Tratamento de esgotos sanitários em sistema combinado anaeróbio/aeróbio utilizando lodo como fonte endógena de carbono

Abstract

The research aimed to treat sewage through combined anaerobic/aerobic system, using primary sludge and lysed excess sludge as an endogenous carbon source for removal of nutrients, aiming to produce effluent with low concentrations of organic material and nutrients and lower production excess sludge. The experiment was conducted in three phases. In the first, were performed respirometric tests as tool to assess the biodegradability of lysed biological sludge, through by techniques of cellular lysis induced: mechanical action, thermal and acid-base reaction. In the second phase, was monitored a Sequential Batch Reactor (SBR) together with Fermentation and Hydrolysis Reactor (FHR), which received excess sludge of SBR, tritured by mechanical action and primary sludge. SBR and FHR were operated with TRC of 3.36 and 10 days respectively. The third phase consisted of an anaerobic reactor followed by Immobilized Submerged with support Medium (polyurethane synthetic sponge) Aerated Reactor (ISMAR) operated in recirculation batch system. The results obtained from the respirometric tests found that the thermal sludge showed concentration biodegradable readily material greater than the tritured sludge and treated sludge by acid-base reaction. Values of the percentages of COD solubilized varied from 1.6% to 4.2%, with an average of 2.6%. The system presented promising results for the removal of nutrients, with removal efficiency of 85%, 93% and 98% for phosphorus soluble, nitrate and nitrite, respectively. However, the final effluent was maintained with concentration average of ammonia of 27 mgN-NH , considered out of the discharge standards. The combined system, anaerobic reactor and Immobilized Submerged with support Medium Aerobic Reactor (ISMAR), removed efficiently carbonaceous material (88%), TSS (86%), SSV (90%), TKN (94%) and N-NH4 - (96%). Producing effluent with average concentrations of nitrite and nitrate, respectively of 0.19 mgN-NO2-.L-1 and 2.52 mgN-NO3-.L. After addition of primary sludge the system, this presented a better performance with efficiency of COD removal gross and filtered 95%. However, the process of phosphorus removal was considered unsatisfactory since there was sludge disposal in the ISMAR reactor. Introducing an efficiency of removing just 20% for total phosphorus and 22% for the orthophosphate.