CHEMICAL INTERACTIONS TO CLEANUP HIGHLY POLLUTED AUTOMOBILE SERVICE STATION WASTEWATER BY BIOADSORPTION-COAGULATION-FLOCCULATION

The present study addresses an ecofriendly solution to treat automobile service stations effluents with high concentrations of oily substances, surfactants, organic matter and heavy metals. Bioadsorption using sawdust from pine trees, sugar cane bagasse and coconut coir without any chemical modification removed colloidal contamination up to 70%. Polyaluminium chloride, ferric chloride and polyacrylamide were applied to remove dissolved and colloidal pollutants under saline conditions without change of initial pH. Both bioadsorption and coagulation-flocculation removed up to 97.8% of BOD, COD, surfactants and heavy metals at a saline concentration of 1.5% NaCl. The increase of ionic strength promoted a high sludge index and a representative cost saving in chemicals consumption of almost 70%. High levels of pollution removal with the minimal use of chemicals is herein presented.