Wastewater Treatment
Municipality Optimizes Wastewater Operations With Ultrasonic Flow Meters
Case Study / 10 min read
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Wastewater Treatment
Case Study / 10 min read
Needed Accurate Flow Measurements to Optimize Lift Station Operation
Lift stations are an integral part of each municipal water and wastewater treatment network. Flow measurement at such stations is a critical component for optimal performance. Operators need detailed information from flow meters for inflow and infiltration (I&I) studies, flow surveys and lift station performance analysis, and to determine the volume of wastewater conveyed to treatment plants from specific basins throughout town.
As sewage networks and wastewater treatment plants strive for greater efficiency and cost reduction, it is imperative that they monitor and control operations more precisely. When heavy rainfall or other abnormal events occur, wastewater levels in the collection system and wet wells can rapidly reach critical levels and accurate information from the flow metering equipment is needed to take appropriate actions.
Like other municipalities, the Village of Lombard, Illinois, relies on sanitary lift stations to pump wastewater from lower to higher elevations, particularly where the elevation of the source is not sufficient for gravity flow or when the use of gravity conveyance will result in costly excavation depths and high sewer construction costs.
Key elements of lift stations include a wastewater receiving wet well, sometimes equipped with a screen or grinding device to remove coarse materials; pumps and piping with associated valves; motors; a power supply system; an equipment control and alarm system; odor control and ventilation systems; and a backup generator for an emergency power supply.
Municipalities have a significant financial stake in the performance of lift stations. When groundwater and stormwater enter city collection systems, treatment processes become less efficient and sanitary sewer systems become strained. Lift station pumps run for a longer duration after a rain event and have a larger number of starts and stops—indicating stormwater has entered the sanitary sewer system and is on its way to be treated. This additional stormwater costs municipalities money by increasing pump operation and wastewater treatment.
Reliable, uninterrupted operation is an essential component for wastewater lift stations. Communities with large residential and commercial complexes discharging to a single station cannot afford extended downtime for maintenance, repairs or the installation of new equipment.
According to Luke Sharp, Water Treatment and Wastewater Pumping Supervisor for the Village of Lombard, the Village has 14 existing sanitary lift stations that require 24/7 monitoring. Moreover, the amount of wastewater entering and being treated by the local treatment plant is a key metric.
“We had no idea of the actual flow we were pumping from the different lift stations, whether it was dry weather or wet weather flow. We knew our sanitary stations ran a lot more due to I&I and sump pump connections and we needed to address this problem quickly so we could generate better flow data”, Sharp stated.
In recent years, the Village of Lombard has experienced several sanitary sewer overflows and basement backups as a result of heavy rains in the spring and fall, as well as when warm temperatures in the winter melt snow quickly. These events would overwhelm the sanitary sewer collection system.
Experience has shown that flow measurement is a valuable tool for optimizing lift station operation. Accurate flow data helps operators understand whether systems are running efficiently. Monitoring flow in lift stations provides important reference points for general billing processes, evaluating pump efficiency, analyzing the impact of I&I, and planning maintenance programs.
The Village of Lombard previously used ultrasonic doppler flow meters at its sanitary lift stations, but these low-cost devices did not provide sufficient measurement accuracy. Furthermore, the meters had experienced a number of failures and were in poor working order and had never been adequately repaired. The investment needed to repair the existing meters was cost-prohibitive.
Flow monitoring is the first step in identifying inflow and infiltration to determine where problems are occurring in order to isolate basins with the worst I&I characteristics. The Village of Lombard’s water and wastewater treatment division decided that an instrumentation upgrade was necessary to:
The Village evaluated several common flow metering technologies based on known constraints, such as the inability to shut down station operations due to high demand as well as the difficulty of installing in-line flow meters into existing piping.
Although traditional in-line devices, such as electromagnetic flow meters, provide high measurement accuracy, they also require electricity to operate, including submersible, watertight connections. This cost, along with the associated excavation work, would have driven up the project scope and installation price.
After careful consideration of different manufacturers’ flow measurement solutions, the Village of Lombard found that ultrasonic transit time flow meters were the best approach for its lift stations. Ultrasonic transit time meters enable improved diagnostics to accurately measure flow, help identify potential pump failures and initiate appropriate preventative maintenance programs on equipment at the stations, thus extending the life of assets.
Transit time ultrasonic flow meters measure flow rate by propagating ultrasound waves into liquid-filled pipes and measuring the time of flight. With clamp-on technology, the meter is non-intrusive—a design that provides advantages such as reduced installation costs, uninterrupted production, installation flexibility across a wide range of pipe sizes, no pressure head loss, no contact with internal liquid, and no moving parts to maintain. This approach allows for routine maintenance activities throughout the life of the meter without having to cut into piping.
The Village of Lombard had an existing relationship with Badger Meter, an innovator in flow measurement, control products, and communications solutions that serves water utilities, municipalities, and commercial and industrial customers worldwide, and chose to deploy the company’s Dynasonics® ultrasonic transit time flow meters.
“Based on our previous experience working with Badger Meter, we knew they had good products and customer support,” Sharp said. “Our goal was to install working, reliable flow meters at each of our lift stations in the most economical way and their team was great to work with.”
The Dynasonics TFX-5000 ultrasonic clamp-on flow meter is the latest solution for measuring volumetric flow rates containing clean liquids as well as liquids with small amounts of suspended solids such as surface water or raw sewage. The meter is available in a variety of configurations in order to meet particular application requirements. It is easy to use and has helpful diagnostics to take the guesswork out of programming. Depending on programming and integration into the programmable logic controller (PLC), users can be alerted to out-of-specification flow conditions and access a history with the most recent alarms, error and event codes. In addition, the flow meter supports an encoder output for use with cellular endpoints for connecting to the AquaCUE® or BEACON® Advanced Metering Analytics (AMA) cloud-based software suite. This software collects measurements at 15-minute intervals that are uploaded to the cloud on a regular schedule (up to twice per day) to help with tracking and analyzing water and wastewater information.
The TFX-5000 flow meter features a large, easy-to-read graphical display and provides Modbus RTU, Modbus TCP/IP, BACnet MS/TP, and BACnet/IP connectivity options. Configuration and troubleshooting are done through an optional keypad or via a Universal Serial Bus (USB) cable using the SoloCUE® Flow Device Manager software. The meter uses a four-level passcode security system for applications requiring unit lockdown.
For outdoor installations below the water line such as in meter pits or manholes, Badger Meter recommends utilizing the Dynasonics DTTN Series submersible, IP68-rated transducers with silicon-based room temperature vulcanizing (RTV) characteristics, which greatly reduces the need for future maintenance.
Within the Village of Lombard’s wastewater treatment system, monitoring of lift stations is through a supervisory control and data acquisition (SCADA) system. All information is sent back to a centralized location where operators monitor and maintain each station. The SCADA system data is continuously monitored to ensure the highest possible level of efficiency.
Dynasonics ultrasonic transit time flow meters provide a 4-20 mA analog output, which gets terminated to a PLC input. The flow rate information and all lift station metrics are transmitted back to the SCADA machine using a communication SCADA network. All data is then trended on the main SCADA server and made available at the central monitoring site where operators keep a close eye on flow rates, pump run times and other operating parameters for the lift stations. Daily flow rates, pump run times and cycles are added to an XLR reporter program in the SCADA machine so monthly reports can be generated.
Sharp’s team of four operators installed the ultrasonic clamp-on meters using existing conduits in the lift station flow meter manholes. A confined space entry was needed for each site in order to perform the work. The operators then pulled the transducer cables, mounted the transducers to the discharge piping, installed the head unit in the SCADA cabinet, and wired the units to the PLC. Badger Meter representatives assisted with startup by visiting each site with a portable ultrasonic device to verify actual flow readings and calibrate the installed flow meters. The Village’s integrator was also involved in the process and the entire project took just two days to complete.
“The Dynasonics ultrasonic flow meters give us dry and wet weather flow readings right from the station so that we can extrapolate pertinent information and analyze I&I conditions related to sump pumps, leaky laterals or sewer mains. This allows us to focus future repair work in basins using the data we’re seeing from the meters,” Sharp said. “At the same time, access to detailed flow data enables our department to calculate the existing capacity of lift stations to support any new commercial or residential developments in the area.”
In the Village of Lombard, routine maintenance programs based on continuous monitoring activities have proven effective in increasing efficiencies at the lift stations. With accurate flow data, operators are able to quickly respond to pumps showing a decline in performance. Operators inspect and remedy issues before they become critical problems, which could lead to basement backs ups or SSOs.
As demonstrated by the Village of Lombard, non-invasive flow measurement instruments like the Dynasonics TFX-5000 ultrasonic clamp-on flow meter are an ideal solution when users cannot shut down their wastewater operations to install a traditional in-line meter. As the ultrasonic meter measures from the pipe wall outside, there is no wear on the device—making it virtually maintenance free. The entire flow meter system, consisting of ultrasonic transducers and a measuring transmitter, can easily be taken to the site and installed by a small crew. There is no need to work on the discharge piping, cut in new valves, perform excavations, or run electric to the manholes.
Thanks to the use of clamp-on technology, the TFX-5000 flow meter enables a very simple and cost-effective deployment of flow measurement points within an existing lift station, even though conditions are often not easy due to lack of straight pipe lengths and proximity to pumps.
According to Sharp, the use of ultrasonic transit time flow metering has provided a significant return on investment (ROI) for his department’s wastewater pumping operations.
“The ultrasonic clamp-on meters were easy to install, which reduced our overall project costs,” Sharp said. “We can use the accurate flow data to better plan for capital improvement projects related to I&I and verify the costs from the wastewater treatment plant in order to prioritize our budget allocations.”
He added, “Badger Meter is known for its quality products, and this is one of the primary reasons we felt comfortable choosing their flow meter.”
Demanding lift station applications in the water and wastewater industry call for a reliable, accurate and non-invasive flow measurement solution. Crucially, the flow metering equipment has to be easy to set up at a lift station without the need to shut down normal operations.
The Village of Lombard’s Water Treatment and Wastewater Pumping Division evaluated various flow meter manufacturers, obtained proposals and viewed product demos, but ultimately decided the Badger Meter Dynasonics ultrasonic transit time flow meter was the answer to optimizing the performance, reliability and total cost of ownership of its sanitary lift stations.
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Customer Care representatives are available by phone Monday–Friday, from 9am–5pm CST.
Badger Meter is an industry-leading innovator in flow measurement, water quality and control products, serving water utilities, municipalities and commercial and industrial customers worldwide.