Identification, quantification and treatment of fecal odors released into the air at two wastewater treatment plants.

Odorous emissions from wastewater treatment plants (WWTPs) are an annoyance for neighboring communities. This article, for the first time, quantitatively reports on an evaluation of the presence of fecal odorants identified in air samples from two exemplary WWTPs by the odor profile method (OPM) and chemical analysis. The fecal odorants indole and skatole were identified by Gas Chromatography-Mass Spectrometry. The odor threshold concentration of skatole was determined to be 0.327 ng/L (60 pptV) in Teflon Bags by an expert panel. Skatole was found to be the primary chemical leading to fecal odor, due to its odor concentration to odor threshold concentration ratio that ranged from 2.8 to 22.5. The Weber-Fechner law was followed by pure skatole, but was not applicable when there was a mixture of fecal odorants and other odorant types present in WWTP air emission samples. This is probably caused by antagonism with other odorant types. Several existing odor control treatment methods for fecal odorants were evaluated at different wastewater treatment operations at two WWTPs by the OPM and chemical analysis for indole and skatole. Chemical scrubbing and biofiltration performed best in removing fecal odors among current control technologies.

Evaluation of three granular activated carbon filters for the treatment of collections foul air entering a water resource recovery facility.

The treatment of raw foul air that could escape to the atmosphere from the head space of the incoming wastewater sewer lines into a Southern California Water Resource Recovery Facility was evaluated by using a 1/20th scale pilot unit consisting of three different granular activated carbon filter technologies, operating side by side, under similar operating conditions, each having an average 3.8-s contact time. The three activated carbon filters contained each 0.07 m3 of coconut, coal, and coconut mixed with permanganate media. The foul air entering the granular activated carbon filters contained 82% to 83% relative humidity. No moisture removal mechanism was used prior to treatment. The removal of six different odor characters from eight chemical odorants present in the foul air were assessed. These were rotten egg (hydrogen sulfide), rotten vegetables (methyl mercaptan), canned corn (dimethyl sulfide), rotten garlic (dimethyl disulfide), earthy/musty (2-methyl isoborneol and 2-isopropyl 3-methoxy pyrazine), and fecal (skatole and indole). This is the first time a study evaluates the removal of specific odors by simultaneously employing sensory analyses using the odor profile method, which defines the different odor characters and intensities, together with chemical analyses of the odorants causing these odors. The results show that the three granular activated carbon filters, before hydrogen sulfide breakthrough, provided significant improvement in odor intensity and odorant removal. Breakthrough was reached after 57 days for the coconut mixed with permanganate, 107 days for the coconut, and 129 days for the coal granular activated carbon filter. Breakthrough (the critical saturation point of the activated carbon media) was considered reached when the hydrogen sulfide percentage removal diminished to 90% and continued downward. The coconut mixed with permanganate granular activated carbon filter provided the best treatment among the media tested, achieving very good reduction of odorants, as measured by chemical analyses, and reasonable removal of odor intensities, as measured by the odor profile method. The coconut mixed with permanganate granular activated carbon is recommended for short-term odor control systems at sewer networks or emergency plant maintenance situations given its shorter time to breakthrough compared with the other granular activated carbons. The coal and coconut granular activated carbon filters are generally used as the last stage of an odor treatment system. Because of the observed poor to average performance in removing odorants other than hydrogen sulfide, the treatment stage(s) prior to the use of these granulated activated carbons should provide a good methyl mercaptan removal of at least 90% in order to avoid the formation of dimethyl disulfide, which, in the presence of moisture in the carbon filter, emit the characteristic rotten garlic odor. The differences observed between the performances based on odorant removal by chemical analysis compared with those based on sensorial analyses by the odor profile method indicate that both analyses are required to understand more fully the odor dynamics. PRACTITIONER POINTS: Three virgin granulated activated carbon media were evaluated in a field pilot unit using raw collections foul air. Coal, coconut, and coconut mixed with permanganate were tested until breakthrough. Samples were analyzed both chemically (odorants) and sensorially (odors). Coconut mixed with permanganate proved to be the media that better reduced odorants and odors.

An evaluation of masking nuisance odors from a source by chemical and sensory analyses.

There are many products in the market advertised as masking agents used to overpower strong nuisance odors, such as in or around water resource recovery facilities, solid waste processing facilities, landfills, composting sites, and so forth. Very little is known about the chemical component of these masking agents because they are protected by trade secrets. This is a problem for the parties involved, as the process of choosing the most adequate agent for the particular odor source falls into guesswork. This paper demonstrates that it is possible to determine how effective the masking product would be before spending time and resources in trials. It proposes to show this by comparing the Weber-Fechner curves of the odor-causing compounds known to be emitted at the facility with the curves from the potential masking agents prepared in the laboratory using an olfactometer. Several sensorial examples show that when the Weber-Fechner curves of the odorants and those of candidate masking agents are compared, it is possible to define the effectiveness of the masking agent tested. This is a novel use of the Weber-Fechner curves. The results show there is direct correlation between what is observed by a panel with real life odor samples subjected to incremental dilution and the Weber-Fechner odor intensity-odor concentration curve interaction between the odorants involved. Future work characterizing additional potential masking compounds by Weber-Fechner accompanied by odor profiling with dynamic olfactometry should shed light on the definitive effectiveness of this method in predicting masking effects and discovering useful masking compounds. PRACTITIONER POINTS: Weber-Fechner curves provide relationships between odorant concentration and odor intensity. Dynamic olfactometry, in which real-life air samples are sensorially analyzed by the odor profile method after subsequent dilutions, shows that odor masking occurs. Analyzing the Weber-Fechner curves of the odorants present in the dynamic olfactometry test show the existing odorant interactions. It is possible to predict the extent of the masking of potential compounds by comparing Weber-Fechner curves of masking agents against odorants causing nuisance. This methodology could help avoid spending resources in masking field trials that may result in further exacerbating the affected public.

Evaluation of bioscrubber and biofilter technologies treating wastewater foul air by a new approach of using odor character, odor intensity, and chemical analyses.

The treatment of raw foul air that could escape to the atmosphere from the head space of the incoming wastewater into a Southern California Water Resource Recovery Facility was evaluated by using a 1/20th scale pilot unit consisting of five different biological media technologies, operating side by side, under different operating conditions. The removal of six different odor characters from eight chemical odorants present in the foul air were assessed. These were rotten egg (Hydrogen Sulfide), rotten vegetables (Methyl Mercaptan), canned corn (Dimethyl Sulfide), rotten garlic (Dimethyl Disulfide), earthy/musty (2-Methyl Isoborneol and 2-Isopropyl 3-Methyl Pyrazine) and fecal (Skatole and Indole). This is the first time a study evaluates specific odors by simultaneously employing sensory analyses using the Odor Profile Method, which defines the different odor characters and intensities, together with chemical analyses of the compounds causing these odors, known as odorants. The paper discusses the efficiencies in removing odor characters as well as odorants by two different bioscrubbers (reticulated polyurethane cube foam and polypropylene mesh with layered polyester foam) and three different biofilters (engineered media, seashells, and lava rock). The results show that the two bioscrubbers, even with greater empty bed gas retention times, did not provide significant improvement in odor intensity and odorant removal. However, the biofilters showed that larger empty bed gas retention times provided significant improvements in diminishing the odor intensities and better odorant removal. The biofilter with lava rock media at 45 s empty bed gas retention time provided the best treatment among the technologies tested, achieving the following odorant reductions: 99.8% for hydrogen sulfide, 98.4% for methyl mercaptan, 57.0% for dimethyl sulfide, and 52.7 for dimethyl disulfide. This biofilter also achieved the following odor intensity reductions: 47% for rotten vegetable odors, 50% for earthy/musty odors, and 100% for fecal odors. The odor panel detected odors by the Odor Profile Method that were below the detection limit of the corresponding chemical analytical method for specific chemical compounds causing these odors. Differences were observed between the performances of bioscrubbers and biofilters, based on odorant removal compared to those based on sensorial analyses, indicating that both analyses are required to understand more fully the odor dynamics. Furthermore, a total odor removal of 99.2% was observed by the dilution to threshold olfactometer method even though nearly half of the rotten vegetable and earthy/musty odors remained based upon the Odor Profile Method. This shows the olfactometer method did not correctly define the degree of odor nuisance in the foul air in this study. Bioscrubbers have in general a better economic return when used at low EBGRTs and as preliminary (first stage) treatment systems. Biofilters are more effective when used at high EBGRTs and can be used as stand-alone or polishing systems.

Corrective factors applied to reduced sulfur compounds in wastewater foul air.

To determine accurately odorant concentrations at its worst-case condition for planning and odor treatment design purposes, corrective factors need to be factored into the foul air monitoring results of water resource recovery facilities. These corrective factors will adjust each odorant concentration for usual seasonal and daily odor variations. Typically, corrective factors are taken from hydrogen sulfide continuous readings and applied to all identified sulfur odorants. This paper demonstrates that it is incorrect to assume all reduced sulfur compounds mimic the daily fluctuations observed in hydrogen sulfide. Reduced sulfur odorant results from the foul air tested at two different water resource recovery facility process areas over a portion of the daily cycle have been found to behave independently from hydrogen sulfide. Tests have shown that the corrective factors for each reduced sulfur odorant vary notably from facility to facility and enormously from process area to process area. This discovery is important for the improvement of the science of odor control because accurately determining worst-case odor concentrations affects the modeling (the magnitude of odor nuisance) and the level of treatment (choosing a technology or combination of technologies) needed for odor abatement. PRACTITIONER POINTS: When conducting foul air assessments, corrective factors are recommended to adjust the results for daily and seasonal variations. H2 S continuous monitors are readily available and of widespread use, therefore they are certainly useful to determine corrective factors. H2 S continuous monitors, however useful for H2 S, do not necessarily apply to the rest of the reduced sulfur compounds. Intermittent sampling and analysis for reduced sulfur compounds at each facility process location over a daily cycle should be conducted. Results will show the independence of each reduced sulfur compound and the importance of this testing to obtain corrective factors applicable to the facility being assessed.

Estimated effects of disinfection by-products on preterm birth in a population served by a single water utility.

OBJECTIVES: We evaluated the association between drinking-water disinfection by-products and preterm births using improved exposure assessment and more appropriate analysis methods than used in prior studies. METHODS: During 1999-2001, vital record data were obtained for a large, racially diverse population residing in 27 Massachusetts communities that received drinking water from a single public utility. This water system was monitored weekly for total trihalomethanes (TTHM), and it maintained geographically stable total TTHM levels system-wide during the study period. We employed proportional hazards regression to examine the effects of trimester-specific and shorter-term peak exposures to TTHM in drinking water late in pregnancy on preterm births in 37,498 singletons. RESULTS: For all women, our data suggested no more than a small increase, if any, in risk for delivering a preterm baby when exposed to > or = 60 microg/L TTHM during the 4 weeks before birth [hazard ratio (HR) = 1.13; 95% confidence interval (CI), 0.95-1.35]. However, women who depended on a governmental source of payment for prenatal care were at increased risk when exposed at such levels late in gestation (HR = 1.39; 95% CI, 1.06-1.81). In contrast, exposure to high levels of TTHM during the second trimester and high exposure throughout pregnancy resulted in a 15-18% reduction in risk for preterm delivery in our population. CONCLUSIONS: This finding confirms previous reports of a negative association during the second trimester. Our data also suggested a possible positive association with shorter-term third-trimester TTHM exposure in mothers of lower socioeconomic status.

The effect of natural organic matter polarity and molecular weight on NDMA formation from two antibiotics containing dimethylamine functional groups.

N-nitrosodimethylamine (NDMA) is a disinfection byproduct preferentially formed in chloraminated water. NDMA may be formed from certain chemicals containing dimethylamine (DMA) functional groups. This reaction may be slowed by the presence of natural organic matter (NOM). In this study, NOM fractionated by size or polarity was tested for its ability to slow or impede the formation of NDMA from two DMA-containing precursors, the antibiotics tetracycline and spiramycin. The high molecular weight NOM fractions (>10KDa) were shown to be the most effective in reducing the amount of NDMA formed from the precursor chemicals. The filtrate of a C-18 non-polar cartridge was also effective at reducing NDMA formation from tetracycline (spyramycin not tested). Therefore, polar and charged NOM components may be responsible for the reduction in NDMA formation. A possible mechanism for the reduction of NDMA formation from tetracycline is complexation due to the hydrogen bonding of the DMA functional group on tetracycline to polar phenolic functional groups in the NOM.

Predicting runoff induced mass loads in urban watersheds: Linking land use and pyrethroid contamination.

Pyrethroid pesticide mass loadings in the Ballona Creek Watershed were calculated using the volume-concentration method with a Geographic Information Systems (GIS) to explore potential relationships between urban land use, impervious surfaces, and pyrethroid runoff flowing into an urban stream. A calibration of the GIS volume-concentration model was performed using 2013 and 2014 wet-weather sampling data. Permethrin and lambda-cyhalothrin were detected as the highest concentrations; deltamethrin, lambda-cyhalothrin, permethrin and cyfluthrin were the most frequently detected synthetic pyrethroids. Eight neighborhoods within the watershed were highlighted as target areas based on a Weighted Overlay Analysis (WOA) in GIS. Water phase concentration of synthetic pyrethroids (SPs) were calculated from the reported usage. The need for stricter BMP and consumer product controls was identified as a possible way of reducing the detections of pyrethroids in Ballona Creek. This model has significant implications for determining mass loadings due to land use influence, and offers a flexible method to extrapolate data for a limited amount of samplings for a larger watershed, particularly for chemicals that are not subject to environmental monitoring. Offered as a simple approach to watershed management, the GIS-volume concentration model has the potential to be applied to other target pesticides and is useful for simulating different watershed scenarios. Further research is needed to compare results against other similar urban watersheds situated in mediterranean climates.

NDMA formation during drinking water treatment: A multivariate analysis of factors influencing formation.

The formation of the carcinogen N-nitrosodimethylamine (NDMA) during drinking water treatment has raised concerns in the drinking water industry. Many bench-scale laboratory tests and pilot plant studies have been completed to try to determine which factors during water treatment increase or decrease the amount of NDMA formed in drinking water. This study used data from over 20 drinking water treatment plants in the United States and Canada to determine which factors are most highly correlated with the NDMA concentration in delivered water using a mixed effects model with a random intercept. This type of analysis has not been used previously with trihalomethane (THM) models due to the fact that those studies did not sample such a large number and range of plants as was done in this NDMA study. Ultraviolet absorbance at 254 nm (UV254) in the plant influent and pre-chlorination time used at the plant were highly correlated in all models with NDMA concentration in finished water as well as the percentage change between NDMA formation potential in the plant influent and actual formation in the finished water. Specifically, an increase in UV254 absorbance in a model was associated with an increase in NDMA and an increase in pre-chlorination time in a model was associated with a decrease in NDMA. Other water quality parameters including sucralose concentration in the plant influent, polyDADMAC polymer dose, pH, and chlorine-to-ammonia weight ratio used in the plant were also correlated with NDMA concentration in the distribution system. Lastly, NDMA precursor loading was correlated with the use of polyDADMAC (where precursors were added) and the use of ozone and granular activated carbon (GAC) treatment (where precursors were removed).

Growth of estuarine fish is associated with the combined concentration of sediment contaminants and shows no adaptation or acclimation to past conditions.

We tested whether the growth rates of small benthic fish (Gillichthys mirabilis) in three southern California estuaries corresponded with the local concentrations of contaminants. Fish originating from each estuary were transplanted to cages in each estuary in two reciprocal transplant experiments. The growth rates of caged fish, and the size-distribution of natural populations, showed the same pattern of difference among estuaries. Twelve metals and organic contaminants occurred in bulk sediments at concentrations close to their individual ERL values, and a simple index of their combined concentration (the mean ERL quotient) was inversely correlated to the growth of caged fish. Metals in the water column occurred at lower concentrations, relative to toxicity thresholds, than those in sediments and were unrelated to fish growth. Fish used in the field caging experiments, and other fish held in the laboratory under constant conditions, showed no difference in growth according to their estuary of origin. Fish originating from different estuaries also showed no consistent differences in their tissue burden of organic contaminants. Our results thus suggested no genetic adaptation or physiological acclimation to the past contaminant regime, but revealed a possible association between fish growth rates and the combined concentration of multiple sediment contaminants.

Influence of aeration on hydrophobic organic contaminant distribution and diffusive flux in estuarine sediments.

Dredging operations, resuspension events during storms, and bioturbation alter the oxic state of estuarine sediments and induce changes in the composition of dissolved and particle-associated natural organic matter. These changes may alter the distribution of hydrophobic organic chemicals (HOCs) in sediments and their diffusive flux across the sediment-water interface. In this study, the impact of aerating anoxic sediments on the distribution and diffusive flux of a model HOC, 2,2',4,4'-tetrachlorobiphenyl (TeCB), was investigated. Anoxic estuarine sediments collected from three sites along a salinity gradient were used to determine site-specific apparent sorption coefficients for porewater dissolved organic carbon (Kpwdoc) and sediment organic carbon (Koc) under anoxic and oxic conditions. A two-compartment sediment flux model was employed to examine the diffusive flux of TeCB under both oxic states. Aeration of anoxic porewaters resulted in significant decreases in porewater dissolved organic matter (DOMpw) aromaticity as indicated by declines in molar absorptivity at 254 nm (p < 0.005). Aeration also resulted in a 9-13% decrease in DOMpw concentration (p < 0.005) at the two sites exhibiting lower ionic strengths; the high ionic strength site did not exhibit a significant change in DOMpw concentration (p > 0.10). The impact of aeration on TeCB distribution and diffusive flux appeared to be site-specific. Aeration of anoxic sediments induced a significant 1.4 log unit reduction in Kpwdoc at the lowest ionic strength site (p < 0.0005), while sediments from the intermediate ionic strength site exhibited a significant 0.6 log unit increase (p < 0.005). No significant change in sorption to DOMpw was observed for the high ionic strength site (p > 0.10). The sediment displaying the drop in Kpwdoc also exhibited a significant 0.4 log unit drop in Koc (p < 0.01), while the other two sites did not exhibit significant aeration-induced changes in sorption to particle-associated organic matter (p > 0.10). No significant change in diffusive flux was observed for two sites (p > 0.10), while a significant 89-110 mg m(-2) yr(-1) increase in diffusive flux was observed at the low ionic strength site (p < 0.10). This latter result represented approximately a doubling in diffusive flux. In the systems studied, facilitation of TeCB transport across the sediment-water interface by organic colloids did not appear important.