Wastewaters contain sulfur in either the sulfite or the sulfate form. Municipal wastewaters do not usually contain enough sulfur to be a design problem, but industrial wastewaters from petroleum refining and Kraft paper mills can be a concern. Sulfate is limited to 250 mg/L in drinking waters and 200 to 600 mg/L for irrigation, depending on the type of vegetation. Sulfur is weakly adsorbed on soils, so the major pathway for removal is by plant uptake. The grasses typically used in land treatment can remove 2 to 3 kg of sulfur per 1000 kg (4 to 7 lb per 2200 lb) of material harvested (Overcash and Pal, 1979). The presence of sulfites or sulfates in wastewater can lead to serious odor problems if anaerobic conditions develop. This has occurred with some hyacinth systems, and supplemental aeration is then needed to maintain aerobic conditions in the basin.
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