Study On Remediation Of Polychlorinated Biphenyls In Soil By Combining Fenton-like Reagent And White Rot Fungus

Polychlorinated biphenyls (PCBs) are artificial persistent organic pollutants, which can lead to abnormality, cancer and mutation. PCBs are resistant to biodegradation and are chemically stable, so they are able to accumulate in biota, and have been detected in rivers, air and soils in China.There are several ways to treat PCBs contaminated soils, including physical, chemical, biological methods. Physical methods only transport PCBs. Chemical methods can remove PCBs from contaminated soils completely, however its process is complex and it is expensive. Bioremediation is a cheap method and clean technology compared with other technologies, but the rate of bioremediation is very slow, and it could be affected by many factors seriously. Up to now, we still have no perfect way to treat PCBs in soils. The removal of PCBs has been mainly performed by incineration at a high temperature. The procedure brings additional risk of producing toxic chlorinated dioxins when operated improperly, furthermore, incineration is ineffective for soil contaminated by PCBs. The contamination of soils and sediments by PCBs is one of most difficult environmental problems.Aiming at the problem, a study has been conducted to enhance degradation of a mixture of polychlorinated biphenyls (PCBs, Aroclor1242) by combining biodegradation with hydrogen peroxide oxidation in a synthetic PCB contaminated soil. PCBs biodegradation by White rot fungus Pleurotus ostreatus was carried out, and Fenton-like reaction was applied to enhance bioremediation.Combination of chemical and biological methods could show their own advantages sufficiently. This study evaluated the effects of chemical and biological methods on the rate and extent of PCBs removal, and it was researched whether Fenton-like oxidation as pretreatment of biodegradation was more effective than the reverse order. The conclusions were as follows:1. The recovery of PCBs using ultrasonic extraction was higher than Soxhlet extraction. The recovery of PCB₃ and PCB₄ was more than 80%, and it was near to 70% for PCB₂ and PCB₅2. Fenton-like oxidation destroyed more PCBs than White rot fungus Pleurotus ostreatus biodegradation. Biodegradation efficiency decreased with increasing number of chlorination in PCBs. White rot fungus Pleurotus ostreatus biodegraded near to 20% PCB₂, more than 10% PCB₃, less than 10% PCB₄ and PCB₅ in soil. Compared with biodegradation, Fenton-like reagent ( H₂O₂ +Fe³⁺) was more efficient, more than 30% PCB₂ was degraded, and the degradation rate of PCB₃, PCB₄ ,PCB₅ were between 10% and 20%.3. By combining the Fenton-like reaction and biodegradation, the removal of PCBs was increasing significantly compared with Fenton-like reaction or biotreatment alone. Biodegradation pre-treatment followed by Fenton-like reaction was not so efficient as the reverse order.More than 20% PCB₂, PCB₄, near 30% PCB₅, and more than 10% PCB₃ was removed in bio-treatment followed by Fenton-like reaction removed. In a chemical -biological treatment, 24h of Fenton-like pretreatment followed by 4 weeks of Pleurotus ostreatus biodegradation, more than 40% PCB₂, PCB₃, and PCB₅ in soil were destroyed, only PCB₄ was 35%～40%.The results indicated that combination of Fenton-like reaction and Pleurotus ostreatus biodegradation increased PCBs removal, Fenton-like reaction was compatible with biological treatment,and it was economical and efficiently. It supplied PCBs field-scale treatment with valuable technics...