A simple and reliable technique has been developed and used to detect odorous gases, i.e. propionic and butyric acids, carbon disulfide, dimethyl sulfide, dimethyl disulfide, and trimethylamine, emitted from various materials generated by the wastewater treatment process. The method detection limits are in the low ppb range and comparable to the odor threshold for human detection. In this study solid phase microextraction (SPME) was employed to characterize and quantify odorous compounds in the headspace over samples collected from various unit processes at the District of Columbia Wastewater Treatment Plant, Washington DC, USA. The patterns of odorous chemicals released from wastewater influent, thickened sludge, dewatered sludge and biosolids were evaluated. Volatile reduced sulfurs were more prevalent in samples collected from downstream processes and corresponded with decreased oxidation-reduction potential (ORP) conditions. Volatile fatty acids were consistently identified in the primary gravity thickeners, while trimethylamine could only be detected from biosolids after the post-liming process.

Although aluminum-and iron-based chemicals have been broadly used as the two most common types of coagulants for wastewater treatment, their impacts on the performance of downstream sludge management can be quite different and have not been well understood. This work reviewed and analyzed their similarities and differences in the context of the anaerobic digestion performance, dewaterability of digested sludge, and odor emission from dewatered biosolids. In short, iron-based coagulants tend to show less negative impact than aluminum-based coagulants. This can be attributed to the reduction of ferric to ferrous ions in the course of anaerobic digestion, which leads to a suite of changes in protein bioavailability, alkalinity and hydrogen sulfide levels, and in turn the sludge dewaterability and odor potential. Whether these observations still hold true in the context of thermally hydrolyzed sludge management remains to be studied. Practitioner Points• The impacts of aluminum-/iron-based coagulant addition on municipal sludge anaerobic digestibility, dewaterability, and odor emission are reviewed.• Iron-based coagulants show less negative impact on the sludge digestibility than aluminum-based coagulants.• Conclusions may aid practitioners in selecting coagulants in practice and better understanding the mechanisms behind the phenomena.

This study for the first time investigated the turnover of dissolved organic nitrogen in lab-scale thermal hydrolysis pretreatment at different temperatures with and without mesophilic anaerobic digestion at a solids retention time of 15 days.

Lime stabilized biosolids produced from a wastewater treatment plant can often emit odors, especially 'fishy' and 'decaying' odors. These odors can generate public opposition to biosolids land application programs, although it is an environmentally friendly recycling of organic material that is beneficial to 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 de-watered limed biosolids show increased TMA production with further increases with 1 hour and 4 hour storage times prior to liming. Further experiments with water/silica slurry reaction media reveal that enzymaticallyfacilitated degradation of polymer and protein is the over-riding factor in TMA and DMDS production. It is hypothesized that macromolecules like polymer and proteins in biosolids are first broken down enzymatically, following which, the addition of lime causes TMA and DMDS to be released.

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.