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.

Levels, source apportionment, and risk assessment of polycyclic aromatic hydrocarbons in vegetable bases of northwest China.

Dietary consumption of contaminated vegetables is the main route of human exposure to polycyclic aromatic hydrocarbons (PAHs). However, there is a lack of research on PAHs in vegetables from northwest China. In this study, the concentrations, sources, and risk assessment of PAHs in the soil and vegetables of Urumqi, an urbanized city in Xinjiang, China, were investigated. The total concentrations of 16 PAHs in soil and vegetable samples ranged 10.58-77.20 and 93.7-1071.8 ng/g, with average values of 2.86 and 242.76 ng/g, respectively. Among vegetable samples, the concentrations were in the order: leafy vegetables (299.08 ng/g) > fruits (192.65 ng/g) > vegetable roots (152.05 ng/g). The source apportionment of PAHs was identified using positive matrix factorization. The primary sources of PAHs in soil samples are oil spills, traffic emissions, coal combustion, and coke combustion. The main sources of PAHs in vegetable samples are oil spills and burning of grass, wood, coal, and coke. In soil samples, the ecological risk caused by PAHs is at a safe level, and the incremental lifetime cancer risks (ILCRs) of ingestion exposure exceed 1.0 × 10-6, which will pose potential risks to human body. The ILCRs of vegetable samples revealed that all groups had potential risks from onion and cabbage consumption (ILCRs > 1.0 × 10-6). In particular, adult women had a higher risk of cancer (ILCRs > 1.0 × 10-4). These results emphasize the importance of combating PAHs pollution in vegetable bases.

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.

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.