Wastewater reuse means taking water that is otherwise treated as a waste product and finding a use for it, reducing the amount of water taken from the freshwater supply. For most industrial processes, this wastewater must be reprocessed on site so that it is pure and free from all contaminants.
Evides Industriewater is a company that provides water solutions for industry. UK and Ireland business manager Colin Robinson says: “We take tap water, river water or wastewater and turn it into pure water, demineralised water, or cooling water. We might even take wastewater and turn it into river water that can be discharged back into the environment.”
Around 90% of Evides’ core business is in the petrochemical industry, but it also has customers in food and beverage and non-petrochemical power.
Robinson says that it is physically impossible to get to 100% water reuse, or a closed loop, because there will always be some waste. This means there will always be a need to take in water. The question is: Where does this water come from?
“We look externally at other sources of wastewater nearby that we can connect the site up to, Robinson explains. “For example, we could connect a site to a public sewage treatment works where residential wastewater is treated and usually put back in a river. Instead, that can come on-site, get cleaned up further and become a replacement for tap water.”
ENVIRONMENTAL BALANCE
Careful water management is crucial when extracting water from rivers due to its impact on the natural water cycle. The ideal approach is to withdraw water from the river for use, treat it, and then return it to the river. Overusing water without replenishing it can deplete the river, affecting downstream businesses and residents who rely on it. Additionally, droughts can further exacerbate river levels. Large-scale wastewater treatment works, usually located near coasts or estuaries, are less affected by this environmental balancing issue.
Robinson adds: “One of the great things about sewage treatment works is that people flush the toilet the same number of times a day regardless of drought. So, the flows through sewage treatment works are fairly constant even when river flows fluctuate, which is good for an industrial site, because there’s always a constant flow of water.”
Water reuse systems are custom-made, since each process and water type require specific treatment methods. The output of this treatment is demineralised water, containing only hydrogen and oxygen. Evides primarily supplies this demineralised water for steam boilers used in petrochemical refinery processes. (Nondemineralised water, particularly wastewater with organics and bacteria, can lead to biofouling).
Robinson explains that designing a new system needs at least a year’s worth of data, and samples of the wastewater. “There are lots of complexities you can only really understand by getting on site and measuring them with the customer.”
“One of the challenges of water reuse is that wastewater flow can vary in quality,” says Robinson. “If it hasn’t rained, the sewage going into a treatment works is more concentrated. You must be able to change the way you operate your water reuse treatment process daily; you’ve got to understand the chemistry and be able to react in the right way to ensure that your water quality is stable. Whereas, with a normal demineralisation process with river or tap water, you just do the same thing day in day out and it always works.”
Robinson adds that Evides’s smallest customers use around 100 tonnes of water per hour, a water treatment plant for this would measure around 50x50 metres. This is a two-to-three-year civil engineering project involving building foundations, pilings, and putting in control systems, electrical connections, and drainage connections. This is why the pilot project is so important as, if the data isn’t accurate, the £20-40 million plant may not work efficiently.
A NATURAL APPROACH
Evides has found that focusing on pre-treatment (the clearer the initial wastewater is before it goes on to demineralisation) the more reliable and efficient the process is. “We did a pilot few years ago using a wetland,” says Robinson. “We dug a hole in the ground, lined it, filled it with plastic beads, planted some reeds in it, and then poured the wastewater in at one end. It flowed down through the wetland and the biology that lives on the roots of the grasses consumed a lot of the pollutants. That helped the grass to grow, and the water was slightly cleaner then when it went in.”
He added that other than the capital cost of building it, this project didn’t cost anything, and it made the process 5-10% more efficient.
“Nature has been doing this for 3.5 billion years,” Robinson explains. “Since liquid water first formed on the Earth, it’s been recycling it, treating it, cleaning it, and reusing it in a process that takes around 4,000-10,000 years. We’re looking at how nature does that and accelerate the process, so we can avoid water being locked in the sea and remaining there for 4,000 years before it comes back to the land.”
BOX: WASTEWATER AS A RESOURCE
Grundfos, the Danish pump producer, employs cathodic electrodeposition (CED) to coat components with paint. This process uses around 5,000m³ of water annually, equivalent to 100 households’ yearly consumption. Previously, Grundfos sent the used CED process water to an on-site pre-treatment centre, which then flowed to the city’s municipal wastewater treatment facility. Now, it has implemented a comprehensive wastewater treatment and recycling system. The water goes through a tripartite filtration system, followed by reverse osmosis, and is then returned to the CED tanks. With this system, Grundfos recycles 80% of the process water back to the treatment baths, while the remaining 20% is either solid matter or used to flush the filters. Currently running at half capacity, the closed water circuit is expected to eventually treat 10,000m³ of water annually.
BOX: CLEANING CARBON FROM WASTEWATER
A government-funded collaboration between climate tech company Levidian and water service provider United Utilities aims to use Levidian’s LOOP technology to decarbonise biogas generated during wastewater treatment. The initial LOOP100 demonstrator can process approximately 15m³ of biogas per hour and serves as a foundation for larger installations, enabling sustainable hydrogen production from biogas.