What new technologies have you been evaluating or implementing?
Like many wastewater utilities across the nation, the Metropolitan Sewer District of Greater Cincinnati (MSD) is challenged to find a solution to a knotty issue: how to make a multi-billion-dollar Consent Decree to reduce combined sewer overflows (CSOs) more affordable to our customers while confronted with shrinking usage, high rates of poverty, and increasing rain intensity. To protect the health of our rate payers (both environmentally and economically) we decided to invest in a monitor and control array to maximize use of our existing collection and treatment system to reduce CSOs instead of solely relying on building new infrastructure.
Dubbed “Smart Sewers,” this system allows MSD to take the helm and steer rather than merely riding out storms. Since 2015, MSD has been deploying a Wet Weather SCADA system to transform our operational relationship with our collection and treatment system. Using advanced sensors and intelligent global algorithms we are transitioning to active management to optimize performance of the entire system during wet weather. By recognizing, in real-time, system response to temporal and spatial differences in precipitation, we can identify available opportunities such as storage capacity in pipes and tanks, as well as un-utilized treatment capacity. Utilization of these options can limit the need for costly additional construction.
New low-cost sensor units with extremely low power requirements and robust communications options were installed in 2015 at every CSO location and at other operable stations in the system. In addition, an array of precipitation gauges have been positioned throughout the service area. The units are widely deployed to provide input to this SCADA system in real-time which then graphically displays the data including maximum dry weather flow levels, high warning and overflow levels along with the precipitation depths, intensity, and coverage. Two types of level sensors are used, depending on the site conditions, to detect the depth of the flow in the sewer. An ultrasonic level sensor is mounted above the flow and it sends out an ultrasonic signal that is reflected by the top of the water surface and then is converted into a depth of flow. Pressure transducers are also used, but they are mounted in the flow at the bottom of the pipe to detect the amount of water pressure above it, which is translated to a depth of flow. Both types of sensors are configured to collect level data frequently, typically once every minute. Each sensor is coupled with a recording telemetry unit which records, analyzes, and transmits the collected data.
With real-time data from the Wet Weather SCADA and the aid of automatic control logic, system managers can then take active measures before, during, and after storm events to maximize conveyance and treatment of wastewater. Using in-system gates, flows can be diverted to high-rate treatment facilities when downstream bottlenecks arise or stored in-pipe using inflatable dams or control gates for later release when transmission capacity returns. Treatment systems needing advanced warning prior to operation are provided flow rate predictions based on remote precipitation and level sensors in conjunction with our collection System Wide Model.
In addition to our Smart Sewers, MSD is also actively evaluating peracetic acid as a potential alternative disinfectant to liquid sodium hypochlorite or as an adjunct system to our existing ultraviolet light disinfection systems for higher level of service with reduced energy use.
What new technologies are you interested in investigating?
Consistent with our mission to protect public health and the environment, MSD is interested in real-time monitoring of water quality parameters. We believe data driven decision making will improve our level of service while also controlling costs.
In remote settings we are interested in determining adequate surrogate parameters to inform real-time management decisions regarding which flows should be prioritized for early capture to minimize pollutant discharges system wide. Conventional field parameters such as dissolved oxygen and pH are being considered alongside known pollutants such as Suspended Solids, E. coli, phosphorus, and ammonia. Alternative surrogates such as turbidity are also being investigated. Remote sensing must consider a myriad of issues such as the often harsh environment, lack of power, signal and measurement stability, ongoing maintenance as well as initial and ongoing cost of ownership.
We are also interested in real-time facility monitoring in an effort to improve energy efficiency and optimize consumable chemical use. This includes a search for effective and reliable microorganism measurements for disinfection control.
However, not all of our research is centered on instrumentation. As we navigate our costly wet weather consent decree, we continue to evaluate CSO technologies in the following technology focus areas: alternative disinfection; advanced filtration; first flush control; modular and scalable systems; and hydraulic control devices. We have conducted side by side filtration and disinfection testing, including up-flow compressible media as well as conventional cloth filtration in a high-rate application. High-rate disinfection testing continues.
What are your facility drivers/needs?
Cost containment remains a dominant factor in decision making. At the same time our level of service requirements, from collection to effluent quality, continue to be more demanding. Most significant is a court mandate to capture and control more combined flows. Some other near-term examples, where our control of circumstances is constrained, are sewer backups and facility odors.
Due in part to shifts in the climate, recent storms of high intensity have caused dramatic increases in sewer backups into dwellings. At the core of our existence as a utility is protecting the public by safely transporting and treating wastewater. However, we face the challenge of fulfilling this purpose without direct control of the weather and given existing piping networks in heavily developed settings.
As the built environment comes closer to some of our facilities, tolerance of off-site odors has decreased. A district wide zero off-site odor goal has been established. Here again weather and perception, neither in our control, play a direct role in providing this level of service.
The principle of gaining additional control through sensing and operable dynamic control systems to cost effectively meet the increasing level of service requirements requires robust, low cost, low power, and flexible monitoring devices.
How has LIFT helped, or how would you like LIFT to help your facility?
One of our research chemists received a LIFT Scholarship Exchange Experience for Innovation & Technology (SEE IT) award in 2017 to visit the Resource Recovery facility in Grand Rapids, MI, to evaluate the Zero Angel Phot Spectrometry (ZAPS) instrument. This instrument can monitor and measure up to 30 water quality parameters, including E. coli, in real-time providing data to optimize treatment processes.
In addition, MSD has submitted as part of 3 different teams for LIFT’s Intelligent Water Systems Challenge. The “challenges” we submitted are: exploring low-power/low-cost telemetry for infrequently operated remote gates, identification of dynamic underflow control opportunities using “big data”, and transitioning to water quality-based operations.
MSD and USEPA have teamed to designate Cincinnati as a member of the LIFT National Test Bed Network.
MSD believes LIFT could play a valuable role in advancing sensor technology deployment by expanding this as a technology focus area.
If there were one technology you would pilot or collaborate on tomorrow, what would it be?
The focus of our Wet weather Improvement Program under the Consent Decree has been controlling CSO volume, but our Smart Sewers provide an exciting opportunity to reduce our impact on water quality through pollutant capture. If sensors detecting water quality parameters were tied into the same monitoring and control infrastructure as is used now to collect volumetric data, they could inform operational decisions in real time to reduce impacts to our waterways. MSD is interested in components of, or a complete end-to-end solution for, collecting water quality data at CSOs and generating operational action recommendations to our industrial control system/SCADA (GE Proficy Suite). Demonstrating proof of concept using a simple parameter to measure cheaply, like nitrates, ahead of advancements in real-time sensing technology for E. coli for example, would be of great interest.