CHLORINE DISINFECTION OF GREY WATER FOR REUSE: EFFECT OF PARTICULATES AND ORGANICS

Adequate disinfection of grey water prior to reuse is important to prevent the potential transmission of disease-causing microorganisms. Chlorine is a widely utilised disinfectant and as such is the leading contender for disinfection of water intended for reuse. However, organic and particulate matter in grey water limit the efficacy of chlorine disinfection. This study examined the impact of organics and particulates on chlorine disinfection of grey water. Increased organic concentration of grey water was found to have no protective effect for total coliforms provided a free chlorine residual was maintained. A protective effect from particles in grey water was observed and disinfection efficacy decreased with increasing particle size. Blending to extract particle associated coliforms (PACs) following chlorine disinfection revealed that up to 90% of total coliforms in chlorinated grey water are particle associated and remain undetected by standard enumeration techniques. It is recommended that grey water treatment ensures good suspended solids removal to ensure removal of PACs and allow effective chlorine disinfection of treated grey water effluents.