Professor John Williams’ wastewater talk

In May 2025 ERA was lucky enough to have John Williams come and talk to us at Henry Warren Hall, Nyewood.

John is Professor of Environmental Technology in the Faculty of Technology at Portsmouth University and Director of the Environmental Technology Field Station, based at the Petersfield Wastewater Treatment Works. Here he and his team work on water quality improvements in wastewater and on sustainable drainage solutions (SUDS), their overriding objective being to develop low impact solutions to real world environmental problems.

The set-up at the Environmental Technology Field Station at Petersfield Wastewater Treatment Works allows the scientists there to pump wastewater samples from 3 different places along the treatment path. Southern Water (SW) fund 2 full-time staff who work in the Field Station, with the University and SW carrying out collaborative research on some of the challenges facing the water industry, including: removing phosphorous, removing pharmaceuticals, removing metals.

Given that different contaminants keep being discovered in wastewater, their research has to adapt to these changes too. Much of the issue with wastewater is that it contains excess nutrients which then damage our waterways by causing eutrophication. Wastewater also obviously contains pathogens, infectious microorganisms such as viruses, bacteria or fungi.

The water industry is an intensive user of energy but aims to be net zero by 2030.

Phosphogeddon!

Phosphorous is dug out of the ground, used in agriculture so that it is then in the food we eat and ends up in what is flushed down the pipes to our WWTWs. There is currently massive investment in then removing it from the wastewater, with a target of being able to remove 87% of it by 2027.

There are currently 2 ways of removing it, a biological treatment (only available at 20 sites in the UK at the moment) or by ferric dosing. The ferric dosing happens both at the beginning of the treatment process and then at the end of it, if the phosphorous readings call for it. This means that this corrosive substance which can cause secondary contaminants is in the sludge which can then be sold on to farmers and distributed over our fields.

Alternative approaches, some involving a variety or reactive media, form part of the research that John and his team undertake, with Ofwat having an innovation funds pot for potential use here. These alternatives can include use of managed wetlands, biochar, and sea shells, all of which create a filter for the phosphorous. Side effects can include unacceptable ph values, which then need working around, possibly by using wood bark filters.

For now, ferric dosing remains the cheaper option.

John’s team have developed a mini-lab within a container that can be moved to different sites, an approach that is creating a lot of data but has not been without its teething problems. The holy grail would be to be able to get the phosphorous back for re-use.

Nitrogen

The processes that wastewater goes through at a treatment works can lead to nitrous oxide, N2O, which is a potent greenhouse gas, being released.

Combined Sewer Overflows (CSOs) management

CSOs were always designed to provide a system that would allow untreated wastewater to be release into the environment, usually into a nearby waterway, at times when the flow into a treatment works is greater than it can accommodate. The alternative would be for wastewater to back up into nearby dwellings. Increase in population size and changes in rainfall patterns due to climate change will only increase the frequency and duration of spills from CSOs.

Solutions include increasing the storage capacity for untreated wastewater and increasing the rate at which it can be processed through the treatment centre. It would be even better if not so much of the rainfall ended up at the treatment works in the first place, or if its arrival their was staggered over a longer period of time.

When rain hits the ground it can: evaporate back up; run off the surface; or infiltrate into the soil. We are increasingly sealing surfaces, such as with concrete, tarmac, or buildings. Leading to less infiltration and greater run-off. This all increases the chance of flash flooding. Culverts and canalisation of waterways to channel this water away simply moves the problem further along. The Thames Tideway Tunnel could be seen as a way of moving the problem out of the city.

Both urban run-off and road run-off are known to contain many significant contaminants. John showed a photo of road run off collected during the first 15 mins of heavy rain after a prolonged dry period and it was black! Pollutants in the wastewater can include: Metals, Hydrocarbons (TPH, PAH), Silt, Organic Matter, Salt, Bacteria+, Rubber, Nutrients, Herbicides etc.

In other countries CSOs spill into constructed, managed wetlands, not straight into waterways as we do here. Wastewater spilling from a CSO is filtered such that nothing larger than 6mm x 6mm can pass through, but long thin things such as cotton bud sticks can still get through. (Editor’s note: This is why if sewage spills including anything larger than this are seen on waterways they should be reported to the Environment Agency for immediate investigation as this should not happen if the system is working as it is designed to.)

Due to government regulations we do now have access to data such as Southern Water’s Rivers and Seas Watch, so we can at least know when CSOs are spilling.

Solutions

The problems are numerous as discussed above but John is a firm believer in nature based solutions.

There is value to increasing the use of slow release water butts which allow each building fitted with them to hold back a certain amount of the rainfall, releasing it slowly over the next few days.

Spills will be reduced if peak flow is reduced. If you can keep the rain as near to where it falls as possible, for longer periods the WWTWs will not become inundated. Sustainable Drainage Systems (SuDS) could do much to help with this, in many cases mimicking pre-development hydrology. These systems could include surface storage (ponds, lakes) or underground storage, or swales which are  large grassy ditches, or rain gardens. SUDS are good at improving water quality as well as holding waters back, especially in urban settings and can also provide amenity value and biodiversity gains.

Well designed and managed SuDS can be a valuable addition to the local environment, being visually attractive, creating new habitats and forming connectivity between habitats that otherwise may have become isolated following the new development.

The A34 Newbury Bypass was the first major SuDS development, including 9 vegetated ponds.

Major developments should all now include SuDS, but they do take up land that is valuable to the developers. If, instead of building SUDS, they build more WWTWs then they would have an asset to sell, which they do not get with SUDS. Driveways can be permeable to allow for greater water infiltration and less run-off.

The Pitt Review: Lessons learned from the 2007 floods was pro SUDS all that time ago, but the Flood and Water Management Act 2010 Schedule 3, Sustainable Drainage, which would address many of the issues around flooding and inundation of WWTWs leading to spills, has still not been enacted in England.

The National Planning Policy Framework, 2019, stated:

John finished by showing us some photos of a development he recently visited in Brazil where he was delighted to see constructed wetlands in use.

There is so much more that could be being done here!