Surface active agents and microbiological cultures treatment of oil hydrocarbons contaminated soil

Abstract

Contamination of soil with crude oil, diesel, gasoline, motor-oil hydrocarbons etc is one of the most important ecological problems in terrestrial ecosystems. This paper provides information about the ability of a biological (P. Aeruginosa DS-10-126 produced) surfactant and a synthetic (anionic sodium dodecylsulphate SDS and nonionic polyoxyethylene(20) oleyl ether “Brij 98”) surfactants to remove diesel and motor-oil mixture from contaminated soil under varying washing conditions. Soil was prepared in the laboratory by mixing black soil, clay and gravel at equal parts and then contaminated by mixing diesel, motor-oil and soil. Soil physical properties (density, humidity, granuliometric composition) was determined for both contaminated and clean soils. The washing parameters for syntethic surfactants usage were as follows: temperature 21 ◦C, time 20 min, shaking speed 200 rpm, surfactant concentration (below the CMC and CMC). Parameters for bacterial washing were the same as synthetic surfactant, except temperature (37 ◦C) and time (till the stationary optical density and 1 hour after reaching stationary optical density). The concentration of remaining hydrocarbons in soil was determined using GC/MS. The surfactants were found to have considerable potential in removing crude oil from contaminated soil. The removal of oil products contamination by biological surfactants was about 50% more effective than synthetic surfactants. Synthetic surfactants cleaned about 30% of oil hydrocarbons from contaminated soil, when biological surfactants cleaned more than 70% of them. The most influential parameters on oil removal were surfactant type and concentration.