What biological process is responsible for the reduction of sulfate to sulfide in wastewater?

The biological process responsible for the reduction of sulfate to sulfide in wastewater treatment is anaerobic digestion. This process occurs in environments devoid of oxygen, allowing specific microorganisms—particularly sulfate-reducing bacteria—to thrive. During anaerobic digestion, these bacteria utilize sulfate as a terminal electron acceptor in their metabolic processes, converting it to sulfide. This process is vital in environments with high sulfate concentrations and is significant in treating wastewater to prevent the release of harmful sulfates into the environment.

In contrast, aerobic respiration requires oxygen and does not facilitate the reduction of sulfate to sulfide. Denitrification focuses on the reduction of nitrates to nitrogen gas in anaerobic conditions, while nitrification is the aerobic process by which ammonia is converted to nitrate, neither of which involves the conversion of sulfate to sulfide. Anaerobic digestion effectively harnesses the unique metabolic pathways of sulfate-reducing bacteria to achieve this transformation, making it the correct answer for this question.