Treatment of greywater using a non-aerated combined horizontal and vertical flow constructed wetland

Abstract

Human, animal, and plant health is universally paramount, yet the release of poorly treated wastewater into the environment poses a significant risk to all life forms. Hence the need to employ wastewater treatment technologies to curb these health risks. Due to the need to adopt sustainable wastewater treatment technologies, this study investigated the use of a non-aerated hybrid horizontal and vertical flow constructed wetland for the removal of heavy metals and microorganisms from greywater. This was done at six different hydraulic retention times. Results showed significant reductions (p < 0.05) in heavy metal (manganese, zinc, cadmium, magnesium, chromium, and iron) concentrations, with some showing compliance to Ghana's Environmental Protection Agency and the United Kingdom National Environment Regulation recommended discharge limits. Heavy metal concentrations in effluent samples ranged from as low as 0.00 ± 0.15–0.23 ± 0.06 mg/L. Furthermore, there were significant reductions in Escherichia coli and Salmonella typhi (p < 0.05), which also showed compliance to Ghana's Environmental Protection Agency effluent discharge standards. The effluents from the system at HRT 3 days showed high removal efficiency ranges of 82–90% of bacteria. It is recommended that hybrid constructed wetlands should be incorporated in the treatment of greywater.