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Build-up of fat, oil and grease in sewerage systems has become a big problem in many cities around the world, resulting in sewer overflows, health and environmental issues, and costly remedial works.
The problem can often be sourced to commercial kitchens, such as those in fast-food restaurants, where in some cases discharges directly enter local authority sewers without treatment.
Various means are used for dealing with this, including installation of grease traps and water jetting of sewer lines, but a solution that has become more prevalent in recent times is the use of bacteria to consume and disperse the fat, oil and grease – or FOG.
US-based company Environmental Biotech uses a technology known as bio-remediation to clear blockages caused by FOG in sewerage systems. Vegetative bacteria micro-organisms are injected into the system to feed on fat, sugar and starch wastes. The company has undertaken projects in several countries for a range of customers including hospitals and McDonald’s restaurants.
Managing director Aziz Tejpar says bio-remediation is not new – it is nature’s way of breaking down waste – but all applications do not necessarily work.
“It is important to ensure that the right bacteria are selected for individual jobs – that is the key to success with this technology.
“The cost of pump-outs and spillage clean-ups can be substantial for water utilities and individual companies, so it is better to follow a preventive rather than a reactive strategy with FOG problems.
“We take a fully integrated approach when managing drainage systems. This includes a thorough inspection of the customer’s drainage system and its effectiveness, analysing the type, volume and frequency of waste being discharged to the system, then selecting the appropriate form of bacteria and dosing method.
“Dosing is controlled by a timer to release the live bacteria into the system at an appropriate point, such as through a grease trap in the premises. Fully trained technicians carry out regular inspections of the site once dosing has commenced to ensure its effectiveness and to replenish the bacterial solution.
“Bacteria can be injected into the system up to 12 times a day, and the reservoirs containing the bacteria are replaced every 14 days. The hydrocarbon-based fats are digested by the bacteria and reduced to carbon dioxide and water, thereby ensuring that wastewater flow through the drain lines is not impeded.
“The food service industry is the largest contributor to FOG-related sewer blockages, so our bio-remediation technology is now benefiting restaurants, hospitals, schools, factory cafeterias and prisons, as well as food processing and manufacturing. Because Environmental Biotec operates on a global level, frozen bacteria can be quickly air couriered to mobile service units operating in various countries.”
In the UK, Environmental Biotec has been carrying out bio-remediation trials over the past four years in conjunction with Anglian Water, the largest water authority in England and Wales, and the Water Research Council. This includes a trial to clear FOG from an 18" (45cm) sewer in Baddow Road in Chelmsford, Essex, where about 20 food outlets are located and there is a history of sewer blockages, overflows and odor problems.
Gary Collins of Anglian Water says the trials were conducted with the co-operation of local businesses in adopting preventive drain line management, including the installation and effective operation of grease traps to reduce the amount of FOG entering the sewerage system.
“Sewer blockages are 75% FOG driven, so it was pointed out to the food business operators that significant cost savings can be achieved through the use of an appropriate preventive system. Reactive measures, such as high-pressure water jetting, can be very expensive.Continued...