Decreasing the grease

Environmental Biotech is working with Anglian Water to rid Essex pumping stations of fat, oil and grease contamination problems

Anglian Water, the largest water authority within England and Wales, has been working with Environmental Biotech, the provider of a revolutionary drain line management service, to solve recurring blockage and odour problems at pumping stations located throughout Essex.

Despite scepticism within the industry about the effectiveness of some systems to deal with fats, oils and grease (FOG) contamination problems, Environmental Biotech has had significant success in working with Anglian in alleviating some of the most problematic areas. The results of a trial using Environmental Biotech by Anglian at a pumping station near Brentwood in Essex, which was particularly prone to severe FOG contamination problems, highlights the importance of using a dedicated team of trained technicians to provide a bespoke service tailored to combat drainage problems associated with FOG.

The problem

The true impact of FOG in sewer systems has never been adequately assessed in the UK, but it is known that it does create serious problems. These include increased operational costs in sewers, pumping stations and treatment works, sewer flooding and pollution leading to the risk of prosecution, and the discharge of FOG into the public sewer without the requirement of trade effluent consent. While industrial premises that discharge to sewers as a consequence of their processes must have trade effluent consent, the same is not true for a high number of commercial premises. While industrial premises have to install complex grease trap systems to meet the discharge requirements, owners of commercial premises such as shopping malls with food halls, supermarkets and restaurants are exempt from the trade effluent regulation. This follows from the age-old contention that cooking a meal for consumption is considered to be a 'domestic' activity.

Although there is legislative power in section 111 of the Water Industry Act 1991 to take action against anyone that discharges any matter liable to cause damage to the sewerage system, sewerage undertakers have failed to use this power to mitigate the effect of FOG. This is made worse by the fact that due to the emulsified nature of FOG and its variation in temperature and flow rate (quiescence), the location affected by the overflow may be far removed from the initial source of the problem.

The reality is that sewerage undertakers are continuously suffering the consequences, with soaring operating costs at pumping stations and inlet works, fines for sewerage overflows and the resulting clean-up operation and detrimental publicity. Inevitably, all this is passed on to the domestic water charge payer - the real instigators of the costs, mainly restaurants and supermarkets, get off scot-free. Anglian Water decided to undertake a trial of Environmental Biotech's system at a pumping station in Shenfield, Essex, which had a history of FOG problems.

The Trial

The pumping station, which discharges into the head of a gravity sewer only 500m away, is situated on the same site as a garage and a fast food restaurant, with an additional ten domestic properties also draining into it. This was identified by Anglian as being particularly troublesome and expensive to operate because of the accumulation of FOG.

The pumping station, located just off the A12 at a junction immediately prior to the M25, is an extremely busy location for the sale of fast food. Records indicate, prior to the trial, that Anglian had frequent problems with the pumping station and its rising main, often resulting in failing pumps causing sewage overflows in the restaurant's toilets.

Prior to the trial, Anglian was pumping out the station every 12 weeks to clear accumulated FOG from the surface of the wet well. The station was assessed in preparation for the trial on June 6, 2003, with the last pump-down having been conducted on April 30, 2003 (tankered waste).

It was decided that in the interests of gathering accurate results, not to tanker out the wet well, pump it down, or even wash down the station walls. While solvent extraction techniques can be used on continuous discharges, with limited success, actual measurement in a pumping station wet well is impractical. Description and photographic records were used to assess the situation in this trial.

Photographs taken at the initial inspection on June 6, 2003, demonstrate the extent of FOG in the station and downstream at the point of discharge into the gravity sewer at the time. Following the inspection, Environmental Biotech devised a dosing system, which was installed on June 12, 2003. A 20-litre reservoir for vegetative bacteria was placed in the electrical control kiosk together with a peristaltic pump and a small air compressor. Controlled by a timer mechanism, the air and bacterial solution were introduced via a plastic stilling chamber near the surface of the sewage.

Although the bacteria used in the process remains active for up to 14 days, the station was replenished on a weekly basis. During each visit (of approximately 30min), the Environmental Biotech technician examined the dosing arrangements, replenished the bacterial solution and inspected the wet well, spraying a more concentrated solution of bacteria onto the fat layer on the wet well walls, the pumps and the floats.

The hot, dry summer of 2003 provided Environmental Biotech with the ultimate test it needed to prove its resilience to override the increased odour that pumping stations face during hot weather. The dosing regime was changed, via an Environmental Biotech technician to accommodate for potential odour, dosing mainly in the hours shortly after the midnight rush. In fact, there were no odour related complaints about the station during the entire trial. Within a matter of five months, there was clear evidence of the removal of FOG, as seen by the photograph taken in December 2003. A significant increase in fat build-up would have been expected rather than the decrease demonstrated in the photograph.

THE Results

When comparing the time allocated to the station from emergency call-outs both before and during the trial, the cost-effectiveness of implementing the Environmental Biotech system can easily be identified. Analysis of the pumping station's telemetry alarm call-outs for pump failure, for high wet well levels and sustained high wet well levels, highlights this.

During the 17-month period prior to the trial, 70 alarm visits involved expending 219 hours on site, with two operators attending each alarm call-out. However, during the first five months of the trial, there were only 11 alarm call-outs involving 38 hours on site - ie on average 12.8h/month without treatment versus 7.6/month with dosing.

This provides considerable saving of both direct and indirect costs of pumping station failures. In addition, no tankering charges were incurred over the trial period, which up until the start of the trial were being implemented on a 12-weekly cycle. On December 10, 2003, the pumps were overhauled and new impellers and wear rings fitted. A month later there had been no call-outs or visits recorded at the station, and the photograph taken at the end of the trial on March 6, 2004, shows the extent to which the pumping station had been cleared. The extent of FOG was slight and was of a very soft and 'fluffy' nature both on the wet well surface and on the walls between pump start and stop levels.

Gary Collins, collection manager for Anglian, commented: "We are absolutely delighted with the results we have achieved with the Environmental Biotech system. Previous to the installation, the station was breaking down on a near weekly basis, which resulted in exorbitant call-out charges." The results were so impressive that Anglian has introduced the system into other sites around Essex.

Examples include the installation of a further grease eradication system into a sewer in the Parkway area of Chelmsford, an odour control system into a pumping station in Chelmsford and three odour control systems into the Park Drive Promenade area of Maldon, all of which are performing exceptionally well


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