Pollutant removal capability of a constructed Melaleuca wetland receiving primary settled sewage

Abstract

This paper investigates the potential for constructed Melaleuca wetlands to provide buffering for sewage spills. The experimental site was a 4.5 m × 32 m surface flow constructed wetland planted with the tree species M. quinquenervia and M. alternifolia. Primary settled sewage was discharged into the wetland at flow rates of 300 and 600 lh−1, and the concentrations of commonly measured sewage pollutants were monitored at the inlet, middle, and outlet. The constructed wetland was an excellent sediment trap, with TSS removals of up to 98%. BOD5 and turbidity had correspondingly high removals of up to 93% and 97% respectively. At both flow rates there were was 100% reduction in faecal coliform. Nitrogen removal was dependent on the flow rate, with removals of 84% and 58% at 300 and 600 lh−1 respectively. Organic P removal was high, however the wetland system was a source of PO4-P. A conceptual model is presented for a constructed Melaleuca wetland designed for tea tree oil production, effluent polishing and emergency buffering for sewage spills.