Sifting through top screen firms
Mono Pumps' business manager for Waste-Tec Products, Ian Hallows, assesses the current state of the CSO programme and outlines his criteria for success in AMP4
Prominent among these are the numerous commercial changes and restructuring of companies that have taken place within the industry, along with more practical matters, such as coastal schemes and water supply issues, which caused resources to be generally diverted away from wastewater and stormwater discharge projects. Yet AMP3 has certainly had a strong bearing, particularly on stormwater handling. The tightening of EU regulations covering stormwater discharge prompted manufacturers to both improve their existing products and develop new ones. As a result of the demands of AMP3, an independent means of assessing storm screen performance was established.
Representatives of all ten UK water companies and Scottish Water came together to create the UK Water Industry Research group (UKWIR), which provided a valuable testing ground for new and existing screens. The Wigan WwTW played host to the testing programme, which put both new and improved products through their paces and published comprehensive results. Despite the fact UKWIR approval for new products is not mandatory, the Wigan report provided a comparative and valuable benchmark against which manufacturers and customers can assess screen performance.Water pressure
In order for the water companies to work closely with industry regulator Ofwat, a transparent approach was agreed to make visible their collective plans and requirements. Plans were submitted in autumn for review early this year, where the water companies issued assurances any outstanding AMP3 improvements would be delivered within the EU and Environment Agency (EA) required timescales.
This could mean screening equipment manufacturers may, in the future, see the new business opportunities they are gearing up for during the AMP4 period. Combined sewer overflows (CSOs) screening to eliminate aesthetic pollution will remain prominent over the next few years. Under AMP3, a total of 4,800 CSOs were identified as being in need of improvement. In many cases the water companies were faced with a choice between installing a mechanical solution to improve the quality of stormwater being discharged, or designing/ redesigning the civils to separate the discharge. To date, both solutions have proved equally popular, but those water companies which chose to install mechanical screening equipment posed a new challenge to the equipment manufacturers. Like Mono, many manufacturers already had existing, proven equipment that was purpose-designed for screening heavy solids at the inlet level to a treatment works. Typically designed to operate on a 24-hour basis, this equipment often proved to be too large and to have the wrong operating envelope to suit CSO installations. This prompted manufacturers to create a new generation of screen solutions that were generally simpler in design, less heavily engineered, more cost-effective and, above all, self-cleaning.THE BEST SOLUTION
The solutions that evolved resulted in a number of different types of screening technology. New or enhanced products based on mesh wire, drum, bar and rake screens have all passed through the UKWIR testing facility at Wigan - and although all can provide effective solutions to different screening requirements, some offer features that provide considerable advantages to the end-user. For example, the ability to be operated by flow power alone is considered essential in installations where no electrical power exists. This can not only provide project savings by eliminating the cost of laying power at that location but it also generates ongoing savings in operating costs and reduces the need for ATEX approval for CSO chambers. Similarly, the ability to operate reliably and yet be effectively self-cleaning is another crucial benefit. While no screening technology can claim to be 100% self cleaning - any equipment will need at least a minimal amount of periodic cleaning and maintenance - those systems that require very little attention have a significant advantage in reducing labour costs. The importance of these two features was recently underlined by a United Utilities refurbishment project on a CSO overflow chamber at Bowness, close to Lake Windermere, where the company installed two self-cleaning, flow-powered Stormscreen units. A United Utilities spokesman said: "There is no power available in the chamber, so the ability to start operating automatically and be powered by the flow was vital.
"Since installation, the units have run continuously for up to ten days at a time during storm conditions without suffering any blockages. They have proven very reliable."
Whether it is caused by the tail-end of AMP3 or the future requirements of AMP4, we will almost certainly see an increase in demand for screening equipment, especially as around 1,200 of the CSOs identified for remedial work are still in need of attention.
So although new products are already available and operating benefits to the water companies will drive an increase in demand, there is still some concern within the industry that if demand does suddenly rise, some manufacturers may not have the resources necessary to meet any such peak. Many manufacturers are now examining this potential problem, both independently and via various trade and supply associations, with a view to managing supply. So who will be better positioned when demand does increase? Some manufacturers will naturally be far better placed to take advantage of it than others and those who can provide a single-source solution are expected to benefit most. AMP4 will focus attention on many small-scale refurbishment and up-rating projects and these are often not commercially viable for larger contractors to consider.
This will leave water companies forced to look elsewhere in the hope of identifying a smaller contractor that will undertake the project and then co-ordinating their efforts with those of the screening equipment manufacturer. Any screening manufacturer that can simplify the situation by offering a proven, in-house contracting capability will be far better placed to win this new business, simply because they can provide a single 'one-stop-shop' for equipment manufacture, installation and commissioning. There is, however, another vitally important factor that the screening equipment manufacturer must be able to demonstrate to the water companies if they are to operate as a solution provider - and that is an understanding of how to manage the flow.
Simply adding new screening equipment to an existing CSO may well remove any solids above 6mm from the discharge into the receiving water but it can also increase the flow to treatment. This will have serious implications on operating head levels and on the efficiency of the treatment plant as a whole. Any equipment manufacturer looking to fulfil the roles of supplier and contractor must not only be aware of such problems and understand the reasons behind them but must also be able to offer practical alternatives.
The most effective solutions are likely to be based around modifications that successfully control and balance the various flows of the overall process - and so the successful manufacturers will be the ones who look well beyond their own products and tackle the larger operational requirements. This perfectly underlines the point that a combination of best equipment, best solutions and best practice is what the successful screening equipment manufacturer will need to meet the many demands and challenges that lie ahead