Nitrification-denitrification of UASB effluents highly loaded with nitrogen in an activated sludge reactor operated with short cycled aeration

A conventional activated sludge reactor operated with short cycled aeration was used for total nitrogen removal of UASB anaerobic reactor effluent con taining nitrogen (up to 1,200 mg NKT/L and organic matter (up to 2,000 mg C OD/L). Initially the reactor was fed with synthetic water to progressively introduce the UASB effluent. This favored the acclimation of the microorgan isms to the real environment. The results obtained throughout this study sh owed that initially the tested technology is feasible and can report signif icant cuts on operation and maintenance when compared to conventional activ ated sludge processes. Total nitrogen removal up to 66% was attained treati ng the effluent of an UASB process designed for treating the wastewater of a potato starch factory. Total nitrogen removal capacities ranging between 0. 1 and 0.58 kg of nitrogen per cubic metre per day are reported. Short-cy cled aeration allowed for a more efficient use of the oxygen supply for nit rification and the organic carbon content present in the wastewater for den itrification. This operating protocol has demonstrated serious advantages in terms of ope ration costs and simplicity when total nitrogen removal is wanted. Most of the existing activated sludge processes, i.e. single continuous flow reacto rs, can be updated for total nitrogen removal essentially at no cost, the i nversion (aeration control system) is rapidly returned as reduction in ener gy expenditure.