Examination of Mechanisms for Odor Compound Generation During Lime Stabilization

Abstract

Lime‐stabilized biosolids produced from a wastewater treatment plant often emit odors, especially those described as “fishy” and “decaying”. These odors can generate public opposition to biosolids land‐application programs even though they represent an environmentally friendly recycling of organic material that is beneficial to the agricultural industry. Therefore, it is critical to examine the controlling factors involved in odor production during the lime stabilization process. Results from preliminary experiments examining added polymer and protein material to dewatered limed biosolids show increased trimethylamine (TMA) production with further increases in 1‐hour and 4‐hour storage times prior to liming. Further experiments with water‐silica slurry reaction media reveal that enzymatically facilitated degradation of polymer and protein is the overriding factor in TMA and dimethyldisulfide (DMDS) production. It is hypothesized that macromolecules such as polymer and proteins in biosolids are first broken down enzymatically, upon which the addition of lime causes TMA and DMDS to be released.

Emission characteristics of nitrogen- and sulfur-containing odorous compounds during different sewage sludge chemical conditioning processes

“…Similar phenomena about nitrogen-containing gases were found by other researchers. Kim et al [21] attributed the amine odor trimethylamine generation to increased pH and temperature caused by lime addition. Chang et al [3] believed that the product organic amines volatilized mostly noticeably due to the high pH of lime-added sludge.…”

Real-Time Monitoring and Forecasting of Odor After Dewatering in Wastewater Treatment

“…Therefore, DCWASA now adds polymer in primary process, secondary process, nitrification process, dewatering process and dissolved air Floatation (DAF) process in order to improve clarification or hold sludge particles together. Several studies have shown that polymer added into sludge is a main factor that increases biosolids odor, especially amine product, e.g., Trimethyl Amine (TMA) (Kim 2001a). According to Kim (2001a), microbial activity in waste activated sludge and degradation of polymer added in DAF results in the production of TMA.…”

“…Several studies have shown that polymer added into sludge is a main factor that increases biosolids odor, especially amine product, e.g., Trimethyl Amine (TMA) (Kim 2001a). According to Kim (2001a), microbial activity in waste activated sludge and degradation of polymer added in DAF results in the production of TMA.…”

The Unusual Scent of Toronto Biosolids Investigation of the Causes and Solutions

“…Investigations of odours from biosolids frequently identify the organic sulphur compounds (such as dimethyl sulphide (DMS), dimethyl disulphide (DMDS), dimethyl trisulphide (DMTS) and methyl mercaptans) as significant contributors to odour impacts (Kim et al, 2001, O'Connor et al, 2000, Sutton et al, 1999, Winter and Duckham, 2000, Rosenfeldet al, 2001. Other malodorous compounds associated with wastewater treatment plants may include volatile fatty acids (VFAs), phenolic compounds (such as p-cresol), amines (such as trimethyl amine (TMA)), and heavier compounds that may be the result of the degradation of proteins into amino acids and subsequently into compounds such as indole and skatole (ibid).…”

“…Also of note is the fact that undigested sludges are rich in extra cellular protein that is available for degradation (Kim et al, 2001). Where excess protein is available and pH values are high (such as when liming is used for stabilization of undigested sludge), the potential for generation of malodorous compounds is increased (Kim et al, 2001 andSutton et al, 1999).…”