Water & Wastewater Treatment

WWT October 2018

Water & Wastewater Treatment Magazine

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Page 23 of 43

24 | OCTOBER 2018 | WWT | www.wwtonline.co.uk much leachate was allowed to discharge into the environment and water systems. This has now ceased but many emerging economies are still only beginning to tackle this problem. China is noteworthy in now taking strong regulatory steps to ensure proper handling and disposal of leachate. Q: What solutions have traditionally been used to deal with leachate? A: As mentioned above, the typical solution is a combination of biological and membrane processes in series, which concentrates the liquid, plus high temperature controlled incineration to dispose of the leachate. Each of these elements require large investment in plant and equipment and can be very infl exible as far as volume and make-up of the liquid to be handled. The consequence is that much leachate is trucked, produced varies by season depending on the heat and hence biological activity, thus sizing of a plant is the fi rst challenge. A bigger problem is the sheer mix of diff erent contaminants – traditional water treatment processes can deal with specifi c contaminants but struggle with a varying mix of diff erent contaminants. Current methods involve a series of processes involving biological and membrane fi ltration but can only partially reduce the volumes involved. In many cases the leachate has to be trucked away to a hazardous liquid treatment site many kilometres away from the landfi ll creating further negative environmental impacts. A typical site LAT Water is working with in the UK involves fi ve tanker movements a day, each over 60 km. The ultimate energy consumption to dispose of a cubic metre of leachate is typically over 75 kWhr and can cost upwards of £25+ per m³. It is one of the biggest costs of managing a landfi ll even ignoring the environmental impacts. Q: What are the con- sequences of failing to deal with leachate properly? A: Leachate is many times stronger and more toxic than conventional foul sewage. Discharges to the environment where it can enter the water system either through aquifers or river water are thus totally unacceptable and can result in massive contamination. A typical active landfi ll site in the UK produces around 100 – 250 m3 of leachate with smaller closed sites producing 15 – 25 m3 per day. A landfi ll operator must monitor the production and ensure systems are in place to remove and dispose of the leachate on a continuous basis. Today the Environment Agency maintains strict monitoring to ensure that there are no discharges to the environment. In the past though in Europe, The Knowledge Getting to Grips with… landfi ll leachate frequently long distances to suitable disposal sites. This of course adds to the environmental impact and cost of handling the leachate problem. Q: What innovative technology is now available in this fi eld? A: The LAT (Low temperature Ambient pressure Technology) process is a novel approach utilising waste heat from the onsite biogas generators that would be otherwise discharged into the environment. The process uses an interlinked pair of humidifi cation and condensing columns at ambient pressure, thus reducing the costs of manufacture, operation and maintenance. Importantly LAT can simultaneously handle high levels of organics, dissolved solids, metals and ammonia together with variable feed volumes. Typically LAT can recover up to 90% of the water from the leachate leaving a small residue to be removed to the hazardous chemical disposal process. This enables installation at the landfi ll site reducing the trucking requirements and potentially reducing the costs to the landfi ll operator by up to 50%, even a er including the capital costs of the system. Q: How much of an is- sue is landfi ll leachate in the UK, and what is the potential for im- provement? A: Leachate management is a major cost and environmental problem for landfi ll operators, but because the amount of waste being land fi lled is declining it has been ignored by many of the waste water companies and so has not benefi tted from new products or major innovation. Despite this, it is important to note that even if landfi lls are closed, the leachate problem continues. For this reason, leachate management is a vital part of the waste water industry. Today the costs in the UK of handling leachate are estimated at over £250 million per year. Even more signifi cantly the lessons learned in handling leachate can be applied to many other contaminated industrial waters. Overall there remain many opportunities for improved processes and technologies to reduce costs and improve the environmental impact of the treatment. Q&A Above: An example of leachate for treatment. Below: The results of the LAT solution

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