Conclusion of Long-Term Field -Scale Study of the Use of Paper Industry Residuals ad Hydraulic Barrier Material in Landfill Cover Systems, 1996 Environmental Conference Proceedings

Four pilot-scale landfill cover test cells were constructed in order to facilitate a comparison of the field performance of wastewater treatment plant residuals and clay hydraulic barriers. Two covers contained clay as the barrier material, one contained paper mill primary residuals, and one contained paper mill combined (primary and biological) residuals. For the duration of the field study, both residuals cells produced smaller volumes of seepage and greater volumes of runoff than the clay cells. Hydraulic conductivity calculations from overall water balance and by SDRI determinations for the paper mill residuals are lower than those values for the clay. Data from conventional operation of SDRIs on residuals barriers may overestimate the hydraulic conductivity of residuals barriers. The residuals barrier layers consolidated approximately 33 percent of the original thickness in response to overburden stress. The clay barriers did not consolidate over the duration of the study. Dye impregnation followed by systematic excavation indicated numerous macroscopic flow pathways in both of the clay barriers. One macroscopic flow pathway was detected in one of the residuals barriers. Little evidence exists to suggest that significant biodegradation took place in the residuals barriers.