An innovative system to use return effluent from the Cape Recife wastewater treatment works (WWTW) in Port Elizabeth, designed by local multidisciplinary engineering consultancy Afri-Coast Consulting Engineers, will significantly increase the water available for industrial and irrigation use – and, in turn, reduce demand on Port Elizabeth’s precious fresh water supply.

Return effluent is treated, purified sewage water that, instead of being released back into nature or the ocean, is returned for industrial use, irrigation and other uses, says Afri-Coast Consulting Engineers project manager Gerrie van der Merwe, noting that the water quality conforms to standards set by the Department of Water Affairs.

Van der Merwe says the firm’s professional responsibilities, in addition to construction monitoring and project management, include the physical designs of the pumpstation, rising main, balancing reservoir, gravity irrigation feeder pipeline, irrigation reticulation systems and measurement of usage.

“Cape Recife WWTW’s upgrade is currently under design. Once completed, the capacity of the treatment works will increase from a current maximum daily production of treated effluent of about 9 Mℓ/d to a daily average of 18 Mℓ/d, effectively meeting the demand for reclaimed irrigation water,” he says.

Van der Merwe notes that, currently, gardens and sports fields across the city are being irrigated with expensive potable, or drinking, water – an invaluable resource in the water-scarce Nelson Mandela Bay metropolitan area. Although borehole water is used to augment the supply of irrigation water, this has negative environmental outcomes, including lowering the water table.

“Yet in the meantime, thousands of litres of useable, treated effluent is being discharged every day through a wetland system and into the ocean, in the vicinity of the Noordhoek Lighthouse,” he laments.

Therefore, the Cape Recife return effluent scheme aims to use this currently wasted return effluent instead of the potable and borehole water used to irrigate the beachfront gardens and sports fields within economically viable reach.

The concept was initiated with the Nelson Mandela Bay municipality Parks Department and beach managers. The beachfront, Port Elizabeth’s primary tourist attraction, currently uses potable water in flower beds, but the grassed areas are not irrigated, leaving them less appealing than they could be.

Van der Merwe says a lack of funding and other priorities has slowed the project, which was initially designed and proposed by Afri-Coast in 2006 and again re-examined in 2011. However, work on the return effluent scheme is now being implemented in parallel with the expansion of the Cape Recife WWTW.

He says approval for the proposal, as well as the environmental-impact assessment, is expected to be obtained by the first half of 2016, with construction taking about one year.

“Water supply is a critical priority for the municipality and its stakeholders. There is increased demand on the available water sources owing to expansion and densification of areas within the metropolitan area.

“If all goes according to plan, returned irrigation water should be available to consumers by 2018,” he says. The beachfront, golf course, schools and Nelson Mandela Metropolitan University (NMMU) will benefit through the availability of irrigation water from return effluent at a substantially reduced price than that of potable water.

An existing return effluent scheme has been supplying the NMMU North and South Campuses and the Humewood Golf Course with irrigation water since the early 1980s. The water is extracted from the primary holding pond at the treatment works and pumped up to supply reservoirs and ponds at the university and the golf course via metered connections.

“However, the system is more than 30 years old and in very bad shape. It will eventually be abandoned and replaced with the more comprehensive and sustainable proposed Cape Recife return effluent scheme,” he says.

Provincial Impact
Port Elizabeth-based Afri-Coast is also the lead consultant for the return effluent scheme between the Fish Water Flats WWTW and the Coega industrial development zone. The firm is also the lead engineering consultancy for the multimillion-rand Nooitgedacht water treatment works project, which recently received financial input from government in its promise to provide a long-term fresh water solution for the Nelson Mandela Bay area.