Waste & Wastewater Treatment
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1917 The BBC Panorama team (Britain’s Dirty Beaches, 7th September, 8.30pm BBC1) argued that pollution on UK beaches was due to combined sewer overflows (CSOs) discharging increased levels of stormwater into the marine ecosystem. Louise McIntyre of ITT Water & Wastewater explains some of the possible solutions being explored and developed in the industry to ensure harmful pathogens are not discharged.
The problem with CSOs lies with the increased surface water run-off due to the combination of urban development and unseasonal, heavy rainfall. If the sewer or wastewater system is overloaded with a sudden surge in capacity, CSOs discharge the excess wastewater into seas or rivers to alleviate the problem. Apart from rudimentary screening, the discharge is rarely processed through any treatment works and this release of essentially raw wastewater into the environment has drawn much criticism. However, if CSOs were not allowed to discharge, the wastewater would back-up the system and lead to sewage flooding UK streets. Managing this delicate balance between public health and environmental equilibrium is, unfortunately, a worldwide problem.
Indeed ITT have already had a lot of experience throughout North America and Europe in providing systems to treat Stormwater and these solutions could provide a viable and affordable solution for the UK water industry.
The level of organic matter released into the ecosystem can, arguably, be too much for the local wildlife to sustain. Marine life depends upon such material for nourishment but large influxes of solids – typically from CSO discharges - have been considered to do more harm than good.
Ideally to prevent these problems CSOs should be protected by solids removal, disinfection and monitoring systems. Installing a filter system to reduce the level of solid matter will be of significant benefit. This will not solve the problem entirely as the remaining, harmful microbes present in the wastewater will still need to be dealt with. However, with a filter system in place to reduce the solids present in the wastewater, eradicating microbes using UV becomes easier and more efficient.
Because of the nature of CSOs – they are only meant as a last resort when systems are overloaded – the equipment would have to be operated remotely as demand required throughout the year. Monitoring and Control systems that can remotely assess and react to changes in water quality and flow are already in the market.
Appropriate precautions have to be taken when specifying Monitoring and Control systems for CSOs. Because of the nature of the outlets, any equipment mounted within the chamber must be ATEX (the name commonly given to the framework for controlling explosive atmospheres and the standards of equipment and protective systems used in them) approved by the British Approval Service for Electrical Equipment in Flammable Atmospheres (BASEEFA). These products can be safely installed in CSOs and can remotely report on discharges concerning CSO thresholds, providing valuable information to the water authorities. Alternatively if an application lends itself for the monitoring and control equipment to be mounted outside of the chamber in a safe area then a Deployable Field Device (DFD) can be considered housing the logger, batteries, sensor wiring and communication equipment within a street mounting bollard.
Technology is now available to water companies which provides remote CSO monitoring to engineers including actual flow volume, total flow duration, total flow volume and number of overflows. This solution is being used on many sites across the country to help address the problem of unmonitored discharges.
As a company, we are able to offer a full range of products and technologies - including ITT WEDECO UV Disinfection, ITT Leopold filtration systems, and ITT Monitoring & Control technology.
The combination of filters and UV treatment has shown itself to be extremely effective. During trials in the United States, Leopold filters systems were able to reduce the high solids contained in the stormwater by nearly 70 per cent. This made subsequent UV Disinfection by ITT WEDECO much more effective.
These trials show that the combination of the two technologies can make a tangible difference to water quality in problem areas.
When supported by a complete and flexible Monitoring & Control solution, problems with CSO discharges can be identified and managed – minimising any impact on the local marine environment.
As the products and technologies are available to identify problem CSOs and provide effective solutions, there should now be no barrier to ensuring the blue flags are flying high over all British beaches.
