Remoção de nitratos de água de drenagem agrícola em biorreator com suporte de sabugo de milho e espuma de poliuretano

Abstract

This work aimed to evaluate the efficiency of nitrate removal in fixed bed bioreactors composed of corn cob and polyurethane foam (Mini Biobobs®).Two bench scale reactors were used: bioreactor 1, filled with pieces of corn cob, and bioreactor 2, with pieces of corn cob and Mini Biobobs®. The reactors were fed with agricultural drainage water enriched with sodium nitrate at a concentration of 20 mg L-1. The removal of nitrate was evaluated at different hydraulic retention time (HRT), from 4 to 0.67 days, and an estimate was made using the Most Probable Number (MPN) method of denitrifying bacteria present in the reactors at the highest and lowest HRT. The removal of nitrate was observed in all tests studied in the two reactors. The best nitrate removal averages occurred in the trials with the highest HRTs. In reactor 1, in the trial of 1 day HRT, the nitrate removal efficiency was 81.99%, the average of nitrate and nitrite in the inffluent was 3.95 mg L-1 and 0.02 mg L-1 respectively, in the reactor 2 in trial 2 (2 day HRT) the average of nitrate and nitrite was 1.66 mg L-1 and 0.02 mg L-1 respectively, and the nitrate removal efficiency was 92.32%. The lowest removal rates occurred in trial 6, for reactor 1 the nitrate removal was 42.90%, and for reactor 2 it was 48.90%. The temperature, pH and alkalinity values remained within the optimal standards for the development of denitrifying bacteria. In the analysis of the MPN of denitrifying bacteria, results showed that there was the presence of these bacteria in the biomass of the two reactors, proving that denitrification occurred in this system. In the denitrification system studied, nitrate removal rates above 70% were obtained in both reactors. It can be concluded that the studied denitrification system can effectively remove nitrate from drainage water.