An integrated sewage treatment pond-wetland challenges conventional process treatment performance

This paper presents a case example showing how integrating a constructed free water surface (FWS) wetland with sewage treatment ponds system can deliver effluent quality results that rival conventional sewage treatment plants (STP). Treatment ponds, commonly used in regional and remote communities, provide low cost and operationally simple wastewater treatment. Despite the benefits of sewage ponds, many systems struggle to achieve modern environmental standards. This paper focuses on the treatment performance of a pond-wetland STP throughout the initial 15-month establishment period of a 2,000 sqm FWS wetland at Helidon Queensland, Australia. The pre-existing STP comprised a two-stage pond with chlorination. In 2013, a two-cell FWS wetland was built to achieve long-term licence compliance at the STP for biological oxygen demand (BOD), total suspended solids (TSS) and pH. Post establishment, the effluent quality out of the wetlands was BOD <10 mg/L; SS < 20 mg/L; pH of 7–8 despite the influent BOD and TSS levels being well above the values used for the system's design. This paper demonstrates that FWS wetlands can easily integrate into existing or new sewage pond systems to deliver high quality and reliable treatment outcomes.