Reduction of biomass in a bioscrubber for waste gas treatment by limited supply of phosphate and potassium ions

  Elimination of n-butanol from the gas phase was examined with a mixed culture in a compact bioscrubber. The extent of the cell concentration was limited by the supply of n-butanol, phosphate or potassium, and the growth rate was determined by the dilution rate. With n-butanol as the limiting substrate the cellular yield was 0.53 g dry cell weight/g n-butanol. Phosphate limitation decreased this yield to 0.34 g and potassium limitation to 0.31 g dry cell weight/g n-butanol at a dilution rate of 0.1/h. Under these conditions n-butanol was eliminated from the gas phase by 84%–100%. In the same order of limitations the specific degradation rate ranged from 0.19 g to 0.32 g n-butanol g dry cell weight⁻¹ h⁻¹. The fraction of n-butanol required to satisfy the needs for maintenance energy increased significantly depending on the limiting nutrient. Limitation by n-butanol, phosphate or potassium caused a maintenance requirement of 0.07, 0.16 and 0.34 g n-butanol g dry cell weight⁻¹ h⁻¹, thus showing a fivefold increase. This high demand for the carbon source demonstrated the feasibility of operating a bioscrubber under mineral limitation to reduce biomass formation significantly, and to maintain a high degree of substrate elimination from the gas phase. Received: 22 May 1996 / Received revision: 23 July 1996 / Accepted: 5 August 1996