A laboratory investigation of anaerobic microbial clogging in granular landfill drainage media

A laboratory investigation was made of the clogging of landfill drainage systems due to microbial growth in anaerobic conditions. The factors addressed included the flow rate and composition of the leachate, the saturation conditions, and the mineralogy and particle size of the drainage material. Reductions in drainable porosity of 1-12% occurred in columns modelling anaerobic landfill drainage systems following periods of 400-800 days of continuous operation. Within the range of parameters covered by the investigation, the principal factor governing the rate and degree of this reduction in pore volume was the typical particle size of the drainage material: a D10 size of at least 10 mm may be necessary to guard against long-term microbial clogging. The rate of clogging was also influenced by both the biological load and the hydraulic conditions (i.e. saturated, unsaturated or varying) within the column, probably because of their potentially limiting effect on the distribution and rate of nutrient supply. The impact of aggregate mineralogy on the clogging rate was not significant.