Investigation of Suitable, Readily Available, Sources of Sulfate-Reducing Bacteria Inoculum, and Evaluation of Sulfate Reduction Rates Achieved at Different pHs.

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This study investigated the suitability of readily available and naturally occurring sources of microorganisms (inoculum) to use for the cultivation of sulphate-reducing bacteria (SRB) for acid mine drainage (AMD) remediation. The selected inocula included AMD water (AMD), mud (MUD) and reed-bed mud (RM) from the AMD surrounds, mealworms (MW), cow dung (CD) and raw sewage sludge (RS). The suitability of the different inoculum sources was evaluated by comparing the SO4 2- reduction and sulfide (S2-) production rates at three different pHs. Experimental results showed that the AMD, MW, MUD and CD inoculum did not produce appreciable reduction of SO4 2- to S2- and were unsuitable sources of SRB inoculum. The inoculum evaluated in pH 2 media did not achieve SO4 2- reduction. Of the inoculum assessed in pH 4 media, only the RM inoculum achieved SO4 2- reduction (40%) with S2- production (36 mg/L). In contrast, a notable S2- production, RS (114 mg/L) and RM (99 mg/L), accompanied the SO4 2- reduction achieved in the pH 7.5 RS (44%) and RM (30%) samples. The improved S2- produced/SO4 2- removed conversion ratios for samples pH 7.5 RS (0.14) and pH 7.5 RM (0.17) are indicative of increased SRB activity and the suitability of these inoculum as SRB sources.