Ozonation for Low-Load Greywater Treatment: A Review and Experimental Considerations for Small-Scale Systems

The effectiveness of ozone (O3) in eliminating various types of microorganisms, as well as in oxidizing a wide range of contaminants present in wastewater, and drinking water, is extensively documented in the literature, along with the required concentrations, contact times (Ct values), reaction mechanisms for different pollutants, and overall efficiency. This article presents a comprehensive review on the use of aqueous O3 for treatment and disinfection, specifically for low-contaminant domestic greywater (LGW), providing information for its integration into the design of small-scale treatment systems. Additionally, to complement the theoretical findings, experimental tests were conducted using a portable O3 generator in an operational facility treating greywater (GW) from handwashing sinks. The results confirmed that O3 concentration increases over time but decreases as the volume of water to be treated increases. Water analysis results showed significant reductions in BOD5, turbidity, and total suspended solids after treatment. Furthermore, the results demonstrated that the presence of microorganisms in LGW is minimal, as in the case of fecal coliforms, ensuring a 1 Log disinfection level in this type of system. O3, as the sole treatment and disinfection system, with an oxidation potential nearly twice that of chlorine, proved to be highly effective in small-scale treatment systems, promoting sustainable practices, water resource conservation, environmental protection, and public health.