Assessment of Sewage Application in Southeastern Nigeria

Abstract

The impact of sewage sludge and effluent on soil and underground water after about 40 years of application was evaluated in this study, with a particular focus on selected soil chemical properties, some trace element (Zn, Cu) and heavy metal (Pb and Cd) accumulation, mobility in the soil profile and possible contamination of the underground water. The chemical properties of the soil studied included pH, exchangeable cations and acidity, cation exchange capacity (CEC), available P, organic matter and total N. Long-term disposal of sewage sludge and effluents on the soils significantly (P < 0.001) increased the exchangeable bases, exchangeable acidity, available P, soil organic matter, total N and CEC, but significantly lowered the pH of the soils. The fertility status of the sewage-treated soil was thus enhanced. The study also showed that both trace elements and heavy metals were significantly (P ≤ 0.05) higher in the sewage-amended soils than in the unamended soils. The accumulation of the trace and heavy metals in the former implies that the agricultural utilization of the sewage sludge and effluent should be done with care. The study showed no obvious adverse impact of the sewage sludge and effluent on underground water quality, but contamination by Pb is possible in the future.