Abstract

The research study was carried out in Moshi-Mabogini Tanzania to manage municipal wastewater using horizontal subsurface flow constructed wetland (HSSFCW) to obtain a standard outlet for reuse in aquaculture and agriculture. The aim of the study was to control environmental pollution and human toxicity emanating from heavy metals in order to reuse the safe resources. The grab wastewater samples were collected three times a week seasonally in one year from March 2010 to February, 2011. Fecal coliforms were measured in laboratories using standard methods of water and wastewater treatment (APHA, 2005). Heavy metals Cd, Cr, Cu, Pb, and Zn were analyzed in wastewater by an atomic adsorption spectrometry for evaluation of potential toxicological effects in fish. Temperature, DO, and pH were measured in situ using spectrophotometer (model 156, 2001). Heavy metals analyzed in wastewater were higher than the WHO (2006) and TBS (2005) standards as shown: the Cu mean concentration was 12.56 ± 0.18 mg/L with a factor of six times more than permissible limits of 2.0 mg/L, while Pb 15.03 ± 3.47 mg/L was 150 times more, and Cd 1.68 ± 0.54 mg/L was about 16.8 times more than the standards of 0.1 mg/L for both Cd and Pb. The values of Zn and Cr were not significant (0.11 ± 0.12 and 0.26 ± 0.18 mg/L), respectively. Thus, it is dangerous to eat fish with high concentrations of Cd, Pb, and Cu found in water. The linear regression of Cu, Pb, and Cd showed a decreased trend of the concentration from the sampling points S1–S4 with (R ² = 0.97, 0.93, and 0.91), respectively, showing significant levels in toxic heavy metals removal effectiveness by the HSSFCW. It is recommended to treat the wastewater more to remove the free heavy metals before going to the fish pond. More studies should focus on heavy metal concentrations in the sediments and the biotic components in the agricultural products to safeguard human health and other end users.