An N-2 strip gas was used in a packed bed sulfate-reducing bioreactor to recover the dissolved sulfide product and improve sulfate conversion. The highest volumetric productivity obtained was 261 mol H2S m(-3) d(-1). Lowering the initial pH of the medium from 7 to 6 increased the H2S content of the strip gas from 3.6 to 5.8 mol%. The ratio of strip gas to liquid flow rates (G/L) was found be to a suitable basis for scaling the process. Calculations indicated that modest G/L values (< 10(2)) were required to recover the residual dissolved sulfide in a downstream stripping column.