Sewage flow optimization algorithm for large-scale urban sewer networks based on network community division

By considering the flow control of urban sewer networks to minimize the electricity consumption of pumping stations, a decomposition-coordination strategy for energy savings based on network community division is developed in this paper. A mathematical model characterizing the steady-state flow of urban sewer networks is first constructed, consisting of a set of algebraic equations with the structure transportation capacities captured as constraints. Since the sewer networks have no apparent natural hierarchical structure in general, it is very difficult to identify the clustered groups. A fast network division approach through calculating the betweenness of each edge is successfully applied to identify the groups and a sewer network with arbitrary configuration could be then decomposed into subnetworks. By integrating the coupling constraints of the subnetworks, the original problem is separated into N optimization subproblems in accordance with the network decomposition. Each subproblem is solved locally and the solutions to the subproblems are coordinated to form an appropriate global solution. Finally, an application to a specified large-scale sewer network is also investigated to demonstrate the validity of the proposed algorithm.

Emission of greenhouse gases from sewer networks:field assessment and isotopic characterization

Sewer networks play a vital role in sewage collection and transportation,and they are being rapidly expanded.However,the microbial processes occurring within these networks have emerged as significant contributors to greenhouse gas(GHG)emissions.Compared to that from other sectors,our understanding of the magnitude of GHG emissions from sewer networks is currently limited.In this study,we conducted a GHG emission assessment in an independent sewer network located in Beijing,China.The findings revealed annual emissions of 62.3 kg CH_(4) and 0.753 kg N20.CH_(4) emerged as the primary GHG emitted from sewers,accounting for 87.4%of the total GHG emissions.Interestingly,compared with main pipes,branch pipes were responsible for a larger share of GHG emissions,contributing to 76.7%of the total.A GHG emission factor of 0.26 kg CO_(2)-eq/(m:yr)was established to quantify sewer GHG emissions.By examining the isotopic signatures of CO_(2)/CH_(4) pairs,it was determined that CH_(4) production in sewers primarily occurred through acetate fermentation.Additionally,the structure of sewer pipes had a significant impact on GHG levels.This study offers valuable insights into the overall GHG emissions associated with sewer networks and sheds ight on themechanismsdriving theseemissions.

Flow Simulation of Urban Sewer Networks

Flow in an urban drainage network is usually unsteady with backwater near junctions. The routing of hydrographs through a network is an important aspect of the design and analysis of urban drainage networks. Various numerical methods to analyze flow in urban drainage networks were compared and a new hybrid interpolation scheme was developed which combined time-line reachback interpolation, implicit interpolation and space-line interpolation. Numerical simulations show that the improved method more accurately models flows in urban drainage networks.

Current state and future perspectives of sewer networks in urban China

Chinese authorities and the public have largely ignored sewer networks; however, various problems are emerging nationwide with the increase construction of new sewers. The current state of sewer network construction, administration, and maintenance in China is comprehensively reviewed in this study. Serving about 444 million people, 511,200 km of sewer lines are located in urban areas. In 2014,$7 billion was invested in sewer network construction. However, both the sewer pervasion rate and the per capita sewer length were significantly lower than those in developed countries. Sewer administrative agencies in local governments are uncoordinated. Laws, regulations, and standards are incomplete, and some practices are unscientific. The future situation of sewer maintenance is extremely grim because sewer corrosion control measures have not been launched. Moreover, inspection and rehabilitation chiefly rely on traditional approaches. In contrast, the overall market share of innovative technologies is very low owing to high cost, funds shortage, and technical limitations. Approaches such-as liner inversion cured-in-place pipe, pull-in ultraviolet light cured liners, and spiral wound lining are applied mostly in economically developed regions. According to status and problem analyses, China＇s top priority will be to conduct aggressive maintenance work in sewer networks in the future. New technical route, corrosion control - periodic visualized inspection - trenchless rehabilitation, could be the best option for future sewer maintenance in China. Instmctions and opportunities for applying this technical route are discussed in detail in this study. Finally.additional factors in the development of sewer networks in China are suggested.