Water & Wastewater Treatment

www.wwtonline.co.uk | WWT | APRIL 2015 | 35 In the know Getting to grips with… hydrothermal oxidation W et waste disposal has long been a contentious issue the world over. As the race to find a safe, sustainable and secure solution gathers momentum, Irish environmental firm SCFI is part of a groundbreaking new EU project - Eco-Innovation - that is leading the way. The company has been awarded just under €1m in funding to develop commercial opportunities for its sustainable wet waste treatment technology, AquaCritox. Using a process of hydrothermal oxidation (HTO), AquaCritox not only destroys organic waste safely, it also Feeling the burn A new process which has recently attracted €1m in EU funding could provide a sustainable solution for sludge treatment and energy generation simultaneously generates renewable energy whilst recovering valuable by-products. What is hydrothermal oxidation (HTO) and how does it work? HTO is a method of wet waste treatment that uses high temperature and pressure to provide a single-step, sustainable solution for the disposal of a variety of industrial, municipal and sewage sludges. The combination of pressure and temperature causes water to enter a state where it behaves neither as a liquid, nor a gas. In this state, water becomes a universal solvent for organic materials (even those normally insoluble in water). By adding an oxygen supply, the process converts the organic materials present in the waste stream into inert by- products (CO2, nitrogen and clean water). The reaction also generates thermal energy that can be harnessed to produce renewable heat/power. What are its potential applications in sludge and wastewater treatment? HTO is especially suitable for the treatment of sewage and drinking water sludges, as well as industrial and municipal organic wet waste streams. It is a sustainable, economical alternative to current waste disposal practices – including land spreading, landfill and incineration. As well as providing a solution for disposal (reducing waste volume by 97%) and allowing for renewable energy generation and resource recovery, HTO also removes contaminants – producing a treated effluent that is safe for disposal via sewers. Harnessing the HTO process, AquaCritox can be installed as a standalone, on-site, single-step solution for wastewater treatment plants (WWTPs), or can be combined with an existing anaerobic digestion system (where it is used to recover low-grade energy present in the digestate). What are its advantages over the alternatives? Using the HTO process to reduce the volume of wet waste (and to produce a safe effluent with no hazardous by-products) totally eliminates the need for disposal via land application or landfill. These methods are facing increasing social and legislative opposition due to the perceived potential for land contamination, as well as changes in landfill acceptance criteria to reduce methane formation. These issues – along with the ever- increasing costs associated with disposal – are completely mitigated by HTO. HTO delivers a destruction rate equal to that of incineration and much greater than that of conventional wet air oxidation, in one single, straightforward step – without the need for pre-treatment, expensive dewatering/drying or gas cleaning. The small quantity of inert residue remaining a"er treatment can be JOHn O'Regan ChIEf ExECUTIvE, SCfI

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