REMOÇÃO DE MATÉRIA ORGÂNICA CARBONÁCEA E NITROGENADA DE ÁGUAS RESIDUÁRIAS DA INDÚSTRIA DE RAÇÃO ANIMAL EM REATOR DE LEITO ESTRUTURADO

Abstract

The treatment of wastewater generated in the pet food industries, characterized by the high organic carbon and nitrogen content, becomes necessary to meet the standards required by the legislation and minimize environmental impacts on water bodies. Biological treatment is an effective way to treat potentially polluting wastes from agroindustries processes. However, conventional systems for treating industrial wastewater do not allow the simultaneous removal of organic carbon and nutrients. Thus, the present study aimed to evaluate the performance of a structured bed reactor with continuous flow, for the simultaneous removal of carbon organic, expressed as Chemical Oxygen Demand (COD), and nitrogen from wastewater of a pet food industry, under conditions of intermittent aeration. The system was composed by a structured bed reactor under 30oC of temperature, and recirculation ratio of 5 times the flow. The reactor was initially operated in differents Hydraulic Retention Times (HRT) of seven, five, three and one day under continuous aeration. In such conditions were verified removal of COD above 80% and Total Nitrogen (TN) above 60%. The best results were obtained with HRT of three days (91.8% of COD removal and 93.3 % of TN). The response surface methodology was used to evaluate the effect of aeration and load of TKN (Total Kjeldahl Nitrogen) in the removal of COD and TN, with HRT fixed in 1 day. It was observed that the parameter aeration was the most important for the results. The removal of COD reached levels of 85% when the reactor was aerated on 100% of the time. Aeration also was positive for nitrification and negative for denitrification. The best responses obtained for the removal of COD and TN, nitrification and denitrification were 80.03%, 88.16%, 99.13% and 88.92%, respectively, and were obtained with 158.2 minutes of aeration in a cycle of 180 minutes, and 255.1 mg.L-1 of the TKN affluent. In view these results, it was concluded that this new system was effective in simultaneous removal of nitrogen and carbon organic matter.