In May 2022, we completed a Sustainable Asset Valuation (SAVi) for different wastewater treatment options in improving water quality in the Hartenbos estuary in South Africa. The assessment also explores opportunities for reusing water for irrigation and related impacts on nutrient loads to the estuary.
The Hartenbos estuary is located in Mossel Bay, a municipality in South Africa’s Western Cape Province, visited by around 85,000 tourists every year. Water quality issues in the estuary strain the health of the ecosystem and are expected to worsen as population and tourist numbers grow. Most sewage from the Bay is treated in a plant in Hartenbos, and the cleaned effluent flows into retention ponds before being discharged into the lagoon. Despite complying with national water quality standards, the discharged water contains high loads of nitrogen and phosphorus.
Working with stakeholders from the Western Cape Government and Mossel Bay Municipality, we co-developed this assessment of the Hartenbos estuary, comparing three different approaches to wastewater treatment: first, the installation of an improved traditional treatment plant, secondly, the installation of a hybrid NBI and grey infrastructure ‘Organica plant’, and thirdly, the construction of an artificial wetland. Each of the options has its benefits and this report highlights the importance that planners and policymakers carefully consider the benefits and trade-offs of the different options.