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Perfluorooctanoic acid (PFOA) as emerging pollutants was largely produced and stable in nature environment. Its fate and effect to the wasted sludge digestion process and corresponding microbial mechanism was rarely reported. This study investigated the different dose of PFOA to the wasted sludge digestion process, where the methane yield and microbial mechanism was illustrated. The PFOA added before digestion were 0-10000 μg/L, no significant variation in daily and accumulated methane production between each group. The 9th day methane yield was significantly higher than other days (p < 0.05). The soluble protein was significantly decreased after 76 days digestion (p < 0.001). The total PFOA in sludge (R 2  = 0.8817) and liquid (R 2  = 0.9083) phase after digestion was exponentially correlated with PFOA dosed. The PFOA in liquid phase was occupied 54.10 ± 18.38% of the total PFOA in all reactors. The dewatering rate was keep decreasing with the increase of PFOA added (R 2  = 0.7748, p < 0.001). The mcrA abundance was significantly correlated with the pH value and organic matter concentration in the reactors. Chloroflexi was the predominant phyla, Aminicenantales, Bellilinea and Candidatus&#95;Cloacimonas were predominant genera in all reactors. Candidatus&#95;Methanofastidiosum and Methanolinea were predominant archaea in all reactors. The function prediction by FAPROTAX and Tax4fun implied that various PFOA dosage resulted in significant function variation. The fermentation and anaerobic chemoheterotrophy function were improved with the PFOA dose. Co-occurrence network implied the potent cooperation among the organic matter degradation and methanogenic microbe in the digestion system. PFOA has little impact to the methane generation while affect the microbe function significantly, its remaining in the digested sludge should be concerned to reduce its potential environmental risks., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

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., (© 2023. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

Perfluorooctanoic acid (PFOA) as nonbiodegradable organic pollutant, its presence and risks in wastewater treatment system has aroused wide concern. This study investigated the effect and underlying mechanism of PFOA on anaerobic digestion sludge (ADS) dewaterability. Long-term exposure experiments were set up to investigate the effect with various concentration of PFOA dosed. Experimental results suggested that the existence of high concentration PFOA (over 1000 μg/L) could deteriorate ADS dewaterability. The long-term exposure to 100,000 μg/L PFOA of ADS increased specific resistance filtration (SRF) by 81.57%. It was found that PFOA promoted the release of extracellular polymeric substances (EPS), which was strongly associated with sludge dewaterability. The fluorescence analysis revealed that the high PFOA concentration could significantly improve the percentage of protein-like substances and soluble microbial by-product-like content, and then further deteriorated the dewaterability. The FTIR results showed that long-term exposure of PFOA caused loose protein structure in sludge EPS, which led to loose sludge floc structure. The loose sludge floc structure aggravated the deterioration of sludge dewaterability. The solids-water distribution coefficient (K d ) decreased with the increase of initial PFOA concentration. Moreover, PFOA significantly affected microbial community structure. Metabolic function prediction results showed significant decrease of fermentation function exposed to PFOA. This study revealed that the PFOA with high concentration could deteriorated sludge dewaterability, which should be highly concerned., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier Ltd. All rights reserved.)

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.

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., (Copyright © 2020 Elsevier Ltd. All rights reserved.)

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., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020 Elsevier Inc. All rights reserved.)

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 H 2 S generation and water-related pathogenic bacteria in rural SDGS biofilms., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020 Elsevier Inc. All rights reserved.)

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 H 2 S 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., Competing Interests: Conflicts of interest All the authors declare no competing financial interests and are aware of and accept responsibility for this manuscript., (Copyright © 2019. Published by Elsevier B.V.)

With rapid urbanization, sewer systems are extensively being constructed for the collection and transportation of sewage to minimize the severe environmental and health issues, especially relating to the spread diseases. The existence of abundant biofilms on the inner walls of sewers could lead to potential risks such as sewer explosions, poisonous gas leaks, and pipe corrosions with the transformations of various kinds of pollutants. Therefore, it is urgent to clarify their inner mechanisms to safely govern sewer systems. In this study, the characteristics of sewer biofilms including their structure, influencing factors, and substance transformations were analyzed in-depth. The results reveal that sewer biofilms (1.0 mm depth approximately) consist of large quantities of inorganic and some organic substances, while the abundant functional genus of the bacteria and archaea are summarized. Sewer biofilms influencing factors were determined to be sewer operation mode, sewage characteristics, and shear stress. Further, the transformation of organics, sulfur, and nitrogen as well as emerging micropollutants (such as, biomarkers, antibiotic resistance genes, and engineered nanoparticles) was investigated to guarantee sewer security and public health. Therefore, the current review could be considered as guidance for researchers and decision-makers., (Copyright © 2019 Elsevier B.V. All rights reserved.)

Truck-wash facilities have become popularized globally on construction sites, and the wastewater was frequently treated by three-stage sedimentation basins. The wastewater and bacterial characteristics in three-stage sedimentation basins need to be studied, which might affect the treatment cost and reuse security. In this study, the wastewater characteristics, bacterial communities, and pathogenic bacteria distribution of three-stage sedimentation basins on four construction sites were investigated. Results indicated that truck-wash wastewater contained a high concentration of suspended solids (29–211 mg/L) and bacteria (4.2×103 to 2.7×104 colony forming units/mL). Proteobacteria (mean at 72.3%), Firmicutes (mean at 11.3%), and Bacteroidetes (mean at 10.6%) were the predominant bacterial phyla and Acinetobacter (mean at 18.4%), Chryseomicrobium (mean at 6.3%), and Paracoccus (mean at 6.1%) were the predominant bacterial genera. Truck-wash wastewater contained pathogenic bacteria, identified by the Illumina sequencing method. Acinetobacter, Shigella, or Escherichia (about 0.2%) and Legionella (about 0.2%) were the main pathogenic bacteria and Legionella should be a concern due to the wastewater reuse method. Traditional three-stage sedimentation basins should be simplified and further improved because of the lower suspended solids or pathogenic bacteria removal effect. The practical technology for suspended solids and pathogenic bacteria control in truck-wash wastewater should be further studied, and disinfection facilities should be applied to protect construction workers. [ABSTRACT FROM AUTHOR]

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. • Locations and seasons caused significant influences on bacterial communities. • SRB, AOB, NOB, and WPB tended to inhabit in biofilms or deposits. • Total abundance of SRB in summer and autumn was higher than in winter and spring. • Some of SRB, AOB, NOB, and WPB showed significant differences in sewers and ditches. [ABSTRACT FROM AUTHOR]

Determining the rural domestic water consumption (RDWS, L/person-day) and rural sewage production (RSP, L/person-day) of rural residents at the county scale can provide decision support for rural domestic sewage treatment. However, methods for predicting county-scale RDWS and RSP based on geographical, social, and governance factors are rarely reported. This paper proposes an RDWS and RSP prediction method based on Automated Machine Learning (AutoML) for the Inner Mongolia Autonomous Region. The RDWS and RSP in the Inner Mongolia Autonomous Region were successfully predicted from multi-source data. The AutoML model accurately predicted RDWS (mean absolute error = 1.7072, R2 = 0.7759) and RSP (mean absolute error = 0.6580, R2 = 0.65107). Average years of education (AYOS), proportion of resident population, and proportion of elderly and children (POEAC) were key driving factors related to RDWS prediction. The most important factors associated with RSP prediction were AYOS, POEAC, and annual average precipitation (AAP). An explanatory analysis further revealed dependence between the input variables, RDWS, and RSP. The framework was demonstrated to be a practical tool for qualitative and quantitative analyses of rural domestic water consumption and domestic sewage production in the Inner Mongolia Autonomous Region. Overall, this study provides a solution for predicting county-level RDWS and RSP, providing a reference for the design of rural domestic sewage treatment. [Display omitted] • Less than 24% of rural domestic sewage is currently treated in Inner Mongolia. • Planning needs county-scale domestic water consumption and sewage production data. • Best of many models based on data from multiple sources were selected automatically. • Nonlinear relationships between input output variables were quickly revealed. [ABSTRACT FROM AUTHOR]