Biological treatment of an alternating source of organic compounds in a single tube extractive membrane bioreactor

The performance of a single tube extractive membrane bioreactor (STEMB) exp osed to an alternating sequence of toluene (TOL) and dichloromethane (DCM) was investigated. These compounds are two of the most commonly used solvent s in the chemical and pharmaceutical industries, and so were used to simula te the scenario of sequentially alternating pollutants. Undefined microbial cultures were used. During experiments, no TOL accumulation was detected i n the STEMB. It may be possible that a commensal microbial relationship dev eloped in the system, which maintained the microbial culture responsible fo r TOL degradation active throughout experiments. On the other hand, accumul ation of DCM was detected whenever this compound was introduced. These accu mulations resulted in a transient decrease in the removal efficiency of the STEMB. The influence of the membrane-attached biofilm in decreasing DCM di scharges was shown. Investigations into the use of an additional carbon sou rce to improve the system response were carried out during critical periods of operation, eg start-up and starvation periods. This strategy proved a s uccessful tool in reducing DCM discharges. (C) 2000 Society of Chemical Ind ustry.