Date of Award
Master of Science (MS)
Zhiyong Jason. Ren
Soil contamination has become a growing problem worldwide. Common soil remediation technologies including physical excavation, chemical oxidation or reduction are generally energy and chemical intensive. Compare to them, bioelectrochemical systems (BECSs) is a relatively cost-effective and environmentally friendly way to treat contaminated soil. Much work has been done using BECS on soil remediation, both in laboratory scales and in the field. But many limitations still restrict the application and development of soil BECS. One of the great limitations is the soil moisture level. The contaminants degradation highly relays on the growth of hydrocarbon degradation bacteria (HDB), but the growth of HDB highly correlate with the soil moisture level. The decrease of water content in soil can inhibit bacterial activities and lead to reduced performance of soil BECS. To our best knowledge, few studies investigated the methods to maintain soil BECS under unsaturated soil conditions.
This study aims to find a practical approach to improve soil BECS performance under unsaturated soil conditions. As the bacterial activities mainly occur on the anode of the BECS, water retention layers were added around the anode of BECSs in this study. Hydrogel was selected as the water retention materials in this study because of its excellent water retention capacity. Four reactors were settled in this study: soil and hydrogel mixture water retention layer enhanced BECS reactor (SHB), graphite granule and hydrogel mixture layer enhanced BECS reactor (GHB), soil and BECS reactor (SB), and a control tank without BECS (Con). During the 110 days of study, all three BECSs showed great improvement on total petroleum hydrocarbon (TPH) degradation compare to the control. Among the three BECSs, SHB showed the best current production and TPH degradation. During each evaporation test that have been proceed, SHB maintained system performance 40% longer than the SB in unsaturated condition, and this extension increased to 90% compare to GHB. SHB also had the highest TPH removal (37% TPH removal by day 110) among the three BECSs, which is 42% higher than SB, 164% higher than GHB, and 517% higher than control. These result shows the feasibility to use hydrogel as a water retention material to enhance soil BECS performance under unsaturated soil conditions.
Cui, Yixiao, "Moisture Retention Materials Enhance Bioelectrochemical Remediation of Hydrocarbon-Contaminated Soil in Unsaturated Conditions" (2017). Civil Engineering Graduate Theses & Dissertations. 105.