The challenge of inefficient water management, from source to consumption, facing the South African water sector can be mitigated with the use of water and effluent engineering company Resonant Water’s internationally designed Combined Works (CW) technology, says director Marno Raath.

Resonant Water is a subsidiary of environmental engi- neering company Resonant Environmental Technologies.

The CW technology can be beneficial to the South African and African water sectors in a number of ways, says Raath, noting that the technology combines the four main processes associated with wastewater treatment, namely sedimentation, aeration, biofiltration and activated sludge methods, one process.

After preliminary mechanical treatment (to separate sus- pended solids and sands), sewage is drawn into a mixing chamber, where it is mixed with the sludge liquid coming from an aerotank settler.

The mixture of sewage and sludge is drawn from the mixing chamber with a circulation pump and sent to the biofilter sprinkling system which comprises spouting chutes with outlet pipes and reflecting disks.

The water jets are then broken on the disks, irrigating the biofilter feed, after which the liquid leaving the biofilter is collected in a tray and delivered to the aeration zone of the aerotank settler by air-stripping towers.

“This is done using potential energy and, therefore, eliminates the need for blowers and aerators as well as the use of the return- activated sludge pumpstation and the waste-activated sludge pumpstation, which leads to significant electricity savings,” he adds.

Eliminating this equipment also decreases the system’s maintenance requirements and it requires less land space to function effectively, says Resonant Group marketing and business development director Olof Vorster.

Maintenance costs are further reduced owing to the technology, which uses ultraviolet disinfection systems instead of traditional chlorine-based systems.

“The system uses 25% less electricity, requires 30% less maintenance and saves more than 60% on land space, compared with conventional water treatment works, while delivering safe and odourless water,” he adds.

Further, Resonant Water states that the CW process is consistent, irrespective of the size of the plant, which makes skills transfer and the applicability of skills between different plants easier.

“As wastewater treatment plants are traditionally customised, there is little standardisation in this industry, creating difficulties when workers from one plant need to move to another. CW addresses this,” assures Raath.

The CW process was independently investigated by Dr Chris Laubscher from engineering consultancy Sizatech Consulting Engineers. “The CW process is extremely competitive compared with most known wastewater treatment processes, especially with regard to operational costs,” he says.

Laubscher adds: “The CW process has been found to deliver effluent capable of conforming to at least the general standards set out by the National Water Act, while most of the requirements of the special standards can also be met without adapting the current process.”

The CW system was developed in an enclosed format to ensure its compatibility with the severe ambient temperature fluctuations in Russia.

The technology was designed to limit heat exchange between the system and the environment. This is necessary as wastewater treatment is a biological process that makes use of microorganisms, which function better at a stable temperature.

“We recognised that this characteristic could also be beneficial in Africa, as the continent is subject to high temperatures,” says Raath.

The enclosing of the system also leads to greater efficiency, as the pathogens that are generated by the system mainly stay inside the plant, compared with conventional treatment systems, where mixers and aerators release pathogens into the air.

Another benefit of the enclosed system is that the sanitary zone, or the radius around the plant up to which one can build, is much smaller than with conventional plants, Vorster points out.

“Currently, the sanitation zone around conventional water treatment plants is 500 m in circumference, while this technology has a European rating of 16 m,” Raath adds.

The first local plant using this technology was commissioned at a game lodge outside Modimolle, in Limpopo, in November last year. The plant treats 7 500 ℓ/d of wastewater to produce drinking water and water for irrigation purposes.

Resonant Water aims to build a 3.4-million-litre-a-day plant and a 12.5-million-litre-a-day plant within the next two years.

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