“Why Wastewater?”, is the theme chosen this year for World Water Day, which takes place every year on 22 March. According to the UN (1), over 80% of the wastewater generated by society at the global level flows back into the ecosystem without being treated or reused, causing pollution in natural environments. How can the volume of wastewater released into the environment be reduced? How can its reuse be encouraged? How can it be turned into a resource for cities and regions? Samuel Martin, Division Manager of the Wastewater Treatment and Recovery unit at the CIRSEE (2) (the international water and environmental research centre), SUEZ’s Research and Expertise centre near Paris, shares his point of view.
Samuel Martin, Division Manager of the Wastewater Treatment and Recovery unit at the CIRSEE
A solution to ease the pressure on water resources
The constant and rapid growth in the world population, rampant urbanisation and climate change are all piling heavy pressure on resources. By 2050, there will be nine billion of us sharing the planet’s resources, which represents two billion more people than today.
By 2030, it is estimated that 50% of the world population will be living in areas exposed to water stress or drought. So it has become urgent for us to take a new look at how we consume and produce. We must change our behaviours, for we live in a world with limited resources. Raw materials are not inexhaustible. The solution can be summed up in two words: recycling and recovery.
Three main uses: reuse, energy recovery and recovery as fertilisers
Wastewater can be a recovered in three main ways, the first of which being the reuse of treated wastewater. Today, only 2% of the world’s wastewater is reused, mainly in agriculture and industry. Solutions do exist, but they face several obstacles: the investments needed, the perception of a risk by the population, or regulatory constraints. The reuse of wastewater is thus mainly developed in areas where water resources come under real pressure. In Spain for example, where 20% of the wastewater treated by SUEZ is currently recycled, or in Southern California, with examples like the West Basin wastewater recycling plant. Using innovative technologies – ultraviolet technology, reverse osmosis or membrane filtration – every day, this leading-edge plant produces about 150,000m3 of recycled water of five different qualities, that can be used to water parks and gardens, to replenish water tables, or to supply process water as well as water for the boilers and cooling towers in the neighbouring refineries.
The second use is the energy recovery, by producing biogas from sewage sludge through a methanisation treatment. This green gas can then be used as fuel, electricity or heat. In this respect, it is a totally renewable energy source. For instance,in Strasbourg (France), the La Wantzenau wastewater treatment plant provides biomethane to the local natural gas network.
The last use consists of transforming effluents into pellets of fertiliser for use in agriculture. This solution consists in recovering the nitrogen and the phosphorus contained in the effluents. In this respect, we have developed the Phosphogreen technology, which allows the recovery of up to 40% of the phosphorus contained in wastewater in the form of “struvite”, a fertiliser that can be marketed directly. This is a key issue, when we know that recycling could help to cover up to 20% of our domestic needs for phosphorous and that phosphate reserves are running low, resulting in higher prices.
Tomorrow’s challenges: optimising processes and stepping up the production of renewable energy
The energy sector is awash with projects that all share the same priority: reducing consumption by optimising processes and developing the production of renewable energy. The As Samra plant in Jordan is one good example. The hydraulic turbines upstream and downstream of the treatment, working in combination with gas engines fuelled with the biogas produced from the sludge digestion, generate more than 80% of the electricity consumed by the water treatment process. Research is also focusing on the development of new treatment processes that use different bacteria. For example, anammox bacteria can be used to extract nitrogen from water without using any carbon, which can then be used to produce biogas.
Finally, we are looking into the adaptation of advanced wastewater treatment technologies, applied to wastewater reuse, in order to treat new types of pollution, such as endocrine disrupters or micro-plastics. This is the case in Lausanne, Switzerland, where SUEZ has deployed a treatment process that addresses these new issues.
So there are numerous solutions that can effectively contribute to preserving water resources and protecting the environment. It remains to encourage the evolution of mind sets and regulations, for the recovery of wastewater is much more than just an alternative, but a genuine opportunity to rise to the water challenges of the 21st century.