Wastewater Treatment Technology

Esher sewage treatment works alongside the River Mole

The draft, which is open for public consultation until 22 September 2022, aims to ensure an ambitious, resilient and sustainable wastewater service for the future.1

The Drainage and Wastewater Management Plan 2025-2050 (DWMP) details the long-term risks to local infrastructure due to population growth and climate change. To tackle these challenges, the company has unveiled plans to encourage partnerships, which will drive more sustainable solutions with wider societal benefits.

The plan was drafted following 900 hours of interactive stakeholder engagement with Thames Water partners, including input from 550 customer households, 70 local authorities, 50 organisations (including the Environment Agency) and numerous environmental groups at a national, regional and local level.

What are the challenges facing London and the Thames Valley?

The population in London and the Thames Valley region is predicted to grow by 2.7 million by 20502, while extreme weather events resulting from climate change and the loss of ‘spongy’ surfaces and green areas which can absorb water is expected to put extra pressure on the company’s wastewater and drainage services. The need to plan effectively for the long term is essential, and this plan sets out innovative solutions required to overcome these challenges.

Thames Water and partners’ suggested approach

Nature-based infrastructure is at the centre of the proposed plan to tackle flooding, protect homes and reduce storm discharges. This includes:

providing sustainable drainage systems (SuDS) to 7,000 hectares of land in London3 (The company has previously provided sustainable solutions to flood risk areas by delivering rain-gardens, rain-collecting roofs and SuDS installations in parks and streets as well as wetland creation and river restoration)

investment in Thames Water’s sewage treatment works to increase capacity and provide more efficiencies a plan to prevent wastewater pollution; leading wider efforts to restore river health and create thriving natural environments. At the end of the public consultation, comments on the plan will be factored into the finalised plan to be published in March 2023. The finalised DWMP will inform Thames Water’s business plan for 2025-2030. Sarah Bentley, Thames Water CEO, said: “Over the next 25 years and beyond, we must be able to meet the challenges of climate change and population growth, while continuing to provide wastewater services to our customers.

“Flooding can be a devastating experience and we’re seeing more and more the pressures significant rainfall events can put on our network, so we want to take action to stop rainwater getting into the sewers in the first place, so as not needing to be sent to our sewage works for treatment. “Delivering positive outcomes for our customers, the communities we serve and the natural environment across our region is at the heart of this proposed plan and our values as a company. So, I’m excited to be sharing our collective vision for creating a more sustainable and green solutions-based approach to drainage and wastewater, while providing greater access to our sites and green spaces. “Working collaboratively with our partners will make a big difference to wastewater activities for future generations and our precious environment.”

1. The draft DWMP was created in partnership with customers, community and environment groups and regulators such as the Environment Agency,that have responsibilities for,or an interest in,drainage and wastewater services in Thames

Water’s region.

2. Figures based on Local Authority-based growth forecasts alongside population projections from the Office for National

Statistics (as assessed in 2018).

Carbarns Wastewater Treatment Works (WwTW) is located in Wishaw, to the SouthEast of Glasgow, within the Clyde River valley. The site is part of the ‘Clyde 7’ group of Scottish Water treatment facilities, serving a population of over 54,000 from Wishaw and Overtown areas. Along with the inlet works, the site has primary and secondary treatment and phosphorous removal. Treated water from the plant is discharged into the River Clyde.

The 6 mm fine inlet screens at Carbarns WwTW were failing regularly as the screen panels were plastic and very prone to breaking, particularly following storm events when flows were higher than usual and contained more debris. Scottish Water was having to stock spare panels on-site and replace them as often as every week, depending on the weather. When the inlet screens failed, a considerable amount of rag was feeding through to the primary settlement tanks, causing chokes in the sludge pumps. When the screens tripped out in storm conditions the bypass screen would blind up in minutes, not allowing enough time for standby operators to reach the site and causing flooding at a nearby property. The result was a significant amount of time and resources spent on clearing these chokes and blockages and cleaning up by the operations team. The biggest impact of this inlet issue was the financial and carbon implications. Carbarns WwTW would normally send sewage sludge directly to the Daldowie fuel plant, near Glasgow, which processes it into a renewable, low-carbon form of biomass fuel pellet. However, because of the high content of rag in the sludge caused by the inlet screen failures, it could not be sent directly to Daldowie Fuel Plant but had to be taken for further processing to Shieldhall WwTW, some 20 miles away on the other side of Glasgow. This involved up to 23 tankers a week transporting the sludge to Shieldhall for additional treatment before it could be pumped over to Daldowie. The associated costs of transporting the sludge to Shieldhall WwTW were considerable.

image013.jpgScottish Water worked with Hydro International’s UK Wastewater Services team, M&N, to evaluate the site and propose a solution. The team installed a Kuhn KHU-S Multirake Boomerang 70mm coarse screen to provide protection to the FSM escalator screens by removing the larger coarse screenings. Two FSM FRS 111 escalator screens were then fitted at 60°, providing an impressive maximum flow capacity of 770 l/s each, to provide fine screening of the sewage inflow. The screens are running in a duty standby mode, conducted automatically by the control panels which were supplied for all equipment. Each of the screens has the capacity to take the full flow to treatment, should one need to be taken offline for service, maintenance, or repair. The strong screen panels are stainless steel so able to withstand storm flows, combatting the initial issue of weak plastic-based material screens. A launder system was installed to transport rag to two Kuhn KWP-HD 400/1200 wash presses to process, wash and compact the rags. Once the new inlet works package was installed, the Primary settlement tanks and Aeration tanks were cleaned to ensure that no rag was left in the system. This was an additional cost of £106K before Daldowrie Fuel Plant could accept the sludge again. image014.jpgSimon Light, National Sales Manager for Hydro International, said, “We needed to find a high-quality effective solution for the Carbarns WwTW to prevent any further overflows, and to help reduce the high cost and carbon impact the high content of rag in the sludge was creating. Our specialist inlet works team designed and installed a robust, reliable inlet works system that combines screening, washing, transport, compaction and dewatering in a single cost-effective and sustainable standalone solution.”

Stephen Heatley, WW Operations Team Leader at Scottish Water, comments “Knowing the team for over 20 years, we were confident that they would provide a solution that works exceptionally to meet our needs. Since the project’s completion in September 2020, there has been a significant reduction in costs and carbon use now that the sludge can be transported directly to Daldowie Fuel Plant for processing. The amount of reactive time that operation staff previously needed to spend dealing with chokes and cleaning up has dramatically reduced, with a knock-on effect that morale has improved, providing more time to spend on proactive tasks.” The screens will be serviced annually and ongoing maintenance provided. More information at hydro-int.com/ukwws.

Selecting the right filter for the job will save time and prevent potentially expensive capital outlay and unnecessary running costs. A Biofilter may be ideally suited to high concentration, persistent odour removal but might be considered excessive and unsuitable for a tank which occasionally vents to atmosphere during filling. Activated Carbon Filters are best utilised to remove intermittent odours. For example, on a pumping station or sludge tank as opposed to an aeration bed.

Carbon Filters should be sized on the flow rate and odour level. For more offensive odours you would want a larger filter with longer contact time with the carbon to ensure effective removal.

The longer the air is in contact with the carbon the higher the levels of odour removal. EMCEL Filters Ltd manufacture carbon cells with loose fill carbon, utilising 60 plus grades for various applications, to allow for a greater surface area for adsorption to occur. Our unique internal honeycomb construction guarantees even filling and prevents settling. This ensures no bypass through the filter and enhances odour capture, increasing the efficiency of the filter.

Using your carbon filter in optimal conditions will help maintain the high design performance throughout its service life. EMCEL recommends controlling the inlet air to between 20-25ºC and the relative humidity to between 40 -60%. The higher the temperature, the greater the tendency for volatile odours to desorb from the carbon. The higher the humidity, the higher the risk of the carbon being subject to moisture deposition, which would hamper the adsorption of odours.

A range of composite activated carbon Tank Breather filters has been developed by EMCEL Filters to control the pollution effects of displaced air arising from tank filling or temperature effects where odorous, hazardous or toxic vapour contaminants are involved.

A number of filter unit casings, flanges and fixings are available to match the wide variety of tank breather and vent outlet configurations that exist.

Both vertical and horizontal airflows can be accommodated along with a variety of pre-filtration and weather proofing.

Contact our Technical Sales Team for information on how EMCEL can remove odour from your application and for any other Air Filtration requirements. EMCEL Filters Ltd, Blatchford Road, Horsham, West Sussex, RH13 5RA 01403 253215 | info@emcelfilters.co.uk | www.emcelfilters.co.uk

Yorkshire Water will introduce a world first for wastewater treatment when it implements new technology that cuts greenhouse gases and recycles waste material. A partnership between Yorkshire Water and CCm Technologies will see a new ammonia and phosphorus recovery process introduced at one of its wastewater treatment works.

The pioneering technology will use carbon dioxide to stabilise nitrogen and phosphate held within the waste treated at the plant and turn them into sustainable plant nutrients. The new approach, which will cut greenhouse gas emissions and reduce treatment costs to help keep customer bills low, is a world first for the wastewater sector.

Work has begun to identify the first treatment works to implement the new process and it is expected to begin operating later in the year. Nevil Muncaster, Chief Strategy and Regulation Officer commented: “Yorkshire Water’s holistic and integrated approach is critical to the sustainability of our water and wastewater services and our business.

“This is a further example of the innovative measures we, and our partners, are developing to reduce our carbon footprint and ensure we maximise the resources we have available to us. “By helping society benefit from the full value of water, we deliver a wide range of economic, environmental and social benefits for both the short and long term.” Professor Peter Hammond, CCm’s Chief Technology Officer and cofounder, commented: “This is another significant step forward that will allow our technology to demonstrate how sustainable resource use by Yorkshire Water can lock captured carbon back into the soil, allowing the water industry to play a role at the heart of carbon reduction.”

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