Exelys™ is currently the most effective energy enhancement methodology available to the market.

Words Veolia Service Southern Africa


Carbon footprints and escalating energy costs have led Veolia to develop an innovative solution for harnessing the power of domestic sewage – effectively turning bio-waste from our sanitation network into a valuable and environmentally-friendly fuel source.

Veolia has optimised a process known as thermo-hydrolysis, which uses temperatures of between 150 and 190 degrees Celsius as well as pressures of between 6 and 15 bar to crack the long-chain molecules typical of municipal sludge. This increases the reaction rate, making more bio-active carbon available than previously possible with more traditional technologies. Known as Exelys™, this system has already been utilised in Veolia-built and operated plants across Europe and, at current levels of advancement, helps to turn roughly 1.2 megalitres of sewage into enough energy to supply a single average home for one month.

It is estimated that in South Africa, up to 40% of a wastewater plant’s monthly expenses are directly spent on energy and this technology therefore provides a way in which municipalities can reduce this ongoing expense by up to 40% while becoming global leaders in environmental wastewater treatment at the same time. Furthermore, we believe this to be an effective way to mitigate the constant risk of power outages in our country.

Exelys™ is currently the most effective energy enhancement methodology available to the market as it increases biogas production and lowers sludge volumes considerably while simultaneously pasteurising the recovered sludge. It is also proven to help sewage works reduce C02 emissions by between 10% and 30% and returns on investment within an average of approximately nine years. The goal behind this system is to achieve energy neutrality throughout our sanitation networks. With even further innovations, we should advance to a point where we can start to feed electricity into the national grid – which is a very sustainable environmental and clean-energy solution.

In Hong Kong, the future of wastewater treatment plants is already in view. Designed by Veolia, the world’s largest sludge treatment and recovery plant was officially opened in May 2016. Far more than just an industrial plant, it is an ecological complex that is self-sufficient in water and energy and complies with the increasingly stringent environmental standards required by Hong Kong. Incinerating the sludge reduces its volume by 90% and T-Park has the capacity to generate up to 14MW of electricity during the treatment process. Electricity generated that exceeds T-Park’s energy needs is fed into the public grid. No wastewater is discharged into the sea as all the dirty water is treated and recycled through the plant. Fully energy-autonomous, it is also water self-sufficient.

In addition to generating electricity from sewage, the company also helps to optimise energy consumption throughout a sewage treatment plant. With approximately 59% of all energy used up by secondary treatment (activated sludge), Veolia’s Amonit® has become a popular solution to reduce costs and improve environmental performance.

The system continuously measures NH4+ and NO3- during treatment, and optimises nitrogen pollution elimination by means of continuous adjustment of the tank aeration intensities. This has helped plants to lower energy expenses associated with secondary treatment by only aerating the activated sludge as necessary, and not at full power at all times.

These are just some of the many technologies Veolia has developed to help tip the energy balance in favour of self-reliance. This can have numerous knock-on effects, such as lower operating costs, higher standards of water treatment and improved environmental status.

When combined with our digital optimisation tool (Hubgrade), these plants can be operated very efficiently especially under the conditions we face currently in the world. This platform ensures that operational KPIs are maintained and human error is eliminated from these operations. This also provides the customer with a tool that reports performance trends, predictive maintenance schedules, etc. in real-time to any device. Hubgrade provides the client peace of mind in terms of their plant status and performance.