Effect of gray water reuse on toilet flush tank bacterial and scum formation

One of the drinking water usages is flushing, e.g. toilet flush tank. Gray water is an option to prevent water loss and, on the other hand, the formation of sediment and mass inside the reserving tank has a significant impact on the performance of the flush tank and customers’ satisfaction. In this study, the condition of flush tank, in the respect of bacterial and scum formation, fed by simulated gray water was investigated. The gray water was pre-treated in a septic tank. Flush tanks made of PE, ceramic and galvanized steel sheet were used. The effect of disinfection process was studied for biomass accumulation control. The results from pH, XRF, AAS and bacterial colony count indicated that blue toilet tablet was not effective, while UV lamp effectively controlled bacterial growth. No bacterial growth was observed in the galvanized tank even without any disinfector agent. Applying UV lamp caused scum to form on the surface tank. Generally, no accumulation of suspended solids was observed in the all flush tanks (PE, ceramic and galvanized). Kitchen wastewater can be used in the toilet flush tank as an alternative for potable water.