Water & Wastewater Treatment

16 | SEPTEMBER 2014 | WWT | www.wwtonline.co.uk As well as sewage sludge, the system (le ) can process waste from fat traps, spetic tanks and gully cleaning (bottom le ). Project focus: Bio-thermic digestion that it's currently working on projects in the Middle East and the US with this objective, while in the UK, two projects will see the processed water used for washing eet vehicles. So how does this ingenious process work? Well, the use of bacterial cultures in wastewater isn't new, but the trick is getting them to eat the organics (the waste in the water) in a quick and ef- € cient fashion. "I was a marine engineer previ- ously and knew of high temperature organisms that live at the bottom of the ocean where nothing else can survive," explains Craig Shaw, managing director at Advetec. "These aerobic extremo- philic bacteria thrive at temperatures of between 200 and 400°C. In the BTD system, the energy from eating waste is turned into heat, which is used to make electricity that can be applied to the bottom of the unit. We can then take the temperature up to the point where the bacteria 'wake up' – it's a complete closed loop system. "We look at waste in a di" erent way," he continues. "In other composters, the bacteria strains don't tolerate change very well. You throw fat or sugar in there and it makes the machine ine– cient because the bacteria are unhealthy. The cultures are including sewage sludge, reducing volumes of up to 33 tonnes by an im- pressive 97% in 72 hours (on a continu- ous, rolling basis). As well as sewage sludge, waste from fat traps, septic tanks, and gully cleaning can also be digested in the same system. "Sewage type material is the main waste here at Stratford," says John Edwards, director at RWR. "This comes mainly from drain/gulley cleaning, AD cleaning and, since the BTD was installed, a rapidly increasing amount from sewage works." Before the BTD, RWR used its large industrial washer, but the company was leŸ scratching its head regarding leŸ over organic matter such as twigs, leaves and the general garbage that ac- cumulates in locations such as gutters. "With the price to land€ ll expensive and the need to achieve as close to 100% recycling as possible, we decided to trial a small version of the BTD," says Edwards. "We found that the ma- chine was regularly reducing over 90% of organic waste into a small quantity of clean water and sterile powder, so we were con€ dent that the new, larger machine would cope with the huge volumes of solid sludge/organic waste we receive every day." In the two months since installing the 33-tonne model, RWR has been feeding the BTD with ample raw sew- age, typically taken from the centrifuge at wastewater treatment plants, along with some from front-end screening processes. "The conventional washing of raw sewage is problematic because it's full of unpleasant waste items such as used wet wipes, condoms, tampons and sanitary towels," says Edwards. "It's a real headache for the sewage plants because they € ll skip loads of the stu" every day. "High water content makes trans- port expensive, while increasing levels of contaminants such as heavy metals and antibiotics restrict its use as a soil conditioner. The net result is that utili- ties have little choice but to send it to land€ ll." "Using the BTD makes a real dif- ference," he continues. "Sure, a small amount of residue comes out the other side, but it's clean – we've had it tested independently for sewage traces and there simply aren't any. It doesn't even smell. This is great because incinera- tion and RDF [refuse derived fuel] € rms will now take this waste whereas they wouldn't touch it before." According to Advetec, the water that emerges is even clean enough for irrigation purposes. The company says the most important thing – it's about the environment and creating the ultimate conditions for bacteria. Get it right and they will eat a tremendous amount of waste, and fast." In Advetec's BTD, nutrients for the bacteria are dosed automatically at pre-determined intervals, while other automated machine functions include material feed into the vessel, plus temperature, humidity and regulated air supply. Optional telemetry and 24/7 remote computer monitoring ensure that the process can be controlled and optimised. In fact, the whole thing can be run from a smart phone. Presently, RWR feeds its BTD with around 10-14 tonnes of mixed liquid waste every day – of the company's € ve sites, Stratford is RWR's only dedicated © Perspectives The end user "We get on really well with the team at Advetec. They've virtually lived on site for the past 18 months working on the BTD and other initiatives that we have underway. They've been very accom- modating and the technol- ogy is second to none." John Edwards, director, Regional Waste Recycling The supplier "As the fi rst UK site, RWR is proving that this technology can reduce industrial quantities of contaminated water, fatty deposits and co- mingled waste by 97% to water and powder. The BTD is meeting London's strict regulatory stand- ards and dealing with huge volumes of waste to make the goal of zero- to-landfi ll achievable." Craig Shaw, managing director, Advetec

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