Submitted to: Chesapeake Research Conference Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 6/1/2001
Publication Date: N/A
Citation: Interpretive Summary: Wastewater and sludge can contribute to on-site odors generated from the unit processes handling the biosolids product. These odors can persist in downstream management of sludge or biosolids. Therefore, it is important to maintain conditions that minimize production of odorous solids from the unit processes. Odors can be controlled by minimizing the retention time within unit processes and/or by maintaining an oxidized product during processing. Prior to identifying methods to control odors, it is necessary to initially characterize the odors from sludge and biosolids produced from unit processes. SPME utilizes a small, coated fiber that equilibrates with the gas phase prior to direct analysis by gas chromatography. The fibers are relatively inexpensive, reusable, and can be used in ambient and laboratory experiments for analysis of multiple volatile organic compounds. In this study, SPME has been utilized to characterize and quantify the odorous compounds in the headspace over thickened sludge collected from a gravity thickener (GT) and a dissolved air flotation (DAF) thickener at the Blue Plains Wastewater Treatment Plant, Washington DC. Odorous gases from the final biosolids cake produced from the liming and drying processes were also determined. The target analytes were trimethylamine (TMA), carbon disulfide (CS2), dimethyl sulfide (DMS), dimethyl disulfide (DMDS), propionic acid (PA), and butyric acid (BA). CS2, DMDS, PA and BA were detected in headspace over the GT sludge while only DMS and DMDS could be detected over the DAF sludge. Even though polymer was used in the secondary sludge tank, TMA was not detected over the DAF sludge. However, TMA along with DMDS was detected over the final lime stabilized sludge cake.
Technical Abstract: Odors from a wastewater treatment or biosolids management facilities have attracted public attentions and caused many legal actions recently. Therefore, a lot of studies have been carried out to control the odors from the facilities. However, to develop a proper control scheme, it is critical to have an easy and accurate measurement technology for the odorous gases. In this study, an easy method to characterize and quantify odorous gases from sludge and biosolids has been developed. Solid phase microextraction has been applied to analyze the odorous gases flowing out of the head space of sludge and biosolids. A bench scale unit for calibrating SPME fibers against odorous compounds, i.e., trynethylamine, carbon disulfide, dimethyl sulfide, dimethyl disulfide, propionic acid, and butyric acid, was set up. Based on the calibration curve for each compound, odors from samples collected at the Blue Plains Wastewater Treatment Plant were analyzed. For sample analysis, each sludge or biosolid sample of 600mL was transferred into a 1L Teflon jar and the head space was flushed with pure N2 gas at the rate of 72 mL/min. The odorous compounds in the off gas from the head space were extracted by exposing SPME fibers to the off gas for 1 hr. With this experimental procedure and set-up, the odors from sludge and biosolids could be easily analyzed. The method provided in this study can contribute the better understanding of the odor development from sludge and biosolids, and the development of the control scheme to reduce the odor.