Tratamento secundário e terciário de água residuária de micro cervejaria em reator em batelada com aeração intermitente

Abstract

The aim of this work was to evaluate the performance of a batch reactor on a bench scale, using MiniBiobobs® as media supports for biomass fixation and creation of aerobic, anoxic and anaerobic environments in the reactor. The reactor was operated with intermittent aeration, varying the aeration time (AT) and hydraulic retention time (HRT). It was evaluated the reduction of the chemical oxygen demand (COD) and total nitrogen (TN) of the wastewater generated by an artisanal brewery, the so-called microbreweries. COD removal efficiency was obtained from 42 to 92%, and total nitrogen from 21 to 86%. The best results were obtained with TDH of 20 hours, aeration/non-aeration cycle of 3h/1h, affluent with COD and TN of 2682 and 25.60 mg.L-1 , respectively. Under these conditions it was possible to obtain effluent with COD concentration of 209 mg.L-1 , NT of 2.97 mg.L-1 and nitrate 0.67 mg.L-1 . Nitrite was not identified in any of the studied conditions, both in the affluent and in the effluent. The process of ammonification and nitrification was affected by the high organic load of the effluent, which impaired the performance and development of the bacteria, being a limiting factor of the process. It was possible to obtain nitrification rates in the system of up to 86% in the best condition, in which it had a high oxygen availability and a longer reaction time, aiding in the process. In the worst condition, a nitrification rate of 27% was obtained, with a TDH of 8 hours and an aeration/non-aeration cycle of 1h/3h. Denitrification process had rates between 78 and 97%. The reaction kinetic constants (k) obtained in the best condition were 0.1774 h-1 for organic matter consumption and 0.1173 h-1 for nitrogen consumption, and were adjusted to a first-order reaction. In the other experiments it was possible to observe a decrease in the k values, which decreased as the aeration time in the system was lower, which shows that the oxygen supply positively helped the reaction rate. The correction of alkalinity in the affluent positively helped in the removal efficiencies of COD and TN. Without correction of alkalinity, the efficiency of removal of organic matter and nitrogen decreased from 92 and 86%, respectively, to 78 and 43%. The most probable number (MPN) analysis for oxidant bacteria of ammonia and nitrite and denitrifiers performed in the best operational condition showed the presence of these bacteria in the biomass of the reactor, proving the nitrogen removal by the SND system. In this way it can be concluded that the studied system is feasible to be used by breweries for the reduction of COD and TN in a single reactor.