If leachates have a distinguishing characteristic, it is that flows are variable. Flows change according to the weather. The highest leachate generation will occur after rainy periods, decreasing during dry and when the leachate from previous events ceases to percolate through the waste and appear at the base of the landfill. Therefore, waste concentrations can change dramatically according to the weather conditions and as the waste matures over the life of the landfill. It follows that, no landfill leachate is constant over time, and no two leachates are the same. However, large landfills operated according to the EU landfill directive with less than 50% recycling taking place before it reaches the waste are remarkably similar when age of waste and leachate is taken into account.
Landfill Leachate Treatment Strategies
Landfill leachate treatment strategies can vary quite considerably subject to the individual challenges on each site as well as relative strengths, composition and volumes of leachate. The experts at the "Leachate Expert website" (see www.leachate.co.uk ) have designed dozens of successful leachate treatment facilities over the last 25 years, and can assist you in the specification, design, build, installation & commissioning of the most appropriate solution for your site. Naturally, we can thereafter provide operation and maintenance services.Based on a minimum of information the leachate experts work with their clients to provide a practical and economical process design which will then form the foundation of the project. Each project consultancy involvement can range from providing feasibility studies, design layouts and process flows, to project management, specification, construction procurement, landfill product selection, HAZOPs, P&IDs, etc, and plant operational support.
A very wide range of treatment processes have been applied to leachate treatment with varying success. The processes which have been consistently successfully applied, for municipal waste landfill leachate from controlled landfills, are biological processes designed by specialist leachate process designers.
In many countries standard national discharge consents limit the applicability of biological processes due to their high stringency of the purity requirements, and removal of salts. Thus can be the result of consents which are designed for simplicity as national standards, and which adopt a requirement that all discharges must meet a high quality standard suitable for all cases.
Regulators often suggest that leachate should be pumped to a sewer for treatment at a urban Wastewater Treatment Plant (WWTP). However, this may historically have been driven by concerns that leachate treatment on site is challenging and difficult to achieve reliably, than by a detailed appraisal of the best options available. This however is no longer true, especially for designs from experienced specialist LTP designers, such as those at the "Leachate Expert website".
Is Leachate Treatment at Any Sewage Works A Good Idea Environmentally?
In reality it is not usually a good policy to treat strong leachate from modern sanitary landfills after discharging it into sewer. The act of mixing it with sewage makes it more difficult to treat by sewage treatment plants. Sewage works are not designed for such high ammonia effluents. Leachate has an extremely high ammoniacal nitrogen ("ammonia”) concentration when compared with the much weaker contamination levels in domestic, commercial, and industrial foul sewage.This is why treating strong leachate at a Wastewater Treatment Plant, as if it were sewage, is not efficient and leads to unnecessarily cost. Unless the WWTP has a high efficiency nitrifying process set-up already ammonia removal may be very poor. The result is that ammonia, which is one of the most potentially damaging types of contaminants in leachate, may simply be being diluted by its addition to sewage which is much weaker in ammonia, and the WWT may comply with its discharge consent by dilution, and even not treat the ammonia.
