WET News

Caption if needed sdkvjb sdkvjnsdlk dvsdvdvsdvsdvsdv dv skjbdv lskdjvbsdkljvbsdkv J ersey – the largest of the Channel Islands – is famed for its Royal new potatoes as well as its dairy products from its iconic purebred cattle. And now, for those with an interest in exemplary engineering stand- ards of management, research, design, efficiency, easy mainte- nance and high performance... its sewage treatment works. Granted, the STW may never feature in any Channel Islands tourism brochure but, as home to one of the world's leading international finance centres, Jersey certainly knows a thing or two about how to invest money. When the time came to replace the sludge plant, which had been built in 1959, at the island's STW to meet future environmental standards (and the needs of a population already in excess of 105,000), both customer and main pro- cess engineering contractor soon found that their respective drivers to meet a 2035 design horizon had plenty in common. Three years on, the plant at Bellozanne – which is at times carbon neutral – still shines like new. This isn't some strange coincidence or due to Jersey's kind Gulf Stream climate. From the outset, Jersey's Department for Infrastructure (DfI), together with main con- tractor Doosan Enpure, knew that with the logistical chal- lenges faced by the island, the criteria of efficiency, ease of maintenance and high perfor- mance was crucial, particularly for the plant's pumps and mix- ing systems. Fog or high winds can soon stop goods from reach- ing Jersey, so Bellozanne STW had to be self-sufficient – and ONSITE ANAEROBIC DIGESTION 8 WET NEWS AUGUST 2018 | wwtonline.co.uk ourselves," King says. "As well as seeing the GasMix digester mixing system, the set-up and the people were impressive the moment we walked in – which gave us confidence too in the type of service and back-up that we were going to get. "We didn't want any breaks that would interfere with our gas production. Lowest possible price wasn't our objective, not for one second. We were making decisions on what was most appropriate – for the long-term. A mixing system that could pro- duce the most gas yet be the lowest on maintenance made perfect sense." Utilising its proven chopper pump to break down particle size, Landia's GasMix also includes multiple venturi noz- zles, depending upon requirements. Doosan Enpure's Macleod adds: "Landia were very helpful because we wanted everything at ground level, meaning no access platforms at the side of the tanks – which saves time and money – putting the sole- noid valves that power the pneumatic actuators down to a solenoid box at ground level in an explosion-proof enclosure. "We also wanted an isolation valve included between digest- ers and the actuated valve so that we wouldn't have to decom- mission an entire digester if we had a problem with a valve. Operating times also came into the decision to choose Landia, rather than systems that run flat-out, so in effect it gives the operator the flexibility and con- fidence to fine-tune the mixing for maximum gas yields." At the old Bellozanne plant, The installation uses Landia's GasMix system The new sludge facilities at Bellozanne, Jersey Jersey's shining sludge plant sets new standards • When Jersey's Department for Infrastructure and Doosan Enpure had to replace Bellozanne sewage treatment works, they seized the opportunity to engineer out longstanding problems By Chris French have back-up. "The new plant gave us the perfect opportunity to engineer out old, unwanted problems," says Bob King, senior engineer (waste strategy – mech & pro- cess) at the DfI. "Previously, for example, we had an ongoing nightmare with very costly maintenance for compressors, which went down even if there was just a small amount of foam in our old gas mixing system. We also suffered with ragging and problems with pipework and fittings that simply weren't of a design." Weighing up Bellozanne's drive towards a highly robust plant where downtime would be a thing of the past, Doosan Enpure was also busy sourcing kit that would meet key require- ments, especially for low maintenance. "We certainly agreed straight away that for the three new anaerobic digesters, all pipe- work and moving parts should be on the outside of the tank," says Michelle Macleod, princi- pal mechanical engineer at Doo- san Enpure. "External- ly-mounted equipment would also improve heath and safety by eliminating the need for working at height and confined space entry." Together with Bellozanne STW principal engineer Gary Davies, King – who has spent 25 years working at the plant – car- ried out several field trips to research suitable mixers, seek- ing equipment that would also mix the whole tank, away from systems that provide little or no rotation. "Eventually we visited Lan- dia in Denmark to see for

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