RESUMEN
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.
Asunto(s)
Carbón Orgánico , Filtración , Odorantes , Carbón Orgánico/química , Filtración/métodos , Cocos/química , Carbono/químicaRESUMEN
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.
Asunto(s)
Odorantes , Instalaciones de Eliminación de Residuos , Odorantes/análisis , Recursos HídricosRESUMEN
The odor threshold concentration and the odor nuisance concentration of the nine persistent odorants at two wastewater treatment facilities were determined by Weber- Fechner curves for each odorant using dynamic olfactometry combined with the odor profile method. The odor threshold concentration results, representing each odorant's concentration at odor intensity of one (I = 1), were within range in the literature. The nuisance concentrations were determined by interpolation along the curves intersecting with the arbitrary odor intensity of three (I = 3). There is no reference that exists in the literature about determining odor nuisance concentrations for a complete set of odorants from any facility. The nuisance concentration results presented here are novel to odor control because they can provide information defining the nuisance odorant's isopleths in modeling and in designing effective odor control systems that avoid public nuisance. Dynamic olfactometry combined with the odor profile method was also used with actual foul air samples from different sources. When analyzed from raw to increased dilution, it was observed that the fecal and sulfur odors initially prominent (with no musty odors detected) gradually changed with increased dilution. Musty odors began to gradually appear while the fecal and sulfur odors became undetectable. We named this observation the "peeling of an onion effect". It is speculated that this occurs because the musty odors in the concentrated foul air sample are masked by the fecal and the sulfur odors.
Asunto(s)
Odorantes , Aguas Residuales , Odorantes/análisis , OlfatometríaRESUMEN
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.
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Sulfuro de Hidrógeno , Aguas Residuales , Odorantes/análisis , Compuestos de Sulfhidrilo , Aguas Residuales/análisisRESUMEN
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.
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Contaminantes Atmosféricos , Compuestos de Azufre , Contaminantes Atmosféricos/análisis , Odorantes/análisis , Azufre , Aguas ResidualesRESUMEN
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.
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Contaminantes Atmosféricos/análisis , Odorantes/análisis , Olfato , Aguas Residuales , Adolescente , Adulto , Anciano , California , Femenino , Cromatografía de Gases y Espectrometría de Masas , Humanos , Masculino , Persona de Mediana Edad , Instalaciones de Eliminación de Residuos , Purificación del Agua/métodos , Adulto JovenRESUMEN
Los objetivos generales del proyecto fueron: determinar la eficiencia de un sistema experimental que utiliza efluentes tratados para la acuacultura controlando las condiciones ambientales de las lagunas para mejorar el crecimiento de los peces; demostrar la viabilidad económica; y evaluar los riesgos a la salud ocasionados por el consumo de los pescados y camarones. Los objetivos principales de la participación del CEPIS fueron: realizar los análisis y evaluar la calidad de los efluentes en relación a los criterios establecidos para la acuacultura; determinar los niveles de pre-tratamiento necesarios para mantener la calidad requerida en las lagunas; monitorear y mantener una adecuada calidad del agua en el pretratamiento y en las lagunas; colaborar en el entrenamiento de investigadores y diseminar información sobre acuacultura con efluentes tratados sin diluir. Presenta los materiales y métodos; resultados; dimensiones; conclusiones. El segundo volumen contiene tablas con los resultados obtenidos
Asunto(s)
Lagunas de Estabilización , Efluentes Tratados , Control de la Calidad del AguaRESUMEN
Muestra generalidades sobre la importancia del tratamiento de aguas residuales, historia y tipos de lagunas de estabilización. Trata sobre su manejo en lo referente a trabajos de supervisión, hidráulicos, de rutina (observaciones de campo y análisis en el sitio) y muestreos. Analiza los trabajos de procesamiento de datos sobre flujos diarios, DBOs y cargas orgánicas semanales, períodos de retención y dispersión, balance mensual de agua. Presenta consideraciones sobre llenado inicial de lagunas, control de olores y limpieza de fondo