Dichloromethane levels in wastewater discharged from chemical laboratories were measured. The average concentrations of this compound in wastewater untreated and treated by a chemical wastewater treatment plant were 0.17 and 0.07 mg/l, respectively. Using a vacuum pump instead of aspirator to evaporate this solvent in the laboratories effectively reduced the amount of dichloromethane in wastewater. Furthermore, the removal efficiency of dichloromethane in the treatment plant of chemical wastewater by use of activated carbon adsorption and coagulation precipitation processes was investigated. The results of monitoring for one year showed that the removal efficiency of dichloromethane from wastewater in the treatment plant was on the average 67.4%. Our experiments showed that the prolongation of reaction time of activated carbon adsorption to 30 min sufficiently improved the removal efficiency of dichloromethane. Activated carbon adsorption process was very effective to remove this compound, but coagulation precipitation process was not effective.
