Effluent polishing with nature-based technologies (Zimbabwe)

Due to inefficiencies in the treatment of wastewater at Binder Abattoir, a tertiary wastewater treatment system was proposed. In this paper, experimental research methods were employed to assess the existing treatment system as well the proposed prototype. It was found out that the treatment efficiency of the existing treatment system was 5.9, 14, 11.1, 14.6, 14.6, 37.1 and 28.9% for TSS, nitrate nitrogen, phosphate phosphorus, TDS, EC, COD and BOD respectively. With these treatment efficiencies, the treatment plant failed to meet EMA SI6 effluent standards. Using the wastewater quality results obtained, a tertiary wastewater treatment system was developed which was a vertical constructed wetland which had an HRT interval of 2 days. The average planting density is 5 plants/m2, and wetland depth – 0.6m. The treatment efficiency was 98, 95.5, 99.3, 98, 94.1, and 92.9% for COD, BOD, nitrate nitrogen, phosphate phosphorus, EC and TDS respectively. The treatment efficiency however corresponded to EC, TDS, BOD, Nitrate nitrogen and phosphate phosphorus to meet the SI6 standard. COD failed to meet the SI6 standard as the final concentration exceeded 60 mg/L. The final concentration was 350 mg/L, 26.2 mg/L, 89.1 mg/L, 0.4 mg/L, 9 mg/L, 742.9 Us/cm for EC, BOD, COD, phosphate phosphorus, nitrate nitrogen and TDS, respectively.