Hydraulic modeling using InfoWorks CS has played a significant role in delivering optimized options for the Shanghai World Bank Loan project - the West Trunk Line renovation project Phase 2, which is part of the World Bank-funded Shanghai Urban Environment project (with a value of $512 million).
Built in 1970s with a design capacity of 154,000MGD (700,000 m 3 /d), the West Trunk line is one of the main wastewater systems in Shanghai. Due to the city's rapid urban development, this capacity is already below the current wastewater load received from its designated drainage area, which is causing significant environmental problems for the Shu Zhou Creek, the important river that flows through the city center.
The key aim of the West Trunk line renovation project is to look at short and long-term engineering solutions for improving collection, trunk sewers, pumping stations and wastewater treatment plants, as well as restructuring the drainage areas to connect with the neighboring Combined Phase 1 System.
SOGREAH Consultants on behalf of Shanghai Municipal Government and their wastewater utility Shanghai Municipal Sewerage Company worked together with Shanghai Water Planning and Design Research Institute to establish hydraulic models to simulate the complicated West Trunk Line system under different projected time and design flow conditions using Wallingford Software's InfoWorks CS software solution.
By analyzing the simulation results, the Institute has already been able to check and validate the design results and put forward an optimal scheme to improve the system to meet future demand and alleviate the sewer system's deficiencies.
The modeling project has simulated the typical performance of both the existing and new design elements of the West Trunk Line in dry and wet seasons and over both the short and long terms. It also examined the behavior of the Combined Phase 1 Sewer System under its design flow. An interlinked model looked at the effect of receiving extra flows from the Shi Dongkou sub-catchment in wet weather conditions, when it was proposed that the West Trunk system would transfer part of its flows to the Combined Phase 1 System.
The results from the model have been used to examine the feasibility of the renovation scheme and refine the improvements to the West Trunk System.
By using the established InfoWorks CS models under various scenarios, several critical findings were made that assisted in identifying sound engineering decisions. An important element of the project involved reviewing the year 2020 wastewater flows in the West Trunk Line service area. The model predicted an inflow some 150,000 m 3 /d (same comment on units) higher for the year 2020 than the previous estimate.
There were two main proposed options within the project: one was to construct a treatment works north of Wen Zhaobang, and the other was to build a regulating tank in the same place. The modeling results demonstrated the major differences between these two options and showed that the regulating tank scheme would suffer poor hydraulic conditions, be complicated to operate and create a high risk of environmental pollution.
However, building a treatment works was found to have many advantages – it would provide better hydraulic conditions, simpler operation, and would enable excellent utilization of the west trunk line and Combined Phase 1 Sewer System trunk line, as well as being an extremely adaptable and flexible solution.
Vice director of the Institute JianPing Zhang said: ‘Through the research undertaken using InfoWorks CS, we find it much easier to examine the performance of various elements of the system and make financially and environmentally sound engineering decisions.'