9 minute read
Wastewater Treatment Technology
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Electrifying advanced oxidation processes
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A collaboration between HPNow, Evonik and Xylem is showing how sustainable treatment processes can turn wastewater into healthy drinking supplies.
Strong population growth, contamination from industrial and municipal uses, and critical regional droughts are placing great stress and challenges on global water resources and, consequently, on water purifiers. In addition to decades of proven drinking water treatment processes of surface and ground waters, there is a strong future need to recycle municipal wastewater in order to relieve the growing pressure on water resources.
For this purpose, advanced oxidation processes (AOPs) are an essential part of the treatment chain. AOPs are used to remove harmful trace substances (e.g., 1,4-Dioxane, ibuprofen) that find their way into the water cycle – for example, through the use of hygiene products, medicines, or industrial production – and that would accumulate to critical concentrations in drinking water if not removed. In addition to eliminating micropollutants, established AOPs act as an effective disinfection barrier against viruses, bacteria, and protozoa. A key component of AOPs is hydrogen peroxide (H2O2). This is converted by ozone or UV light into highly reactive, extremely shortlived hydroxyl radicals, which remove harmful trace substances in an environmentally friendly, economic, and efficient manner. On-site generation of hydrogen peroxide holds strong benefits to logistical, handling safety, and regulatory challenges and can complement today’s established hydrogen peroxide production and supply chain. Copenhagen-headquartered HPNow has developed and brought to market a technology solution, branded as HPGen, which can make use of low-concentration H2O2. Utilizing proprietary direct electrochemical synthesis, HPGen generates low-concentration H2O2 directly at the point of use, in a secure and sustainable manner.
The collaboration: HPNow, Evonik and Xylem
The innovative approach of this project is to produce hydrogen peroxide directly at the point of use, thus demonstrating the safe and reliable integration of this technology into a typical water treatment scheme using a UV AOP solution.
For this purpose, an HPGen – UV AOP facility was installed in April 2021 at Evonik’s premises in the Industrial Park in Hanau-Wolfgang,
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Complete test setup
HPGen H2O2 generator from HPNow
Spektron 6 UV-reactor from Xylem
Oxidation chart - Log reductions of the tested compounds in each experiment
Germany. The test plan focused on evaluating the removal efficacy of four emerging contaminants using this unique combination of in-situ H2O2 and UV. HPNow’s HPGen on-site H2O2 generator was integrated with Xylem’s WEDECO low-pressure UV reactor. HPGen produces hydrogen peroxide using only tap water, electricity, and oxygen from the ambient air. Xylem’s UV reactor “activates” the H2O2 into the desired hydroxyl radicals. Due to the very high reactivity of the hydroxyl radicals with micropollutants and other water constituents, the substances are oxidized within fractions of a second and no hydroxyl radicals remain in the water.
Ibuprofen, caffeine, dichlorobenzamide, and 1,4-Dioxane were spiked to the process water as target pollutants and the degradation behavior was investigated in UV-AOP using the environmentally friendly oxidant H2O2. Within this process, hydrogen peroxide decomposes into oxygen and water only.
The results
Both test series with 5 and 10 mg H2O2/l showed good to very good degradation results of all substances. In both tests, the same pattern was revealed with the strongest reduction of ibuprofen, followed by caffeine, dichlorobenzamide, and finally, 1,4-Dioxane, with the double H2O2 dose increasing the log reduction by a factor of about 1.4.
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Benefits for users
The test results support the treatment processes practiced worldwide with AOP to produce drinking water. 1,4-Dioxane is a particularly resistant micro-pollutant to oxidative wastewater and drinking water treatment processes. Consequently, good 1,4-Dioxane reduction suggests even better reduction of most other micropollutants. By combining HPNow’s decentralized HPGen hydrogen peroxide generators with UV, an advanced and environmentally friendly technology can be implemented while eliminating the need to transport, store, and handle high-concentration peroxide. Of no less importance is the positive impact on sustainability. A substantially reduced carbon footprint is achieved through the combination of highly efficient direct electrochemical generation, as well as the elimination of transportation emissions. In fact, with the use of green electricity, HPGen-UV’s carbon footprint can be reduced to near zero. This project has successfully demonstrated how combining the expertise, products, and technologies of Xylem, HPNow, and Evonik opens up sustainable opportunities in treatment processes to reuse wastewater for potable purposes and can provide people with healthy drinking water. HPNow provides hydrogen peroxide generation solutions for clients’ water treatment needs. More details at hpnow.eu For information on Evonik, visit active-oxygens.evonik.com/en/markets/ environmental-applications More details about Xylem at xylem.com/en-us/products-services/ treatment-products-systems/disinfectionand-oxidation/advanced-oxidationprocesses-aop
Four steps to follow for successful sewage AD plant design
Embarking on a new wastewater anaerobic digestion project can be daunting, but a comprehensive design phase to determine the most successful layout for your site can reduce the risk. Here are Anaergia’s four design cornerstones to set your sewage AD project on the path to success…
By Steven Cotterill
3D CAD Designer, Anaergia UK
1. Follow the process flow
Process dictates positioning; design the layout of your plant to follow the flow of material. This will enable feedstock to be conveyed over the shortest distance, reducing the likelihood of downtime from blockages and lessening equipment wear and tear. This principle can be applied across the whole site, as a smaller footprint means less land, less concrete and less labour will be required to build the plant. However, make sure to factor enough space for landscaping, planting and shielding, often required by planners.
2. Enable easy access to equipment
Ensure that forklifts, small vehicles or lifting machinery can easily access key equipment such as tanks, pumps and mixers. This will enable service engineers to quickly remove, repair and replace parts, reducing downtime. Ensure that high level equipment can be easily reached, with a sufficient platform for working, or that there is room for a cherry picker or scissor lift. If the plant has a flexible membrane roof, accommodate access for cranes, as the lifetime of the membrane is shorter than the subsidised life of UK AD plants. Finally, avoid siting equipment that will need regular maintenance within a DSEAR (Dangerous Substances and Explosive Atmospheres Regulations) zone, to reduce the time that operatives spend in this high-risk area.
3. Protect your people
The potential for explosive atmosphere increases near to pressure relief valves so avoid locating electrical equipment or instrumentation within the biogas release zone.
Establish clear personnel routes throughout the facility. Inside the reception building, provide designated walkways, as well as barriers and/or handrails to protect people from tipping vehicles and bucket loaders. Arrange process pumps and pipework away from walkways to avoid trip hazards and consider placing pipe runs and electric cables above head height on support frames to keep floors clear.
Take into account the maximum number of personnel that could be on site and ensure adequate facilities are available, including good washing facilities and toilets in both clean and dirty areas. Showers, changing rooms, laundry rooms and a sufficient-sized mess room for operatives and contractors are also essential.
Consider placing pipe runs and electric cables above head height on support frames to keep floors clear for access
Ensure service engineers can easily access key equipment to reduce downtime
4. Take care of transport
Consider vehicle movements in and out of the site, as well as within the site boundary. A traffic management plan is a good starting point, and a traffic light system may also be required. Locate the weighbridge close to the operations office to enable efficient communication between drivers and site personnel. If the weighbridge needs to be located further away, then install a serviceable automated ticketing system. Make certain there is enough vehicle turning and reversing space. If delivery vehicles are tipping into a reception building, it should be high enough to accommodate the bulk trailer at full tipping height. Include sufficient parking spaces to accommodate all staff and contractors and situate car parks close to the reception. This will ensure that new personnel can safely get to reception prior to signing in and being inducted.
Finally, ensure that the bund size is adequate (110% of the largest vessel or 25% of total tank volume, whichever is higher) and that vehicles can easily access it, whether via a ramp or flood gate. To conclude, a comprehensive site design coupled with strong 2D and 3D concept artworks can help developers to visualise their proposed sewage AD plant and correct any potential layout issues before building works commence, saving both time and money. For expert AD design and layout advice, contact ukoffice@anaergia.com
Yorkshire Water working with Anglian on sludge trade deal
Yorkshire Water is working in partnership with Anglian Water to ensure sludge can be treated efficiently. As part of the short-term partnership, sludge will be transported from Anglian’s treatment works in Great Billing to Yorkshire Water’s wastewater treatment facilities.
Yorkshire Water can accept the additional sludge after increasing its sludge treatment capacity with the introduction of the new Huddersfield anaerobic digestion plant. The trade deal makes use of this spare capacity in the market and is a first for Yorkshire Water, with the utility company also speaking with other water and sewage companies to explore further use of its internal sludge treatment expertise. Kevin Spink, bioresources waste services manager at Yorkshire Water said: “This sludge trade deal is a first for Yorkshire Water and illustrates the benefits available to our sector through collaboration with other companies. “We currently have some short-term sludge capacity available as a result of our new Huddersfield site beginning operation and we are pleased to be working with Anglian Water to deliver efficiencies. We are also working closely with others in the sector to expand trade deals and ensure sludge can be treated more efficiently.” Gary Cunliffe, bioresources trading manager for Anglian Water said: “We are pleased to be able to help Yorkshire Water maximise their treatment assets and make sludge trading a reality between us.”
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