REDUCED SULFUR COMPOUND PRODUCTION AS AN INDICATOR OF STABILITY IN LIMED BIOSOLIDS
Abstract:A key issue with respect to public acceptance of the processing and land application of wastewater residuals is odor production, e.g., due to the release of reduced sulfur compounds. The overall goal of this project was to evaluate if the production of reduced sulfur species from post lime-stabilized biosolids can be minimized by improving lime incorporation. Efforts reported here focused on developing an experimental approach for quantifying the release of total reduced sulfur species from limed residual mixtures as a measure of lime incorporation and product stability. The relationship between extent of lime incorporation and emission of reduced sulfur compounds was evaluated in laboratory experiments and tested in a full-scale wastewater treatment plant. In the laboratory, dewatered sludge samples were prepared with varying levels of lime incorporation, the degree of which was assessed visually and via fecal coliform measurements. Production of reduced sulfur species in the lime-amended sludge samples was measured after nominal incubation times of 30 minutes and/or 24 hours. Samples with good mixing and complete lime incorporation released a relatively small amount of reduced sulfur compounds immediately (within 30 minutes). This release was probably due to abiotic physical/chemical processes and, as a result, the concentration remained relatively constant up to 24 hours. Poorly-mixed samples, on the other hand, released very small amounts of reduced sulfur compounds after 30 minutes of incubation. However, this concentration increased after 24 hours, probably due to microbial metabolism. These trends were confirmed at the full-scale, using samples taken at various points along the post-lime stabilization system, which had experienced different degrees of mixing and lime incorporation. Based on these results, if reduced sulfur compound release is to be used as a measure of lime incorporation and stability of post lime-stabilized biosolids, as well as odor production potential, the analysis should be performed on samples incubated on the order of 24 hours, to allow for microbially-mediated release of reduced sulfur compounds in poorly mixed samples.
Document Type: Research Article
Publication date: January 1, 2003
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