Wet weather flow management
For years, population explosion, demographic shifts, urbanization, aging infrastructure, limited water resources, and economic development have driven our water market, and with that our world’s need for total water solutions.
By Raja Kadiyala, Ph.D., Director, Intelligent Water Solutions, CH2M; and Kenneth Thompson, Deputy Director, Intelligent Water Solutions, CH2M
For years, population explosion, demographic shifts, urbanization, aging infrastructure, limited water resources and economic development have driven our water market, and with that our world’s need for total water solutions. However, in the past decade, we’ve seen these traditional drivers become amplified by climate change and severe weather events around the world—like Superstorm Sandy; floods in the United Kingdom; and severe drought in California, Australia, and Brazil. In many parts of the world, and right here in the United States, there is either too much or too little water.
Climate change is making it difficult to accurately predict how sea-level rise and the variability and intensity of future storms will impact certain regions, which is why we have seen a trend in clients looking for holistic solutions to address their water system challenges and build resiliency into them for future severe events.
Management of raw sewage overflow during wet weather events is a challenge that has plagued utilities since wastewater collection and treatment began. There are two types of systems in the United States. The first type is combined sewer systems, where the wastewater and stormwater are combined into the same collection system and treated at a downstream treatment plant. The combined flow is treated like a wastewater flow, with strict compliance requirements. The second type is separate systems, where the city or utility operates separate systems for wastewater and stormwater. In these systems, the wastewater is treated at a downstream treatment plant. The stormwater is handled in different ways based on the downstream receiving waters, and typically has a much reduced set of treatment processes due to lower compliance requirements.
In both cases, extreme wet weather events create problems with pipelines surging because of flow that exceeds capacities and causes untreated sewage to be released. The high flow for combined systems is apparent because the added component of stormwater flows directly into the collection system.
Separate systems suffer, in varying degree, from infiltration of stormwater through faulty or poorly placed manholes, illicit connections, or damaged sewer pipelines, which can result in overflow of sewage.
The Internet of Things is creating new sensing and monitoring opportunities for utilities to use to manage the far reaches of their collection systems. The IoT explosion will have 50 billion connected devices by 2020 and 100 billion connected devices by 2025. To take advantage of the IoT, CH2M’s Intelligent Water Solutions Team has started to deploy smart technology and advanced data analytics to produce near-real-time information and control for utilities to be able to improve their response and minimize overflows into the environment, without having to invest in large and costly storage or capacity expansion. The systems include using cellular sensors for weather conditions (like rainfall), pipeline flows, manhole levels, and water quality sensors. The data from the sensors are merged with weather radar data and processed through advanced analytics and real-time models to adjust operations preemptively. The existing system capacity is optimized by drawing down storage tanks in advance of wet weather, moving wastewater to areas that have capacity based on weather models and hydraulic models, and performing analytics on the wastewater’s water quality to drive treatment decisions. Two examples of different visualizations are illustrated below.
The first example illustrates the impact of an initial rain event at a lift station that has wet weather overflows. The graph shows two large peaks associated with infiltration. The continued infiltration that occurs after the event is a strong indicator of groundwater infiltration into the upstream collection system. The IoT-enabled data from multiple locations were used by the utility to determine where their greatest infiltration problems were and where future capital expenditures should be focused.
The second example is for an agency that is working under an Environmental Protection Agency consent decree for excessive combined sewer overflows. A system was developed to integrate data from multiple sensors for rain, flow, and level in the collection system, and water quality to provide realtime collection system management and minimize overflow. The figure above is a graphical illustration of the asset readiness (on the left) and also the reduction in combined sewer overflows that were avoided through real-time control.
Utilities are faced with many challenges today, and new capabilities can become available by leveraging the IoT explosion, which will require three steps. First, integrating the new technologies, data processing applications, and response protocols will require upfront vision by utilities, ideally preventing a hodgepodge of implemented solutions that cannot be effectively managed or do not provide full benefit for the utility. Second, cultural acceptance will need to be part of the program, as these systems require that processes that have been in place for years be modified or changed. Last, utilities will need to define roles that are dedicated to the program. The end goal is to take advantage of this new wealth of data and maximize the return on investment for the rate payers.
This is a copy of case study that originally appeared in the U.S. Chamber of Commerce Foundation Corporate Citizenship Center released “From Scarcity to Abundance: Business Solutions for a Water Constrained World”. Get access to the full edition by visiting CCC's website.