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.

In this work, Ag–ZnO nanocomposites were prepared by a green synthesis route using aqueous leaf extract of Tetradenia riperia and investigated for antibacterial activity against Escherichia coli and Staphylococcus aureus. To optimize the synthesis of the Ag–ZnO, the effects of precursor concentrations, pH, and temperatures were studied. The Ag–ZnO nanocomposites were characterized by XRD, ATR-FTIR, FESEM, and TEM. Results show that the concentration of 8% Ag, the temperature of 80 °C, and a pH of 7–8 were optimal for the synthesis of Ag–ZnO nanocomposites. The XRD analysis showed the decrease in particle size of Ag–ZnO from 23.6 to 14.8 nm with an increase in Ag concentrations, which was further supported by FESEM analysis. TEM image of 8% Ag provides more information on the coexistence of Ag on ZnO where an average particle size of 14.8 nm was determined. The ATR-FTIR analysis confirmed the presence of phenolic compounds, which work as reducing and stabilizing agents. The antimicrobial activity results show that Ag–ZnO nanocomposite demonstrated a higher antimicrobial potency on E. coli than on S. aureus. Therefore, Tetradenia riperia leaf extract is a viable route for the synthesis of Ag–ZnO nanocomposites to be used for various applications, including water disinfection.

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