Influência do processo de eletrocoagulação em reator tipo UASB para remoção de fósforo em efluente sintético

Abstract

The lack of sewage treatment is a problem that affects Brazil. Sanitary sewage, for example, presents a polluting load of organic matter and nutrients such as phosphorus, whose discharge into the aquatic environment can cause eutrophication in receiving water bodies. Combined treatment systems that use anaerobic reactors, as well as combined treatments with electrocoagulation, have drawn the attention of scientists to the removal of different pollutants. In this sense, the present research aimed to evaluate the influence of electrocoagulation in an aerobic reactor of slable blanket and ascending flow (25.1 L of useful volume), called UASB-EC reactor, using iron electrodes (Fe) to remove phosphorus from synthetic effluent. To observe the reactor performance, parameters such as temperature, pH, turbidity, Chemical Oxygen Demand (WFD) and phosphate and iron concentration were investigated. The Rotational Central Composite Design (DCCR) 22 was applied to optimize reactor performance and verify the influence of independent variables electrical current density and electrolysis time in relation to the response variable – phosphate removal. The best treatment condition identified in the results of the statistical study was current density of 5.13 mA cm-2 and electrolysis time of 55 minutes. Under these conditions, the UASB-EC treatment reached an average removal of 80% phosphate. They were also monitored in optimal condition, average temperature of 20.5º C, pH 7.5, turbidity of 29.5 UNT, alkalinity of 121.6 mg CaCO3 L-1, volatile acids of 42.4 mgHAC L-1, removal of chemical oxygen demand of 82% and iron concentration of effluent and sllime of 3.3 mg L-1 and 162.8 mg kg-1, respectively. Finally, in the best operating condition, the reactor was operated with electrocoagulation continuously to verify the useful life of the electrodes and under these conditions the UASB-EC system removed 100% of phosphorus during 8 days of treatment. Thus, the positive evidence of the study suggests the applicability of the UASB-EC reactor for effluent treatment.