Towards a generic solution to onsite wastewater treatment

Abstract

Decentralized wastewater treatment, specifically onsite treatment, is fundamental to recent wastewater management paradigms. However, onsite solutions often produce inadequate effluent quality for reuse and are ineffective in removing organic micropollutants (OMPs). This study suggests a multistep onsite system for treating wastewater in varying conditions. The system comprises biological treatment in a recirculating vertical-flow bioreactor (RVFB) followed by ozonation and ultrafiltration. The system was constructed on a farm in the Israeli Negev desert and tested year-round for its effluent quality and removal of two model OMPs. Additionally, laboratory-scale experiments were conducted to understand the field data. The system has demonstrated stable performance over varying climate conditions and wastewater qualities during one year of operation. The RVFB reduced the total suspended solid (TSS) concentration by up to 96 %, the dissolved organic carbon by up to 88 %, and the biodegradable OMP, Ibuprofen, by approximately 82 %. Ozonation had limited impact on effluent quality, most likely due to low ozone concentrations, but interestingly efficiently reduced Carbamazepine, a recalcitrant OMP, by around 87 %. Additionally, the laboratory experiments using the farm's wastewater demonstrated the ozone's potential efficiency in improving effluent quality. The final membrane filtration treatment step fully removed the residual TSS and E. coli, achieving effluent quality that meets the standards for wastewater reuse. The membrane exhibited stable performance over one month without chemical cleaning, probably due to the pre-ozonation step. Overall, this study highlights the potential of the suggested system to effectively treat diverse wastewater types and produce high-quality effluent suitable for reuse.