Determination of the dynamics of the odour release from a pig house, using an electronic odour sensor.

The widely fluctuating operating conditions in pig husbandry, due to climatic and biological changes (changes in temperature and air flowrate between day and night, as well as between summer and winter, increasing animal mass during the fattening process, etc.) exert a significant influence on the amount of actual odour emission. The project presented here comprised the measurement of seasonal (fattening course), daytime-related, and short-term (feeding) dynamic effects of odour release, as well as the identification of potential factors which influence the amount of odour emitted. In parallel with "classic" olfactometry, an electronic odour sensor with a chemosensor array of ten metal oxide sensors was employed. The highest odour emissions are measured on hot summer days, while the lowest emissions were determined on cold winter days. On the one hand, the sensor signals of the electronic odour sensor exhibited considerable differences on days with large volume flow alterations. On the other hand, continuous measurement with the electronic odour sensor allowed changes in the gas- and odorant composition of the exhaust air during feeding times to be shown. From the measurement results, recommendations for odour sampling, the consideration of seasonal odour emission fluctuations, and the use of electronic odour sensors for the evaluation of odour emissions have been derived.     

The effect of two ammonia-emission-reducing pig housing systems on odour emission.

Odour nuisance from agricultural activities is increasing in densely populated countries like the Netherlands. To develop adequate regulations, a large-scale, government-financed monitoring programme was started in the mid-1990s to establish odour emission levels for both conventional and low ammonia emission housing systems for cattle, pigs and poultry. The results indicate that high- and low-odour emission housing are difficult to distinguish because of the large variation within housing systems. Measurements on different farm locations within the same housing system show both a large variation between locations and within one location (in time). The latter, however, is significantly smaller, which suggests that farm management is an important determinant in odour emission that interferes with the effects of housing systems. The current research was aimed at determining the effect of two common ammonia-reducing pig-housing systems on odour emissions compared to conventional housing systems under similar management conditions. The respective reduction principles of these systems are reducing the emitting surface of the manure pit and cooling of manure in the manure pit (both pits beneath slatted floor). Five farms that combined conventional housing with one low-ammonia system (three reduced emitting surface and two manure cooling) were selected for a direct, pair-wise comparison of (olfactometric) odour emission measurements. The results show a highly significant effect (p < 0.01) for two of the three reduced emitting surface systems and for one of the two manure cooling system. The average odour reduction percentages of these systems are 35% (from 24.9 to 16.0 OUE/s per animal) and 23% (from 30.1 to 24.0 OUE/s per animal) respectively. Although odour emission reduction through the type of housing system is possible, management factors interact with the system and thereby determine whether the system reduces odour emission or not.     

Taste and odour research: a utility's perspective.

Tastes and odours issues constitute not only a rich field for research, but also a major challenge for water utilities. Addressing such problems requires sustained research programmes and the development of long-term proactive control measures; individual water utilities have found this hard to achieve, but collaborative approaches are proving successful. This is highlighted by taste and odours incidents in the 1990s in the Lake Ontario region that led to the formation of the Ontario Water Works Research Consortium. This collaboration of utilities with scientists and technical expertise in universities and government has enabled the linking of resources to a far more extensive programme than individual utilities could conduct, avoiding duplication of work, and providing a central mechanism for effective public outreach.     

Periphyton: a primary source of widespread and severe taste and odour.

In the last decade, a late summer-fall taste and odour problem has been a prolonged and annual event in the St Lawrence River (SLR). Earlier work identified the earthy/musty compounds geosmin and particularly, 2-methylisoborneol (GM-MIB), and ruled out Lake Ontario as a major source, but did not identify the biological origins. In 2000, we investigated the source(s) and underlying causes. We sampled littoral sites in the SLR near Cornwall, ON, and found that macrophytes (or associated biofilms) may be primary GM sources. Zebra mussel homogenate yielded low GM-MIB levels, but several associated actinomycetes generated high in vitro amounts. Periphyton from rocks showed significant yields, with cell-bound GM-MIB up to one hundred times the levels in overlying water. In 2001, we followed seasonal changes at some of these sites. Periphyton GM-MIB showed intriguing spatial and temporal patterns. Several cyanobacteria in these biofilms were identified as potential odour sources, notably Oscillatoriales. We conclude: i) periphyton is a major odour source in the SLR; ii) other biota such as macrophytes and mussels may also contribute; iii) seasonality in GM-MIB production and ratios indicate changes in cell production and/or taxa in response to environment. These results may account for the recent onset of the problematic odour events, which represent chemical signals of the increased water transparency and littoral surface area following the widespread dreissenid mussel invasion to the Great Lakes. Our data raise key questions about the processes that trigger the tremendous variability in biota and GM-MIB production in the SLR, the subject of our continued research.     

Anoxic control of odour and corrosion from sewer networks.

Anoxic processes can effectively control odour and corrosion in sewer networks. However, the absence of fundamental knowledge on the kinetics of anoxic transformation of sewage prevents the engineering applications of anoxic control in sewers. This paper focuss on a basic understanding of the anoxic transformations needed for a conceptual simulation of the water phase processes. Experiments conducted in batch reactors have shown that nitrite builds up in wastewater during denitrification. Part of the nitrate-reducing biomass is capable of utilizing nitrite after nitrate is depleted. Compared with aerobic transformation, anoxic processes have low values of maximum growth rate of the biomass and also a low endogenous respiration rate. Heterotrophic yield determined under anoxic conditions, at level of 0.25 mmol e-eq (mmol e-eq)(-1), accounted for less than 40% of the corresponding aerobic values.     

Needs and perspectives of odour research in the aquatic sciences.

Over more than four decades odour research in the aquatic sciences has increasingly focused on cyanobacteria and the common odour-causing compounds, geosmin and 2-methylisoborneol. Success in future research requires a long-term perspective. Key areas for investigation are secondary metabolites and cyanobacteria, regulatory mechanisms for geosmin and other compounds' synthesis; understanding their spatial and temporal distribution (particularly relating to the food web in a habitat); and molecular mechanisms for liberation of geosmin by microorganisms.     

Synthesis and odour thresholds of mixed halogenated anisoles in water.

Earthy-musty off-flavour compounds in water samples are usually associated with the presence of geosmin and 2-methylisoborneol. However, the presence of 2,3,6- and 2,4,6-trichloroanisoles or other halogenated anisoles can impart objectionable tastes and odours to the water even at very low trace levels. This paper shows the synthesis of non-commercial 2,3,6- and 2,4,6- mixed chloro/bromoanisoles which can be present in bromide rich waters and could also be suspected of imparting earthy-musty off-flavours to the water. All the synthesized compounds were subjected to the flavour profile analysis (FPA) method and their odour threshold concentrations (OTC) in water were carried out giving values in the low ng/L range.     

The anatomy of odour wheels for odours of drinking water, wastewater, compost and the urban environment.

In the drinking water and air pollution fields, odour quality characterisation and intensity of each odour characteristic needs to be developed to evaluate the causes of the odours present. Drinking water quality characterisation has matured to the point where an "odour wheel" is described and the primary chemicals producing the odour are known and therefore a potential treatment can be defined from the odours reported. Sufficient understanding of the types of odorous compounds that can arise from wastewater and compost treatment processes and odours in the urban environment are starting to emerge. This article presents the anatomy of the odour wheels. It is hoped that the foundation of odour wheels will evolve as odour quality data are reported and linked with chemical causation. The compost and urban odour wheels are presented in print for the first time.     

An analytical method for shipboard extraction of the odour compounds, 2-methylisoborneol and geosmin.

Extractions for the analysis of geosmin and 2-methylisoborneol (MIB) were carried out on board a research vessel by extracting water samples in the collection bottles with dichloromethane. The extracts are stable and can be stored for up to two months with no apparent loss of analytes. Workup and analysis could be done at the rate 15-20 samples per week. Approximately 150 samples from Lake Ontario were analyzed in 2000 and 120 samples in 2001. Concentrations as low as 1 ng/L could be detected, but reliable determination was only attained above 5 ng/L (> 80% qualifier ion match within +/- 50%). Reproducibility between duplicates was generally better than 10%, and recovery of surrogate standards from reagent water averaged ca. 80% and from lake water ca. 60%. In early September, 2000, geosmin concentrations in Lake Ontario ranged from 1-13 ng/L and MIB from 1-31 ng/L. In 2001, the ranges were 1-47 and 1-56 ng/L for geosmin and MIB, respectively. Lowest concentrations occurred in the western and central regions and highest concentrations in the eastern region and St Lawrence River.     

Study of the effect of DMSO on VOS odour production in a wastewater plant.

Odours caused by volatile organic sulphides (VOS) have a history spanning over 20 years for Philadelphia's Northeast Water Pollution Control Plant (NEWPCP). A "canned corn" type of odour has caused residential complaints. Traditional odour control approaches based on hydrogen sulphide failed. This study confirmed that dimethyl sulphoxide (DMSO) from a chemical facility was the dominant cause of the "canned corn" nuisance odour in the form of dimethyl sulphide (DMS). During a discharge, DMSO concentrations up to 12 mg/L were found in the influent of the NEWPCP. Each DMSO concentration peak induced a DMS peak. DMS concentrations increased from less than 50 microg/L to 6 mg/L with a corresponding decrease in DMSO. Approximately 79% of DMSO from the primary sedimentation influent was passed to the effluent, and to downstream processes, such as the aeration tanks where the DMS was volatilised by the aeration. The DMS partial pressure in ambient air of NEWPCP can be between 0.03 and 0.18 x 10(-3) atm during a DMSO discharge. From the above information, the potential of VOS production is estimated and a practical plan for remediation can be designed.     

Evaluating odour impacts from a landfilling and composting site: involving citizens in the monitoring.

The City of Montreal operates a large sanitary landfill site within a densely populated urban area. Adjacent to the landfill site is a yard waste composting facility that processes 10,000 metric tons per year using the windrow technique. Over the years, numerous complaints have been received from citizens in the surrounding area regarding odours, particularly during the fall period. Aware of this nuisance, the City of Montreal wanted to identify odour sources, management operations leading to odours, and weather conditions accentuating odours, as well as to quantify actual odour impact. Forty-three (43) citizens living adjacent to this site were recruited and trained to make odour observations during the fall of 2000. This paper presents the methodology used to select and train the citizens chosen to make odour observations, to quantify and to identify odours. It also presents the main results of the study.     

Identification of the odour and chemical composition of alumina refinery air emissions.

Alcoa World Alumina Australia has undertaken comprehensive air emissions monitoring aimed at characterising and quantifying the complete range of emissions to the atmosphere from Bayer refining of alumina at its Western Australian refineries. To the best of our knowledge, this project represents the most complete air emissions inventory of a Bayer refinery conducted in the worldwide alumina industry. It adds considerably to knowledge of air emission factors available for use in emissions estimation required under national pollutant release and transfer registers (NPRTs), such as the Toxic Releases Inventory, USA, and the National Pollutant Inventory, Australia. It also allows the preliminary identification of the key chemical components responsible for characteristic alumina refinery odours and the contribution of these components to the quality, or hedonic tone, of the odours. The strength and acceptability of refinery odours to employees and neighbours appears to be dependent upon where and in what proportion the odorous gases have been emitted from the refineries. This paper presents the results of the programme and develops a basis for classifying the odour properties of the key emission sources in the alumina-refining process.     

Advanced treatment for taste and odour control in drinking water: case study of a pilot scale plant in Seoul, Korea.

Taste and odour problems of tap water in Seoul are attributed to 2-methylisoborneol (2-MIB) and trans-1,10-dimethyl-trans-9-decalol (geosmin), which are the result of metabolism of algae and chlorine for disinfection. This study was carried out to measure 2-MIB and geosmin in the raw water from the Han River, to investigate removal efficiency of GAC and BAC integrated with post-ozonation, and to minimise and quantify the required chlorine concentration as a final disinfectant through the candidate process.     

A methodology for identifying vulnerable locations to taste and odour problems in a drinking water system.

In this research, methodology was developed to identify locations vulnerable to taste and odour problems in a distribution system. The methodology was based on a multicriteria procedure combining spatial information on consumer complaints and popular perception of tap water. The first step in the described methodology consisted of mapping complaints regarding tap water made by the population between 2002 and 2004 using a geographical information system (GIS). The second step consisted of analysing results of a questionnaire-based mail survey, also through GIS. The information generated using the above steps was integrated using a multicriteria and spatial approach allowing segregation of the distribution system into delineated zones, according to their vulnerability to occurrences of taste and odour problems. The identification of vulnerable sectors in a distribution system will help water managers to implement a better-targeted water quality monitoring programme--one that considers odours and tastes of drinking water--within the management process.     

Design and application of a GC-SNIff/MS system for solving taste and odour episodes in drinking water.

This paper describes the implementation of a GC-Sniff/MS system that allows the simultaneous determination of the odorous properties of compounds eluting from a GC column and their identification by MS. The technique was first tested with standard compounds then applied to real cases of taste and odour episodes. This approach allowed the identification of geosmin at low levels and suggested the possible implication of methylnaphthalene in the development of chemical odours. It provided the first clue of the presence of a halophenol with a very low odour threshold involved in a chlorophenolic odour episode. The chemical was finally identified as 2,6-dibromophenol. The method was also applied to the characterization of a complex mixture of additives leaching from a flexible rubber pipe. In the latter case, Time-of-Flight MS was also used to confirm the identity of the additives.     

The odour of digested sewage sludge--determination and its abatement by air stripping.

This paper describes a project to investigate the odour of sewage sludge after anaerobic digestion. The impact of air stripping on the odour of liquid sludge and on the quality of the dewatered product was evaluated at a full-scale sludge treatment installation. A continuous and a batch air-stripping mode were tested. Odour samples were collected during air stripping from the liquid sludge and from the biosolids surface during long term storage. The biosolids were also analysed for hedonic tone and for their potential odour expressed as an odour unit per unit mass. The odour emission profiles for continuous and batch air stripping demonstrated a reduction in the overall (time weighted) emissions during a 24 hr-period compared with emissions from the quiescent liquid storage tank. The averaged specific odour emission rate (Esp) of the biosolids derived from the continuous process was only 13% of the Esp of the biosolids derived from unaerated liquid sludge during the first month of storage. The results of the total potential odour and the hedonic tone of the biosolids underpin the beneficial effects of the air stripping. Odour dispersion modelling showed a noticeable reduction in overall odour impact from the sludge centre when air stripping was applied. The reduction was primarily associated with the reduced odour from stockpiled biosolids. The continuous air-stripping mode appeared to provide the greatest benefits in terms of odour impact from site operations.     

Water Environment Research Foundation (WERF) anaerobic digestion and related processes, odour and health effects study.

Biosolids odour emissions can affect the ability of wastewater utilities to implement beneficial biosolids processing and reuse programs. Communities often become more sensitised and vocal about biosolids issues, once they experience odours emanating from a nearby site. Odour impacts from biosolids, including potential human health effects, have been targeted recently by many national and local newspapers, citizens' groups, and regulatory agencies, who have raised significant concerns, ranging from viable disposal methods/sites to outright bans. Many national and local regulatory agencies in the United States are considering biosolids disposal bans in their communities because of misinformation, poor science, and citizen pressure, but primarily because of odour impact concerns. The wastewater industry has a relatively poor understanding of the operations and treatment parameters that influence biosolids odour emissions. Thus, wastewater treatment plants are often unable to control the odour quality of the biosolids that are delivered into communities. A research study to demonstrate the influence of anaerobic digestion, mechanical dewatering, and storage design and operating parameters on the odour quality of the final product was performed and is the subject of this paper. Established and new sampling and analytical methods were used to measure biosolids odour emissions from 11 test sites in North America. By determining the impacts of these control variables on biosolids odour quality, design and operations of anaerobic digestion systems might be enhanced. This paper also summarises a corollary study performed as part of the WERF research study that addresses the health effects of biosolids odours.     

Ambient odour testing of concentrated animal feeding operations using field and laboratory olfactometers.

The Missouri Air Conservation Commission regulations include regulations that limit the amount of acceptable odor from confined animal feeding operations (CAFOs). The regulations concerning odor designate the use of a scentometer as a screening tool. The rules dictate that if an odor is detectable by an investigator at a dilution ratio of 5.4 using a scentometer then an air sample should be collected and sent to an olfactometry laboratory for an odor panel to determine the detection threshold and the intensity of the odor sample. The detection thresholds are determined following ASTM E679-91 and EN13725. The intensity is determined following ASTM E544-99. If the olfactometry laboratory determined the detection threshold of the sample to be above seven, then the CAFO would be in violation. If the olfactometry laboratory determined the intensity level to be above a level equivalent to 225 ppm of n-butanol, then the source of odor would be in violation. The CAFO odor rules came under scrutiny by representatives of the largest hog producer in the State of Missouri. Specifically, they argued that the detection threshold limit of seven in the CAFO portion of the rule was too low for the rule to realistically identify a violation. This paper presents the results of a study to find the appropriate regulatory level of odor as determined by laboratory olfactometry. The study took place from November 2001 to October 2002. Samples were collected from field locations that exhibited odor produced by confined animal feeding operations and from areas exhibiting no apparent odor. The odors were categorized based upon the scentometer level at which the odors were detectable, and then samples were sent to an odor evaluation laboratory for analysis by olfactometry.     

Monitoring of biological odour filtration in closed environments with olfactometry and an electronic nose.

Air treatment with a compact biological membrane filter, and air quality monitoring with an electronic nose were tested in the laboratory on air from a cage containing six mice. Additional analyses of air to and from the filter were performed using olfactometry and ammonia and hydrogen sulphide gas detection tubes. The biological air filter is a module containing biofilm-coated membrane fibres that separate a closed liquid loop from a gas phase. Odour compounds and oxygen diffuse through the membranes from the gas phase to the biofilm, where they are degraded to carbon dioxide and water. The prototype "ENQBE" electronic nose is based on an array of eight thickness shear mode resonators (TSMR), also known in the literature as quartz microbalance sensors. The chemical sensitivity is given by molecular films of metalloporphyrins and similar compounds. Chemical interaction of compounds in the air with the vibrating sensors induces a frequency change of the vibration that can be measured as a signal. The air from the mouse cage had a strong odour (3490 OUE/m3). The biological membrane filter performed well, achieving over 80% odour and ammonia reduction. The electronic nose signal could be correlated with the inlet and outlet air-quality of the biological filter, making it a promising method for monitoring air quality in closed environments.     

Odour emission inventory of German wastewater treatment plants--odour flow rates and odour emission capacity.

Wastewater Treatment plants can cause odour emissions that may lead to significant odour annoyance in their vicinity. Thus, over the past 20 years, several measurements were taken of the odour emissions that occur at WWTPs of different sizes, treatment technology, plant design and under different operating conditions. The specific aspects of odour sampling and measurement have to be considered. I presented some of the results of my odour emission measurements 11 years ago. However, it is now necessary to update the figures by evaluating newer measurement results obtained from measurements taken from 1994 to 2003. These are presented in this paper. Also, the paper highlights the odour emission capacity (OEC) measurement technique which characterises liquids and can be used to assess the results achieved by different types of treatment in the liquid phase, e.g. in a sewerage system. In addition, the OEC is a suitable parameter to set standards for the odorant content of industrial wastewaters that are discharged into the publicly owned sewerage system.