Evaluation of Health Hazard Due to Emission of Volatile Organic Compounds from Various Processing Units of Wastewater Treatment Plant

Release characteristics and risk assessment of volatile sulfur compounds in municipal wastewater treatment plants

In recent years, the malodorous gases generated by sewage treatment plants have gradually received widespread attention due to their sensory stimulation and health hazards. The emission concentration, sensory evaluation and health risk assessment of volatile sulfur compounds (VSCs) were all explored in two municipal wastewater treatment plants (WWTPs) with oxidation ditch and anaerobic/oxic treatment process, respectively. The VSCs concentration showed the highest amount in the primary treatment unit in both the two WWTPs (73.3% in Plant A and 93.0% in Plant B), while the H2S took the main role in the composition of VSCs. However, H2S took a larger percentage in Plant A (84.5% ∼ 87.0%) rather than Plant B (61.2% ∼ 83.5%), which may be due to the different operating conditions and sludge properties in different treatment process. Besides, H2S also gained the first rank in the sensory evaluation and health risk assessment, which may cause considerable sensory irritation and health risk to workers and surrounding residents. Furthermore, the influencing factor analyses of VSCs emission showed that the temperature of water and air, ORP of sludge made the greatest effect on VSCs release. This study provides theoretical and data support for the research of VSCs emission control in WWTPs.

Release characteristics and risk assessment of volatile sulfur compounds in a municipal wastewater treatment plant with odor collection device

Due to the malodorous effects and health risks of volatile sulfur compounds (VSCs) emitted from wastewater treatment plants (WWTPs), odor collection devices have been extensively utilized; however, their effectiveness has rarely been tested. In the present investigation, the characteristics of VSCs released in a WWTP equipped with gas collection hoods are methodically examined by gas chromatography. The obtained results indicate that the concentration of VSCs in the ambient air can be substantially reduced, and the primary treatment unit still achieves the highest concentration of VSCs. Compared to WWTPs without odor collection devices, the concentration of H2S in this WWTP is not dominant, but its sensory effects and health risks are still not negligible. Additionally, research on the emission of VSCs from sludge reveals that the total VSCs emitted from dewatering sludge reaches the highest level. Volatile organic sulfur compounds play a dominant role in the component and sensory effects of VSCs released by sludge. This study provides both data and theoretical support for analyzing the effectiveness of odor collection devices in WWTPs, as well as reducing the source of VSCs. The findings can be effectively employed to optimize these devices and improve their performance.

Multi-dimension analysis of volatile sulfur compound emissions from an urban wastewater treatment plant

Long-term monitoring of volatile sulfur compounds (VSCs) released at the water-air interface from different treatment units of an anaerobic/oxic (A/O) wastewater treatment plant (WWTP) was carried out to assess the temporal and spatial emission characteristics of VSCs, to explore relationships between wastewater quality and VSC release. The VSC from non-aerated and aerated units were collected using dynamic and static chambers, respectively, and determined using gas chromatography. The VSC emission fluxes diminished in the order of primary sedimentation tank (PST) > anaerobic areas (ANA) > oxic section 1 (OX1). VSCs were not detected in the oxic section 2 (OX2), the oxic areas section 3 (OX3), and the final setting basin (FSB). Release capacities of VSCs descended in the order of summer > fall > spring > winter, with July, August, and September being the months with the highest VSC release capacities. VSC emission fluxes correlated well with wastewater temperatures, sulfate concentrations, and COD. VSC emission flux empirical equations based on wastewater temperature, sulfate concentrations, and COD were established. Based on the established VSC emission empirical equation, a control strategy to reduce the operating costs of deodorization facilities was proposed. This strategy is economically efficient and reduces the consumption of electrical energy.

Wearable Device for Cumulative Chlorobenzene Detection and Accessible Mitigation Strategies

Chronic exposure to low concentrations of volatile organic compounds (VOCs), such as chlorobenzene, is not being monitored in industrializing countries, although VOC exposure is associated with carcinogenic, organ-toxic, and endocrine-disrupting effects. Current VOC-sensing technologies are inaccessible due to high cost, size, and maintenance or are ineffective due to poor sensitivity or reliability. In particular, marginalized individuals face barriers to traditional prescription VOC treatments due to cost, lack of transportation, and limited access to physicians; thus, alternative treatments are needed. Here, we created a novel cumulative wearable color-changing VOC sensor with a paper-based polydiacetylene sensor array for chlorobenzene. With a single smartphone picture, the sensor displays 14 days of logged chlorobenzene exposure data, interpreted by machine-learning (ML) techniques, including principal component analysis. Further, we explored the efficacy of affordable and accessible treatment options to mitigate a VOC's toxic effects. Vitamin D and sulforaphane are naturally found in cruciferous vegetables, like broccoli, and can be used to treat chlorobenzene-mediated bone degradation. Our platform combines these components into a smartphone app that photographs the sensor's colorimetric data, analyzes the data via ML techniques, and offers accessible treatments based on exposure data.

Wastewater Treatment Plants as a Source of Malodorous Substances Hazardous to Health, Including a Case Study from Poland

Using Poland as an example, it was shown that 41.6% of the requests for intervention in 2016-2021 by Environmental Protection Inspections were related to odour nuisance. Further analysis of the statistical data confirmed that approximately 5.4% of wastewater treatment plants in the group of municipal facilities were subject to complaints. Detailed identification of the subject of odour nuisance at wastewater treatment plants identified hydrogen sulphide (H₂S), ammonia (NH₃) and volatile organic compounds (VOCs) as the most common malodorous substances within these facilities. Moreover, the concentrations of hydrogen sulphide and ammonia exceed the reference values for some substances in the air (0.02 mg/m³ for H₂S and 0.4 mg/m³ for NH₃). A thorough assessment of the properties of these substances made it clear that even in small concentrations they have a negative impact on the human body and the environment, and their degree of nuisance is described as high. In the two WWTPs analysed in Poland (WWTP 1 and WWTP 2), hydrogen sulphide concentrations were in the range of 0-41.86 mg/m³ (Long-Term Exposure Limit for H₂S is 7.0 mg/m³), ammonia 0-1.43 mg/m³ and VOCs 0.60-134.79 ppm. The values recognised for H₂S cause lacrimation, coughing, olfactory impairment, psychomotor agitation, and swelling of the cornea with photophobia. Recognition of the methods used in practice at WWTPs to reduce and control malodorous emissions indicates the possibility of protecting the environment and human health, but these solutions are ignored in most facilities due to the lack of requirements specified in legislation.

The impact of endocrine disrupting compounds and carcinogens in wastewater: Implications for breast cancer

The incidence of breast cancer is often associated with geographic variation which indicates that a person's surrounding environment can be an important etiological factor in cancer development. Environmental risk factors can include exposure to sewage- or wastewater, which consist of a complex mixture of pathogens, mutagens and carcinogens. Wastewater contains primarily carbonaceous, nitrogenous and phosphorus compounds, however it can also contain trace amounts of chemical pollutants including toxic metal cations, hydrocarbons and pesticides. More importantly, the contamination of drinking water by wastewater is a potential source of exposure to mammary carcinogens and endocrine disrupting compounds. Organic solvents and other pollutants often found in wastewater have been detected in various tissues, including breast and adipose tissues. Furthermore, these pollutants such as phenolic compounds in some detergents and plastics, as well as parabens and pesticides can mimic estrogen. High estrogen levels are a well-established risk factor for estrogen-receptor (ER) positive breast cancer. Therefore, exposure to wastewater is a risk factor for the initiation, progression and metastasis of breast cancer. Carcinogens present in wastewater can promote tumourigenesis through various mechanisms, including the formation of DNA adducts, gene mutations and oxidative stress. Lastly, the presence of endocrine disrupting compounds in wastewater can have negative implications for ER-positive breast cancers, where these molecules can activate ERα to promote cell proliferation, survival and metastasis. As such, strategies should be implemented to limit exposure, such as providing funding into treatment technologies and implementation of regulations that limit the production and use of these potentially harmful chemicals.

Characterization of odour emissions in a wastewater treatment plant using a drone-based chemical sensor system

Conventionally, odours emitted by different sources present in wastewater treatment plants (WWTPs) are measured by dynamic olfactometry, where a human panel sniffs and analyzes air bags collected from the plant. Although the method is considered the gold standard, the process is costly, slow, and infrequent, which does not allow operators to quickly identify and respond to problems. To better monitor and map WWTP odour emissions, here we propose a small rotary-wing drone equipped with a lightweight (1.3-kg) electronic nose. The "sniffing drone" sucks in air via a ten-meter (33-foot) tube and delivers it to a sensor chamber where it is analyzed in real-time by an array of 21 gas sensors. From the sensor signals, machine learning (ML) algorithms predict the odour concentration that a human panel using the EN13725 methodology would report. To calibrate and validate the predictive models, the drone also carries a remotely controlled sampling device (compliant with EN13725:2022) to collect sample air in bags for post-flight dynamic olfactometry. The feasibility of the proposed system is assessed in a WWTP in Spain through several measurement campaigns covering diverse operating regimes of the plant and meteorological conditions. We demonstrate that training the ML algorithms with dynamic (transient) sensor signals measured in flight conditions leads to better performance than the traditional approach of using steady-state signals measured in the lab via controlled exposures to odour bags. The comparison of the electronic nose predictions with dynamic olfactometry measurements indicates a negligible bias between the two measurement techniques and 95 % limits of agreement within a factor of four. This apparently large disagreement, partly caused by the high uncertainty of olfactometric measurements (typically a factor of two), is more than offset by the immediacy of the predictions and the practical advantages of using a drone-based system.

Assessment of exposure to dust, gaseous pollutants and endotoxins in sewage treatment plants of Ahmedabad city, India

BACKGROUND: Sewage treatment plant workers (STPs) are exposed to gaseous pollutants (H2S) and bioaerosols and their health is at risk. OBJECTIVE: The aim of the study was to evaluate exposures to dust, 1,3 Beta D Glucans, endotoxins and gaseous pollutants in different process plants and to provide suitable recommendations. METHODS: Gaseous pollutants and bioaerosols (inhalable dust, 1,3 beta D-glucans and endotoxins) were evaluated in two sewage treatment plants (STPs) of Ahmedabad city, India. The concentration of H2S, CO, CH4 and Cl2 were monitored in two process areas of STPs using real-time gas detectors. The dust, 1,3 beta D-glucans and endotoxins were evaluated as per standard methods. RESULTS: The mean concentration of H2S exceeded the permissible exposure limit of 10 ppm, whereas the concentration of other gaseous pollutants (CO, Cl2 and CH4) were below the permissible exposure limits of Indian Factories Act, 1948. The inhalable dust concentration was also within the permissible exposure limit of 10 mg/m3 as per Indian Factories Act, 1948. CONCLUSIONS: Significant exposures to gaseous and bioaerosols were found in the work environment of STPs. The paired t-test result showed a significant difference between two STPs for H2S, 1,3 beta D-Glucans and endotoxins. STPs were advised to reduce the exposure to H2S and bioaerosols as per CPCB guidelines applicable to India to prevent health effects.

Metagenomics analysis of probable transmission of determinants of antibiotic resistance from wastewater to the environment - A case study

During mechanical-biological treatment, wastewater droplets reach the air with bioaerosols and pose a health threat to wastewater treatment plant (WWTP) employees and nearby residents. Microbiological pollutants and antimicrobial resistance determinants are discharged to water bodies with treated wastewater (TWW), which poses a potential global epidemiological risk. In the present study, the taxonomic composition of microorganisms was analyzed, and the resistome profile and mobility of genes were determined by metagenomic next-generation sequencing in samples of untreated wastewater (UWW), wastewater collected from an activated sludge (AS) bioreactor, TWW, river water collected upstream and downstream from the wastewater discharge point, and in upper respiratory tract swabs collected from WWTP employees. Wastewater and the emitted bioaerosols near WWTP's facilities presumably contributed to the transmission of microorganisms, in particular bacteria of the phylum Actinobacteria and the associated antibiotic resistance genes (ARGs) (including ermB, ant(2″)-I, tetM, penA and cfxA2) to the upper respiratory tract of WWTP employees. The discharged wastewater increased the taxonomic diversity of microorganisms and the concentrations of various ARGs (including bacA, emrE, sul1, sul2 and tetQ) in river water. This study fills in the knowledge gap on the health risks faced by WWTP employees. The study has shown that microbiological pollutants and antimicrobial resistance determinants are also in huge quantities discharged to rivers with TWW, posing a potential global epidemiological threat.

Dynamic Olfactometry and Oil Refinery Odour Samples: Application of a New Method for Occupational Risk Assessment

Refineries are characterized by relevant odour impacts, and the control and monitoring of this pollutant have become increasingly important. Dynamic olfactometry, a sensorial analysis that involves human examiners, is currently the most common technique to obtain odour quantification. However, due to the potential presence of hazardous pollutants, the conduction of occupational risk assessment is necessary to guarantee examiners’ safety. Nevertheless, the occupational risk for olfactometric examiners, specifically correlated with oil refineries emissions, has not been investigated yet. Therefore, this paper applies a new methodology of risk assessment for workers involved in dynamic olfactometry, focusing on odorous refineries emissions. The chemical characterization of refinery emissions was obtained by TD-GC-MS, analysing odorous samples collected at different refinery odour sources. A database of chemical pollutants emitted from a refinery plant was built up, and the minimum dilution values to be adopted during the analysis of refinery odorous samples was calculated. In particular, this evaluation highlighted that, in this scenario, a non-negligible carcinogenic risk may exist for panellists exposed to refineries’ samples, and the carcinogenic risk is sometimes higher than what is acceptable. Therefore, a minimum dilution value between 1.01 and 5, according to the specific sample, must be set to guarantee the examiners’ safety.

Evaluation of Odor Prediction Model Performance and Variable Importance according to Various Missing Imputation Methods

The aim of this study is to ascertain the most suitable model for predicting complex odors using odor substance data that has a small number of data and a large number of missing data. First, we compared the data removal and imputation methods, and the method of imputing missing data was found to be more effective. Then, in order to recommend a suitable model, we created a total of 126 models (missing imputation: single imputation, multiple imputations, K-nearest neighbor imputation; data preprocessing: standardization, principal component analysis, partial least square; and predictive method: multiple regression, machine learning, deep learning) and compared them using R2 and mean absolute error (MAE) values. Finally, we investigated variable importance using the best prediction model. The results identified the best model as a combination of multivariate imputation using Bayesian ridge as the missing imputation method, standardization for data preprocessing, and an extremely randomized tree as the predictive method. Among the odor compounds, Methyl mercaptan, acetic acid, and dimethyl sulfide were identified as the most important odor compounds in predicting complex odors.

Odor emissions: A public health concern for health risk perception

The olfactory nuisance, due to the emissions of active molecules, is mainly associated with unproperly managed waste disposal and animal farming. Volatile compounds e.g., aromatics, organic and inorganic sulfide compounds, as well as nitrogen and halogenated compounds are the major contributor to odor pollution generated by waste management plants; the most important source of atmospheric ammonia is produced by livestock farming. Although an odorous compound may represent a nuisance rather than a health risk, long-term exposure to a mixture of volatile compounds may represent a risk for different diseases, including asthma, atopic dermatitis, and neurologic damage. Workers and communities living close to odor-producing facilities result directly exposed to irritant air pollutants through inhalation and for this reason the cumulative health risk assessment is recommended. Health effects are related to the concentration and exposure duration to the odorants, as well as to their irritant potency and/or biotransformation in hazardous metabolites. The health effects of a single chemical are well known, while the interactions between molecules with different functional groups have still to be extensively studied. Odor emissions are often due to airborne pollutants at levels below the established toxicity thresholds. The relationship between odor and toxicity does not always occurs but depends on the specific kind of pollutant involved. Indeed, some toxic agents does not induce odor nuisance while untoxic agents do. Accordingly, the relationship between toxicity and odor nuisance should be always analyzed in detail evaluating on the characteristics of the airborne mixture and the type of the source involved.

Health risks of inhalation exposure to BTEX in a municipal wastewater treatment plant in Middle East city: Shiraz, Iran

Benzene, toluene, ethylbenzene, and xylene, known as BTEX, adversely affect human health. This study aimed to measure BTEX concentration and assess the health risk through inhalation exposure to these compounds in a municipal wastewater treatment plant. The ambient air samples were collected using the active sampling method in summer and winter. Sampling sites were close to wastewater treatment units, including bar screen & grit chamber (Site-1), aeration tank & secondary clarifiers (Site-2), anaerobic sludge digester (Site-3), and office & control building (Site-4). Results indicate that the mean levels of benzene and toluene in winter were higher than in summer. The levels of benzene and toluene were below the occupational exposure levels of the American Conference of Governmental Industrial Hygienists (ACGIH) and Occupational Safety and Health Administration (OSHA). The carcinogenic risk (CR) and hazard quotient (HQ) were assessed using the United States Environmental Protection Agency (U.S.EPA) method, and Monte Carlo simulation (MCS) was applied to quantify the uncertainty and sensitivity analysis. The CRs for all sampling sites were below the U.S.EPA threshold limit (1.0 × 10^-4). The HQ values for benzene nearby Site-2 were above 1.0, indicating inhalation exposure could pose a health hazard. Besides, the HQ results for exposure to toluene in all sampling sites were less than 1.0. The sensitivity analysis had shown that the risk determinant for carcinogenic and non-carcinogenic risk was exposure time, followed by concentration.

Emission, dispersion, and potential risk of volatile organic and odorous compounds in the exhaust gas from two sludge thermal drying processes

Emissions of odorous and volatile organic compounds (VOCs) were investigated between two sludge drying methods. A total of 37 chemical compounds were identified and quantified from the off-gases from sludge drying by indirect drying method. The total number of VOCs detected ranged from 3.45 × 10^-3 to 4.53 mg/m³, which includes benzene series, volatile organic sulfur, and nitrogenous organic compounds. High emissions were found in the exhaust gas released from drying workshop that used direct drying method. Sulfur dioxide, aromatics, and chlorinated compounds were dominant. Based on the olfactory effect analysis and cancer risk assessment, the main odor-causing gaseous pollutants were methyl mercaptan and methyl sulfide (for indirect sludge drying process) and SO₂ (for direct sludge drying process), while the dominant carcinogens were benzene, carbon tetrachloride, chloroform, and methylene. This study provides new insights into the emission characteristics, olfactory effects, and cancer risks of VOCs and odorous compounds in the exhaust gas from thermal sludge drying processes.

An innovative biofilter technology for reducing environmental spreading of emerging pollutants and odour emissions during municipal sewage treatment

Wastewater treatment plants (WWTPs) are known sources of contaminants of emerging concern (CECs) spreading into the environment, as well as, of unpleasant odors. CECs represent a potential hazard for human health and the environment being pharmaceutical or biologically active compounds and they are acquiring relevance in European directives. Similarly, the public concern about odour emissions from WWTPs is also increasing due to the decreasing distance between WWTP and residential areas. This study focuses on the effectiveness of the recently developed MULESL technology (MUch LEss SLudge; WO2019097463) in removing CECs and limiting odour emissions from WWTPs. MULESL technology has been developed for its ability to reduce up to 80% the sludge production from WWTPs. However, it is ought to evaluate if the benefits coming from sludge production reduction do not invalidate CECs removal or negatively affect odour emissions. Thus, the performances of a MULESL and a conventional WWTP (flow rate of 375 m³/d and 3600 m³/d, respectively) were compared while treating the same municipal sewage. Whereas both plants succeeded in removing the traditional gross parameters characterizing wastewaters (e.g. chemical oxygen demand, nitrogen), the MULESL was much more effective than the conventional one in terms of CECs removal for about 60% of the identified compounds showing, however, the same or lower effectiveness for about 30% and 10% of them, respectively. This result was attributed to the high sludge retention time and biomass concentration in the MULESL (enabling enrichment of slow growing microorganisms and forcing biomass to use unusual substrates, respectively), and to the biomass feature to grow in the form of biofilm and granules (favoring micropollutants absorption on biomass). Furthermore, odour impact analysis has shown that the MULESL was characterized by a much lower impact, i.e. 45% lower than that of primary and secondary treatments of the conventional WWTP.

A review of the emergence of antibiotic resistance in bioaerosols and its monitoring methods

Despite significant public health concerns regarding infectious diseases in air environments, potentially harmful microbiological indicators, such as antibiotic resistance genes (ARGs) in bioaerosols, have not received significant attention. Traditionally, bioaerosol studies have focused on the characterization of microbial communities; however, a more serious problem has recently arisen due to the presence of ARGs in bioaerosols, leading to an increased prevalence of horizontal gene transfer (HGT). This constitutes a process by which bacteria transfer genes to other environmental media and consequently cause infectious disease. Antibiotic resistance in water and soil environments has been extensively investigated in the past few years by applying advanced molecular and biotechnological methods. However, ARGs in bioaerosols have not received much attention. In addition, ARG and HGT profiling in air environments is greatly limited in field studies due to the absence of suitable methodological approaches. Therefore, this study comprehensively describes recent findings from published studies and some of the appropriate molecular and biotechnological methods for monitoring antibiotic resistance in bioaerosols. In addition, this review discusses the main knowledge gaps regarding current methodological issues and future research directions.

Data Analytics Determines Co-occurrence of Odorants in Raw Water and Evaluates Drinking Water Treatment Removal Strategies

A complex dataset with 140 sampling events was generated using triple quadrupole gas chromatography-mass spectrometer to track the occurrence of 95 odorants in raw and finished water from 98 drinking water treatment plants in 31 cities across China. Data analysis identified more than 70 odorants with concentrations ranging from not detected to thousands of ng/L. In raw water, Pearson correlation analysis determined that thioethers, non-oxygen benzene-containing compounds, and pyrazines were classes of chemicals that co-occurred, and geosmin and p(m)-cresol, as well as cyclohexanone and benzaldehyde, also co-occurred, indicating similar natural or industrial sources. Based on classification and regression tree analysis, total dissolved organic carbon and geographical location were identified as major factors affecting the occurrence of thioethers. Indoles, phenols, and thioethers were well-removed through conventional and advanced treatment processes, while some aldehydes could be generated. For other odorants, higher removal was achieved by ozonation-biological activated carbon (39.3%) compared to the conventional treatment process (14.5%). To our knowledge, this is the first study to systematically identify the major odorants in raw water and determine suitable treatment strategies to control their occurrence by applying data analytics and statistical methods to the complex dataset. These provide informative reference for odor control and water quality management in drinking water industry.

Wastewater treatment plants as a reservoir of integrase and antibiotic resistance genes - An epidemiological threat to workers and environment

Conventional mechanical and biological wastewater treatment is unable to completely eliminate all pollutants, which can therefore enter surface water bodies together with treated wastewater. In addition, bioaerosols produced during wastewater treatment can pose a threat to the health of the wastewater treatment plant staff. In order to control the impact of a wastewater treatment plant (WWTP) on the surrounding environment, including its employees, samples of wastewater and water from a river which received treated wastewater were analysed in terms of their content of antibiotics and heavy metals, levels of selected physiochemical parameters, concentrations of antibiotic-resistance genes (ARGs) and genes of integrases. Furthermore, a quantitative analysis of ARGs in the metagenomic DNA from nasal and throat swabs collected from the WWPT employees was made. Both untreated and treated wastewater samples were dominated by genes of resistance to sulphonamides (sul1, sul2), MLS group of drugs (ermF, ermB) and beta-lactams (bla_OXA). A significant increase in the quantities of ARGs and concentrations of antibiotics was observed in the river following the discharge of treated wastewater in comparison to their amounts in the river water upstream from the point of discharge. Moreover, a higher concentration of ARGs was detected in the DNA from swabs obtained from the wastewater treatment plant employees than from ones collected from the control group. Many statistically significant (p < 0.05) correlations between the concentration of the gene of resistance to heavy metals cnrA versus ARGs, and between the ARGs content and the concentrations of heavy metals in both wastewater and river water samples were observed. The study has demonstrated that the mechanical and biological methods of wastewater treatment are not efficient and may affect the transmission of hazardous pollutants to the aquatic environment and to the atmospheric air. It has been shown that an activated sludge bioreactor can be a potential source of the presence of multi-drug resistant microorganisms in the air, which is a health risk to persons working in WWTPs. It has also been found that an environment polluted with heavy metals is where co-selection of antibiotic resistance may occur, in the development of which integrase genes play an essential role.

Toxicological assessment method for evaluating the occupational risk of dynamic olfactometry assessors

The paper aims to propose a new method to evaluate the occupational exposure risk for examiners involved in dynamic olfactometry. Indeed, examiners are possibly exposed to hazardous pollutants potentially present in odorous samples. A standardized method to evaluate the examiners' occupational safety is not yet available and the existing models present some critical aspect if applied to real odorous samples (no uniform reference concentrations applied and presence of compounds for which no toxicity threshold is available). A deepening of assessment procedure to evaluate the occupation exposure risk for olfactometric assessors is necessary. This paper proposes a standardized approach for risk assessment in dynamic olfactometry. The proposed approach allows the quantification synthetic and conservative risk indices. In this model, the use of the hazard index for the odorous mixture was proposed to assess the non-carcinogenic risk; the calculation of the inhalation risk was applied to estimate the carcinogenic risk. Different databases can be used to retrieve proper occupational exposure limits, according to the proposed hierarchical basis. These implementations allow obtaining the complete characterization of real samples which can be used to calculate the minimum dilution factor for protecting the panellists' health.

Emission characteristics of odorous volatile sulfur compound from a full-scale sequencing batch reactor wastewater treatment plant

Volatile sulfur compounds (VSCs) generated and discharged as air pollutants from wastewater treatment plants (WWTPs) pose a threat to human health and the environment. This study characterized VSC emissions from a full-scale sequencing batch reactor (SBR) WWTP at the water-air interface for one year. Results demonstrated that higher ambient temperatures and aeration contributed significantly to VSC emissions as the highest emissions occurred over summer during the feeding synchronous aeration period. VSC emissions were related to chemical oxygen demand and sulfate concentrations in wastewater, and empirical formulas based on these values were proposed that can be used to model VSC emission fluxes from SBR WWTP. VSC emission factors (μg·ton^-1 wastewater) throughout the SBR treatment process were: 361 ± 101 hydrogen sulfide (H₂S), 82 ± 76 methyl mercaptan (MT), 61 ± 31 dimethyl sulfide, 17 ± 5 carbon disulfide, and 46 ± 24 dimethyl disulfide. H₂S and MT were the dominant odors released. Findings from this study may be applicable for calculating VSC emissions during SBR wastewater treatment stages, and may be beneficial for determining methods and strategies to reduce VSCs.

Review of Methods for Assessing the Impact of WWTPs on the Natural Environment

Environmental management in facilities such as wastewater treatment plants (WWTPs) allows for the implementation of the Deming cycle, and thus the constant improvement of the mitigation of the environmental impact. The correct diagnosis of the current state of functioning of the WWTPs, the identification of aspects that may have a measurable impact on the environment, and their assessment are of key importance. The article discusses the possible causes of the impact of WWTPs on the natural environment. Among other problems, such issues as energy consumption, noise and the formation of bioaerosols and odor nuisances were taken into account. Different ways of assessing the impact of wastewater treatment plants on the environment were collated, taking into account the need to assess not only the technological process itself but also the buildings during their use. The results of methods for assessing the environmental impact of wastewater treatment plants in selected countries were also compared.

Integral evaluation of granular activated carbon at four stages of a full-scale WWTP deodorization system

Odor emissions from wastewater treatment plants (WWTPs) have always been a public concern. In this work, the physico-chemical, olfactometric and textural characterization of granular active carbon (GAC) used by an urban WWTP as a deodorization system, as well as the chromatographic quantification of the retained odoriferous compounds, have been carried out. These techniques have allowed an integral evaluation of the contaminated GAC and the characterization of the retained gaseous emission from four different stages of the wastewater treatment (pretreatment header: GAC-1; sand and fat removal: GAC-2; sludge thickening: GAC-3; sludge dehydration: GAC-4). A larger amount and variety of retained odoriferous compounds were found in GAC samples from the wastewater line deodorization (GAC-1 and GAC-2) after the same operation time (one year), GAC-1 being the adsorbent bed that retained the highest mass of volatile compounds (approximately 150μg/g GAC). Furthermore, some variables such as the removed specific odor concentration and free micropore volume were inversely correlated (R²=0.9945). The analysis of odor contribution showed that sulfur-containing compounds were the major odor contributors (61-97%). However, hydrogen sulfide cannot be considered a key odorant in this particular WWTP, since the elimination of this compound does not reduce the significant contribution of other (organic) sulfur compounds to the global odor (especially dimethyl disulfide). Consequently, multi-technical analysis might be a suitable alternative to better understand odor removal by GAC adsorption.

Gaseous emissions from wastewater facilities

A review of the literature published in 2019 on topics relating to gaseous emissions from wastewater facilities is presented. This review is divided into the following sections: odorant emissions from Water Resource Recovery Facilities (WRRFs); greenhouse gas (GHG) emissions; gaseous emissions from wastewater collection systems; physiochemical odor/emissions control methods; biological odor/emissions control methods; odor/GHG characterization and monitoring; and odor impacts/risk assessments. © 2020 Water Environment Federation PRACTITIONER POINTS: Provide a quick reference list for readers who do not have time to go through the 2019 published articles. This prescreening of relevant literatures will save them time and effort. Utilities, engineers, and researchers can identify knowledge gaps, which help them to plan for future testing and R&D needs. Designers can make use of the lit review findings to support their design.

Impact of Odor Nuisance on Preferred Place of Residence

Context of the research: Research is increasingly carried out to take into account the social behavior of residents, the type of industry located in the area, and perceived preference for the place of residence. The quality of life in urban space is increasingly seen as a problem of cooperation between various stakeholders. These studies not only identify factors and sources of odor emissions, but also serve as the basis for creating systems to alert people living in areas adjacent to industrial areas or harmful and unpleasant industrial emissions. In recent years, environmental issues, particularly unpleasant sensory experiences, have been one of the most important acceptance criteria. Aim of the article: The aim of the study is to assess the impact of odor nuisance in the south-eastern part of Kraków (Płaszów) on the residents’ decision to leave their place of residence. In particular, the research goal was achieved to indicate which of the unpleasant odors may cause a change of residence, as well as to assess the degree of their impact on the decision to move, taking into account the social and demographic characteristics of residents. New in the article: The novelty of the work was the finding out of the residents’ opinions about the quality of life by accepting the place of residence, taking into account the aspect of odor nuisance. Previous studies on odor nuisance have focused on the emission of odors from individual plants. A novelty of this research is its implementation in an urban area, in which numerous industrial plants are located, with various odors emitted. Research methodology: To assess odor nuisance, a measuring tool developed in accordance with VDI 3883 guidelines was used, based on the latest research results on odor and noise nuisance. The questionnaire was developed based on German experience. Conclusions from the research: The data obtained as a result of the research allow us to state that specific smells are so burdensome that they may cause the necessity to leave the place of residence, because the respondents feel various unpleasant smells that have an adverse impact upon the quality of life that they perceive. A possible need for relocation of domiciles out of the current place of residence due to unpleasant smells would affect the perceptible, specific level of grief—the greater it is, the more attached the residents are to their current place of residence.

Assessment of the Effects of Wastewater Treatment Plant Modernization by Means of the Field Olfactometry Method

Methodological aspects of odor studies in ex-post analyses for Polish wastewater management facilities were analyzed based on the example of a modernized and enlarged wastewater treatment plant (WWTP) in Mazovia, in the vicinity of the Warsaw agglomeration. It is a mechanical–biological treatment plant with increased efficiency of biogen removal, using activated sludge in the treatment process, with a maximum hydraulic capacity of 60,000 m3/day. Olfactometric research was carried out by means of a method based on identification and characterization of the odor plume emitted from the examined source. This paper presents the results of odor intensity assessment (in sensory examinations according to a 6-stage scale) and odor concentration measurement (using portable field olfactometers) after the completion of the project, and compares them with similar studies conducted before the commencement of the investment. A total of 10 measurement series were carried out before modernization, and 12 after modernization of the WWTP. Odor concentration and intensity were determined, and the current meteorological situation was assessed at the measurement and observation points (receptors) located within the premises (in total 462 points) and around the WWTP (342 points). In each series of measurements on the windward side of the treatment plant, the background of air pollution with odorous substances was marked. The research showed that air flowing into the area of the sewage treatment plant is clean in terms of odor. During the research, basic sources of odor nuisance were identified, and their impact before and after modernization was characterized. The results presented in radar diagrams show changes in the percentage distribution of frequency of occurrence of individual intensity values at receptor points within and outside the area of the treatment plant. After modernization, a significant decrease in the concentration of odor emitted from the sludge dewatering building and sludge containers was determined. The air-tightness of the sewage channel (covered with concrete slabs and sealed) resulted in a significant decrease in the concentration of odor emitted from this source. Waste (in particular, sewage sludge) collected in the emergency waste storage yard was identified as the main source of odor nuisance. The waste, even after modernization, was an emitter of odorous compounds spreading outside the area of the WWTP. Nevertheless, as a result of the investment, the desired effect of reduction of the degree of odor nuisance was achieved.

The Use of Artificial Neural Networks and Decision Trees to Predict the Degree of Odor Nuisance of Post-Digestion Sludge in the Sewage Treatment Plant Process

This paper presents the application of artificial neural networks and decision trees for the prediction of odor properties of post-fermentation sludge from a biological-mechanical wastewater treatment plant. The input parameters were concentrations of popular compounds present in the sludge, such as toluene, p-xylene, and p-cresol, and process parameters including the concentration of volatile fatty acids, pH, and alkalinity in the fermentation sludge. The analyses revealed that the implementation of artificial neural networks allowed the prediction of the values of odor intensity and the hedonic tone of the post-fermentation sludge at the level of 30% mean absolute percentage error. Application of the decision tree made it possible to determine what input parameters the fermentation feed should have in order to arrive at the post-fermentation sludge with an odor intensity <2 and hedonic tone >−1. It was shown that the aforementioned phenomenon was influenced by the following factors: concentration of p-xylene, pH, concentration of volatile fatty acids, and concentration of p-cresol.