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Musty Odor in Treated Wastewater

Novel and simple method for quantification of 2,4,6-trichlorophenol with microbial conversion to 2,4,6-trichloroanisole

ABSTRACT; S. Goto, T. Urase, K. Nakakura. Microorganisms, 11, 2133, (2023). Doi: 10.3390/microorganisms11092133

Contamination with 2,4,6-trichloroanisole (TCA) often causes taste and odor (T&O) problems in drinking water due to its low odor threshold concentration. Microbial O-methylation of the precursor 2,4,6-trichlorophenol (TCP) would be the dominant mechanism for TCA formation. Simple and rapid measurement of TCP in the low concentration range is necessary to control the problems induced by TCA. In this study, the combination of microbial conversion and instrumental analysis was proposed as a method of TCP quantification. Fungi and bacteria were isolated from various water samples and examined for their ability to produce TCA from TCP. As a result, a strain exhibiting quantitative TCA production and a high growth rate was obtained and named Mycolicibacterium sp. CB14. The conversion rate of TCP to TCA by this strain was found to be high and stable (85.9 ± 5.3%), regardless of the applied TCP concentration, although within the range of 0.1–10 µg/L. The limits of detection and quantification for TCP by this proposed method were deter-mined to be 5.2 ng/L and 17.3 ng/L, respectively. By improving the methods, Mycolicibacterium sp. CB14 could be used for the quantification of TCP at very low concentration levels, which is sufficient to manage the T&O problem caused by TCA.

Concentrations of earthy and musty odor coumpounds in treated wastewater from different treatment plants

ABSTRACT; T. Urase, H. Tsutsui. Japanese Journal of JSCE, 75, 7, III_25-III_33 (2019). Doi: 10.2208/jscejer.75.7_III_25

The concentrations of earthy and musty odor compounds were measured for 123 samples of treated wastewater taken from 25 treatment plants. 2,4,6-trichloroanisole was detected from 22 treatment plants with the average concentration of 8.4 ng/L out of the 25 target plants with the detection limit of 1 ng/L. Geosmin was detected from 24 treatment plants with the average concentration of 8.4 ng/L. The concentrations of 2,4,6-TCA and geosmin in the treated wastewater was usually higher than their odor thresholds, while the contribution of 2-MIB to the odor of treated wastewater was considered not to be significant. Higher cooncentrations of the target odorous compounds were detected for large-scale wastewater treatment plants compared with those for small-scale plants with the oxidation ditch process. 2,4,6-TCA was produced in the aeration tanks in the activated sludge process whereas the chlorination process (disinfection) did not affect the concentration of odorous compounds in the treated wastewater.

Analysis of odor of treated wastewater by gas chromatography with olfactometry detection

ABSTRACT; T. Urase, H. Tsutsui, K. Nakamura. Journal of Japan Socity on Water Environment, Vol.41, No.1, pp11-17 (2018). doi: 10.2965/jswe.41.11

A gas chromatography – olfactometry analysis was conducted for biologically treated wastewater samples from seven different plants to clarify the compounds responsible for the odor of biologically treated wastewater. The odor of 2,4,6-trichloroanisole was detected with the highest or second-highest odor intensity for the treated wastewater samples from large-scale plants whose biological reactors are covered with a roof. The treated wastewater from these large-scale plants contained 11.6 – 21.2 ng/L of 2,4,6-trichloroanisole, and this range of concentration was approximately 100 times as high as the olfactory threshold. Earthy and musty odors, probably caused by geosmin and 2-methylisoborneol, were also detected with high odor intensities in all samples. A large contribution of an unidentified compound with a sweet odor was also observed in the analysis of treated water samples. In addition to earthy and musty odors, sulfuric and septic odors were detected in the samples from small-scale plants.

Keywords; Earthy and musty odors; Treated wastewater; 2,4,6-Trichloroanisole; Gas chromatography – olfactometry

Occurrence of earthy and musty odor compounds (geosmin, 2-methylisoborneol and 2,4,6-trichloroanisole) in biologically treated wastewater

ABSTRACT; T. Urase and Y. Sasaki. Water Science and Technology, 68, 9, 1969-1975 (2013). doi: 10.2166/wst.2013.451.

The concentrations of earthy and musty odor compounds (2-methylisoborneol (2-MIB), geosmin and 2,4,6-trichloroanisole (TCA)) in treated wastewater were measured. Concentrations of 2,4,6-TCA (4.3-37.7 ng/L) and geosmin (3.7-42.2 ng/L) higher than their odor thresholds were detected for effluents from large-scale treatment plants. The effluent from a small-scale wastewater plant treating toilet and kitchen wastewater contained the target earthy and musty odor compounds below the odor thresholds. The ozonation applied as an advanced wastewater treatment process was considerably more effective for the removal of 2,4,6-TCA than for the removal of 2-MIB and geosmin. The measured concentrations of 2,4,6-TCA in river environments without the influence of large-scale wastewater effluents were less than the odor threshold.

Keywords; geosmin, odor, treated wastewater, trichloroanisole

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