Comparative analysis of spatio-temporal exposure assessment methods for estimating odor-related responses in non-urban populations

Impact of Bacillus subtilis on manure solids, odor, and microbiome

A study was conducted to determine the effectiveness of supplementing swine manure with Bacillus subtilis (BS) to improve digestion of manure solids and lower odor emission. Large bioreactors (400 L) with manure (100 L) were treated with commercially available BS at a rate of 1% manure volume by either directly pouring or surface spraying the manure with inoculum. Manure physicochemical properties, gas emissions, and microbiome were monitored. Manures treated multiple times with BS or surface sprayed had significantly (P < 0.05) lower electrical conductivity, volatile solids, and chemical oxygen demand, by 3-5% compared to non-treated control manures. Volatile sulfur compound emissions (VSCs) were reduced by 20-30% in both experiments, while ammonia and volatile organic compounds were reduced by 40% and 15%, respectively, in surface spray experiment only. The manure indigenous microbiome remained relatively stable following treatment and BS were never detected in the raw or treated manure following multiple treatments. The reduction in manure organic carbon and VSCs emissions were a result of physical mixing during manure treatment and biological material in the microbial inoculum stimulating microbial activity and not growth of BS.

Parameters influencing population annoyance pertaining to air pollution

Annoyance caused by particulate matter qualifies as a public health problem, as it can be seen as an ambient stressor causing stress, diseases and affecting the quality of life. Previous studies have shown a complex relationship between annoyance and perception of air pollution, health problems occurrences, air pollutants concentration levels and location within the urban area, which should be better investigated. The objective of this work is to identify the parameters that influences perceived annoyance caused by air pollution. Additionally, we propose the analyses of exposure-response relationship between perceived annoyance and concentration levels of particulate matter (TSP and PM₁₀). Questionnaire-based surveys were conducted in sub regions around of the air quality monitoring stations in metropolitan area of Vitoria, Brazil. Logistic regression was used to identify the associations between qualitative questionnaire variables and air pollution expressed by PM concentrations. Results have shown that 90% of the population reports nuisance by air pollution and about 80% of respondents frequently perceived air pollution by dust. The determinants parameters and subjective factors related to particles annoyance perception can be used in order to predict air pollution impact on the studied region population. By exposure-response relationship when the concentration level of PM increases, the probability of being annoyed also grows. The results and the methodology discussed here can be very useful for planning purposes where the stakeholders usually do not have access to detailed information, especially for micro-management in a regional or city-planning level.

Swine diets: Impact of carbohydrate sources on manure characteristics and gas emissions

Swine growers seeking to lower costs and environmental impact have turned to alternative carbohydrate feed sources. A feeding trial was conducted to determine the effect carbohydrate sources have on manure composition and gas emissions. A total of 48 gilts averaging 138 kg BW were fed diets consisting of (a) low fiber (LF) grain, or (b) high fiber (HF) aro-industrial co-product (AICP). The LF diets included corn and soybean meal (CSBM) and barley soybean meal (BSBM). The HF AICP diets were CSBM based and supplemented with one of the following materials: beet pulp; corn distillers dried grains with solubles; soybean hulls; or wheat bran. Diets were fed for 42 d with an average daily feed intake of 2.71 kg d-1. Feces and urine were collected twice daily and added to manure storage containers in which manure slurries were monitored for gas emissions and chemical properties. Manures of animals fed HF diets had significantly (P < 0.05) more excretion of solids, C, N, and organic N, but less total S compared to pigs fed the LF diets. Animals feed HF diets had significantly (P < 0.05) higher levels of ammonia, sulfide, volatile fatty acids, and phenols in manure compared to pigs fed the LF diets. Manure of animals fed HF diets had 30% (P < 0.05) lower NH3 and 17% lower hydrogen sulfide emissions; however, fiber had no impact on odor emissions. Based on the partitioning of nutrients, animals fed HF fiber diets had increased manure retention for C and N but decreased levels of N gas emissions and manure S. There were little differences in manure and gas emissions for animals fed LF diets, but the source of HF AICP diets had a significant impact on manure composition and gas emissions.

Microbial sulfate reduction by Desulfovibrio is an important source of hydrogen sulfide from a large swine finishing facility

There is still a lack of understanding of H₂S formation in agricultural waste, which leads to poor odour prevention and control. Microbial sulfate reduction is a major process contributing to sulfide formation in natural and technogenic environments with high sulfate and low oxygen concentration. Agricultural waste can be considered a low-sulfate system with no obvious input of oxidised sulfur compounds. The purpose of this study was to characterise a microbial community participating in H₂S production and estimate the microbial sulfate reduction rate (SRR) in manure slurry from a large-scale swine finishing facility in Western Siberia. In a series of manure slurry microcosms, we identified bacterial consortia by 16S rRNA gene profiling and metagenomic analysis and revealed that sulfate-reducing Desulfovibrio were key players responsible for H₂S production. The SRR measured with radioactive sulfate in manure slurry was high and comprised 7.25 nmol S cm^-3 day^-1. Gypsum may be used as a solid-phase electron acceptor for sulfate reduction. Another plausible source of sulfate is a swine diet, which often contains supplements in the form of sulfates, including lysine sulfate. Low-sulfur diet, manure treatment with iron salts, and avoiding gypsum bedding are possible ways to mitigate H₂S emissions from swine manure.

Determination of Dose–Response Relationship to Derive Odor Impact Criteria for a Wastewater Treatment Plant

Municipal wastewater treatment plants (WWTPs) inside cities have been the major complained sources of odor pollution in China, whereas there is little knowledge about the dose–response relationship to describe the resident complaints caused by odor exposure. This study explored a dose–response relationship between the modelled exposure and the annoyance surveyed by questionnaires. Firstly, the time series of odor concentrations were preliminarily simulated by a dispersion model. Secondly, the perception-related odor exposures were further calculated by combining with the peak to mean factors (constant value 4 (Germany) and 2.3 (Italy)), different time periods of “a whole year”, “summer”, and “nighttime of summer”, and two approaches of odor impact criterion (OIC) (“odor-hour” and “odor concentration”). Thirdly, binomial logistic regression models were used to compare kinds of perception-related odor exposures and odor annoyance by odds ratio, goodness of fit and predictive ability. All perception-related odor exposures were positively associated with odor annoyance. The best goodness of fit was found when using “nighttime of summer” in predicting odor-annoyance responses, which highlights the importance of the time of the day and the time of the year weighting. The best predictive performance for odor perception was determined when the OIC was 4 ou/m3 at the 99th percentile for the odor exposure over time periods of nighttime of summer. The study of dose–response relationship could be useful for the odor management and control of WWTP to maximize the satisfaction of air quality for the residents inside city.

Swine manure dilution with lagoon effluent impact on odor reduction and manure digestion

Manure management systems have a major impact on odor from swine operations. A study was conducted to compare deep-pit manure management systems to flushing barn manure management systems for odor reduction and organic matter degradation. Bioreactors were used to mimic manure management systems in which manure and lagoon effluent were loaded initially, and subsequent manure was added daily at 5% of its storage capacity (1 L). Final manure-to-lagoon effluent ratios were 10:0 (deep-pit manure management system), 7:3 (Korean flushing systems), 5:5 (enhanced flushing systems), and 2:8 (enhanced flushing systems). At the end of the trial, at 4 (2:8), 10 (5:5), or 14 (10:0, 7:3) d, manure and gas concentrations of odorants were measured, including total solids (TS), total N (TN), and total C (TC) of manure. Odor was evaluated using the odor activity values (OAVs), and regression analysis was used to determine the effects of dilution and TS on manure properties and OAVs. Solids in the manure were positively correlated to TN, TC, straight chain fatty acids (SCFAs), branch chain fatty acids (BCFAs), total phenols, and total indoles and positively correlated to OAV for SCFAs, BCFAs, ammonia, total phenols, and total indoles. Reducing TS by 90% reduced BCFA, ammonia, phenols, and indoles by equal amounts in air. Carbon dioxide was the main C source evolved, averaging over 90%, and CH₄ increased with dilution quadratically. Overall, reducing solids in manure by dilution had the biggest impact on reducing odor and increasing organic C degradation.

Swine diets impact manure characteristics and gas emissions: Part II sulfur source

Sulfur is a key nutrient in swine diets and is associated with hydrogen sulfide (H₂S) emissions, odor, and respiratory distress of animals. Due to potential increases in S levels in swine diets by using alternative feedstuffs, a feeding trial study was conducted to determine the effect of dietary S source has on manure slurry chemical properties and gas emissions. A total of 24 gilts averaging 139 kg BW were fed a control diet formulated with corn and soybean meal (CSBM) containing 1.80 g S kg^-1 or diets containing 3.50 g S kg^-1 feed as supplied by calcium sulfate (CaSO₄), distillers dried grains with solubles (DDGS), or feather meal (CFM). Diets were fed for 41 d with an ADFI of 2.70 kg/d. Feces and urine were collected twice daily after each feeding and added to the manure storage containers. At the end of the study, manure slurries were monitored for gas emissions and chemical properties. Dietary S source had a significant effect on excretion of DM, C, N, and S in manure. Pigs fed the diets containing DDGS had significantly higher levels of NH₃, VFAs, and phenols in manure compared to pigs fed the CSBM diet. Pigs fed diets with organic S (i.e., DDGS and CFM) had lower emissions of H₂S compared to pigs fed the diet with inorganic sulfur (CaSO₄). In contrast, there were no significant differences in C or N emissions as affected by dietary treatment. Odor and odorant emissions differed by dietary treatment, with pigs fed the CFM diet having the highest odor emissions as compared to pigs fed the control CSBM diet. Pigs fed diets containing CFM and DDGS had a greater percentage of their chemical odor associated with volatile organic compounds while animals fed the CSBM diet or the diet with CaSO₄ had greater percentage associated with H₂S emissions.

Odorous compounds sources and transport from a swine deep-pit finishing operation: A case study

Odor emissions from swine finishing operations are an air quality issue that affects residents at the local level. A study was conducted at a commercial swine deep-pit finishing operation in central Iowa to monitor odorous compounds emitted and transported offsite. Gaseous compounds were sampled using either sorbent tubes or canisters with GC/MS analysis, and particulates matter (PM₁₀) were sampled with high volume samplers and thermally extracted onto sorbent tubes for GC/MS analysis. Major odorous chemical classes detected at the swine facility included volatile sulfur compounds (VSC), volatile fatty acids (VFA), phenol and indole compounds. Manure storage was the main source of odorous compounds of which hydrogen sulfide (H₂S), methanethiol, 4-methylphenol, and 3-methylindole were key offenders. Only H₂S and 4-methylphenol were detected above odor threshold values (OTV) at all locations around the facility and both 4-methylphenol and 3-methylindole were detected above their OTV 1.5 km downwind from the swine facility. Odorous compounds generated during agitation and pumping of the deep pits was mainly H₂S. Odorants were mainly transported in the gas phase with less than 0.1% being associated with PM₁₀. Odor mitigation efforts should focus on gaseous compounds emitted from deep-pits and especially during manure agitation and deep-pit pumping.