Study On Enhancing Microbe Remediation Of DDT Contamined Soil By Surfactants

The soil in many areas of China have been suffering DDT pollutants in different degree, which has become a focus issue causing domestic and overseas concern. As a kind of environmentally friendly treatment, it is the point of the national and international research that the micobe remediation for the soil contanimated by DDT. But there are two main problems in this technology, including the low efficiency of bio-degradation and the limited bio-availability. Surfactants, which can solubilize organic pollutants and enhance the organochlorine microdegradation in soil-water systems under certain conditions, have great potential application capability for the remediation. However, traditional surfactants have several problems about the effection of solubilization, the toxicity to organisms and the use-cost. For finding a technology of surfactants enhanced DDT microdegradation with high-efficiency and the relevant surfactants, three aspects were introduced and tested in this study: the solubilization capability of different kinds of surfactants(SDS,SDBS,TW80,TX100,RL) and their mixed systems for DDT, the toxicity of the surfactants for wheats and degradation bacteriaⅠand the effection of enhanced DDT-microdegradation. And the main results are shown as follows:(1) According to the solubilization efficiency of the singal usage of the 5 kinds of surfactants, anionic surfactants have better effection on solubilization of p,p’-DDT than nionic surfactants, the best elution rate is above 44%(additive amount:15000mg/L). The effect of surfactants flushing follows the order: SDS>SDBS>RL>TW80>TX100.(2) The mixed systems of anionic surfactants and the nonionic can promote the solubilization of p,p’-DDT with lower dosage. The mixed system with SDS-TW80(4:1) has the highest solubilization efficiency of 42% at the additive amount of 10000mg/L.(3) The toxicity of anionic surfactants is higher than that of the nonionic surfactants. The nonionic surfactant, TW80, has no effcetion for wheats sprouting, and can promote the growing of degradation bacteriaⅠ. The toxicity of the surfactants for wheats sprouting follows the order: SDS >SDBS>RL>TX100>TW80. The toxicity of the surfactants for the bacteria follows the order: SDS>SDBS>TX100>TW80.(4) The mixed system of SDBS-TW80 with mix-ratio of 2:3 can dramatically enhance the efficiency of DDT degradation by the two kinds of bacteria, and the highest removal efficiencies are 63.5%, 1.56 times higher than the removal efficiency without surfactants.(5) In the dosage of 70mg/kg, the rhamnolipid(RL), a kind of biosurfactants, can also effectively promote the microdegradation of DDT for degradation bacteriaⅠwith the removal efficiency of 62.1%. However, RL can not promote the microdegradation of DDT for degradation bacteria Ⅱ.