Abstract:
The objective of this research was to study the ability of excess activated sludge comparing with soil on the adsorption of heavy metals as well as COD from landfill leachate when applied as daily cover. Lead and zinc were studied metals, other conjugatedparameter, permeability was also investigated.IN the batch experiment, Freundlich adsorption model can be applied to interpret the batchtest data. It was found that lead and zinc in leachate could be adsorbed on activated sludge better than soil. Freundlich K values of lead and zinc adsorbed on soil were 0.33and 0.12 (mg/g)(1/mg)1n respectively, which were less than those adsorbed on activatedsludge of 2.55 and 0.37 (mg/g)(1/mg)1n respectively. In column test, the results showedthat activated sludge had more ability to treat the metals in leachate than soil. The breakthrough volume of lead and zinec adsorption by soil were 2000 and 1240 ml respectively, when lead and zinc in leachate were 2 and 20 mg/l respectively at flow rateof 300 ml/day. However, for COD removal there were no difference between using activatedsludge and soil.The compaction test following standard ASTM D1557-70 and Permeability tested by Variablehead method for soil, activated sludge and soil mixed with sludge of 33,50 and 67 percentby weight were analyzed. The maxiumum dry density of soil decreased with increasing of activated sludge while the optimum moisture content was inversely. For compacted activatedsludge, the permeability of 2.2 x 01-5 cm/sec was less than 6.4 x 10-5 cm/sec belonged tocompacted soil. The lowest permeability of compacted mixture of 1.88 x 10-5 cm/sec was obtained when soil was added with activated sludge of 33 percent by weight. However, it was still larger than that allowed for use as liner in landfill.