Chemically stabilised clay contaminated biosolids as compacted landfill liners.

In Australia, landfill is the most commonly used method for waste disposal due to its low cost. The landfill liners which protect the underlying soil and groundwater are normally made up of compacted clay or geosynthetic materials. These are expensive and also associated with number of shortcomings. Therefore, investigations on alternative low cost and environmental effective and efficient liner material are important to prevent land and groundwater contaminations due to land filling. A series of laboratory tests were conducted on biosolids, which was stockpiled at the Eastern Treatment Plant at Bangholme, Australia to assess whether it could be compacted as hydraulic barriers in waste disposal landfills. Index properties, linear shrinkage characteristics, cation exchange capacity, compaction characteristics, hydraulic conductivity of the biosolids were the tests carried out to assess the suitability of the material. Although index properties, shrinkage and cation exchange capacity show that the biosolids have suitable properties to use as a liner it does not have the acceptable level of hydraulic conductivity. Therefore the second phase of study was aimed in investigating how hydraulic properties of biosolids could be modified through chemical means to achieve the desired level. The second phase of study revealed that stabilised biosolids with cement, lime and bentonite improved properties in plasticity, activity, shrinkage and cation exchange capacity than untreated biosolids. The addition of 4% of cement and bentonite was found to be sufficient to achieve the desired level of saturated hydraulic conductivity (1x10^-9 m/s) imposed by the Environmental Protection Authority (EPA) Victoria. The 12% lime stabilised biosolids achieved a value very close to 1x10^-9 m/s. Findings suggest that that stabilized biosolid admixtures with lime, cement and bentonite could be potentially used in place of clay and geosynthetic materials as effective and low cost compacted landfill liner material for reducing the leachate. [ABSTRACT FROM AUTHOR]