Development and Evaluation of a Filter-Bed-Based System for Full-Scale Treatment of Industrial Landfill Leachate
Abstract: It is well known that nature offers an abundance of materials and processes that can be adapted in low-tech fashion, to fabricate systems capable of removing pollutants from wastewater. During the last decade, extensive basic and engineering research on such natural treatment systems have led to improvement of the quality of discharged wastewaters. However, the mechanisms of natural treatment and their application for leachate treatment in temperate climates are not fully understood due to a large number of interacting factors. A complex, interdisciplinary research project was therefore undertaken to develop strategies for construction and evaluation of full-scale leachate treatment systems. The main objective of this Thesis was to develop and characterise a vertical-flow filter-bed-based system for treatment of leachate from an industrial landfill containing shredder residue (SR) of end-of-life vehicles (ELV) and white goods. The strategy for development of the treatment system involved laboratory batch and column experiments, and progressed to long-term field studies in a pilot plant at the landfill site. Several locally available low-cost natural or residual waste materials and mixtures thereof were investigated for removal of different types of pollutants from leachate. A mixture of peat and carbon-containing ash was found to be most efficient for removal of a number of toxic metals and various polar and non-polar organic compounds. Effective removal of phenolic compounds and an abundance of phenol-degrading and heterotrophic bacteria observed in the filter show that it also acts as a biofilter. Given the climatic character of Sweden, 60–70% of the annual leachate volume might be produced during a few months, resulting in possible overloading of the full-scale filter-bed-based treatment systems. To ensure stable hydraulic loading of the biofilter system, a retention pond with a storage volume of about 23,000 m3 was needed to even out annual leachate volumes up to about 35,000 m3 in the particular location. Such retention pond also equalises peak concentrations and allows pre-treatment of leachate. Sedimentation was found to be essential to decrease the initial load of pollutants (e.g. iron and suspended solids) and reduce the risk for clogging. Long-term performance of the vertical-flow biofilter was studied in the pilot and the full-scale plants. Efficient year-round performance of a filter-bed-based system can be achieved in a temperate climate zone like Sweden, if measures are taken to protect the filter from seasonal extreme of climate. The results obtained show that on-site natural treatment systems based on readily available materials with low environmental “footprint” can be used for treatment of leachates from an industrial landfill.
CLICK HERE TO DOWNLOAD THE WHOLE DISSERTATION. (in PDF format)