Reduction of the contamination level of cheese whey wastewater by basic precipitation

The cheese wastewater can cause serious environmental problems due to its physicochemical composition in terms of organic matter with values of about 25000 mg L-1, total solids of approximately 9000 mg L-1 and phosphorus around 3500 mg L-1. In addition, it is an effluent that has generally an acidic pH, with values between 3 and 5. Thus, this work had the purpose of applying treatment by basic precipitation to wastewater from cheese industry, in order to reduce its level of contamination. The raw cheese wastewater studied had a pH of 4,52, conductivity of 5,23 dS m(-1), chemical oxygen demand (COD) of 4917 mg L-1, phosphorus of 3411,8 mg L-1, and bicarbonates of 1339,7 mg L-1 CaCO3. The characteristic absorbances were also studied, using a 1:50 dilution factor, of low molecular weight compounds (0,639 cm(-1)), aromatic and unsaturated compounds (0,180 cm(-1)), color (0,092 cm(-1)) and cellular optical density (0,060 cm(-1)), obtained at the spectrophotometric wavelengths of 220, 254, 410 and 600 nm, respectively. The treatment consisted of the application of different dosages in order to obtain a pH increase between 6 and 13. The COD maximum removal was obtained at a pH of 11, with an efficiency of approximately 30%. This process proved to be efficient in reducing phosphorus, with elimination values of 62 - 94%, for a pH range of 8 - 13. For the characteristic absorbances, maximum removals of 48, 71, 92 and 95%, respectively, were obtained.