Groundwater Quality Assessment at Cemeterial Area and Non-Cemeterial Area: A Case of Mwanakwerekwe and Kiembesamaki in Urban District of Unguja, Zanzibar
Raya Rashid Amour*, Abdul AJ Mohamed and Said S Bakar
ABSTRACT
This study presents a comparative analysis of groundwater quality in Mwanakwerekwe Cemetery and the non-cemeterial area of Kiembesamaki, both located in the Urban/West District of Unguja Island, Zanzibar. Groundwater is the primary source of drinking water in Unguja, Zanzibar, yet its quality is threatened by anthropogenic activities such as burial practices near residential areas where water sources are found including wells. This study assesses the physicochemical parameters of groundwater in dug wells at the cemeterial area (Mwanakwerekwe) near the Mwanakwerekwe cemetery and the noncemeterial area (Kiembesamaki). A total of 15 water samples were collected 9 from Mwanakwerekwe and 6 from Kiembe Samaki in Urban West region of Zanzibar Island. These samples were analysed for various parameters including, salinity, hardness, pH, EC, TDS, NO2-, Cl-, Ca2+, Mg2+, SO42-, Na+,K+, PO4 3- and Fe2+ through both in-situ measurements following standardized water testing protocols and laboratory analysis carried out by the Zanzibar Water Authority (ZAWA), complemented by statistical evaluation techniques. The results revealed significant variations between the two areas. Phosphate levels were notably higher in Mwanakwerekwe with a mean concentration of 50.67 mg/L compared to 21.70 mg/L in Kemba Samaki (p = 0.035). Similarly, salinity was significantly higher in Mwanakwerekwe (Mean = 0.396 psu) than in Kiembe Samaki (Mean = 0.275 psu, p = 0.024). Magnesium concentrations were also elevated in Mwanakwerekwe, with a mean of 38.83 mg/L compared to 25.91 mg/L in Kiembe Samaki, though this difference was not statistically significant (p = 0.096). Chloride levels were higher in Mwanakwerekwe (Mean = 66.96 mg/L) compared to Kiembe Samaki (Mean =47.27 mg/L), but the difference was not statistically significant (p = 0.091). Other parameters such as pH, EC, TDS, and Hardness did not show significant differences between the two areas. The pH ranged from 6.73 to 7.66 in Mwanakwerekwe and 7.13 to 7.77 in Kiembe Samaki, while EC values averaged 861.22 μS/cm in Mwanakwerekwe and 674.17 μS/cm in Kiembe Samaki. TDS concentrations averaged 560.67 mg/L in Mwanakwerekwe and 456.67 mg/L in Kiembe Samaki. Hardness values were generally higher in Kiembe Samaki (Mean = 635 mg/L) than in Mwanakwerekwe (Mean = 538.89 mg/L), but the difference was not statistically significant (p = 0.189). A strong positive correlation was observed between electrical conductivity (EC) and total dissolved solids (TDS) at M/Kwerekwe with a coefficient of determination (R²) of 0.987, indicating a near-perfect linear relationship. At K/Samaki, the correlation between EC and TDS was moderate (Figure 4b), with an R² value of 0.716. These findings suggest that both parameters are predominantly influenced by the concentration of dissolved constituents present in the water. The findings suggest that groundwater wells in Mwanakwerekwe, particularly near the cemetery, is more prone to contamination, with phosphate, salinity, and magnesium levels exceeding the World Health Organization (WHO) permissible limits. In contrast, Kiembe Samaki groundwater wells generally met these standards, posing fewer risks to human health. Based on these results, it is recommended that regular wells monitoring and mitigation strategies be implemented, particularly in areas close to cemeteries.
