Nitrificação em sistemas de lodo ativado.

Abstract

In domestic sewers, total nitrogen Kjeldahl (NTK) with concentration around 40 mg/L the 60 mg/L, this being approximately 75% in the ammoniac nitrogen form and the remain (25%) as organic nitrogen. The ammoniac nitrogen is a nutrient capable to promote eutrophication in water bodies and, therefore its launching in the environment must be controlled. The nitrification is the biological oxidation o f ammonia, having as end item the nitrate. This process requires the mediation of specific bacteria and i f it carries through in two sequential stages: nitritacao (ammonia oxidation the nitrito) and nitratacao (nitrito oxidation the nitrate). Searching to characterize kinetic of the nitrification in the two different systems of activated sludge, this study it had as objective to operate under the same operational conditions and of sizing, the systems of activated sludge Bardenpho and UCT, comparing them in the removal of nutrients and organic substance; to determine the kinetic constants: of specific growth ( p m ) and maximum specific growth ( p m ) , o f half substratum saturation ((K0 ) , dissolved oxygen; Ka , nitrogen in the ammonia form; e kn , nitrogen in the nitrito form), the constant of decline and the tax of substratum use (bn and rn , respectively) and to study the effect of pH, temperature and OD on the metabolism of the generated autotrophic sludge in systems of activated sludge. The two systems (Bardenho and UCT) had been operated with ages o f silt of 20 and 15 days. For the determination of the kinetic factors of the nitrificacao it was applied theory of activated silt proposal for van Haandel and Marais (1999) and was used it respirometria as tool. The gotten results had shown satisfactory nitrificacao in the two operated systems, reaching an effluent ammonia average below of 1 mgN/L. The respirometry revealed a tool adjusted for the determination of the kinetic constants studied ( u m a x = 0,52 d"1; bn = 0,033 d"1). It was observed that the ambient factors pH, oxygen and temperature, exert significant influence in the kinetic nitrificante, being recommended to values of pH next the 8, temperature of 35°C and band of OD above of 1 mg/L establishing the excellent conditions for the development of the nitrificacao.