Real-time Assessment of the GLWA's Regional Operating Plan Using Digital Twin Technology

INTRODUCTION AND PURPOSE The Great Lakes Water Authority (GLWA) is Michigan's largest regional wastewater collection and treatment system encompassing eighty-six wholesale customer collection systems across three counties and 944 square miles in southeast Michigan. The regional collection system serves approximately three million people, representing one third of the state's population. GLWA operates the regional collection system and Water Resource Recovery Facility (WRRF) through a lease from the City of Detroit. The leased facilities include 183 miles of trunk sewer, interceptors, and outfalls; 6 pumping stations, 16 in-system storage devices, 8 retention treatment basins and screening and disinfection facilities, the WRRF and associated metering and control facilities. The City of Detroit Water and Sewerage Department (DWSD) owns and maintains the wastewater collection system and water distribution system within the City of Detroit. GLWA Member collection systems include 77 untreated CSOs, several points of SSO during large weather events, 12 CSO retention and treatment facilities, and 14 sanitary retention basins, and an estimated 3,000 MS4 separate stormwater outfalls. A high degree of structural optimization has already been achieved through local water quality improvement initiatives, NPDES permit compliance, and operating protocols developed over more than 30 years of combined sewer overflow (CSO) control. The Regional Operating Plan (ROP) is intended to further optimize operations by analyzing the detailed system response to storm events, including expanded sharing of real time SCADA data. This presentation describes the development and integration of GLWA's regional collection system model with a GIS-based digital twin platform that integrates near real time data from SCADA, radar rainfall, and overflow reports with the collection system model. The digital twin is a key element of GLWA's ROP, which was developed to optimize wet weather operational performance across six major wastewater utilities that are wholesale customers to GLWA's regional collection system. This close integration of model and data in the digital twin allows for rapid post-event monitoring and near-real-time analysis of collection system performance during wet weather, facilitating continuous optimization of wet weather operations by GLWA and its Members. BUILDING THE REGIONAL WASTEWATER COLLECTION SYSTEM MODEL AND THE DIGITAL TWIN GLWA developed a new Regional Wastewater Collection System model using EPA's Stormwater Management Model (SWMM) as part of its Wastewater Master Plan project from 2017 to 2020. The collection system model consists of over 4,400 individual model subcatchments and 16,000 pipes covering the entire GLWA service area, including detailed operating rules to represent dry and wet weather operations at key facilities. The model was calibrated to metering data to meet the calibration metrics issued by the Chartered Institution of Water and Environmental Management (CIWEM) Code of Practice for the Hydraulic Modelling of Urban Drainage Systems. The digital twin builds upon the collection system model, and integrates the following elements (Figure 1): - The calibrated and validated collection system model - Gage-adjusted radar rainfall data from Vieux and Associates at a 1-kilometer grid cell resolution adjusted to 36 regional rain gages. The radar rainfall data are sent daily at 5-minute increments and applied to all 4,400 model subcatchments - 540 individual measurement points at 5-minute intervals sent daily from GLWA's Ovation SCADA system. These points represent river stage, pump and gate operating records, and flow metering. - Post Event Reports generated after significant storms to document combined sewer overflow events. The digital twin was built in PipeCAST, a web-based GIS platform that integrates monitoring data and modeling results to facilitate decision-making and post-event analysis in near real time. Its foundation is built upon the concept of the digital twin, which is a virtual copy of the collection system that is used to generate real-time simulations from current weather and precipitation conditions (Figure 2). The PipeCAST system automatically receives data from the radar rainfall grid, climate data from NOAA, and SCADA data through a secure application programming interface (API) connection and runs the collection system model for the previous day. The direct connection to SCADA allows the model to simulate dynamic backwater conditions at each CSO outfall and actual pump station operations. The PipeCAST interface provides a GIS-based visualization of metered and modeled flow, depth, and velocity in the collection system, rainfall statistics, and a dashboard that shows key statistics related to overflow frequency and duration. The GIS-based interface can also provide high-level statistics on system performance, such as pipe capacity during wet weather (Figure 3), which can be used to identify potential locations for additional in-system storage. Since the digital twin integrates data and runs the collection system model daily, GLWA can quickly review system performance after storm events and compare model simulations to observed measurements to use as the basis for ongoing model and measurement improvements. APPLYING THE DIGITAL TWIN GLWA is using the PipeCAST digital twin for post-event analyses, where users review wet weather performance relative to the ROP goals. As an example, GLWA used PipeCAST to evaluate system performance for a recent wet weather event in July 2020. This event was 2.05 inches in 10 hours at the Wayne County Metropolitan Airport, and was approximately a 2-year, 1-hour event. The rainfall was most intense north of Detroit, as seen in the color-coded radar rainfall map in Figure 4. GLWA used the digital twin to evaluate how in-system storage and CSO control facilities conveyed flows from the Conant-Mt. Elliott Sewer that serves Oakland County and central Detroit (Figure 5). Flow and system performance were monitored during this event using the digital twin by reviewing incoming flow from Oakland County, in system storage, and performance at the Leib Screening and Disinfection Facility (SDF) (Figure 6). During this event, the incoming flow from meter SE-S-1, (blue line) peaked at approximately 245 cfs, followed by a short-duration peak from the local combined sewer drainage system in the DWSD collection system (meter DT-S-11, orange line). The in-system storage device, controlled by an inflatable dam, was activated, and no discharge occurred from the Leib SDF facility. Based on the review of data using the PipeCAST digital twin, GLWA was able to conclude that the system performed well during this large event, maximizing in-system storage, and minimizing discharges to the Detroit River. CONCLUSIONS GLWA developed a digital twin of its regional collection system to enable post-event analysis to support the ROP. The digital twin was developed using PipeCAST, a GIS-based tool that integrates metering data and modeling data into a platform that allows for rapid review and assessment of system performance during wet weather. The digital twin is being used to complete post-event analyses following significant precipitation events to further optimize wet weather operations, reducing CSO to receiving waters and maximizing secondary treatment at the WRRF.