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VMAT: Towards Finer Processing of Landfill Leachate in Zhengzhou, China

In this Issue, We continues with the "Zhengzhou Leachate Project" series.

The Municipal Waste Treatment Facility in Zhengzhou City, Henan Province, China continues its upgrading process. In early 2007, Dunwell has provided the state-of-the-art technological solutions, equipped with two sets of VMAT-NF (Nano-Filtration) vibratory membrane system and a set of VMAT-RO filtration system. The pilot tests were successfully and smoothly completed in mid 2007. Through the unique internet-enabled remote monitoring system, Dunwell engineering teams can provide real-time monitoring and implement fast-response to on-site servicing for the client from Hong Kong, which minimizes traffic costs and maximizes the service added values for clients.

Now two years in service, the Zhengzhou Municipal Waste Treatment Facility… The whole facility is designed in accordance with international sanitary landfill construction specifications, with advanced system of lining and underground leachate recovery system preventing soil and water table contamination. With no municipal wastewater treatment plant in close proximity, the Zhengzhou facility has no option but implements on-site environmental treatment of the landfill leachate thus produced in order to fulfil the stringent national environmental standard – 'Category I' emission level in the SEPA's Comprehensive Wastewater Emissions Standard" (GB8978-1996).

The landfill leachate treatment process comprises of several interconnected stages, starting from the Membrane Bioreactor (MBR) to Dunwell’s VMAT-NF membrane filtration technology. Concentrates from the treatment process is subject to incineration, while the permeate is discharged with a small portion of it being recycled through the VMAT-RO system as greywater consumption for gardening at site.

The quantity and quality of landfill leachate varies seasonally. A pool of major scale is usually built for such purpose. Biodegradation treatment of leachate is also highly temperature-sensitive and difficult to be effective, especially during winter's time. In addition, a high level of the biodegradable contents in the leachate proves critical to the effective treatment or it risks unsatisfactory otherwise. The ageing of landfills is closely related to the problem of low biodegradable content levels in incoming leachate. Finally but not least, when the landfill reaches the end of its use life, the biodegradable contents in leachate can have a significant reduction that renders traditional biotreatment ineffective.

In general, the C.O.D. of leachate after biotreatment reaches 500 – 600 ppm. As the National Standard (GB8978-1996) requires the discharge limit below 100 ppm, This is when the membrane filtration technology comes in as a practical final weapon for effective treatment. As we all know, however, conventional membrane filtration technology face deadlock in face of fouling problem and costly cleansing process on a frequent basis. VMAT, with its proprietory vibratory membrane mechanism, provides the perfect solution to this deadlock with a phenomenon called high shear cleansing power to prevent fouling. The success of VMAT application at Zhengzhou speaks for itself, with the project performance living up to its original design with a membrane cleansing cycle of less than 8 hours. We are witnessing VMAT technology as the appropriate solution to effective landfill leachate management than most of conventional membrane packages.

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