Tratamento da água residuária da lavagem de veículos por coluna de sedimentação combinado com processo oxidativo avançado

Abstract

The increase in vehicle fleet worldwide has drawn attention to the car wash system since the discharge of the effluent generated during the washing process is a source of water pollution. The wastewater can contain in its composition high concentration of organic matter, surfactants, oils, greases, solvents, heavy metals, suspended solids, among other substances. The conventional treatment process, consisting of a system of separation of water and oil and sedimentation boxes does not completely remove some substances, this wastewater being thrown into the storm drains and receiving bodies outside the standards established by CONAMA Resolution n° 430 of 2011, which may interfere with the natural processes of self-purification. In order to improve the treatment of wastewater, this work aims to evaluate the physico-chemical characteristics and investigate the effect of different dosages of polyaluminium chloride (PACl) and iron sulfate (SF) from the test in jars. Coagulation, flocculation and column sedimentation were performed using 2 g L-1 of polyaluminium chloride (PACI) followed by the Fenton process. The gross wastewater had turbidity of on average 913 NTU, COD of 1162 mg L-1 and pH 11,5. Both coagulants, PACl and SF at the 2,0 g L-1 concentration showed 99% removal and 98% turbidity, respectively. With the use of PACl it was possible to reduce the COD by 88% with SF 92% of the organic matter was removed. It was observed that under conditions of 0.5 m column height and 45 min sedimentation with 2 g L-1 of PACl, 97% turbidity, 99% color and 87% COD were removed. Then the Fenton reaction was performed using 85 mg L-1 of Fe2+ and 715 mg L-1 of H2O2, which showed 25% and 92% removal of COD and surfactant, respectively. Therefore the physical-chemical treatment of coagulation, flocculation and column sedimentation is an alternative for the treatment of the water resulting from the washing of vehicles and that the Fenton process decreases the surfactant and COD present in the wastewater. In this way, the results demonstrate that the association of the physical-chemical process with the advanced process effectively removes COD, color, turbidity and surfactant concentration, thus improving the quality of the effluent that is discarded in stormwater galleries.