Operation of an integrated algae pond system for the treatment of municipal sewage: a South African case study

Integrated algae pond systems (IAPS) combine the use of anaerobic and aerobic bioprocesses to effect sewage treatment. In the present work, the performance of IAPS was evaluated to determine the efficiency of this technology for treatment of municipal sewage under South African conditions. Composite samples were analysed over an 8 month period before and after tertiary treatment. Spectrophotometric assays indicated that the treated water from this IAPS was compliant with the discharge limits for phosphate-P, ammonium-N and nitrate/nitrite-N, and mean values were: 5.3, 2.9 and 12.4 mg L⁻¹, respectively. Chemical oxygen demand (COD), however, fluctuated significantly and was dependent on full function of the IAPS. Mean COD of the final treated water was 72.2 mg L⁻¹. Although these results suggest that the treated water discharged from this IAPS operating under South African conditions meets the standard for discharge, mean total suspended solids (TSS) was routinely above the limit at 34.5 ± 13 mg L⁻¹ and faecal coliforms were higher than expected. Tertiary treatment using a maturation pond series (MPS), slow sand filtration (SSF), or a controlled rock filter (CRF) ensured that the final treated water from the IAPS was of a quality suitable for discharge to the environment with CRF > SSF > MPS.