to the smooth conversion of ammonia to nitrogen gas. (C) 2000 John Wiley & Sons, I nc.