Three four-chloro-aliphatic hydrocarbons (carbon tetrachloride (CT), tetrachloroethylene (PCE) and 1, 1, 2, 2-tetrachloroethane (1, 1, 2, 2-PCA)) were spiked individually at concentrations from 0.145 mg/L to 2.4 mg/L to anaerobic batch reactors treating young landfill leachate undergoing competition between main microbial groups of anaerobic consortia for an experimental period of four months. The effect of chlorinated compounds on the reactors' organic matter removal performance and microbial activities was examined. Dissolved organic matter was removed at similar rates in all reactors. Gas production ceased in CT receiving reactors and decreased in PCE receiving reactors revealing inhibition on methanogens with no effect in PCA receiving reactors. Sulfate-reducing bacteria's activity was less inhibited by chlorinated aliphatic compounds than methanogenic activity. Chlorinated aliphatic hydrocarbons (CAHs) were monitored and biotransformation of PCE and PCA to TCE and 1, 1, 2-TCA was observed via reductive dechlorination and dehydrohalogenation.