Performance Evaluation of a Combined Anaerobic Pond and Constructed Wetland System for Wastewater Treatment in Sumbawanga Municipality, Tanzania

Abstract

Effective wastewater treatment is essential for achieving Sustainable Development Goal (SDG) 6 and 3. Despite global commitments to clean water and improved public health, access to safe sanitation remains a critical challenge in sub-Saharan Africa, including Tanzania, where inadequate wastewater management continues to pose significant threats to public health and environmental sustainability. This study evaluated the treatment performance of the combined anaerobic pond and constructed wetland system at Sumbawanga Municipal Wastewater Treatment Plant in Rukwa Region, Tanzania. A quantitative cross-sectional survey was conducted over six consecutive days, with samples collected twice daily from raw influent, anaerobic pond effluent, and constructed wetland effluent. Physical, chemical, and microbiological parameters were analyzed following Standard Methods and compared with Tanzania Bureau of Standards (TBS) effluent discharge limits (TZS 860:2019) and World Health Organization (WHO) guidelines for the safe use of wastewater. Raw influent exhibited high-organic strength characteristics, Biochemical Oxygen Demand (BOD₅) 688.8 mg/L; Chemical Oxygen Demand (COD) 1074 mg/L. Anaerobic ponds achieved substantial organic removal (BOD₅: 70.6%; COD: 71.6%) but limited nutrient reduction. The constructed wetland provided additional polishing, reducing final effluent to BOD₅ 59.4 mg/L, COD 107.7 mg/L, TSS 68.8 mg/L, and faecal coliforms to 12.5 × 10³ CFU/100 ml. However, only pH, temperature, TSS, and turbidity met both national and international discharge standards, while BOD₅ (59.4 mg/L), COD (107.7 mg/L), nitrate (173.8 mg/L), ammonia (122.3 mg/L), phosphate (29.7 mg/L), and faecal coliforms exceeded permissible limits set by TBS (TZS 860:2019) and WHO (2006). The study concludes that while the integrated system effectively reduces organic loads and suspended solids, critical performance gaps in nutrient and pathogen removal result in non-compliance with both national and international standards, establishing a technical baseline that justifies the investigation of enhanced tertiary treatment technologies.