Odor Control Research Articles

Numerical Simulation of the Diffusion Characteristics of Odor Pollutants of Waste Bunkers in Waste Incineration Plant

This paper utilizes the waste bunker of a waste incineration plant as the analysis model. It analyzes the airflow characteristics under various unloading door opening states and the air flow velocity through CFD simulation. The simulation analysis results show that when one unloading door is opened, it is recommended to adjust the opening amplitude or set an air outlet to optimize the airflow distribution. If two unloading doors are opened, it is advised to prioritize the two middle unloading doors (M4, M5) or the two rightmost doors (M7, M8). Furthermore, the exhaust port located relatively far from the unloading door should be closed to reduce the turbulence of the airflow. When all unloading doors are opened, the air flow velocity at the unloading door needs to be increased to achieve an efficient exhaust effect and prevent negative pressure problems at low speed. The results offer theoretical support for odor control technologies and provide valuable design recommendations for air outlets and unloading doors in municipal waste incineration plants. Additionally, this study proposes optimization strategies and effective solutions for addressing odor pollutant diffusion in waste incineration facilities.

Competition & UV254 projection in odorants vs natural organic matter adsorption onto activated carbon surfaces: Is the chemistry right?

Powdered activated carbon (PAC) adsorption remains an indispensable method for addressing odor problems in drinking water. While natural organic matter (NOM) is ubiquitous and competes strongly in deteriorating odorant adsorption capacity, it can also serve as a promising indicator for predicting odorant adsorption through online measurement. However, the impact of PAC surface chemistry on NOM competition and feasibility of prediction across various adsorbents are not well understood. Here, we examined the role of PAC properties (pore structure and surface chemistry) in the competitive adsorption between odorants and NOM components, aligned with the applicability assessment of using NOM optical properties for odorant adsorption projection across various PAC samples. Chemical oxidation and thermal treatment achieved considerable changes in surface functional group composition, alongside minimal changes in pore structure, of two typical PAC products with microporous/mesoporous pore characteristics. The effect of NOM interference on the reduction of odorant adsorption exhibited a similar level regardless of the PACs with different pore structure (average pore size of 1.7 nm vs. 4.2 nm). Surface modification increased the equilibrium adsorption capacity (qe50) of odorants by 15.1% to 146.4% (thermal treatment) or decreased by -81.3% to -34.1% (chemical oxidation), respectively, but minimal changes in odorant-NOM selectivity. For various odorants, hydrophobicity (log D) influenced the adsorption capacity while the structural flexibility (reflected by the rotatable bonds) affected the vulnerability of odorant adsorption to NOM competition. It was found for the first time that four-parameter Richards model (RMSE = 2.6%) is superior to the linear model (RMSE = 12.5%) or logarithmic model (RMSE = 77.6%) to describe the S-shape UV254 projection curves associated with odorant adsorption on PAC. Moreover, the feasibility was confirmed to use UV254 projection curves of pristine PAC fitted with the Richard model to predict the odorant adsorption on surface-modified PAC in two different surface waters (RMSE 9.2% and 7.4%, respectively). This study provides insight into the role of PAC surface chemistry and pore characteristics in odorant adsorption in NOM-containing waters and enhances the feasibility of the NOM surrogate model for odorant monitor and control during PAC adsorption.

Основные подходы к снижению запахового загрязнения окружающей среды предприятиями животноводства (обзор)

Modern industrial livestock production is accompanied by emissions into the environment of a wide range of odorforming substances (OFS), which negatively affect the health and quality of life of the population. The problem of protecting atmospheric air from odour pollution (OP) is of high relevance and practical significance. The review critically appraises scientific publications on the control of OP from livestock and poultry farms. Methods of control include the processing of manure with deodorizing materials (reagents, sorbents, enzymes, etc.); inoculation with microorganism strains; adjustment of animal diets; air purification from pollutants; optimization of dispersion; isolation of ОР sources; and odor masking. Agriculture’s focus on adopting green technologies has increased interest in searching environmentally friendly methods of odor control. These are the use of plant extracts, natural sorbents, effective microorganism strains, biofilters, bioscrubbers, biogas plants, planting of protective forest belts that promote the absorption of dust and dispersion of OFS. Each method of OP control has both advantages and disadvantages. Modern “green” methods effectively eliminate odors in large farms, but require high investment and operating costs, which limits their implementation in practice, and relatively low-cost methods (the use of reagents, sorbents, flavoring agents, feed additives) are usually not effective enough. An acceptable result can be obtained by combining various methods of limiting the OFS emission. Control strategies should be selected based on the source of the odor, the effectiveness of the technology on the particular farm, and the cost/benefit ratio of the odor control technology into practice.

Odor emission pattern of the waste storage workshop of kitchen waste treatment plant and control strategy study with CFD simulation.

Odor emission has become a great issue for kitchen waste management plants. Among all, unorganized emission source such as waste storage tank is the key cause. It is necessary to understand the odor emission characteristics and provide a proper control solution. In this study, a typical kitchen waste treatment plant located in Guangdong Province of China was selected to investigate the odor emission characteristics. According to the survey, the main complaint due to odor emission is on waste storage workshop. Hence, its odor emission has been investigated in this study. The gas samples were collected from the workshop in different season. According to the results, the odor emission during summer is the worst. In total, 105 odorous gases were detected from the waste storage workshop. The main odorous gases can be categorized into sulfur compounds, oxygen-containing organic compounds and terpenes. In specific, ethanol, acetic acid, methylmercaptan, α-pinene, methioether and limonene were the major odorous pollutants. Based on grey correlation, principal component analysis (PCA) and step-up regression analysis, methylmercaptan contributes the most to the odor concentration. It suggests that the odor emission control should pay more attention on methylmercaptan. The Computational Fluid Dynamics (CFD) stimulation was employed to investigate the odor distribution with applying air blowing as a curtain to separate the inside and outside atmosphere or suction to vacuum the inside air to prevent the odor emission. It was found that it could efficiently prevent odor emission by setting a 45° inclined air suction port at the top of the entrance gate. The study provides a theoretical basis on odor control for the waste storage workshop of kitchen waste management plants.

From pollution to resource: advancing swine waste treatment in the USA

Concentrated animal feeding operations (CAFOs) have led to environmental challenges, specifically waste management. Swine CAFOs generate large amounts of waste, requiring proper treatment to avoid air and water pollution. Conventional waste management technologies, such as lagoon and spray field systems, do not prevent air and water pollution impacts. Research for the past few decades led to recommendations for waste treatment technologies superior to lagoons and spray fields. Private environmental sustainability initiatives focused on reducing greenhouse gas emissions in the food supply chain have implemented biogas digester projects for capturing methane in covered swine lagoons to reduce greenhouse gas emissions. However, research indicates that methane capture alone does not solve the broader pollution issues associated with lagoon and spray field systems still in use at these CAFOs to dispose of digested effluents. The Environmentally Superior Technologies (EST) initiative in North Carolina set public standards to eliminate waste discharge, reduce atmospheric emissions, and control odors and pathogens. Research has confirmed that technologies coupling solids separation with water treatments to remove volatile organic carbon, pathogens, and reactive forms of nitrogen can meet EST standards. A designated EST—the Super Soil System—substantially reduced odor by 99.9%; pathogens by 99.99%, nutrients (phosphorus and nitrogen) by >90%, and heavy metals (cooper and zinc) by 99%. The ammonia emissions were reduced by 94.4% for the warm and 99.0% for the cool season with respect to a conventional lagoon system. Corresponding greenhouse gas emission reductions were 96.7%. Components of designated EST can be applied to retrofit covered lagoons and anaerobic digestion systems with significant environmental benefits. Recommendations are proposed, based on the collective experience with EST and current trends in animal production concentration, for environmentally safe technologies to handle excess manure produced in the USA.

DESIGN OF LANDFILLS AND THE UTILIZATION OF WASTES AS SUSTAINABLE LINER MATERIALS: A MINI-REVIEW

Modern landfills, designed to minimize environmental and health risks, play a crucial role in solid waste disposal. Poorly managed municipal solid waste facilities have severe environmental consequences, prompting intervention and remediation. Landfill construction is not enough; regular maintenance is essential to prevent harm. Landfills' historical evolution reflects societal needs, technological advancements, and environmental awareness. The 20th century saw engineered landfills with practices like compaction, daily covering, and leachate collection. Despite progress in recycling and incineration, landfills remain dominant, posing challenges like methane emissions, leachate contamination, and land use. Research emphasizes integrating landfills with recycling, composting, and waste-to-energy technologies for a sustainable future. Engineered landfills are advantageous over dumpsites, in terms of groundwater and air protection, odor control, energy generation, and job creation. Seismic analysis of landfills addresses deformation and seismic reactivity, emphasizing proper liner construction to reduce seismic impact. Leachate, a potential environmental hazard, requires careful management with effective liners to prevent groundwater and soil pollution. Various materials, including fly ash, paper mill sludge, waste foundry sand, recycled concrete aggregate, rice husk ash, and plastic waste, are reviewed for landfill liners. Research shows these materials can offer effective barriers, reducing environmental impact and promoting sustainability. Future studies should continue exploring alternative materials, considering factors like strength, hydraulic conductivity, and environmental protection.

Treatability of odorous dioxanes/dioxolanes in source water: How does molecular flexibility and pre-oxidation affect odorant adsorption

Odorous dioxanes and dioxolanes, a class of cyclic acetals often produced as byproducts in polyester resin manufacturing, are problematic in drinking water treatment due to their low odor thresholds and resistance to conventional treatment technology. Our research focuses on the removal of ten dioxane/dioxolane compounds through oxidation and adsorption processes, exploring the key molecular properties that govern the treatmentability. We discovered that both chlorination and permanganate oxidation were largely ineffective at degrading cyclic acetals, achieving less than 20% removal even at high applicable doses. Conversely, powdered activated carbon (PAC) adsorption proved to be a more effective method, with a removal of > 90% at a PAC dosage of 10 mg/L for seven out of ten compounds. The presence of natural organic matter (NOM) reduced PAC adsorbability for all odorants, but the deterioration level substantially varied and mostly affected by structural flexibility as indicated by the number of rotatable bonds. The results of both the experimental investigation and molecular simulation corroborated the hypothesis that more rotatable bonds (from one to three here) are indicative of greater structural flexibility, which in consequence determines the susceptibility of cyclic acetals to NOM competitive adsorption. Increased structural flexibility could facilitate greater entry into silt-like micropores or achieve preferential adsorption sites with more compatible morphology against NOM competition. When pre-oxidation (chlorination and permanganate oxidation) and adsorption were applied sequentially, additional low molecular weight NOM components produced by pre-oxidation resulted in intensified NOM competition and decreased odorant adsorbability. If this combination is inevitably required for algae and odorant control, it would be beneficial to utilize a wise screen for oxidants and a reduced oxidant dose (less than 2 mg/L) to mitigate the deterioration of odorant adsorption. This study elucidates the roles of structural flexibility in influencing the treatability of dioxanes and dioxolanes, extending beyond the solely well-established effects of hydrophobicity. It also presents rational practice guidelines for the combination of pre-oxidation and adsorption in addressing odor incidents associated with dioxane and dioxolane compounds.

Medidas de control de olores para un tanque homogeneizador de una planta de tratamiento de aguas residuales en Costa Rica

[Objective] This study aimed to evaluate the short-term response of four different odor control measures in a homogenization tank of a university Wastewater Treatment Plant (WWTP). [Methodology] The following were implemented: aeration, adding lime, adding iron sulfate, and adding the commercial product BiOWiSH® Odor over four hydraulic retention times. The effluent and the unit were monitored during each period, using a baseline to compare the measures. Hydrogen potential, oxidation-reduction potential, dissolved oxygen, and dissolved sulfide concentration were measured in triplicate every 30 minutes. An odor perception survey was administered to WWTP visitors to evaluate intensity, offensiveness, and character (15 surveys per monitoring period). Differences were determined between control measures and the baseline using Student’s t-tests (quantitative data) and Mood’s median tests (qualitative data). Minitab 2019 was used with a 95% confidence level. [Results] All control measures significantly reduced the dissolved sulfide concentration in the unit. Aeration prevented oxygen depletion, reductive regime, and acid fermentation, which favored the oxidation of odorants. Aeration was also the only studied control measure that reduced odor intensity and offensiveness. [Conclusions] Applying aeration changed unit behavior and odor perception, which confirms its effectiveness, while adding iron sulfate, lime, and BiOWiSH® did not significantly change odor perception.

Odor control technologies for municipal solid waste mechanical biological treatment plant: a review

Odor control technologies for municipal solid waste mechanical biological treatment plant: a review

Research on pollution identification and safety thresholds based on the olfactory effect on a halogenated hydrocarbon contaminated site

To effectively address odor control issues at sites contaminated with halogenated hydrocarbons, it is essential to establish an odor risk prediction system for evaluating potential risks that may impact future planning. This research focuses on a representative halogenated hydrocarbon-contaminated site, examining the spatial and temporal distribution characteristics of key pollutants in soil gas. By analyzing odor contribution rates, the study identifies significant odorants in soil gas, which enables the derivation of both probabilistic and deterministic safety thresholds for soil and groundwater based on olfactory effects. The findings indicate that 1,1-dichloroethylene, vinyl chloride, chloroform, and 1,1-dichloroethane are prevalent throughout the contaminated site, displaying elevated concentration levels and substantially influencing the overall contamination extent. These substances are highlighted as critical pollutants requiring attention. Correlation analysis (P < 0.05) reveals a strong relationship between the concentrations of vinyl chloride, 1,1-dichloroethane, and chloroform with groundwater depth and air temperature. Additionally, the analysis of odor activity values (OAV) identified 1,1-dichloroethene, 1,4-dichlorobenzene, chlorobenzene, chloroform, and vinyl chloride as key olfactory factors at the site. The corresponding probabilistic safety thresholds are 0.68, 1.65, 0.50, 7.87, and 3.72 mg kg−1 for soil, and 9.29, 3.46, and 1.09, 69.55, and 47.01 mg L−1 for groundwater, respectively. Among them, the odor risks of chlorobenzene and 1,1-dichloroethylene warrant more attention than soil contamination risks; regarding 1,4-dichlorobenzene, it is recommended to concurrently consider odor risks during human health risk assessment; as for vinyl chloride and chloroform, their odor risks can be largely eliminated based on human health-oriented pollution management.

Effectiveness of Malodor-Reducing Ostomy Pouch Additives: An Assessment of Odor Intensity, Hedonic Tone, and Odor Character.

Background Ostomy pouch odor can have a negative impact on the quality of life of people living with a stoma. This study assessed the effectiveness of malodor-reducing ostomy pouch additives under simulated conditions. Methodology The following six commercially available products with different odor control technologies plus a control were assessed: soyethyl morpholinium ethosulphate, zinc ricinoleate (ZnR), ZnR with orange terpenes (ZnR-Orange), a proprietary copper-based deodorant, a proprietary ion mix deodorant, and a terpene blend (TB). Each was added to an ostomy pouch with skatole (a substitute for human fecal odor). Professional olfactometrists rated odors according to intensity, hedonic tone (pleasantness), and character. Results The TB and ZnR-Orange had very weak (<1.0) malodor intensity, with mean (standard deviation [SD]) ratings of 0.6 (1.1) and 0.9 (0.9), respectively. All other products (2.7-3.0) and control (3.7) were statistically higher (stronger intensity) compared with the TB(p < 0.001). The mean (SD) hedonic tone for the TB was 0.8 (1.7) (considered slightly pleasant); all other products (-0.8 to 0.1) and control (-0.9) were statistically lower (p < 0.001). Odor character profiles were broadly comparable, but products with scent additives (TB and ZnR-Orange) were predominantly associated with fragrances. Conclusions This information may help nurses and other healthcare providers when educating ostomates about their options. Other factors such as application mode and recommended dosage may also influence the choice of product. Future research on real-world populations (i.e., ostomates), as well as assessment of lubrication properties, is warranted.

Dual roles of odor cleaners and pollutant producers for chemical scrubbing and biological treatment: Evidence in a food waste anaerobic digestion plant

The odor generated during municipal solid waste and wastewater treatment is a major source of public complaints worldwide. Chemical scrubbing and biological treatment are commonly used to control the odor. However, in this study, such odor control measures were found to produce derived odorous compounds and greenhouse gases, leading to reduced efficiency or uncertainty in odor treatment. In a food waste anaerobic digestion plant, a series of site and lab investigations were conducted on the odor control performance and mechanisms, as well as secondary pollutants of chemical scrubbing and biotrickling. Methanethiol, hydrogen sulfide (H2S), propanethiol, and acetaldehyde were identified as the top four odor contributors to the gas collected in the plant. The mechanisms of acetaldehyde and propanethiol removal in the chemical scrubbers were studied using gas-washing bottles. Acetaldehyde was mainly removed via physical absorption, whereas propanethiol could be completely removed via oxidation by sodium hypochlorite (NaClO). However, acetaldehyde was desorbed from the absorption solution and generated from the oxidation of ethanol by NaClO in the chemical scrubbers, leading to low, or even negative removal efficiency. H2S, methanethiol, propanethiol, and acetaldehyde could be abated by the biotrickling filters. However, H2S, methanethiol, propanethiol, and greenhouse gases could be also produced under anaerobic conditions, particularly when the packings were compacted. Furthermore, acetaldehyde could be produced from ethanol by bacteria possessing dehydrogenase under aerobic conditions. Both chemical scrubbers and biotrickling filters demonstrated the dual roles of odor removal and pollutant production.

Compliance of private ventilated improved pit latrines to odour and fly control guidelines: A technical audit in selected regions of Ghana

The ventilated improved pit (VIP) latrine offers a promising route to safely managed sanitation to many households in developing countries. However, some technical guidelines must be followed in order to realise the technology's advantage of odour and fly nuisance control. This study sought to audit private VIP latrines in selected regions of Ghana to assess their compliance to conventional technical guidelines and to understand the major factors that influence the latrine designs. An inspection checklist was developed to assess 296 private VIP latrines in the Central, Ashanti and Northern Regions of Ghana while semi-structured interviews were conducted among the latrine owners to enquire the factors that influenced the designs of their latrines. The results show that provision of a window in the superstructure (86 %), and the avoidance of an insect screen in the window(s) (77 %) were the most complied guidelines. The use of 150 mm diameter vent pipe was the least satisfied guideline (5 %). On the average, a latrine satisfied about half (3.6) of the technical guidelines that were assessed. The decision or advice of local artisans is the most influential factor in the design of the latrines. Cost was the least mentioned factor cited by the latrine owners. There is the need to establish information desks at the various Metropolitan, Municipal and District Assemblies (MMDAs) to guide prospective owners on the proper design and construction of the VIP latrine. In addition, toilet construction should be incorporated in the curriculum for the basic training of building and construction students in Technical and Vocational Education and Training (TVET) institutions in Ghana. Further research is required to ascertain the basis of the decisions of local artisans and the potential impact of the use of accessories that are ‘borrowed’ from the WC toilet on odour and fly control in the latrine.

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.

Exploration of Composting Strategies for Sustainable Organic Waste Management in Urban Environments

&lt;p&gt;The management of organic waste in urban environments poses significant challenges due to the high volume of waste generated and limited disposal options. Composting is a promising technique for converting organic waste into valuable compost that can be used to improve soil health and reduce the environmental impact of waste disposal. However, there is a need to assess various composting methods to determine their efficacy, feasibility, and environmental benefits in urban settings. This research aims to conduct a comprehensive assessment of composting methods for organic waste management in urban environments. The study will focus on evaluating different composting techniques, including traditional composting, vermicomposting (using worms), and aerobic composting systems. Factors such as process efficiency, compost quality, nutrient content, odor control, and greenhouse gas emissions will be considered in the evaluation. The research will involve field experiments to compare the performance of various composting methods using different types of organic waste commonly generated in urban areas, such as food waste, yard waste, and agricultural residues. Parameters such as temperature, moisture content, pH levels, and microbial activity will be monitored throughout the composting process to assess decomposition rates and nutrient retention. In addition to technical aspects, socio-economic factors and feasibility in urban contexts will be examined, including cost-effectiveness, scalability, community acceptance, and regulatory compliance. The study will also explore the potential for integrating composting into existing waste management systems and strategies for promoting compost use in urban agriculture and landscaping. The findings of this research will contribute to enhancing organic waste management practices in urban environments by identifying the most effective composting methods and providing recommendations for sustainable waste management policies and practices.&lt;/p&gt;

Pulsed processing by cold plasma, applied to industrial emission control.

A promising pollution control technology is cold plasma driven chemical processing. The plasma is a pulsed electric gas discharge inside a near atmospheric-pressure-temperature reactor. The system is energized by a continuous stream of very short high-voltage pulses. The exhaust gas to be treated flows through the reactor. The methods applied involve the development of robust cold plasma systems, industrial applications and measuring technologies. Tests of the systems were performed at many industrial sites and involved control of airborne VOC (volatile organic compound) and odor. Electrical, chemical and odor measuring data were collected with state-of-the-art methods. To explain the test data an approximate solution of global reaction kinetics of pulsed plasma chemistry was developed. It involves the Lambert function and, for convenience, a simple approximation of it. The latter shows that the amount of removal, in good approximation, is a function of a single variable. This variable is electric plasma power divided by gas flow divided by input concentration. In the results sections we show that in some cases up to 99% of volatile pollution can be removed at an acceptable energy requirement. In the final sections we look into future efficiency enhancements by implementation of (sub)nanosecond pulsed plasma and solid state high-voltage technology and by integration with catalyst technology.

Quantifying Methane Influx from Sewer into Wastewater Treatment Processes.

Wastewater treatment contributes substantially to methane (CH4) emissions, yet monitoring and tracing face challenges because the treatment processes are often treated as a "black box". Particularly, despite growing interest, the amount of CH4 carryover and influx from the sewer and its impacts on overall emissions remain unclear. This study quantified CH4 emissions from six wastewater treatment plants (WWTPs) across China, utilizing existing multizonal odor control systems, with a focus on Beijing and Guiyang WWTPs. In the Beijing WWTP, almost 90% of CH4 emissions from the wastewater treatment process were conveyed through sewer pipes, affecting emissions even in the aerobic zone of biological treatment. In the Guiyang WWTP, where most CH4 from the sewer was released at the inlet well, a 24 h online monitoring revealed CH4 fluctuations linked to neighborhood water consumption and a strong correlation to influent COD inputs. CH4 emission factors monitored in six WWTPs range from 1.5 to 13.4 gCH4/kgCODrem, higher than those observed in previous studies using A2O technology. This underscores the importance of considering CH4 influx from sewer systems to avoid underestimation. The odor control system in WWTPs demonstrates its potential as a cost-effective approach for tracing, monitoring, and mitigating CH4.

Complete long-term monitoring of greenhouse gas emissions from a full-scale industrial wastewater treatment plant with different cover configurations

The greenhouse gas (GHG) emissions from wastewater treatment plants (WWTPs), consisting mainly of methane (CH4) and nitrous oxide (N2O), have been constantly increasing and become a non-negligible contributor towards carbon neutrality. The precise evaluation of plant-specific GHG emissions, however, remains challenging. The current assessment approach is based on the product of influent load and emission factor (EF), of which the latter is quite often a single value with huge uncertainty. In particular, the latest default Tier 1 value of N2O EF, 0.016 ± 0.012 kgN2O–N kgTN−1, is estimated based on the measurement of 30 municipal WWTPs only, without involving any industrial wastewater. Therefore, to resolve the pattern of GHG emissions from industrial WWTPs, this work conducted a 14-month monitoring campaign covering all the process units at a full-scale industrial WWTP in Shanghai, China. The total CH4 and N2O emissions from the whole plant were, on average, 447.7 ± 224.5 kgCO2-eq d−1 and 1605.3 ± 2491.0 kgCO2-eq d−1, respectively, exhibiting a 5.2- or 3.9-times more significant deviation than the influent loads of chemical oxygen demand (COD) or total nitrogen (TN). The resulting EFs, 0.00072 kgCH4 kgCOD−1 and 0.00211 kgN2O–N kgTN−1, were just 0.36% of the IPCC recommended value for CH4, and 13.2% for N2O. Besides, the parallel anoxic-oxic (A/O) lines of this industrial WWTP were covered in two configurations, allowing the comparison of GHG emissions from different odor control setup. Unit-specific analysis showed that the replacement of enclosed A/open O with enclosed A/O reduced the CH4 EF by three times, from 0.00159 to 0.00051 kgCH4 kgCOD−1, and dramatically decreased the N2O EF by an order of magnitude, from 0.00376 to 0.00032 kgN2O–N kgTN−1, which was among the lowest of all full-scale WWTPs.

Assessment of the efficacy of Piper methysticum (Micrembryeae: Piperaceae) as a bioinsecticide, and/or spinosad combined with attractive plant volatiles for a novel lure and kill strategy against Bactrocera tryoni (Diptera: Tephritidae) in laboratory.

The Queensland fruit fly, Bactrocera tryoni (Froggatt) (Diptera: Tephritidae), is a crop pest of global economic importance because of its wide range of hosts and its invasiveness capacities. To develop a novel integrated and sustainable crop protection, we have investigated the insecticidal properties of different varieties of kava (Piper methysticum [Frost]) extracted by two methods and the attractive effects of six plant volatiles identified from B. tryoni host plants to female, mated or not. We did not identify any significant insecticidal effect of the traditional Pacific kava plant at the tested concentrations. Among mated females, ethyl acetate compared to the no odor control elicited the highest attraction (87%, of which 60% for this odor), while ethyl butyrate was preferred compared with ethyl acetate in dual choice assays. Flies' preferences for specific odors depended on their mating status and the odor landscape they were confronted with. Combination with the commercial ingestion insecticide (Success 4: spinosad, 480 g/l, Dow AgroSciences, Valbonne, France) with the plant volatiles were tested to detect an increase in mortality related to the addition of an attractant. The 2-heptanone slightly showed a tend to increase the attractiveness of mated females within 4-6 h to the food bait, but the results were not statistically significant after 8 h. Further tests should be performed with other concentrations or mixtures of the identified host plant volatiles to develop a strong lure and kill strategy.

Integration of nontarget analysis with machine learning modeling for prioritization of odorous volatile organic compounds in surface water

Assessing the odor risk caused by volatile organic compounds (VOCs) in water has been a big challenge for water quality evaluation due to the abundance of odorants in water and the inherent difficulty in obtaining the corresponding odor sensory attributes. Here, a novel odor risk assessment approach has been established, incorporating nontarget screening for odorous VOC identification and machine learning (ML) modeling for odor threshold prediction. Twenty-nine odorous VOCs were identified using two-dimensional gas chromatography-time of flight mass spectrometry from four surface water sampling sites. These identified odorants primarily fell into the categories of ketones and ethers, and originated mainly from biological production. To obtain the odor threshold of these odorants, we trained an ML model for odor threshold prediction, which displayed good performance with accuracy of 79%. Further, an odor threshold-based prioritization approach was developed to rank the identified odorants. 2-Methylisoborneol and nonanal were identified as the main odorants contributing to water odor issues at the four sampling sites. This study provides an accessible method for accurate and quick determination of key odorants in source water, aiding in odor control and improved water quality management. Environmental ImplicationWater odor episodes have been persistent and significant issues worldwide, posing severe challenges to water treatment plants. Unpleasant odors in aquatic environments are predominantly caused by the occurrence of a wide range of volatile organic chemicals (VOCs). Given the vast number of newly-detected VOCs, experimental identification of the key odorants becomes difficult, making water odor issues complex to control. Herein, we propose a novel approach integrating nontarget analysis with machine learning models to accurate and quick determine the key odorants in waterbodies. We use the approach to analyze four samples with odor issues in Changsha, and prioritized the potential odorants.