Sulfidogenic anaerobic treatment to remove organic matter, sulfate and AOX from Kraft pulp mill wastewater

摘要

One obstacle to increase water recycle is the contaminant buildup that occurs as the recycle ratio increases, and sulfur compounds are especially detrimental. Sulfate removal can be achieved sulfidogenic anaerobic microorganisms to reduce the sulfate using organic matter as electron donors. This work was designed to assess the behavior of a sulfidogenic reactor treating wastewater from a kraft pulp mill. A fixed bed horizontal anaerobic reactor (100 cm of length and 5 cm in diameter), operating at 30 + 1℃ and hydraulic detention time of 12 + 1h was used to treat the effluent with the following characteristics: COD: 2270 + 75 mg/L; sulfate: 500 + 55 mg/L and, AOX: 24.2 + 1.5 mg/L. After sulfidogenesis was established the reactor showed steady performance removing 60.1 + 2.6% of the COD; 98.1 + 3.9% of the sulfate and 73.1 + 3.6% of the AOX. Concentration profiles along the reactor length showed that volatile fatty acids, AOX and sulfate were removed in the first one third of the reactor. However, the removal of the remaining biodegradable COD occurred up to the exit section. The AOX and COD removal efficiencies observed in the current work are higher than the ones found by other researchers. An explanation for this performance may rest on the sulfidogenic path that efficiently used the available organic matter for reduction of the sulfate to sulfite. To finish the treatment it is necessary to remove the sulfite, which is easier to be removed than sulfate.