Abstract

ABSTRACT
Multiple Phase Remediation of Contaminated Backfill: Soil Washing, Electrokinetic and Phytoremediation System
The combination of physical and biological treatment methods for remediation of contaminated backfill has the potential for decreasing treatment period, and lowering costs, then, might be more suitable for small volume treatments. e.g. residential mazut leaks. In this thesis, a combination of soil washing, leachate treatment, electrocoagulation (EK) and phytoremediation was investigated. Applied matrices, simulated the conditions where backfill is contaminated with petroleum products. The investigated physical treatments were soil washing with water with and without EK, as well as with and without recirculation. Additional tests considered washing of soil with an anionic surfactant solution. Results showed that an EK system is suitable for turbidity removal from a recirculated oily wastewater after 24 hours of treatment. Results also showed an efficient removal (63.06 +/- 11.65%) of TPH in the trial with an anionic surfactant washing solution. This trial, performed over a period of 5 days, gave 2.5 higher removal of TPH than other trials without surfactants running for 10 days. The phytoremediation of washed soil was added as a biological component of treatment. This media was used for the replanting of Pelargonium crispum which was grown under “greenhouse”-lab conditions for 9 months prior to transplanting.. Following replanting, Pelargonium crispum was grown for an additional 5 weeks in the contaminated media prior to uprooting and TPH determination. TPH determination revealed a further TPH removal of 38.78% +/- 12.42 % from the sand treated by soil washed with anionic surfactant. The combined soil washing-EK-phytoremediation system had a TPH removal of 84.16% +/- 8.27 %. Investigations utilizing phenol as an indicator for high solubility hydrocarbons in wastewater revealed that a three phase treatment system including a phase with EK equipped with graphite anode, following a phase of EK with stainless steel electrodes, and subsequent settling period permitted to remove 80.11% of phenol from wastewater. This research presents a treatment method for contaminated backfill originating from leaking underground storage tanks, which combines advantages of physical and biological methods in order to achieve a high remediation in a shorter than usual periods.

Keywords: contaminated backfill, Pelargonium crispum, soil washing, electrokinetics, total petroleum hydrocarbons, anionic surfactant, polyelectrolytes, phytoremediation.