A novel isolated bacterium Rhodococcus sp. YSPW03 was able to reduce high concentrations (up to 700 mg L(-1)) of perchlorate using acetate as electron donor. Perchlorate reduction rate increased from 2.90 to 11.23 mg L(-1) h(-1) with increasing initial acetate concentration from 100 to 2000 mg L(-1), leading to complete removal of perchlorate (100 mg L(-1)) within 9 h. The bacterium also promoted complete reduction of high perchlorate concentrations (500 and 700 mg L(-1)) at 2000 mg L(-1) of acetate within 48 and 96 h, respectively. Under semi-continuous reactor operation, efficient reduction on varied perchlorate concentrations (80-700 mg L(-1)) was performed by the bacterium in presence of acetate (600-6000 mg L(-1)) over 140 days. The highest perchlorate reduction rate of 280 mg L(-1) day(-1) was observed with an initial perchlorate concentration of 570 mg L(-1) at day 34. Dissolved chloride ions of 1000 mg L(-1) in the semi-continuous reactor (SCR) completely inhibited the biological perchlorate reduction. The findings of this study will help improve the perchlorate bioreactor design and determine the optimal conditions to maximize the perchlorate reduction efficiency.
