PREDICTION OF RADIOACTIVE COMPOUND SEDIMENTATION FROM DEACTIVATION STATION WASTEWATER IN URBAN SEWERAGE SYSTEMS

Chemical dosing is the most used strategy for sulfide and methane abatement in urban sewer systems. Although conventional physicochemical methods, such as sulfide oxidation (e.g., oxygen/nitrate), precipitation (e.g., iron salts), and pH elevation (e.g., magnesium hydroxide/sodium hydroxide) have been used since the last century, the high chemical cost, large environmental footprint, and side-effects on downstream treatment processes demand a sustainable and cost-effective alternative to these approaches. In this paper, we aimed to review the currently used chemicals and significant progress made in sustainable sulfide and methane abatement technology, including 1) the use of bio-inhibitors, 2) in situ chemical production, and 3) an effective dosing strategy. To enhance the cost-effectiveness of chemical applications in urban sewer systems, two research directions have emerged: 1) online control and optimization of chemical dosing strategies and 2) integrated use of chemicals in urban sewer and wastewater treatment systems. The integration of these approaches offers considerable system-wide benefits; however, further development and comprehensive studies are required.

BackgroundThe urban sewer system is an important component of urban water infrastructure for sewage collection and transportation, and in-sewer transportation of sewage can cause multitudinous contaminant degradations which lead to formation of gaseous products. Although the greenhouse gases of methane and carbon dioxide have been confirmed to consist in the gaseous products, the mechanisms of greenhouse gas generation were unclear and the significances of greenhouse gases emission from sewers were generally underestimated.ResultsIn this study, 3 years of monitoring was conducted to evaluate the greenhouse gases emission in 37-km-long urban sewer systems covering 13 km2. The results showed that the emission of carbon dioxide and methane was extensively existing in sewers, and especially, exhibited a characteristic of regional difference. In order to reveal the formation mechanism of carbon dioxide and methane in sewers, the metagenomic approach was utilized to analyze the annotated pathways and homologous bio-enzymes, and it indicated that fourteen pivotal annotated pathways were involved in the carbon dioxide and methane generation. According to the metagenomics and 3-year monitoring results, the total amounts of carbon dioxide and methane emission in sewers were calculated by the transformation venation of contaminants (such as methyl alcohol, methylamine and acetic acid along branch sewer, sub-main sewer and main sewer, respectively). The calculation results showed that the total greenhouse gas emissions in sewer were calculated to be 199 t/day in Xi’an, and if scaling up as population proportion, the greenhouse gas emission from sewer systems in China could be 30,685 t/day. Comparing with the greenhouse gas emissions from different metropolises (New York City, London and Tokyo) and industries (dairy farms, automobile production and steel enterprises), the amount of greenhouse gases produced by the urban sewer system is much higher.ConclusionsThis study revealed the transformation pathways of contaminants which promoted the generation of greenhouse gases in sewers. Based on this analysis, the greenhouse gas emissions along sewer systems were calculated. The results indicate that the greenhouse gas emission from sewer systems is non-negligible, and should be attracted sufficient attention.

"Intensities of short-term rainfalls are the basic design parameters for the dimensioning and design of urban sewerage systems.However, in connection with climate change, there is a change in rainfall characteristics, which are represented i. a. also byincrease of the short-term rainfall intensity. This means an increased hydraulic load on urban sewerage systems, which can beresolved by increase of the sewerage system capacity or by reducing the of rainwater inflow into the sewerage system. Currently,within the framework of adaptation measures for climate change mainly the second option is preferred, i.e. reduction of the inflowinto the sewerage system. This has to be realized prioritizing the green adaptation measures (green infrastructure). The paperdeals with impact of the of green infrastructure implementation in urban sewerage system on the operational safety of the urbansewerage system from the point of view of the floods occurrence in the urbanized area. As shown by the results of the model study,the biggest effectiveness of green infrastructure in terms of preventing the occurrence of flooding is shown in case of short-termrainfalls with a lower return period (1-2 years). With increase of the return period (up to 10 years), the effectiveness of greeninfrastructure in terms of the occurrence of flooding decreases."

Bacterial hosts, distribution patterns, and risk burden of antibiotic resistance genes in urban sewers:From the perspective of horizontal and vertical chains.

Carbon emission fluxes in urban sewer systems and the microbial community structure in sewer sediments remain unclear. In this study, a sewer system located in southern China was utilized to investigate the water quality characteristics. The results showed that the chemical oxygen demand loss rates in the branch pipe and sub-main pipe were 27.1% and 14.1%, respectively. The estimated carbon emission flux was estimated by the carbon emission factor method. The results revealed that the total carbon emission flux from the sewer system was 1.39 kg CO2-eq/m3 and the emission fluxes of methane and carbon dioxide were 0.87 kg CO2-eq/m3 and 0.51 kg CO2-eq/m3, accounting for 62% and 36.4%. The microbial community structure was analyzed by 16S rRNA. The results indicated that the methanogenic archaea in the sediments of the branch pipe and sub-main pipe were Methanobacterium, Methanosaeta, and Methanobrevibacter. The methanogenic activity of the sewer sediments was further assessed. This study further confirmed that the branch pipe and sub-main pipe were the main sources of carbon emissions and methane and carbon dioxide are the main greenhouse gases in the sewer system. This study furnishes novel insights for the control of carbon emissions in municipal sewage systems.

Impact of stormwater infiltration on rainfall-derived inflow and infiltration: A physically based surface–subsurface urban hydrologic model

In this study, a dynamic numerical model was developed to examine catchment-scale wastewater management, including urban household wastewater treatment. The model allowed both water quality and energy consumption to be evaluated. This system was applied to an actual sewerage system, and the effects of management strategies on water quality and energy consumption were assessed in a numerical simulation. The entire water resource system of a basin, including a forest catchment and an urban area, was evaluated synthetically from a spatial distribution perspective with respect to water quantity and quality. The life-cycle assessment technique was applied to optimize wastewater treatment management with the aim of improving water quality and reducing CO2 emissions. A numerical model was developed to predict the water cycle and contamination in the catchment and the city; the effect of a wastewater treatment system on the urban region was evaluated; pollution loads were quantitatively assessed; and the effect of excluding rainwater from the treatment system during flooding and the effect of urban rainwater control on water quality were examined. Analysis indicated that controlling the amount of rainwater inflow into a wastewater treatment plant in an urban area with a combined sewerage system has a large impact on reducing CO2 emissions because of the load reduction on the urban sewerage system.

A Constant Pipe Drainage (CPD) capacity for sewer systems is commonly applied when undertaking flood risk assessment, however data that are needed for calibration and validation of numerical models are scarce or unavailable. The CPD model neglects the effect of pressure flow and leads to significant deviation in flood volume estimate. This study proposes a new index Velocity Ratio (VR) to approximate pressure flow. A case study in Guangzhou, China is used to investigate the capability of reproducing a reasonable flood volume for two models, the CPD and the VR-based. Compared to the flood volume simulated by the Storm Water Management Model (SWMM), the CPD model shows a significant overestimation, Mean Relative Deviation (MRD) 192%. The VR-based model has a much better performance, MRD 18%. Therefore, the VR-based model is a simple and effective representation of pressure flow in urban sewer systems and can be easily applied in areas lacking detailed pipe data, especially for planning new pipe networks or updating the old pipes.

Sewage collection, transmission and treatment systems are among the basic infrastructures of any city that should be designed to have the least vulnerability during crises caused by intentional or unintentional disruptions. Therefore, observing the principles of passive defense and safety in the sewage sector to protect and reduce vulnerability with the aim of continuing the necessary services, protection of sewage facilities and equipment, meeting the needs of the people, protecting people's lives (preventing the spread of microbial and chemical contamination), continuing to manage, and managing the people (preventing discontent and creating chaos) and, consequently, stabilizing the country's top management are essential and inevitable. Methods: This paper identifies the risks to the critical infrastructure of the municipal sewer system with a passive defense approach as the first step in assessing the sustainability of urban sewer systems and the overlooked points in the design and construction of collection, transmission and transmission network systems and provides wastewater treatment. The present research method is a descriptive survey and is a type of applied research and distinguishes between risk or actual risk (Danger) and threat or potential hazard (Hazard); it also examines the status of asset parameters, threat and vulnerability in design, and has developed urban sewage systems. Results: The results of the research indicate that the regulations and methods of designing urban sewage systems in Iran are not sufficient to protect and increase the sustainability and resilience of the aforementioned systems and therefore, the solutions of defense knowledge. Passive can be considered a good complement to existing methods of designing and constructing urban sewer systems. The research results also show that these systems have been designed or built in the cities of our country, with the least attention to the principles of passive defense. Conclusion: Based on the findings of this study and the nature of urban sewage systems, 48 types of threats and weaknesses and serious vulnerabilities of urban sewage systems were enumerated.

The research emphasis has always been on sewerage treatment technology in China, though urban drainage system has gained little attention. In the context of urban drainage system and the problem associated with rain, the focus is still mainly toward the simple “emissions”. While the relationship between conservation and utilization of rainwater resources and urban ecology are popular, the relationship between rainwater discharge and non-point source pollution are often neglected. The reasonable choice of sewerage system is dependent on the collection and discharge of urban sewerage, the applicability and economic benefits, along with the ability to meet the water quality requirements and environmental protection. This paper analyzes and summarizes the development of urban drainage system in china, and introduces different drainage forms. The choice of drainage system should be based on the overall planning of the city, environmental protection requirements, the local natural conditions and water conditions, urban sewerage and water quality, the original drainage facilities, and local climatic conditions. It must be comprehensive to meet the environmental protection requirements, through technical and economic comparison.

The release of sewage-derived Hg-methylating (hgcA) microorganisms is found to be the main contributor to global surges of MeHg levels in urban rivers, posing significant risks to ecosystems and public health. However, the sources and drivers of these microorganisms remain unclear. This study integrated global metagenomic analysis, field sampling, and laboratory experiments to investigate their sources and driving mechanisms in sewage. Large-scale public metagenomic analyses revealed that external microbial sources, such as drinking water and feces, contribute negligibly to Hg-methylating communities in sewage. Consistently, in our field sampling, sewage discharged directly from building drainage stacks─prior to entering sewer systems─ contained almost no detectable hgcA genes. However, as sewage flows through sewer systems, hgcA gene abundance increased by 19- to 58-fold, with sequences identical to those in sewer biofilms, suggesting biofilm detachment as the primary source. Laboratory-scale sewer reactor experiments further demonstrated that biofilm maturation was accompanied by an increased hgcA abundance and elevated MeHg production rates. Metabolic profiling of hgcA-bearing MAGs revealed their key adaptive strategies in sewer environments. These findings suggest that urban sewers unexpectedly act as incubators for Hg-methylators, facilitating their prevalence in sewage and increasing the risk of downstream MeHg production. This finding underscores the urgent need to optimize sewer infrastructure and management strategies to address this emerging public health threat.

In this study, analysis of reliability of sewer network was progressed with the number of overflow nodes and overflow volume simultaneously for urban areas considering sedimentation. Reliability analysis shows that it is possible to quantify the difference in the phenomenon of the destruction of sedimentation in urban sewer system under the same design frequency. It is proposed as one of the indicators evaluated as full reliability for sewer system. To analyze detailed changes in conduit designs in urban sewer networks, tried to reduction of sedimentation in sewer networks using modified pipe slope in Bujeon-dong catchment, Busan. The various sewer designs were applied and then, the most effective improvement of reliability over 10%. Suggested reliability process can produce the quantitative evaluations about sewer systems using the results of the system simulations and use of possible the objective function for the sewer network designed with a relative evaluation.

One of the most important properties of concrete is its strength. However, in certain circumstances, like urban sewage systems, concrete is attacked and corroded, being exposed to the sulfuric acid produced from H2S in a biological process, thereby undergoing a decrease in its strength. This paper studies the effect of concrete admixtures on surface strength of concrete in acidic environments, using Twist-Off method. In order to investigate the corrosion process in concrete and consequent decrease in its strength, the calibration curve for the partially destructive twist-off method was firstly determined. Then, 15 concrete samples mixed with air-entraining admixtures, plasticizers, and micro-silica were prepared and placed in acidic and neutral PH environments in sewer pipes and sewage treatment plant. Using twist-off method and calibration curve, surface strengths of the samples were measured in a 135-day period and compared with one another.

Spatial heterogeneity identification for rainfall-derived inflow and infiltration in urban sewer systems based on water level sensor networks: Insights from an interpretable deep learning method.

Characterization of microflora and transformation of organic matters in urban sewer system