Greywater Treatment by UV/H2O2, Fenton and Photo-Fenton Reagents
Greywater has been identified as an important candidate for wastewater-recycling as a means of reducing freshwater consumption for non-potable purposes. Although it does not include any input from toilets and industrial wastewaters, greywater has potentially high chemical and microbial loadings which require robust treatment to ensure its safety in use.
Advanced oxidation processes (AOPs) include a wide range of technologies which, in essence, oxidise the contaminants by highly reactive oxygen-containing intermediates (eg., hydroxyl radicals). While homogeneous AOPs have been applied in wastewater treatment (with substantial focus on surfactants), there is little literature on their application to greywater. Therefore, the aim of this project is to compare three homogeneous AOPs, namely UVC/H2O2, Fenton’s and Photo-Fenton’s processes, for the reduction of chemical oxygen demand (COD) in greywater.
Greywater from shower, laundry and teeth-brushing activities was collected from the researcher’s home (COD ≈ 210 mg/L). Effects of pre-treatment such as settlement and coagulation were studied. Overnight settlement and UVC/H2O2 treatment achieved up to 86% of COD removal. When greywater was pre-treated by alum-coagulation, the required irradiation time and H2O2 dosage could be significantly reduced. Ferrous sulphate and H2O2 were used as Fenton’s reagents and their coagulative and oxidative properties were explored. Preliminary results showed that Fenton’s process did not significantly reduce the COD level, but the Photo-Fenton’s process successfully eliminated 90% of COD present in the greywater sample.