Technical Paper by A.H. Aydilek and T.B. Edil FILTRATION PERFORMANCE OF WOVEN GEOTEXTILES WITH WASTEWATER TREATMENT SLUDGE

Capping of contaminated soft sediments and sludges for in situ contain- ment provides an efficient remediation alternative. Capping design typically involves the use of geosynthetics for multiple functions, e.g., reinforcement, separation, and filtration. Filtration performance becomes a decisive factor for proper long-term performance of a cap. Because of multiple functions required, woven geotextiles are often the choice geo- synthetic in such applications. A research program concerning the filtration behavior of contaminated wastewater treatment sludges was conducted. The laboratory portion of the program included a series of filtration tests with different woven geotextiles. Filtration performance of the sludge-woven geotextile systems was also observed in field test cells. Geotextile samples were exhumed from the cells after exposure and analyzed in the lab- oratory. The results indicate that the sludges can be filtered using woven geotextiles and the selection of a proper filter can be made on the basis of geotextile pore structure param- eters, i.e. percent open area and pore opening size distribution. The standard gradient ratio test did not always reflect the filtration performance and, therefore, other clogging ratios need to be considered. A commonly used geotextile pore opening size-to-soil particle ratio in the existing filter criteria, O 95 /D 85 , did not predict the filtration behavior dis- played by the sludge; however, another ratio, O 50 /D 50 , showed general correlation to clogging and retention.