Use of Solid-State Bioreactors for Microbial Degradation of Organic Contaminants in Soils

摘要

Transport limitations lead to problems like a lack of oxygen which are possible reasons for slow microbial degradation of hydrocarbons in native soils. Mixing the soil leads to sufficient oxygen and nutrient supply of microorganisms and therefore to a higher microbial activity. To prevent an agglomeration of the moist soil a mechanical stress for deagglomeration has to be applied, leading to further increasing of microbial soil activity. Thus mixing and mechanical stress occur simultaneously. Even a short soil treatment shows effects lasting longer than the treatment itself. Therefore a periodic treatment shows advantages in regard to an increasing microbial soil activity. The degradation of hydrocarbons is positively influenced by both single and periodic mechanical stresses. Possible types of solid-state bioreactors are rotary drums and siloreactors. To apply the mechanical stress in order to prevent an agglomeration grinding beads are used in the rotary drum, while in the siloreactor the mechanical stress is imparted to the soil by the discharge means. To justify the use of solid-state bioreactors the soil has to be treated at a moisture content with maximum microbial activity. At this moisture content the physical properties like agglomerate strength, gas permeability and flowability are worst. In spite of that the reactors can be run troublefree by knowing and considering these properties.