Evaluation of vermifilter-treated domestic wastewater for irrigation and fertigation: opportunities and challenges for implementation

Water reclamation can help meet agricultural irrigation and nutrient demands. Due to high nutrient loads, vermifiltration is often considered a suitable treatment solution for reclamation in agriculture. However, the ability of vermifiltration to meet irrigation standards is understudied. This study explores the feasibility of reclamation through irrigation and fertigation from two full-scale vermifilters treating black- and sedimented greywater in parallel and evaluates the removal efficiencies of metallic trace elements (MTEs), E. coli , and 15 organic micropollutants (OMPs). Microplastics in the effluent were also quantified. The results show that, for reclamation in agriculture, post-treatment of the vermifilter effluent is necessary to ensure reliable and sufficient effluent quality. Despite an overall log removal of 3.67, E. coli is the most restrictive parameter, conforming to irrigation standards only after the second post-treatment step. Various constraints, due to high nitrate concentrations and salinity, would also be necessary to avoid negative environmental and agronomic impacts. For fertigation, careful planning is needed to overcome excessive and variable nitrogen loads. Despite low and variable MTE removal, the effluent quality meets irrigation standards. Average removal of OMPs is 91 ± 15 %, and the coefficient of variation is <10 % for two-thirds of the OMPs. Suggested optimizations to improve the usability in agriculture include adding a disinfection step and urine separation. Future studies should focus on the impacts of vermifilter reclamation in agriculture on soil and crops, as well as the potential for designations such as toilet flushing and street cleaning, which are likely more advantageous in urban settings. • With post-treatment, full-scale vermifiltration meets irrigation standards. • To ensure plant and soil health, nutrient loads and salinity require monitoring. • High organic micropollutant removal (>70 %) can be achieved with vermifiltration. • Low microplastic fibers in effluent suggest microplastic retention in vermifilters. • Urine separation and a disinfection post-treatment step would facilitate reclamation.