Effect of pH on elemental sulfur conversion and microbial communities by autotrophic simultaneous desulfurization and denitrification

ABSTRACT pH has an important influence on the elemental sulfur accumulated in an autotrophic simultaneous desulfurization and denitrification process. The influent nitrate to sulfide (N/S) mole ratio was set to 0.5, 0.67, 1.0, 1.33 and 2.0 with a 200 mg/L sulfide concentration. The effect of pH on elemental sulfur conversion and microbial communities was studied. Sulfide removal was achieved to the extent of 98% under near-neutral and weak base conditions after 24 h of reaction. The conversion rate of elemental sulfur was 29.41% under the near-neutral condition. The weak base condition led to greater formation of sulfate, and the nitrate used by the microorganisms was transformed mainly to N2 with a removal rate of 96%. Increasing the retention time from 24 to 48 h caused the removal rate of nitrate increased from 63.58% to 90% under the near-neutral condition. Sulfurovum sp. was the functioning bacterial species, and bands 1 and 2 represent different species of Sulfurovum sp. in the system according to the PCR-DGGE analysis of the microbial community structure. The functional bacteria represented by band 1 produced mainly sulfate, but the functional bacteria represented by band 2 produced mainly elemental sulfur.

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