Performance of constructed wetland integrated with sand filters for treating high turbid water for drinking

The feasibility of constructed wetland integrated with sand filters (CW-SFs) for treating high turbid water for drinking was investigated. Turbid water of >1,000 NTU from Nadosaito dam in Monduli District, Tanzania was used. Along with turbidity; faecal coliform (FC), chemical oxygen demand (COD), total suspended solids (TSS) and nitrate removal were investigated. Furthermore, determination of optimal retention time for pollutants removal to acceptable levels was assessed at retention times of 0.5 to 5 days. Horizontal subsurface flow constructed wetland (HSSFCW) was used as pretreatment stage prior to biosand or slow sand filters. Results showed that HSSFCW produced effluent turbidity of <10–50 NTU at retention time of 3 days. Moreover, integrated CW-BSF needed a total retention time of 5 days to produce effluent of turbidity (0 NTU), FC (0 CFU/100 ml), COD (6.25 mg/L), TSS (0.5 mg/L) and nitrate (4.2 mg/L) whereas, CW-SSF needed 7 days to produce effluent of turbidity (0.6 NTU), FC (0 CFU/100 ml), COD (6.5 mg/L), TSS (1 mg/L) and nitrate (1.79 mg/L), which met drinking water standards of Tanzania Bureau of Standards (TBS) and World Health Organization (WHO). CW-BSF showed better performance than CW-SSF therefore, its application can enhance the availability of potable water in Tanzania rural communities.