Constructed wetland technology for the treatment and reuse of urban household greywater under conditions of Africa's Sahel region

Three pilot systems of a constructed wetland were assessed to advance the urban reuse of greywater for household gardening in areas of the world representative of Africa's Sahel (one unplanted and two planted with local species, namely Andropogon gayanus and Chrysopogon zizanioides). Principal component analysis showed planted systems provided higher removal efficiencies than the unplanted system and A. gayanus performed better for treating most water quality parameters. As expected, removal efficiencies for suspended solids (SS) and chemical oxygen demand (COD) were greater than 90% in all filters. The removal of 5-day biochemical oxygen demand (BOD5) was, however, significantly greater in the filter planted with A. gayanus than in the unplanted control. For parameter valuables such as plant nutrients (NO3-, NO2-, NH4+, and PO43-), the removal in the planted filters was significantly higher than in the unplanted filter (>90% versus 73-78%). The reduction of fecal coliforms was significantly greater in the two planted systems and exceeded 2.5 log(10) removal. However, no significant difference was observed between the planted and unplanted systems for Escherichia coli and enterococci. Analysis of the microbial water quality characteristics showed the concentration of fecal microbial indicators would achieve WHO guidelines for restricted irrigation with retention of some embedded nutrients; thus, reducing pressures on areas experiencing climate variability, water scarcity, and land degradation.