News & Media > Utility Services
25:03:2011
A better place to work and live
The work has also met the requirements of an odour abatement notice and been completed to the satisfaction of the Environment Agency (EA) and local authority environmental health officers (EHOs).
Paul Gibbs, director of waste water operations at Anglian Water, said: “Odours from Whitlingham STW have been an ongoing concern for local residents and local environmental health officers for several years.
“Despite our best efforts in working with the EA and EHOs an odour abatement notice was served on the site in 2010 which gave Anglian Water 12 months to comply.
“A scheme was approved to carry out £1.5m of remedial work on site and within the catchment of the works, the most significant section of which was awarded to May Gurney.
“Although the timescales were incredibly tight and included the coldest December on record, the work was completed in time to meet the requirements of the abatement notice and to the satisfaction of EHOs and the EA.
“Time will be the ultimate challenge but site staff are very positive and confident about the work carried out.”
Chris Penn, May Gurney project engineer, added: “All of these projects were delivered to very tight timescales. The key to success was the very close working relationship that we had with the Anglian Water team.
“This type of refurbishment had not been carried out in this way before so it was a learning curve for all and we encountered lots of issues along the way. Regular on-site meetings meant that each element was discussed in depth, with input from all parties.”
Improving the working environment
The dewatering machines at the Whitlingham STW near Norwich produce toxic ammonia gas and hydrogen sulphide gases. Gas alarms at the plant were constantly going off and operatives were starting to complain of headaches. This was a considerable health & safety issue.
The project team's first task was to design and install bespoke enclosures for each machine - to contain the gas while leaving the machines operational and serviceable. The enclosures have transparent curtain sides with cut outs for valve handles etc. A new fume extraction system has also been installed to draw the toxic gas away, provide treatment and discharge it into the atmosphere.
Dealing with unpleasant odours
The site also had an odour problem which attracted regular complaints from local residents, the Environment Agency and the environmental health officers at Broadland and South Norfolk District Councils.
To combat this, a chemical scrubbing system has been installed to remove ammonia and hydrogen sulphide from the discharged air. Other measures include covering a large sludge blending tank, a de-gassing tank and various smaller areas and ducting these to a biofilter which removes odour biologically.
Enhancing methane production
The site produces its own methane from sludge, which is then used to produce electricity through a 1mW generator. However, the digesters used for this are very old and from time to time gas production dwindles.
May Gurney's task was to drain down the digesters, remove the large amounts of grit that had collected inside and replace the existing pipework. Because the digesters are only drained down perhaps once every 20 years, a whole host of extra works were carried out at the same time including new recirculation lines to enhance gas mixing.
The result is a marked improvement in the amount of gas produced, and in turn the amount of energy Anglian Water is saving by using its own electricity.
