Malodorous Gases Research Articles

Hydrogen Sulphide Inhibition in Cattle Slurry by Use of an Oxygen Based Slurry Amendment

Hydrogen sulphide (H2S) is a malodorous gas that is produced in anaerobic environments where sulphur containing matter is present. Globally, farms in which liquid manure/slurry is stored is a source of H2S which can lead to many acute and chronic health problems and even death. Farming is one of the most dangerous professions globally and reducing the risk of sulphide poisoning on farms will help ensure a safer work environment. The inhibition of H2S production from cattle slurry may also reduce air pollution. In this study, a series of slurry storage experiments were conducted. The first experiment treated 20L of cattle slurry bi-monthly using a mix of hydrogen peroxide and potassium iodide as well as calcium chloride, while the second experiment treated 660L in which the same treatments and schedule were used. A small-scale storage trial was carried out over 29 days in which slurry was treated as before and sulphate concentrations were measured repeatedly. A maximum inhibition of H2S concentrations of 87% and 81% was recorded from the 20L and the 660L storage experiments, respectively. The treatment did not affect sulphate concentrations in slurry which are critical for plant growth.

Molecular dynamics-based targeted adsorption of hazardous substances from rubberized asphalt VOCs by UiO-67

The interplay among UiO-67 and rubberized-asphalt components has been examined according to its molecular scale. The adhesion kinetics of UiO-67 to VOCs molecules in asphalt was modeled. The binding energy, radial distribution function (RDF), solubility parameters (SP), mean square displacement (MSD) and other parameters among UiO-67 to rubberized-asphalt components were evaluated in depth. The Sorption module was simulated the adsorption behavior of UiO-67 on 12 malodorous gases and 5 primary carcinogens. In combination with GC-MS results, the conjugative bonds and target attachment mechanisms for UiO-67 with VOCs were clarified. It was indicated that the binding energy among UiO-67 to the components were all negative. The radial distribution of asphalt was characterized as proximally ordered and remotely disordered. The ΔSP was less than 1.6, which was indicated that UiO-67 could be compatible with asphalt. The overall inhibition effect of UiO-67 on a group of carcinogens was exceeded 70 %. The presence of conjugation effect was allowed the adsorption sites of vinyl chloride and 1,3 butadiene to occur at high densities within the benzenoid. The concentration reduction of UiO-67 for hydrogen sulfide, carbon disulfide, and dimethyl sulfide was more than 80 %. The higher polarity was predisposed substances such as hydrogen sulfide and isobutanol to interact with the non-benzene ring region of UiO-67.

Highly efficient degradation of ethanol, acetaldehyde, and ethyl acetate removal by bio-trickling filter reactors with various fillers

This study investigates the purification performance of bio-trickling filters (BTFs) using different media to treat ethanol, acetaldehyde, and ethyl acetate in kitchen waste malodorous gases. The media compared included a custom composite medium, pine bark, hollow polyhedral spheres, and ceramic particles. Over 25 days, the composite medium outperformed the traditional media, achieving removal rates of 90.13 % for ethanol, 63.89 % for acetaldehyde, and 82.56 % for ethyl acetate during the biofilm initiation phase, with the others below 60 %. Even under low empty bed residence time and high inlet concentrations, the maximum elimination capacity for ethanol, acetaldehyde, and ethyl acetate was 8.34–14.70 g/m3·h, 9.55–15.06 g/m3·h, and 6.18–10.45 g/m3·h. Kinetic analysis showed the Michaelis-Menten model fit well, indicating enhanced removal potential. High-throughput of 16S rDNA sequencing identified dominant microorganisms like Enterobacteriaceae (13.89 %), Stenotrophomonas (29.23 %), and Acinetobacter (4.09 %) in the composite medium, which thrived even at high pollutant concentrations. Principal component analysis (PCA) demonstrated differences in the microbial composition of the custom composite medium compared to traditional media under varying inlet concentrations and loads. This study provides technical support for the treatment of complex malodorous gas mixtures.

Study on the adsorption performance and regeneration of lignin-derived graphitic carbon for H2S

In pursuit of effective adsorption materials for malodorous gases such as H2S and to broaden the utilization avenues of lignin waste, this study employed the direct pyrolysis method to synthesize three types of alkali lignin graphitized carbons, namely C-800, KC-700, and KEC-700. Among them, KEC-700 exhibits a high specific surface area of 1672.9 m2/g, significantly superior H2S adsorption performance compared to other materials, an adsorption breakthrough time of up to 220 min, and a sulfur capacity of 67.1 mg/g. Structural analysis showed that the more oxygen-containing functional groups of lignin charcoal and the larger specific surface area facilitated the adsorption of H2S. After reaching adsorption saturation, the degree of graphitization of lignin carbon diminishes. The H2S adsorption products primarily manifest as elemental sulfur and sulfate within the pores of lignin carbon measuring less than 2 nm. Through thermal regeneration, the charcoal effectively eliminates the elemental sulfur adsorption product. Nevertheless, sulfate removal proved unsatisfactory, as the adsorption efficiency of KEC-700 following two thermal regenerations was approximately 41% of that observed for fresh samples.

Optimum Tuning for the High-efficiency Removal of Malodorous Gas Containing Hydrogen Sulphide Using Biological Treatment

Hydrogen sulfide, as the main pollutant causing stench, has always been one of the main problems in environmental protection. In order to promote the practical application, a pilot study was carried out in this work on the biological treatment of hydrogen sulfide malodorous gas by the combined process of biological drip filtration on the basis of our previous laboratory-scale experiments. After enlarging the reactor in pilot experiment, various factors affecting the deodorization efficiency are compared in pilot scale and laboratory scale, and the optimum pilot condition are obtained. Furthermore, the mechanism of biological deodorization is analyzed. Based on the results of the comparison between the previous laboratory-scale and the pilot-scale of this work, possible bottlenecks and challenges of biological deodorization technology from pilot to industrial application are discussed. The technical approach proposed in this work provides an economical and efficient feasible scheme for biological deodorization in the industrial practice.

Metal-Organic-Framework Derived Co-Mo Multimetal Oxide Semiconductors: Selective Trace-Level Hydrogen Sulfide Detection.

The development of a highly selective and trace-level gas sensing platform for detecting hydrogen sulfide (H2S) remains a formidable challenge. To solve this problem, Co-Mo multimetal oxide semiconductors are rationally tailored by employing metal organic frameworks (MOFs) as self-sacrificial templates. The MOF-derived Co3O4/β-CoMoO4 based gas sensors displays high sensitivity (Rg/Ra = 22) to 10 ppm of H2S and ultralow limit of detection (10 ppb H2S). The formation of p-p heterojunction and multivalence states of Mo play a crucial role in electron transfer and oxygen adsorption. A sensor array constructed from four Co3O4/β-CoMoO4 materials with different Co/Mo ratios demonstrates a superior selective discrimination of H2S from other VOCs and malodorous gases by principal component analysis (PCA). Besides, a H2S gas sensing and alarming platform was designed for monitoring the environment contaminated with H2S. This finding provides a feasible approach for the discovery of highly efficient gas sensors to monitor environmental H2S concentration.

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.

Optimizing the CeO2-MnO2 interface via H2O2 etching for surface lattice oxygen activation in the plasma catalytic degradation of trimethylamine

Trimethylamine (TMA) is a nitrogen-containing malodorous gas that is toxic and hazardous to humans. Plasma catalysis is a promising technique for removing low-concentration malodorous gases. CeO2/MnO2 nanowires with different Ce–Mn contact interfaces prepared by impregnation, physical mixing, and H2O2 etching were investigated for TMA degradation in a plasma catalytic system. The CMO-H sample prepared by H2O2 etching achieved a removal efficiency of 100% at 98 J/L, demonstrating the highest activity. Characterization revealed that H2O2 etching led to the uniform formation of CeO2 nanoparticles on MnO2, promoting the transfer of electrons between Ce and Mn species. Surface lattice oxygen and high-valent manganese were confirmed to be the main active species, consistent with the Mars van Krevelen mechanism. Density functional theory calculations confirmed that the CMO-H sample exhibited the lowest oxygen vacancy formation energy. In situ plasma diffuse reflection infrared transform spectroscopy analysis and gas chromatography-mass spectrometry results showed the possible degradation pathway of TMA. In summary, the H2O2 etching process optimized CeO2-MnO2 interactions and improved the utilization of lattice oxygen active sites, enhancing the catalytic degradation of TMA and providing new insights into the design of an efficient plasma catalytic system for environmental remediation.

Removal of sulfur and nitrogen pollutants in a sediment microbial fuel cell coupled with Vallisneria natans: Efficiency, microbial community structure, and functional genes

The rapid development of the economy has led to an increase in the sulfur and nitrogen load in surface water, which has the potential to cause river eutrophication and the emission of malodorous gases. A lab-scale sediment microbial fuel cell coupled with Vallisneria natans (P-SMFC) was designed for surface water remediation. The enhancement of pollutant removal performance of P-SMFC was evaluated in contrast to the SMFC system without plants (SMFC), the open-circuit control system with plants (C–P), and the open-circuit control system without plants (C–S), while illustrating the mechanisms of the sulfur and nitrogen transformation process. The results demonstrated that the effluent and sediment of P-SMFC had lower concentrations of sulfide compared to other systems. Furthermore, P-SMFC exhibited higher removal efficiency for COD (73.1 ± 8.7%), NH4+-N (80.5 ± 19.8%), and NO3−-N (88.5 ± 11.8%) compared to other systems. The closed-circuit conditions and growth of Vallisneria natans create a favorable ecological niche for functional microorganisms involved in power generation, sulfur oxidation, and nitrogen transformation. Additionally, metagenomic analysis revealed that multifunctional bacteria possessing both denitrification and sulfur oxidation genes, such as Thiobacillus, Dechloromonas, and Bacillus, may play simultaneous roles in metabolizing sulfur and nitrogen, thus serving as integral factors in maintaining the performance of P-SMFC. In summary, these findings provide a theoretical reference for the concurrent enhancement of sulfur and nitrogen pollutants removal in P-SMFC and will facilitate its practical application in the remediation of contaminated surface water.

Experimental study on removal of hydrogen sulfide gas by spray and bubble blowing: A comparative study

H2S (hydrogen sulfide) is widely concerned because of its strong odor and toxicity, which seriously affects the physical and mental health of surrounding residents. In this paper, bubble blowing and spray deodorization experimental systems for H2S gas generation were constructed, with plant-derived deodorant were employed as a deodorizing liquid. The influence factors of spray and bubble blowing deodorization experimental system for deodorization performance were explored. And the effects of spray deodorization method and bubble blowing deodorization method on H2S removal rate were compared. The results show a positive correlation between the removal rate of H2S and the inlet pressure in the spray deodorization system. As the inlet pressure increases, the removal efficiency of H2S exhibits a gain ranging from 22.36% to 23.56%. Within the bubble blowing deodorization system, H2S concentration decreases as the deodorization solution dosage increases. As the deodorizing solution dosage increases from 920 mL to 1800 mL, H2S concentration decreases from 0.46 mg·m−3 to 0 mg·m−3. Furthermore, the bubble blowing deodorization method outperforms the spray, resulting in a 14.60–29.09% increase in H2S removal rate. The bubble blowing deodorization method proposed in this study exhibits promising potential for application in the field of malodorous gas treatment.

Development of CuO/Cu4(OH)6SO4 Nanoparticle Mixtures to Optimize the H2S Adsorption.

In this paper, we report the H2S adsorption behavior of a sorbent composed of mixtures of tenorite (CuO) and brochantite [Cu4(OH)6SO4]. These materials are readily prepared through the addition of NaOH(aq) to CuSO4(aq). They can be loaded onto polymer foams to create effective filters that can remove malodorous H2S gas, as evidenced by breakthrough tests. X-ray diffraction shows that the ratio of the two compounds in the mixture can be finely tuned by varying the amount of NaOH(aq) that is added to the reaction mixture. X-ray photoelectron spectroscopy shows that brochantite, like tenorite, has the ability to chemically adsorb H2S. Correlation of the H2S breakthrough data with scanning transmission electron microscopy measurements shows that the most effective sorbents contain nanoscale needle-like particles. These are likely to be formed largely by the tenorite phase. The samples with the greatest H2S adsorption efficacy contained less than 20% tenorite in the mixture, where these particles had the greatest abundance. The application of this sorbent onto porous substrates to create effective filters, along with the synthetic ease of its production, could allow this methodology to find use in a number of areas where H2S poses a problem. This could include areas where protective clothing is required to adsorb the gas from environments where there is a high level of H2S, for example, in wastewater treatment plants, oil and gas wells, or in the medical sector, where it could be deployed as filter media.

Flue gas suppression and environmental evaluation of deodorizer-modified rubber asphalt based on radar method

Rubber-modified asphalt (RMA) is associated with impaired storage stability and additional harmful emissions during application. Microwave-oil bath activation of waste rubber powder (WRP) to improve its compatibility with asphalt. The treatment of VOCs and malodorous gas emissions from RMA is carried out using powder deodorizers, liquid deodorizers and their combination. The storage stability, high and low temp rheological behavior of RMA were investigated. The effects and machinations of three deodorants on odor removal and VOCs inhibition of RMA were explored. The emission indexes based on the characteristic pollutants of VOCs and malodorous gases were proposed to conduct a comprehensive environmental impact assessment by the Radar method. The results show that the activated WRP has a fluffier morphology and is better encapsulated by the oil film, which enhances the storage stability of RMA. The incorporation of deodorant has not altered the viscoelastic properties of asphalt. The higher specific surfaced areas and extensive pore structures was contributed to the adsorption of VOCs molecules from asphalt. VOCs and odor gases from asphalt could be inhibited by liquid deodorizers based on Lewis acid-base reactions, addition reactions, catalytic reactions, and redox reactions. LMA was the most effective in decreasing odorant gases, with reductions of up to 92.6% and 90.8% for isobutanol and dimethyl disulfide, respectively. PMA had the optimal inhibitory activity for vinyl chloride, which was 67.7%. The decrease of total concentration of VOCs in RMA by PMA (powder deodorant-modified asphalt), LMA (liquid deodorant-modified asphalt), and CMA (complex deodorant-modified asphalt) could be calculated as 51.7%, 34.1% and 46.7% respectively. RMA had a high load on the environment, and the overall advantage of CMA was greater. The environmental impacts of the four modified asphalts were ranked as CMA < PMA < LMA < RMA. Therefore, the utilization of powder and liquid compounding was recommended to improve the environmental impact of RMA.

Nitrogen-containing malodorous gas pollutants emission characteristics and health risk assessment from an A/O wastewater treatment plant

Unpleasant odorous emitted from wastewater treatment plants (WWTPs) have been of great concern for many years, especially among local communities with high population density. Knowledge about characteristics of odorous gas release from WWTP can assist in developing gas pollution reduction technologies. This study investigated the emission and variation of NH3 and organic amines (CH3NH2, C2H6NH, and C3H9N) at the water-air interface and concentrations of ambient air exposure from different treatment units in a wastewater treatment plant in North China, which uses the anaerobic/oxic (A/O) treatment process. Results demonstrated that NH3 and C2H6NH emission fluxes had followed a descending order of aeration treatment units > non aeration treatment units. NH3 and C2H6NH achieved the highest release concentration throughout the whole wastewater treatment process, where 0.0023 g of NH3 and 0.0018 g of C2H6NH were emitted during the treatment of 1 m3 wastewater, while CH3NH2 and C3H9N had never been detected. The emission of NH3 and C2H6NH from biological aeration tanks account for 98 % and 95 % of the total discharge of wastewater treatment plant, respectively. The odor pollution of NH3 and C2H6NH in the ambient air of different treatment units of WWTP was the most serious in summer. At the sensory level, NH3 dominated the malodorous effect and its exposure concentration posed a certain non carcinogenic risk to workers in wastewater treatment plant.

Effect of different moisture contents on hydrogen sulfide malodorous gas emission during composting

The sulfate reduction reaction releases malodorous gases (H2S) during composting, with potential pollution risks to the environment. In this study, chicken manure (CM) with high sulfur content and beef cattle manure (BM) with low sulfur content were used to investigate the effect of control (CK) and low moisture content (LW) on sulfur metabolism. The results showed that compared to CK composting, the cumulative H2S emission of CM and BM composting decreased by 27.27% and 21.08% under LW condition, respectively. Meanwhile, the abundance of core microorganisms related to sulfur components was reduced under LW condition. Furthermore, the KEGG sulfur pathway and network analysis suggested that LW composting weakened the sulfate reduction pathway, and reduced the number and abundance of functional microorganisms and genes. These results indicated that low moisture content had important effects on inhibiting the release of H2S during composting, which provided a scientific basis to control environmental pollution.

Competitive interactions of NH3 and toluene with biochar modified by pre- and post-treatments of H3PO4 in dual adsorption systems

Biochar modified by H3PO4 treatment can be used to purify malodorous gases during bio-drying of sludge, but the current understanding of multi-component adsorption of malodorous gases through biochar is limited. This study examined the adsorption mechanism of mixed malodorous gases including toluene and ammonia (NH3) on two kinds of biochar modified via H3PO4 pretreatment before and after pyrolysis. The biochar obtained by H3PO4 pretreatment of biomass before pyrolysis (C550) preferred to adsorb NH3 whether in the single or the dual system. In contrast, the biochar obtained by H3PO4 reprocessing after pyrolysis of biomass (C350-550) tended to adsorb toluene in the dual system but was more efficient in absorbing NH3 in the single system. The pseudo-second-order kinetic model indicated the synergistic adsorption between NH3 and toluene for all biochar samples. In-situ DRIFTS of C350-550 during adsorption demonstrated the formation of amino functional groups caused by NH3 chemical adsorption with -OH (or -COOH) in the dual system. These increases in basic groups on C350-550 could enhance the surface zero potential point of C350-550, thereby improving the non-polarity of C350-550 and benefit the adsorption of weak polar toluene.

Research on electronic nose for compound malodor recognition combined with artificial neural network and linear discriminant analysis

The foul odor of foul gas has many harmful effects on the environment and human health. In order to accurately assess this impact, it is necessary to identify specific malodorous components and levels. In order to meet the qualitative and quantitative identification of the components of malodorous gas, an electronic nose system is developed in this paper. Both principal component analysis (PCA) and linear discriminant analysis (LDA) were used to reduce the dimensionality of the collected data. The reduced-dimensional data are combined with a support vector machine (SVM) and backpropagation (BP) neural network for classification and recognition to compare the recognition results. Regarding qualitative recognition, this paper selects the method of LDA combined with the BP neural network after comparison. Experiments show that the qualitative recognition rate of this method in this study can reach 100%, and the amount of data after LDA dimensionality reduction is small, which speeds up the pattern speed of recognition. Regarding quantitative identification, this paper proposes a prediction experiment through Partial least squares (PLS) and BP neural networks. The experiment shows that the average relative error of the trained BP network is within 6%. Finally, the experiment of quantitative analysis of malodorous compound gas by this system shows that the maximum relative error of this method is only 4.238%. This system has higher accuracy and faster recognition speed than traditional methods.

Fusiform CuC2O4 loaded porous biochar derived from phosphoric acid-activated bagasse for gaseous ammonia capture

Ammonia gas (NH3) in a relatively high concentration can cause irreversible damage to the environment and humans. Thus, it is important to develop a highly efficient adsorbent for NH3 removal. In this study, a novel fusiform CuC2O4-loaded bagasse-derived biochar (CuC2O4/BGB) was prepared by a combination of pyrolysis of H3PO4-activated bagasse powder and the co-precipitation method as an efficient adsorbent for NH3 capture. Specifically, the CuC2O4/BGB-2–600–0.7 composite with a specific surface area of 1160.77 m2/g was obtained by optimizing the activator amount, activation temperature, and CuC2O4 loading amount. The CuC2O4/BGB-2–600–0.7 composite delivered static adsorption capacity of 8.68 mmol/g at 298.15 K and 1 bar, and maintained the NH3 adsorption capacity above 6.5 mmol/g after 8 cycles of regeneration. The adsorption of NH3 on the as-prepared composite conformed to the Redlich-Peterson adsorption isotherm model and Fick’s diffusion kinetics. The adsorption mechanism was elucidated that well-developed micro/mesoporous structure provided abundant active adsorption sites, of which the acidic sites on the catalyst surface promoted the formation of NH4+ from NH3, and the complexation reaction between Cu2+ and NH3 formed the [Cu(NH3)4]2+ complex. Therefore, the as-prepared CuC2O4/BGB is an efficient and sustainable adsorbent for NH3 removal, which opens a new window for malodorous gas removal.

Screening, identification, and degradation characteristics of 3-methylindole degrading bacteria

3-Methylindole is a major component of organic pollutants in livestock compost, which can contribute to the deterioration of the environment in livestock farms and their surrounding areas. This study demonstrates that using microorganisms to degrade 3-methylindole is an effective method for energy conservation and environmental protection. The microbe capable of efficiently degrading 3-methylindole was isolated and screened from fecal samples. The isolated bacteria were identified as Acinetobacter oleivorans after morphological characterization and 16S rRNA sequencing. This project demonstrated that 3-methylindole was completely degraded under optimal conditions (initial concentration of 3MI: 100 mg/L, 30°C, pH8.0, and shaking at 160 rpm for 48 h). N2-Acetyl-L-ornithine, Phenylacetaldehyde, Phenylacetic acid, Indole-3-carboxylic acid, and Indole-3-carboxaldehyde were the primary metabolites of this degradation process. This study provides a theoretical foundation for other microbe-mediated environmental remediation approaches as well as a basis for future work to apply bacteria that degrade 3-methylindole for the purification of polluted environments. It has a promising application in the control of malodorous gas pollution in the large-scale livestock and poultry breeding industries.

Synthesis of amine grafted Cu-BTC and its application in regenerable adsorption of ultra-low concentration methyl mercaptan

Purification of volatile sulfur compounds is a hot topic since these malodorous gases with low odor thresholds are generated in both community and industry. Adsorption is an effective method, but adsorbent regeneration is usually difficult because of the strong bond between adsorbent and malodorous gases. In this work, an amine-grafted metal–organic framework was synthesized and applied in cyclic adsorption of ultra-low concentration methyl mercaptan (MM). As a result, MM was effectively purified to below 50 ppb for 1062 min, resulting in a breakthrough capacity of 84.9 mg/g. In comparison, the breakthrough time and capacity without grafting amine were 777 min and 58.6 mg/g, respectively. After detailed characterizations, Cu2+ site and amine group were both attributed to MM removal. Although Cu2+ site was unregenerable, the amine group was regenerable with a capacity of 17.9–19.4 mg/g since the N-H bond was weak between amine and MM. In addition, competitive gases CO and CO2 only decreased the breakthrough time and capacity by 10%. The main result of this work is in favor of applying a regenerable adsorbent for purification of ultra-low concentration malodorous gas.

In-situ removal of odorous NH3 and H2S by loess modified with biologically stabilized leachate

The loess regions distribute widely in Northwestern China, North America and Eastern Europe. For these regions, landfill is a suitable technology for solid waste treatment. However, as a landfill cover material, loess is not very effective in controlling the emission of malodorous gases. The present study modified loess with biologically stabilized leachate, and investigated the capacities and mechanisms of the modified loess to remove odorous NH3 and H2S. The removal rates of NH3 and H2S at different acclimation time, targeted gas concentrations and temperatures were measured. It was found that the NH3 removal rate of the modified loess was up to 0.08 μmol/(g·hr), which was 1.8 times that of the virgin loess. The H2S removal rate of the modified loess was up to 1.74 μmol/(g·hr), which was 1.25 times that of the virgin loess. The half-meter loess layer modified by biologically stabilized leachate achieved nearly 100% removal of H2S. The improvement of NH3 and H2S removal ability was mainly due to the enrichment of relevant microorganisms. This work proposed a novel method for in-situ control of malodorous pollutants in landfills in the loess regions, and proved that the in-situ removal of NH3 and H2S using the loess modified with biologically stabilized leachate is feasible and cost-effective.