Cheese wastewater treatment by acid and basic precipitation: application of H2SO4, HNO3, HCl, Ca(OH)2 and NaOH

The performance of five innovative chemical precipitation processes (H2SO4, HNO3, HCl, Ca(OH)(2) and NaOH) for the pretreatment of cheese wastewater was investigated. For acid precipitation, a linear relationship between pH of the effluent and precipitation pH was found. High conductivity values were obtained when applying extreme pH conditions in acid precipitation. Alkalinity in the form of bicarbonates occurred at operating pH conditions of 3.0 and 4.0. H2SO4, HNO3 and HCl were not able to effectively reduce organic matter. However, acid precipitation was revealed to be an appropriate process to reduce total phosphorus (up to 57.0 %), turbidity (up to 90.3 %) and total phenols (up to 49.9 %). For basic precipitation (Ca(OH)(2) and NaOH), high pH and conductivity values in the effluent were obtained when applying extreme conditions (pH 12 and 13). In general, Ca(OH)(2) and NaOH processes presented alkalinity in the form of bicarbonates. These processes showed not only a reduction of chemical oxygen demand (COD) (up to 43.7 %) and total phosphorus (up to 95.6 %) but also an elimination of turbidity (up to 98.9 %) and total phenols (up to 65.5 %). These acid and basic precipitation processes can be effective processes for the cheese whey wastewater pretreatment. Despite the rates of removal, the obtained effluents need the application of a post-treatment, such as a biological or chemical process.