Sulfur Recovery from Wastewater Using a Micro-aerobic External Silicone Membrane Reactor (ESMR)

Sulfide, found in some wastewaters and industrial off-gases, is a toxic and highly corrosive pollutant, especially in wastewater applications. Sulfide removal was studied in a new sulfide-oxidizing reactor (External Silicone Membrane Reactor—ESMR) that employs a tubular silicone rubber membrane for micro-aeration. The chemical and biological sulfide oxidation at pH 8.0, 9.0, and 10.0 were investigated. The applied velocity (Vs) in the membrane was also investigated as a system control parameter. The local overall mass transfer coefficient (R) was estimated for the tubular silicone rubber membrane and had an average value of 0.153 m.h−1. Oxygen mass transfer was found to not be influenced by the applied velocity. The sulfide oxidation to sulfate could be partially avoided and the biotic tests showed larger sulfur aggregates deposited in the silicone membrane, which could easily be washed away upon flushing. By contrast, colloidal sulfur formation observed in the chemical oxidation assays was harder to separate from the liquid phase. This study reveals that the ESMR is a suitable reactor design to promote partial sulfide oxidation because it provides an adequate oxygen supply with minimized aeration costs.