Águas residuárias de abatedouros e frigoríficos de Minas Gerais: avaliação das suas caracteristicas, tratamento e do seu potencial biotecnológico

Abstract

The state of Minas Gerais is one of the largest producers of animal protein in Brazil. Slaughterhouse activities generate highly polluting wastewater. The work consists of a survey of the characteristics and methods of treating wastewater from slaughterhouses in the state of Minas Gerais. The raw wastewater showed a high concentration of organic matter, with maximum values around 30,000 mg.L-1 for COD and 16,000 mg.L-1 for BOD5. For most raw wastewater, the BOD5/COD ratio was above 0.4, inferring that at least 40% of its organic matter is biodegradable. Unlike nitrogen, the amount of phosphorus required for biological treatment, whether aerobic or anaerobic, in some wastewaters was below ideal. In general, the treated wastewater was in accordance with state legislation when considering COD and BOD5 removals. Regarding the processes involved in removing pollutantss, it was found that wastewater treatment plants (WWTPs) use some type of pre-treatment (screens, grease traps) to remove coarse solids and fatty material, commonly followed by biological processes, in most of them anaerobic and/or aerated (or facultative) lagoons. However, the lack of an aerobic process at the end of the treatment of some WWTPs, in addition to a system that allows better removal of biological flocs, may be the cause of values above those allowed for N-NH4 and TSS. Fertigation has shown promise for the disposal of treated wastewater, however the presence of Escherichia coli must be monitored for this agricultural practice. Regarding alternative treatment technologies, most of them have met the most evaluated parameter in studies, the DQO. However, such technologies have limitations that must be overcome in order to be implemented. The accumulation of algal biomass was also verified in some alternative treatments, from which biotechnological products can be obtained, in addition to biosurfactants that can be produced from floated fat.