Reusing backwash-water works swimmingly for school

For the past twelve summers, Ralph Fernandez has regularly backwashed the 12 sand filters that are essential to the maintenance of the Olympic size Water Polo pool he keeps careful watch over. Nowadays, he does so with even more satisfaction, knowing that a new add-on unit attached to the existing filtration system is helping to reclaim up to 45 000 litres of backwash-water per week – clean and ready for reuse to keep the facility at the Antonij Rupert Aquatic Centre at Paul Roos Gymnasium in Stellenbosch filled to exact standards.

Reusing cleaned backwash-water is having a major impact on the school’s green and blue footprint, and its efforts to be a centre of excellence that is conscious of the environmental sustainability of its endeavours. 

Backwashing is an essential part of the duties of swimming pool maintenance managers such as Fernandez. Pumping water in reverse through the sand-based pool filters keeps them free of films of sunscreen, skin, sand, dirt and chemical pool treatment products that collect within the sand in each filter. If not done regularly, the sand becomes too clogged with dirt and the sand filters cannot work effectively.

“The pool is used 7 days a week for Water Polo practices or matches. To keep it clean, I therefore backwash the 12 sand filters at least three times a week,” notes Fernandez.

The colour of ginger beer, backwash-water is typically too murky and mucky to recirculate and reuse as is in the pool. Because of its high chemical content, it should not be used for gardening or discarded into stormwater systems or natural streams. Chlorine and other pool chemicals can disrupt the natural pH level of soil and natural water sources if used untreated and could even kill smaller aquatic species. Pool owners must by law therefore waste backwash-water into the municipal sewage system. In the case of the Paul Roos Water Polo pool, that amounts to up to 45 000 litres of water quite literally “going down the drain” within minutes, every week for eight months per year. A lot of wastage of a scarce resource.

Three backwashes per week adds up to a loss of 180 000 litres per month during the eight peak swimming months of the year, and another 90 000 litres per month during the off-season. This results in the pool having to be topped up with almost 1.8 million litres of municipal water per year, evaporation loss excluded. 

These figures have changed significantly since the school’s Water Polo pool became a real-time research site to fine-tune the development of a South African innovation. It is set to revolutionize the way pool owners, sustainability managers and water planners think more wisely about backwash-water wastage. 

An add-on installation of the VulAmanz Backwash Water Recovery filter was designed to complement the school’s existing Water Polo pool management system at the Antonij Rupert Aquatic Centre. Since then, all backwash-water is pumped from the twelve sand-filter tanks into two 10 000 Litre outdoor storage tanks. From there it gradually drains back into the pool via the VulAmanz Backwash Water Recovery (BWR) filter. The BWR filter contains 24 filter elements made from tightly woven polyester fabric, customized to the VulAmanz specification, and made in South Africa. Cleaned, clear water flows under gravity back into the pool as free ‘top-up’ water. In the process, 100% of all backwash-water previously lost is reclaimed and reused – again and again and again.

The only task added to Fernandez’s general pool maintenance routine is that he has to brush away the muck trapped on the polyester filter elements using a tool resembling a giant bottle brush. This is done as required, but at least once every two months. The VulAmanz research team behind the system is working on an automated filter cleaning system to streamline this process even further. 

The polyester filters are produced in the semi-automated VulAmanz Filter Element factory in Stellenbosch. The filter elements are similar to those that already have proved to be effective in cleaning water to drinking quality standards as part of the VulAmanz point-of-use water filter system. If the membrane is not punctured by accident or deliberately, the robust filter elements have a lifespan of at least 5 years, and do not have to be replaced at all.

The idea behind the BWR filter technology and application was born when Prof Lingam Pillay, the brainchild of VulAmanz, was challenged by one of his gurus in water innovation to help save water using the same technology that has proven successful in the VulAmanz Rural Water Filter for drinking water. The rest is history.

The school managers realize that municipal water is relatively cheap in South Africa, but that topping up the pool using reclaimed water still translates into savings on the school’s utility bill – and overall budget. Furthermore, they are proud of the way that the school lives up to the motto of “every drop counts”. It is answering the Western Cape government’s call to citizenry to reduce water consumption, to use water efficiently, to minimise water waste and to augment water supplies. Using the VulAmanz Backwash Water Recovery filter ticks all these boxes.

Fernandez’ diligence in helping with the research project will hopefully pay itself forward and keep more municipal facilities and school swimming pools open, should a natural disaster such as the 2018/2019 Western Cape drought strike again. Because of severe water restrictions, many municipal, school, and private swimming pools were forced to close. This put an end to training for swimmers and left many learners and adults with no respite from the heat, and a healthy and important pastime to keep children off the street.

Fernandez knows that each litre of drinking quality water saved is not only about the better management of large swimming pools, but about water resilience. It adds up to money saved on the upkeep and supply of municipal water purification systems, sewage systems, storage facilities and reservoirs too. Each reclaimed litre translates into monetary and infrastructure savings to municipalities, and to the environment at large by reducing the volume of polluted water draining away. 

He has heard experts warn that yet another severe drought occurring is not a matter of “if”, but “when”. Hopefully next time the more than 125 swimming pools at schools, gyms and municipal recreational areas in the Greater Cape will be kept open – without the need of having to use potable water, which comes at a premium in times of drought or infrastructure failure. 

If these pools were to be fitted with a VulAmanz Backwash Water Recovery filter system, an average of up to 0.5 million litres of water could be saved per pool annually – the equivalent of enough drinking water for 230 families per year. If installed at 50 pools, 25 million litres of water could be saved per year. This amounts to recovered water worth R75 million, calculated at supermarket prices of R15 per 5 litres of bottled drinking water, or R0.625 million per year of municipal water at R25 per 1000 litres.