WATER REUSE
INNOVATION USED to deter water emergencies Umgeni Water has made a commitment through its environmental sustainability policy to work on aligning with circular economy principles. By Megan Schalkwyk
E
ven though South Africa is struggling to deal with water security, it is slow to embrace a circular economy. This is because there is an incorrect perception that a circular economy requires a lot of redesign and investment. Small, deliberate changes can help drive sustainability and ultimately achieve a circular economy – without losing focus of the primary treatment goals. At Darvill Wastewater Treatment Works (WWTW), Umgeni Water is embracing the change by gradually implementing projects to make a circular economy more achievable. This includes structuring activities and processes to intentionally design out waste, and keep resources in use for longer to reduce the use of additional natural resources. Darvill WWTW A biological nutrient removal plant of the Johannesburg/three-stage Phoredox configuration, Darvill WWTW is currently being upgraded from 65 Mℓ/day to 100 Mℓ/day. With this upgrade, there are two sustainability projects: •M ethane generated by the anaerobic digesters (currently as boiler fuel) will be directed to a gas-to-electricity cogeneration plant. This project is presently in the feasibility phase. •A 2 Mℓ/day direct reuse plant is in the final stages of commission. Currently, sludge generated by the anaerobic digesters is directed to an external commercial enterprise for turf grass manufacture. The reuse plant will treat the final effluent from the WWTW to potable water quality standards. The objective of establishing the plant is to investigate the complexity, efficiency, life-cycle costs
and adaptability of the technology in the South African context. A component of this plant is also a demonstration plant to serve in educating and engaging with the public and water sector stakeholders on reuse and establish a buy-in strategy. Umgeni Water and the Water Research Commission are working together on this project and are aiming to add value at a national level. Since the analysis of contaminants of emerging concern is not readily available in South Africa, Umgeni Water is also in the process of establishing a laboratory for the monitoring of some of these constituents. Daphnia Daphnia, although often called a water flea, is actually a freshwater crustacean closely related to shrimp. Umgeni Water will be testing the ability of Daphnia to treat final effluent to a similar quality as that achieved by conventional reuse technology. Biotechnology, even if merely to polish poor-quality effluent, has lower operating costs, requires less operator intervention and consumes less energy compared to conventional technology. In collaboration with the University of Birmingham, who hold a patent for this technology, Umgeni Water will be evaluating the process at full scale. The expected gains in this type of process are reduced energy use, capital and operating costs – thus leading to lowering greenhouse gases, which will eventually contribute to climate change. Umgeni Water is testing different technologies to ensure the solutions used will promote public safety, economic viability, technical flexibility and sustainability.
Umgeni Water will be testing the ability of Daphnia to treat final effluent to a similar quality to that achieved by conventional reuse technology
At Darvill WWTW, Umgeni Water is gradually implementing projects to make a circular economy more achievable
Darvill WWTW is known for its egg-shaped digesters
Megan Schalkwyk, process engineer, Umgeni Water M A R/ A P R 2022
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