Filtering and drainage of contaminated water

ABSTRACT: This paper provides a summary of relevant field and laboratory studies pertaining to the long-term performance of filter and drainage materials used in leachate collection systems and agricultural drains. It is shown that clogging rate is related to: the leachate strength and mass loading; grain size, grain size distribution, and initial pore volume of the granular drainage material; and the use of a granular or geotextile filter/separator between the waste and the drainage layer or around the drainage pipe. The assessment of likely clog development within geotextiles and granular materials is discussed and techniques for estimating the service life of leachate collection systems due to biological, chemical, and physical clogging are summarized. Recommendations are made regarding means of improving the field performance of leachate collection systems. However, it is concluded that there is no current predictive method to assess either the likely extent of clog formation within the geotextile or surrounding soil for agricultural drains, or the service life of these agricultural drains, and it is concluded that additional research is required in this area