Utility Week

Utility Week 22nd November 2013

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Operations & Assets Briefs Electricity meet these tighter phosphorus consents increases the risk of breaching iron discharge limits, which are themselves tightening. The commonly held view is that to achieve consent standards below 1 mg/l requires dual point dosing of chemical followed by tertiary treatment to meet the associated iron onsent standards. The second dosing c point, prior to secondary clarification, increases the risk of iron carryover in the final effluent – hence the need for tertiary solids removal. Work by MWH has shown that single point dosing into the primary settlement tanks with good site operation and sludge management can eliminate the need for additional tertiary treatment where excessively stringent consents are not in place. The final settlement tank design as well as the quality of the dosing arrangement is key to achieving good quality effluent without tertiary treatment. Even with the excellent design and operational practices in place, there are situations where tertiary filtration either with or without dosing will be increasingly necessary, especially where extremely tight phosphorus (from about 0.8 mgP/l) or iron standards are applied. While this may seem daunting because tight phosphorus consents are new territory in the UK, what is needed is the sound application of basic chemical engineering principles to deliver the desired outcome and not a new coverall technology. Levels of 0.1 mgP/l are achievable using technologies and techniques that have been available for many years; the proper application on a site by site basis is what is needed. The key to meeting the new, tighter phosphorus challenges of AMP6 lies not in simply bolting new technologies on to existing plant but starting at source to rationalise the investment required to deliver maximum environmental benefit. From there it is a case of making best use of the existing assets on each site to meet the required performance level. Once this performance has been secured, additional processes should be considered and their design balanced accordingly. Taking this approach will deliver the overall environmental benefits the industry and legislator strive to achieve. And by being smart through a holistic view, the costs can be partially offset if integrated into an energy production facility. Julie Jeavons is the process engineering technical discipline leader, Ian Cranshaw is technical specialist and Ajay Nair technical director – all at MWH. They are experts in water, wastewater treatment and resource recovery THE problem Phosphorus in water courses encourages alga blooms (massive growth). Excess surface algae prevents light penetration, and lower layers of algae die due to lack of light. Bacterial action decays these algae causing putrefaction. This rapid decay lowers the dissolved oxygen in the water, killing fish and other aerobes and causing more decay and putrefaction. 15 Atomic number 30.973762 Atomic weight P Chemical symbol 50mg Fatal dose PHOSPHORUS factfile  Phosphorus is vital for life as we know it, but in elemental form it is toxic   elemental form it comes in three In allotropes (white, red, and black).   can be extracted from urine (this was the It original commercial production process)   Phosphorus is the sixth most common element in the human body. Phosphoric acid is used in soft drinks   White phosphorus is reactive and dangerous, it has an auto-ignition temperature of around 30 degrees celcius, so it must be kept underwater  Red phosphorus is used in the striker surface of safety matches   White phosphorus glows green when exposed to oxygen (before it ignites spontaneously) Festival generator scheme flops A scheme to ease power network pressure points using back-up generators during peak demand flopped for commercial reasons, it emerged last week. Western Power Distribution (WPD) used mobile generators employed at festivals and pop concerts in summer to reduce strain on overloaded substations. The trial, backed by Ofgem's Low Carbon Network Fund (LCNF), was abandoned due to a shortage of ancillary equipment, capital costs and vandalism fears. Heat UKPN substation to heat homes Waste heat from a UK Power Networks substation and a London Underground vent could heat hundreds of homes under a pioneering project announced last week. More than 700 households and a leisure centre in Islington are heated by the Bunhill Heat and Power district network. A joint project between Islington Council, UKPN and Transport for London is to extend the network to a further 500 homes, harnessing waste heat from a Northern Line ventilation shaft and a high-voltage substation. Water AMK wins Thames Deephams contract Thames Water has named joint venture company AMK as the successful contractor for a £177 million refit of Deephams sewage works. AMK comprises AECOM, Murphy and Kier, and Thames said the deal was "a key milestone" in the company's early contractor involvement procurement process. UTILITY WEEK | 22nd - 28th November 2013 | 25

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