Bacterial distinctions in practical rural sewage collection systems caused by the location, season, and system type.

Bacteria in rural sewage collection systems have the important influences on operation and maintenance risks, such as sedimentation blockage and harmful gas accumulation, and pollutant pre-treatment ability. It is necessary to analyze and interpret the influence on bacterial communities caused by the location (sewage, biofilms, and deposits), season (winter and spring, summer and autumn), and system type (sewers and ditches) to better understand the bacterial characteristics in rural sewage collection systems. To achieve the above purpose, 96 samples obtained from practical rural sewage collection systems in eight villages were analyzed by 16S rRNA whole region sequencing methods. The results indicate that locations and seasons caused significant influences on the overall bacterial communities, which were mainly affected by temperature, sewage quality and bacterial survival preference, and 13 genera of sulfate-reducing bacteria (SRB), 2 genera of ammonia-oxidizing bacteria (AOB), 2 genera of nitrite-oxidizing bacteria (NOB), and 9 genera of water-related pathogenic bacteria (WPB) were detected in rural sewage collection systems. SRB, AOB, NOB, and WPB tended to inhabit in biofilms or deposits rather than in sewage. The total relative abundance of SRB in summer and autumn (∼2.19%) was higher than in winter and spring (∼0.41%), and the WPB distribution in different seasons showed significant distinction. Additionally, some of SRB, AOB, NOB, and WPB also showed significant differences in sewers and ditches. Overall, this study provided a deeper understanding of bacteria in rural sewage collection systems and could further provide the basic parameter for the operation and maintenance risk control.

Evaluation of packing materials for thermophilic biofilter by refined evaluation scheme and application in the treatment of SO2 with high temperature.

The selection of packing materials is essential to maintaining biofilter performance in waste gas treatment. In this study, 12 types of packing materials were evaluated to determine the most suitable for the SO2 removal by a thermophilic biofilter. Scanning electron microscopy and the Baunauer-Emmett-Teller equation were utilized to identify the texture of the tested packing materials, while Fourier transform infrared spectroscopy and X-ray diffraction were applied to analyze the surface functional groups and crystal structures, respectively. Characteristics were accompanied by economic considerations. Results showed that the polyurethane sponge had better porous structure and water retention than other packing materials. In terms of microbial growth and carrier economy, it was chosen for the biofilter used to treat SO2. The performance of a full-scale thermophilic biofilter with polyurethane sponge as the packing material was investigated for the purification of SO2-containing gases at an inlet temperature of 55 °C. The biofilter effectively removed SO2 at an average removal rate of 93.36%. Thermophilic bacteria and sulfur-oxidizing bacteria, e.g., Bacillus thermophilus, could attached growth on the surface of selected packing materials and exhibited degradation activity. This study provides an effective and feasible method of packing material selection for biological waste gas treatment.

Emission behavior and impact assessment of gaseous volatile compounds in two typical rural domestic waste landfills.

Landfill sites are sources of gaseous volatile compounds. The dumping area (LDA) and leachate storage pool (LSP) of two typical rural domestic waste landfill sites in north China (NLF) and southwest China (SLF) were investigated. We found that 45, 46, 61 and 68 volatile organic compounds (VOC) were present in the air of NLF-LDA, NLF-LSP, SLF-LDA, and SLF-LSP, respectively. And there were 27, 29, 35 and 37 kinds of odorous compounds being detected. Oxygenated compounds (>48.88%), chlorinated compounds (>6.85%), and aromatics (>5.46%), such as organic acid, 1-chlorobutane, and benzene, were the most abundant compounds in both landfills. The SLF-LDA had the highest olfactory effect, with a corresponding total odor activity value of 29,635.39. The ozone-formation potential analysis showed that VOCs emitted from SLF landfills had significantly higher potential for ozone formation than those from NLF landfills, with ozone generation potentials of 166.02, 225.86, 2511.82, and 1615.99 mg/m3 for the NLF-LDA, NLF-LSP, SLF-LDA, and SLF-LSP, respectively. Higher chronic toxicity and cancer risk of VOCs were found in the SLF according to method of Risk Assessment Information System. Based on the sensitivity analysis by the Monte Carlo method, concentrations of benzene, propylene oxide, propylene, trichloroethylene, and N-nitrosodiethylamine, along with exposure duration, daily exposure time, and annual exposure frequency, significantly impacted the risk levels. We provide a scientific basis, which reflects the need for controlling and reducing gaseous pollutants from landfills, particularly rural residential landfills, which may improve rural sanitation.

Improving sewage sludge dewaterability via heterogeneous activation of persulfate by Fe-Al layered double hydroxide: Role of generated SO4-•.

In this study, Fe-Al layered double hydroxide (Fe-Al LDH) was prepared and applied to activate persulfate to condition sewage sludge and improve its dewaterability. The results showed that Fe-Al LDH activated persulfate to generate a large amount of free radicals, which attacked extracellular polymeric substances and reduced their content, disrupted microbial cells, released bound water, decreased sludge particle size, increased sludge zeta potential, and improved sludge dewaterability. After sewage sludge was conditioned with Fe-Al LDH (0.20 g/g total solids (TS)) and persulfate (0.10 g/g TS) for 30 min, the capillary suction time of the sludge dropped from 52.0 s to 16.3 s, while the moisture content of the sludge cake decreased from 93.2% to 68.5%. The dominant active free radical produced by the Fe-Al LDH-activated persulfate was SO4-•. The maximum Fe3+ leaching of the conditioned sludge was only 102.67 ± 4.45 mg/L, thus effectively alleviating the secondary pollution of Fe3+. The leaching rate of 2.37% was significantly lower than that of the sludge homogeneously activated with Fe2+ (738.4 ± 26.07 mg/L and 71.00%).

Latticed-Confined Conversion Chemistry of Battery Electrode.

The electrochemical conversion reaction, usually featured by multiple redox processes and high specific capacity, holds great promise in developing high-energy rechargeable battery technologies. However, the complete structural change accompanied by spontaneous atomic migration and volume variation during the charge/discharge cycle leads to electrode disintegration and performance degradation, therefore severely restricting the application of conventional conversion-type electrodes. Herein, latticed-confined conversion chemistry is proposed, where the "intercalation-like" redox behavior is realized on the electrode with a "conversion-like" high capacity. By delicately formulating the high-entropy compounds, the pristine crystal structure can be preserved by the inert lattice framework, thus enabling an ultra-high initial Coulombic efficiency of 92.5% and a long cycling lifespan over a thousand cycles after the quasistatic charge-discharge cycle. This lattice-confined conversion chemistry unfolds a ubiquitous insight into the localized redox reaction and sheds light on developing high-performance electrodes toward next-generation high-energy rechargeable batteries.

The difference between drainage channels and sewers in rural areas: from sewage quality to bacterial characteristics.

Channels and sewers are commonly used to collect sewage during extensively rural areas. The sewage and bacterial characteristics of rural sewage collection systems can influence their operation and maintenance performance which further affect appropriate system decision. In this study, eight rural sewage collection systems (four each of channels and sewers) were applied to evaluate the sewage quality, bacterial characteristics, and their differences of two kinds of collection systems. The results indicate that significantly distinction existed between the rural sewage collection systems of channels and sewers. Sewage in channels had higher suspended solid (SS) concentration but lower sulfide concentration than that in sewers. The SS, sulfate, and chemical oxygen demand (COD) removal capacity in channels was nearly 3.5, 4.0, and 0.6 times than those in sewers. At least 14 genera and 18 species of bacteria showed significantly distinction between channels and sewers even their main phylum, genus, and species of bacteria communities was Proteobacteria (∼70.3%), Acinetobacter (∼22.3%), and Pseudomonas fragi (∼13.8%), respectively. The structural characteristics and bacterial function caused the difference between channels and sewers. Overall, this study revealed the intrinsic and essential differences of channels and sewers, providing basic and meaningful data for rural sewage collection systems decision.

Biofilm development in a pilot-scale gravity sewer: Physical characteristics, microstructure, and microbial communities.

The existence of abundant biofilms on sewer pipeline walls can lead to negative environmental impacts, such as poisonous gas release and pipe corrosions through transforming various pollutants. Investigating the formation process of sewer biofilms is of importance in advancing knowledge of sewer operation and maintenance. In this study, the changes in physical characteristics, microstructure, and microbial communities of sewer biofilm were analyzed in-depth in a pilot-scale gravity sewer during a 45-day operation. The results show that a high specific surface area at the early stage could channel the substrates for stimulating the primary colonizers (e.g., Cytophagia, Sphingobacteriia, Alpha-, and Betaproteobacteria), which could excrete an extracellular matrix to facilitate biofilm growth. The sewer biofilms were gradually formed with 62 g VS/m2 organic content, 1.2 mm biofilm thickness, and 89 mg/cm3 dry density after 45 days operation. Moreover, the biofilm growth promoted the emergence of facultative bacteria and anaerobes (affiliated with Flavobacteriia, Gemmatimonadetes, Deltaproteobacteria, and Epsilonproteobacteria). Microelectrode analysis further verified that an anaerobic zone existed in mature biofilm with a negative oxidation-reduction potential (-105 mV), where approximately 0.1 µmol/L of sulfide was produced. Our results suggest that the migration of the microbial community correlated with the changes in the evolved physical characteristics and microstructure of sewer biofilm, and this can contribute to the strategies for sulfide control for improving sewer maintenance.

Characteristics of microbial aerosol particles dispersed downwind from rural sanitation facilities: Size distribution, source tracking and exposure risk.

Bioaerosols containing pathogens released from waste and wastewater treatment facilities pose potential health risks to workers on-site and residents downwind. In this study, sampling sites were set up at rural garbage stations (GS-1 and GS-2) and sewage treatment station (STS) to investigate the emission and diffusion characteristics of bioaerosols. High-throughput sequencing was utilized to assay the intestinal bacteria population, while the health risks associated with bioaerosols exposure were estimated based on average daily dose rates (DD). Traceability analysis was used to determine the percentages of intestinal bacteria from GS-1, GS-2 and STS. The recorded emission levels of bioaerosols in the air surrounding GS-1, GS-2, and STS were 5053, 6299, and 4795 CFU/m3, containing 1599, 2244, and 2233 CFU/m3 of intestinal bacteria, respectively. Most of the bioaerosols were coarse particles with size larger than 4.7 µm. Methylobacterium, Rhizobium, Pseudomonas, Enterobacteriaceae, and Brucella presented in the air were originally in rural waste and wastewater. STS and GS-2 were potential sources of intestinal bacteria. With increasing distance from the sources, the concentration of bioaerosols decreased gradually. On-site workers and residents were predominantly affected by bioaerosols through inhalation. The exposure risks via inhalation and skin contact for children were much higher than that for adults. The purpose of this study was to provide preliminary data for bioaerosols control and their risks reduction released from rural sanitation facilities.

Removal of tetracycline-resistant Escherichia coli and its genes through ultrasound treatment combined with ultraviolet light emitting diodes.

Antibiotic resistance has gained increasing attention worldwide, and wastewater treatment plants have been regarded as hotspots for antibiotic-resistant bacteria and antibiotic-resistant genes (ARGs). In this study, we evaluated the removal of tetracycline-resistant Escherichia coli and its related genes through ultrasound (US) treatment with different input levels of US-specific energy combined with ultraviolet light emitting diodes (UV-LEDs). Simultaneous US with UV-LEDs effectively eliminated tetracycline-resistant E. coli with the normal suggested UV-LEDs dosage (below 30 mJ/cm2). The removal efficiency increased with the addition of US (specific input energy of 8-16 kJ/L), and simultaneous US treatment with UV-LEDs was relatively more effective than US pretreatment. Analyses of cell damage by K+ leakage and flow cytometry showed that the cell wall kept its integrity during the applied treatment conditions. Consequently, the removal efficiencies of 16 S rRNA, tet M, and tet Q were unsatisfactory because less than 1 log reduction was achieved. Increasing the US energy remarkably damaged the cell wall and potentially promoted the reaction. The removal of ARGs increased four times when using US-specific input energy at 330 kJ/L with 5 mJ/cm2 compared with UV-LEDs alone. The US treatment combined with UV-LEDs is a novel process that does not require chemicals. Results of this research can provide theoretical support for the removal of ARGs.

Analysis of suitable private-secondary-main sewer diameters in rural areas based on cost model and hydraulic calculation.

High cost of sewer systems usually restricts the sewage collection in rural areas. Many rural areas take traditional sewer scheme whose private-secondary-main sewer diameter is 110-200-300 mm without hydraulic calculation and increased the total cost of sewers. The rational utilization of small diameter sewers might contribute to sewer cost reduction. In this study, rural sewer length and cost models were established taking sewer diameter, household number, and length/width ratio of village as parameters to evaluate the cost benefits of using small diameter sewers. Hydraulic calculation of sewers was applied by Storm Water Management Model to ensure the small diameter sewers were feasible. The results indicate that household number and length/width ratio cause obvious impact on sewer length and cost. Main sewer with 200 mm diameter is suitable for the village with less than 1000 households. Using small diameter sewers can reduce the sewer cost by 6-15% compared with traditional sewer scheme and 110-110-200 might be the better scheme to rural areas because of the low cost (including construction cost and operation and maintenance cost) and high tolerance of sewage flow fluctuation. This study provided the suitable diameter of rural sewers based on cost model and hydraulic calculation which might be helpful for the application of rural sewers.

Sewers induce changes in the chemical characteristics, bacterial communities, and pathogen distribution of sewage and greywater.

Sewers may affect the characteristics and bacterial communities of wastewater, and need be studied as they may impact treatment facilities and recycling operations. In this study, the wastewater characteristics and bacterial communities from the inflow and outflow of two sewers (sewage and greywater) were analyzed. The chemical oxygen demand was significantly reduced in the sewage and greywater sewer and the greywater sewer generated less sulfide and methane. Proteobacteria, Bacteroidetes, and Firmicutes as the major phyla in sewage and greywater and sewer biofilms. Sewer conveyance caused changes in the distribution and community interaction of suspended bacteria. Greywater contained abundant water-related pathogenic bacteria (WPB) and some WPB (e.g. Aeromonas, Klebsiella and Shigella) number in greywater were not lower than sewage. Sewers could increase the number of Shigella in sewage and decrease the number of Acinetobacter in greywater. Further treatment or disinfection of greywater collected by sewers was necessary and directly reuse of greywater without treatment should be avoided.

An appropriate technique for treating rural wastewater by a flow step feed system driven by wind-solar hybrid power.

Most rural wastewater treatment facilities require aeration equipment to ensure sufficient dissolved oxygen (DO) during processing. Operation and maintenance are costly, and cannot be met in many areas with poor economic levels. This has led to further deterioration of the rural water environment and aroused much attention. This work reports a plug-flow step feed system utilizing wind and solar hybrid energy for rural wastewater treatment. Under certain climatic conditions, the wind energy and solar energy provided complimentary power generation, and an automatic control system (without batteries) was constructed. The corresponding control logic for multi-energy level operation was developed. Furthermore, the power generation efficiency of the system, the pollutant removal, and its mechanism on the bioreactor were also analyzed. According to the monitoring of meteorological conditions, wind and solar resources at the test site were abundant, and the electricity generated by the power generation was sufficient to meet the operational needs of the equipment. Energy efficiency can reach 80.0%. The characteristics of pollutant removal in each process section were studied on spatial and temporal dimensions. Results showed that the wastewater treatment process reached mean removal efficiencies of chemical oxygen demand (CODcr), NH4+-N, total nitrogen (TN) and total phosphorus (TP) were 90.2%, 94.3%, 61.4% and 63.1%, respectively. Analyses of microbial community richness and group changes in each anoxic/aerobic reaction chamber in the biofilm reactor showed that the population structure was relatively stable and that there were abundant functional bacteria capable of degrading pollutants in each aerobic and anoxic unit. This system can thus be a more sustainable treatment process than traditional techniques used for rural wastewater treatment, providing a new design approach for low-energy consumption and unattended rural wastewater treatment.

Influences of flow conditions on bacterial communities in sewage and greywater small diameter gravity sewer biofilms.

Small diameter gravity sewers (SDGS) have been applied in rural areas to collect sewage or greywater. Flow conditions in rural SDGS are variable and their influences on bacteria in sewer biofilms are still not clear. To investigate the effect of flow conditions on sewage and greywater SDGS biofilms, six sewage SDGS and six greywater SDGS were operated and Illumina HiSeq sequencing was subsequently performed on sewer biofilms. The results indicate that the predominant bacterial phyla in both sewage and greywater SDGS biofilms were Proteobacteria (63.0% ± 9.3%) and Actinobacteria (26.5% ± 8.8%) and co-presence relationship was the main interaction in SDGS biofilm bacterial communities. Compared with stable flow conditions, variable flow conditions altered the bacterial community of SDGS biofilms from the aspect of bacteria compositions and community interactions and the relative abundance of many bacteria showed significant distinctions between stable and variable flow conditions. In sewage SDGS biofilm, the relative abundance of denitrifying, nitrite-oxidizing, and sulfate-reducing bacteria decreased significantly in variable flow conditions while in greywater SDGS biofilms, nitrite-oxidizing and water-related pathogenic bacteria decreased significantly in variable flow conditions. Influences of flow conditions on predicted bacterial functions were also significant in sewage and greywater SDGS biofilms. Variable flow conditions might be conducive to the reduction of H2S generation and water-related pathogenic bacteria in rural SDGS biofilms.

Characteristics of sewer biofilms in aerobic rural small diameter gravity sewers.

Small diameter gravity sewers (SDGS) are extensively used to collect rural sewage as they are low in cost and quick to construct. However, the characteristics of biofilms in rural SDGS are still not clear. In this study, biofilms characteristics of aerobic rural SDGS were investigated using simulations in a lab under different flow conditions and slopes. Results indicated that the average thickness of aerobic rural SDGS biofilms was in the range of 350-650 µm, decreasing at locations with variable flow and high slopes. Protein was the most abundant substance in extracellular polymeric substance of SDGS biofilms. The most abundant bacteria, Proteobacteria, Actinobacteria, and Bacteroidetes, and functional bacteria showed different distributions when analyzed through Illumina HiSeq sequencing of 16S rRNA. The relative abundances of denitrifying bacteria, nitrite-oxidizing bacteria, and sulfate-reducing bacteria (SRB) were lower during variable flow than during stable flow. High slopes (15‰) decreased SRB presence, which could be used to mitigate H2S accumulation in aerobic SDGS. Overall, this study describes the characteristics of aerobic rural SDGS biofilms and provides valuable suggestions for the optimal design of SDGS based on these characteristics.

Pilot-scale experiments on multilevel contact oxidation treatment of poultry farm wastewater using saran lock carriers under different operation model.

A pilot-scale multilevel contact oxidation reactors system, coupled with saran lock carriers, was applied for the treatment of poultry farm wastewater. The removal efficiencies of CODcr, ammonia, and the total nitrogen as well as the elimination performance of CODcr and total nitrogen along the three-level contact oxidation tanks under six designed operational models were investigated. Based on the performance of the nitrogen removal of the saran lock carriers and the distribution of anoxic-aerobic interspace under the suitable operation model, the mechanism of nitrogen removal of the system was also explored. The results revealed that the intermittent aeration under parallel model is the most suitable operation model, while the removal efficiencies of CODcr, ammonia, and the total nitrogen were 86.86%, 84.04%, and 80.96%, respectively. The effluent concentration of CODcr, ammonia, and the total nitrogen were 55.6 mg/L, 8.3 mg/L, and 12.0 mg/L, which satisfy both the discharge standard of pollutants for livestock and poultry breeding industry (GB 18596-2001) and the first grade of the integrated wastewater discharge standard (GB 8978-1996). Moreover, the mechanism for the nitrogen removal should be attributed to the plenty of anoxic-aerobic interspaces of the biofilm and the three-dimensional spiral structure of the saran lock carriers, where the oxygen-deficient distribution was suitable for the happening of the simultaneous nitrification and denitrification process. Therefore, the multilevel contact oxidation tanks system is an effective pathway for the treatment of the poultry farm wastewater on the strength of a suitable operation model and novel carriers.

State of the art on granular sludge by using bibliometric analysis.

With rapid industrialization and urbanization in the nineteenth century, the activated sludge process (ASP) has experienced significant steps forward in the face of greater awareness of and sensitivity toward water-related environmental problems. Compared with conventional flocculent ASP, the major advantages of granular sludge are characterized by space saving and resource recovery, where the methane and hydrogen recovery in anaerobic granular and 50% more space saving, 30-50% of energy consumption reduction, 75% of footprint cutting, and even alginate recovery in aerobic granular. Numerous engineers and scientists have made great efforts to explore the superiority over the last 40 years. Therefore, a bibliometric analysis was desired to trace the global trends of granular sludge research from 1992 to 2016 indexed in the SCI-EXPANDED. Articles were published in 276 journals across 44 subject categories spanning 1420 institutes across 68 countries. Bioresource Technology (293, 11.9%), Water Research (235, 9.6%), and Applied Microbiology and Biotechnology (127, 5.2%) dominated in top three journals. The Engineering (991, 40.3%), China (906, 36.9%), and Harbin Inst Technol, China (114, 4.6%) were the most productive subject category, country, and institution, respectively. The hotspot is the emerging techniques depended on granular reactors in response to the desired removal requirements and bio-energy production (primarily in anaerobic granular sludge). In view of advanced and novel bio-analytical methods, the characteristics, functions, and mechanisms for microbial granular were further revealed in improving and innovating the granulation techniques. Therefore, a promising technique armed with strengthened treatment efficiency and efficient resource and bio-energy recovery can be achieved.

Advanced treatment of wet-spun acrylic fiber manufacturing wastewater using three-dimensional electrochemical oxidation.

A three-dimensional electrochemical oxidation (3D-EC) reactor with introduction of activated carbon (AC) as particle micro-electrodes was applied for the advanced treatment of secondary wastewater effluent of a wet-spun acrylic fiber manufacturing plant. Under the optimized conditions (current density of 500A/m2, circulation rate of 5mL/min, AC dosage of 50g, and chloride concentration of 1.0g/L), the average removal efficiencies of chemical oxygen demand (CODcr), NH3-N, total organic carbon (TOC), and ultraviolet absorption at 254nm (UV254) of the 3D-EC reactor were 64.5%, 60.8%, 46.4%, and 64.8%, respectively; while the corresponding effluent concentrations of CODcr, NH3-N, TOC, and UV254 were 76.6, 20.1, and 42.5mg/L, and 0.08Abs/cm, respectively. The effluent concentration of CODcr was less than 100mg/L, which showed that the treated wastewater satisfied the demand of the integrated wastewater discharge standard (GB 8978-1996). The 3D-EC process remarkably improved the treatment efficiencies with synergistic effects for CODcr, NH3-N, TOC, and UV254 during the stable stage of 44.5%, 38.8%, 27.2%, and 10.9%, respectively, as compared with the sum of the efficiencies of a two-dimensional electrochemical oxidation (2D-EC) reactor and an AC adsorption process, which was ascribed to the numerous micro-electrodes of AC in the 3D-EC reactor. Gas chromatography mass spectrometry (GC-MS) analysis revealed that electrochemical treatment did not generate more toxic organics, and it was proved that the increase in acute biotoxicity was caused primarily by the production of free chlorine.

Performance enhancement of integrating microbial electrolysis cell on two-stage anaerobic digestion of food waste: Electro-methanogenic stage versus electro-two stages.

The effects of microbial electrolysis cell (MEC) integration stage on two-stage anaerobic digestion (TSAD) of food waste (FW) were studied via semi-continuous experiments. The results showed that both MEC (with 1.2 V) integrations enhanced the performances of the TSADs, with the enhancement of electro-two stages being higher. The methane production of TSAD increased from 1.36 ± 0.04 L/L/d to 1.53 ± 0.05 L/L/d (electro-methanogenic stage) and 1.54 ± 0.04 L/L/d (electro-two stages) during the steady period. Electro-acidogenesis decreased propionic acid production and enhanced hydrogen production, while electro-methanogenesis promoted the conversion of volatile fatty acids to methane. The MEC integration improved energy recovery from the organic matter in FW by 11.65-16.15% and reduced the mass loss, with those of the electro-two stages being higher and the electro-methanogenic stage being dominant in the electro-two stages. The integration of MEC enhanced anaerobic fermentation by enriching Olsenella, norank_f__ST-12K33 and Proteiniphilum and improved methanogenesis by enriching Methanobacterium and Candidatus_Methanofastidiosum.

Construction waste ditch: a novel rural household sewage collection and treatment facility.

New low-cost rural sewage collection and treatment technologies should be developed to solve the problem of conventional rural sewage technology caused by rural sewage characteristics. In this study, a novel facility, the construction waste ditch, was established to collect and treat household rural sewage, making use of the collection capacity of ditches and the treatment capacity of construction wastes, and the structure parameters were optimized. Results show that the construction waste ditch achieved pollutant removal phenomenon (average removal rates were above 25% and the maximum rates were more than 50%) and structural parameters (baffles number, height, and angle) influenced the pollutant removal ability significantly. Five baffles, 4-5 cm baffle height and 0-25° baffle angle were effective with different scenarios. This technology had the advantage of high pollutant removal capacity and tolerant of influent concentration fluctuation, having potential for popularization and application.

Dispersion characteristics of bioaerosols during treatment of rural solid waste in northwest China.

In rural China, the release of bioaerosols containing pathogens from solid waste dumps poses a potential health risk to the local population. Here, we sampled bioaerosols from rural solid waste-treatment in four provinces of northwest China to investigate their emission and dispersion characteristics in order to provide a scientific basis for control and risk reduction of bioaerosols released from rural sanitation facilities. The airborne bioaerosol concentrations and particle size distributions were calculated using an Anderson six-stage airborne microbial sampler and counting with its internal Petri dish culture. High-throughput sequencing was used to characterize the microbial composition at different sampling sites and to explore possible influencing factors, while the health risk associated with exposure was estimated based on average daily dose-rate. The highest concentration point values of bacteria and fungi in bioaerosols near the solid waste were 63,617 ± 15,007 and 8044 ± 893 CFU/m³, respectively. Furthermore, the highest concentration point values of Enterobacteriaceae was 502 ± 35 CFU/m³. Most bioaerosols were coarse particles larger than 3.3 µm. Potentially pathogenic genera of winter-indicator species detected in the air were primarily Delftia, Rhodococcus and Aspergillus. The composition of solid waste and environmental conditions are important factors in determining the characteristics of bioaerosols. Local residents are exposed to bioaerosols mainly through inhalation. Children are at a particularly high risk of exposure through both inhalation and skin contact. The results of this study show that bioaerosols in the vicinity of rural solid waste dumps pose a health risk to the surrounding population. More suitable risk assessment criteria for rural areas should be established, and corresponding control and protection measures should be taken from three aspects: generation source and transmission pathway, as well as the recipient.