Analysis of the potential of dumpsite leachates towards circular economy: a case of Pugu dumpsite in Dar es Salaam, Tanzania

Abstract Background There is a challenge with employing dumpsites as waste disposal methods due to the formation of leachates. These leachates may include dangerous chemicals that may harm human health and the ecosystem. Despite the drawbacks of leachates, it contains precious minerals that can be retrieved and used to restore soil fertility for agricultural activities to contribute to the circular economy. Results The chemical composition of leachates from the Pugu dumpsite was assessed to explore their potential in agricultural application. Leachates were alkaline with a pH of 8.88 ± 0.98. The concentrations of NH4-N and PO4-P were 960.80 ± 610.44 and 431.60 ± 209.65 mg/L, respectively. The concentrations of minerals determined were Mg (33.73 ± 9.73), Na (485.70 ± 51.47), Ca (254.66 ± 6.04), and K (113.67 ± 8.53). The concentrations of heavy metals determined were Cd (0.03 ± 0.01), Cu (0.33 ± 0.09), Zn (0.32 ± 0.04), Cr (0.03 ± 0.01), Fe (2.63 ± 0.64), Ni (0.13 ± 0.03), and Pb (0.94 ± 0.06) mg/L. The concentrations of Cd, Cu, Zn, Cr, Fe, and Ni in the leachates under study, with the exception of Pb, were within the Tanzania Bureau of Standards (TBS)-established allowable limits for wastewater from cities and industries. Conclusions The study evaluated the chemical composition of leachate from the Pugu dumpsite to explore its potential in agricultural applications. The results showed that the leachates were alkaline with a pH of 8.88 ± 0.88, with concentrations of NH4-N and PO4-P exceeding the allowable limit for municipal and industrial wastewater effluents. Concentrations of minerals such as Mg, Na, Ca, and K were within limits set by the Tanzania Bureau of Standards (TBS) for city and industrial wastewater. However, the concentrations of PO4-P and NH4-N exceeded the permissible limit of TBS, which could have adverse effects on the ecosystem. The study proposes a subtle method to recover plant nutrients from leachate, thus contributing to the circular economy.