LAWR

LANDFILL MANAGEMENT Understanding leachate Vinod Ramachandran, technical development manager for Ondeo Industrial Solutions, part of Degremont Industry, looks at the issues surrounding leachate and explains how plant operators should go about specifying a safe and efficient solution for leachate management and treatment. eachate is highly variable in terms of flow and quality. It often contains a toxic mix of organic and inorganic compounds, which can fluctuate seasonally. This can make effective and environmentally compliant leachate treatment a tough challenge, especially as there is a wide variety of treatment options available to landfill site operators. Leachate is a liquid emission from waste landfill, created by rainwater. When rain falls on the landfill site it becomes contaminated as it percolates down through the waste. The contaminated rainwater that flows out of the landfill is termed leachate. Contamination varies according to a series of factors, from the age and type of waste to the seasons of the year; in summer the leachate is lower in volume but contains a higher concentration of contaminant, while the reverse occurs in the winter during periods of heavy rainfall. Also, leachate is highly variable in content, with common contaminants including ammonia, phenols and heavy metals that would have a detrimental effect on the environment if discharged. The variability of data caused by issues such as those described above makes the specification of leachate solutions a complex task. Landfill operators are experts when it comes to operating landfill sites however due to the complexities involved in leachate management and treatment specialist support is required to help make the right decisions. No doubt the operator will have some limited data in terms of designing a plant, or even treating it onsite or offsite, but the first thing to do before specifying a solution is to gather data and get an understanding of all the issues surrounding leachate, including what the parameters of the variables can be. Appropriate knowledge and experience of leachate formation, hydrology and composition, and further leachate characterisation and monitoring is essential. There are many different ways of treating leachate, depending on the condition, and objectives, of a particular site. Objectives that decide the requirement for treatment, like leachate contamination levels, are not always the same. It could be, for example, that the customer is sending out a number tankers a day costing thousands of pounds and that cutting costs is a powerful financial driver. It could be that a change in legislation is to be made regarding landfill discharge to sewer and so the level of ammonia must be reduced. The drivers are different and the solutions differ depending on those drivers - that's why all solutions are not the same. Various processes may be applied to landfill leachate treatment. Biological treatment is the most commonly used process through anaerobic and/ or aerobic treatment. These processes use micro-organisms to digest the waste contaminates, resulting in a less harmful effluent with lower levels of BOD (Biochemical Oxygen Demand), COD (Chemical Oxygen Demand), suspended solids and ammonia. There are many other solutions available in the marketplace and these should be evaluated in line with the sites leachate criteria before any treatment is implemented. The key to achieving the right results is to appoint a wastewater treatment solutions provider that takes careful steps towards a solution that suits your specific needs. A typical series of steps would be as follows: Step 1: Appraise: A high level evaluation of the technical feasibility and commercial viability of the project, including identifying the variability limits of the leachate quality. Step 2: Select: An analysis of the various leachate treatment options in relation to your site specifications and the selection of the preferred option. Step 3: Define: Definition of the development plan with full capital costs, considering areas such as civil work, discharge options and consent regulations. Step 4: Execute: Execution of the development plan with timescales, commissioning details and project management. Step 5: Operate: Operations and maintenance of the plant to ensure your assets are protected and the plant continues to run at its optimum. The secret of a successful leachate solution is to compose the right data analysis at the beginning to understand your leachate and then select the technology based on the analysis. A supplier with a breadth of expertise will use its technical and practical knowledge to rapidly identify and then deliver the right solution from the outset that meets the needs of your plant. L March 2014 Local Authority Waste & Recycling 21

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