Evaluating the performance of Livingstonia wastewater stabilisation ponds and their effects on Mpopi stream in Rumphi, Malawi

Abstract

Partially treated effluent contributes to water quality degradation of water bodies in Malawi. This study was aimed at evaluating the overall performance of Livingstonia Wastewater Stabilization Ponds and their effects on Mpopi stream in Rumphi, Malawi. Representative duplicate grab samples (n = 40) were collected from five sampling points from the treatment ponds (inlet and outlet), effluent discharge point (experiment), upstream (control) and downstream in four sampling campaigns executed from October 2022 to January 2023. Physico-chemical and microbiological parameter were analyzed and then the effluent was compared with the Malawi Effluent Standards (MS 539:2013). Data was analyzed using IBM SPSS version 23. The results showed that effluent does not meet the Malawi Effluent Standard (MS 539:2013). High levels of 5-day Biochemical Oxygen Demand (40.80 mg/L), E. Coli (253 cfu/100 mL), Total Phosphorus (1.67 mg/L), Total Suspended Solids (746.00 mg/L), Turbidity (42.65 mg/L) above Malawi Standards specifications for industrial effluents tolerance limits in the effluent (20 mg/L) proved poor performance of the plant. Similarly, high levels 5-day Biochemical Oxygen Demand (3.38 mg/L), E. Coli (65.00 cfu/100 mL), Turbidity (1.65 mg/L), NO3ˉ (6.00mg/L), NH3 (2.50 mg/L), Total Dissolved Solids (26.50 mg/L), Dissolved Oxygen (5.10mg/L), temperature (26.48 oC), Total Suspended Solids (7.48 mg/L) and pH (6.25) on discharge point than upstream point in the stream, were indicative of water pollution resulting from the effluent. Also the study expressed lack of professional ponds maintenance, stream monitoring and inadequate laboratory equipment’s as factors that contribute to poor performance of the wastewater stabilization ponds. Therefore, there is a need for regular maintenance, specialized staff and adequate laboratory services for monitoring of the ponds’ performance and their effects on water quality.