Water & Wastewater Treatment Magazine
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www.wwtonline.co.uk | WWT | MARCH 2017 | 25 food preparation sinks, pot washing, the cleaning of appliances, floor gulleys and so on. For this reason, water companies recommend both the training of staff in good kitchen management and grease disposal, and the fitting of equipment to capture the fats that will otherwise inevitably go down the plughole. Equipment falls into three categories: passive grease traps, hi- tech grease recovery units (GRUs) and biological dosing systems which use bacteria or enzymes to break down the grease. The majority of FSEs that Southern Water has to visit are lacking any such protection, but many also have equipment that is inadequate, which they have maintained poorly or even totally forgotten about, says Williams. "I remember going to quite a well-to-do fish restaurant where they had a nice big appropriately-sized fat trap. When I asked them how o‡en they cleaned it out they said 'what do you mean clean it out?'. It had been in place for 4 years, so it was a like a chemistry experiment when I opened it. You also find dosing systems where they are either not switched on, devoid of fluid, or they haven't replaced the bag at all. So whatever is installed, there's a big staff training and housekeeping piece that needs to go alongside that." Water companies' efforts are now starting to bring about real change, not only in the local chippie and curry house, but among national chains. For example, pub chain Whitbread recently agreed to install 700 GRUs across its national estate, while Sainsbury's, Greene King and Mitchells & Butlers are among those who have recently addressed the issue at a corporate level. As a rule, water companies do not make recommendations about the particular equipment that FSEs should install, although some advise using a supplier which is part of the Grease Contractors' Association (GCA), a specialist trade group within British Water. Stephen Pattenden, Performance Risk and Optimisation Manager at Thames Water, says that both mechanical and biological dosing methods have their merits depending on the individual situation. "I think there is a role for both. Our position at Thames Water is that mechanical or passive separation of water and grease is the most effective method in the first instance, but that dosing systems can be a great supplement to that. We have seen numerous examples where dosing systems are fitted and they are inadequate in size, or they are poorly maintained - they also cost more to service than a fat trap, so you have to bear that in mind." Thames' enforcement team for FSEs is much newer than Southern's, and Pattenden says that a pilot project in Oxford revealed that 95% of FSEs in the city had no effective grease management. For this reason, he sees the agenda primarily about education. "We really don't want to prosecute our customers - we would rather not," he says. "We believe that once we've discussed this with them and explained their obligations, then the majority of them will voluntarily move to a compliant situation of effective grease management." Thames is also putting plenty of resources behind domestic customer education work, which is targeted at its blockage 'hotspots'. To calculate these hotspots, it split its wastewater network area into blocks of roughly 500 properties, and those that had the most blockages logged against them were the subject of intensive campaigns including billboards, local radio, press and council collaboration and on-the-ground presentations, supported by direct mail and social media. Eliminating fatbergs Thames estimates that it spends over £10M a year on clearing customer- related sewer blockages, and it is not hard to see why when you consider the extent of some of the work required to clear them. Blocked drains and smaller sewers are typically cleared by methods such as jetting, but once fat has entered the sewer and congealed, it can form the dreaded 'fatbergs' which can take several days to tackle, explains Dean Hansford, Utilities Division Flooding Manager at Lanes Group, Thames Water's drainage contractors. "Any sewer that's 1100mm or bigger is suitable for manned entry, so what we do is put in a team with full breathing apparatus and shovels, and they have to go in and physically break up the fat to the point where we can get it out of the sewer," says Hansford. "We use suction where possible, but o‡en with those larger sewers it is a very hard physical job to do it. We had one recently where we had guys in there for nine consecutive nights, with two or three man teams working in shi‡s, all wearing full "We get 23,000 blockages a year related to fats, oil and grease and food service establishments and it's costing us a lot of money - so we've made it a priority." Steve Williams, Southern Water "We had a fat blockage recently where we had guys in the sewer for nine consecutive nights, just clearing the fat. People don't realise the level of effort that goes in to keeping sewers flowing." Dean Hansford, Lanes Group "The majority of kitchens either have undersized grease traps or no grease protection at all, and they have to do something about it." James Patterson, CBio Ltd