Civil Engineering August 2022 | Vol 30 No 7

20 August 2022 Civil Engineering T he Kingdom of Eswatini is a landlocked country sharing its borders with South Africa and Mozambique. It is divided into four administrative regions, with its southerly region, Shiselweni, serving as the coun- try’s administrative centre. Within this region, the town of Nhlangano, formerly known as Goedgegun, serves as Eswatini’s economic hub. The town has been experiencing a phenomenal growth in domestic, institutional, industrial and commercial activities which has resulted in increased wastewater flows. Furthermore, the environmental regulations for waste- water disposal in Eswatini have become more stringent. The town’s wastewater stabilisation ponds, commissioned in 1986, could therefore no longer meet the capacity and effluent requirements. PROJECT OVERVIEW To meet the town’s growing effluent treatment requirements, the Eswatini Water Services Corporation com- missioned the 3 MLD Nhlangano Wastewater Treatment Plant (NWWTP). The plant employs a two-stage trickling filter process with anaerobic cold diges- tion to ensure that the sludge is reduced to benign substances. The works is also equipped with chemical phosphorus removal of alum, as well as multimedia and contact filtration. The filtration passes the influent through anthracite, graded sand and gravel layers, which further enhances the removal of odour, colour and suspended solids from the influent, thus enhancing conformance to the effluent require- ments. Key to meeting the requirements for effluent disposal and to mitigate prob- able disinfection by product formation is the use of ultraviolet disinfection in lieu of chlorination. Figure 1 illustrates the process flow. Owing to the proximity of residences, and in endeavour to mitigate unpleasant odour associated with wastewater Ranganai Zizhou Pr Tech Eng Project Engineer Eswatini Water Services Corporation ranganai.zizhou@ewsc.co.sz Construction of the Nhlangano Wastewater Treatment Plant The new Nhlangano Wastewater Treatment Plant will meet the growing wastewater treatment requirements of the town of Nhlangano in Eswatini. But implementing the project, which is nearing completion, was not without its challenges. Treated effluent Sludge disposal Biogas Screenings Screenings Grit Figure 1 Process flow diagram Project details Employer Eswatini Water Services Corporation Engineer Eswatini Water Services Corporation Contractor Stefanutti Stocks Eswatini Infrastructure cost R180 million Concrete volume 2 000 m 3 Steel tonnage 300 tonnes