Fairfield, Ohio Chooses Flo-Dar for Demanding Flow Applications

Expansion and improvement of the City of Fairfield, Ohioâs original wastewater system constructed in 1964 has allowed the city to keep pace with increased population in the region. In particular, a long-term project undertaken in the mid-90âs, the first of many, was to expand the collection and treatment of wastewater from its current 6 million gallons per day (mgd) rating to 10 mgd in the year 2000. Fairfield, with a population of 45,000 has 175 miles of publicly owned sewers. Within this 29 square mile service area there are approximately 12,000 connections. The Cityâs system is classified as a separate system since it does not combine with their storm water system. The accurate monitoring of wastewater flows is integral to the Cityâs future master plan for infrastructure upgrades and improvements. The Cityâs Public Utilities Wastewater Division is responsible for all flowmeter installations and data collection.

According to Drew Young, Public Utilities Supervisor for the Wastewater Division, 'Flowmeters are used at specific sites to monitor the overall sewer system to collect data for trend analysis and to also assist in the calibration of their newest flow model.ä While attending the WEFTEC conference in New Orleans in the late 90âs, Young was intrigued with the new flowmeter available from Marsh-McBirney that monitored flow utilizing an Îabove-the flowâ radar velocity/area sensing technology. Young adds, 'We had a need for a meter at that time to do micro-studies of our sewer system. We have 30 delineated basins and one of the basins really didnât have good data capture exit point due to high velocities in the line. That initiated us to see what new technologies were available.ä Flowmeters with submerged style sensors are also utilized by the department, however they were not suitable for this particular application due to sensor fouling and the hydrodynamic effects the submerged sensor itself can cause as the flow medium passes over the sensor. A flowmeter with a non-contact sensor such as Flo-Dar would allow the city to accurately monitor flow under the high velocity conditions they were experiencing.

Thousands of dollars in maintenance and repeated confined space entry costs can easily be saved at each flow monitoring site with the use of Flo-Dar. The sensor can safely and easily be removed or re-installed from street level without the need for confined space entry after the initial install. Additional benefits include field replaceable/interchangeable sensors and monitors ensuring no lost data in the field, especially during critical monitoring periods. Sensors can be installed with either a permanent mount (affixed to wall) or a portable mount (jack-bar tension rod) dependent upon the specific application. As seen in the photograph below, the City of Fairfieldâs Wastewater Division personnel customized a mount for their application.

Flo-Dar applications that challenge traditional flowmeters include:

• shallow flows
• high velocities
• surcharge flows
• caustic flows
• high temperature flows
• flows with high solids content

Additionally, Young notes that the non-contact nature of the Flo-Dar sensor not only eliminates fouling because the sensor is mounted above the flow stream but also eliminates the sensor drift often seen with submerged sensors. He adds, 'The Flo-Dar meters have good repeatability and are accurate in the pipe sizes weâre working with.ä

'We just finished a flow monitoring capacity analysis study where there were 38 flowmeters installed throughout the system. We are using seven of the Flo-Darâs as more of a control to see if we have problem areas as well as using the data to calibrate our newest flow model to larger rain events that may not have been captured during the study period. Even though we had 38 more points out there weâve had much higher rain events captured by these seven Îquasi-permanent' installations. The Flo-Dar sensor/Flo-Station is used to measure flow coming from a 10 mgd equalization basin." Young continues, 'Weâve had several units installed at the monitoring site and the Flo-Dar is the only one that would work in this difficult application.ä Considered a Îdemandingâ site, Young states, 'The success of this Flo-Dar application was critical to our program. We needed good flow data to be able to maximize the capacity that could be seen during large storm events.ä

Currently, the Cityâs Wastewater Division is preparing for a flow basin study this coming fall. At this time the group will address basin specific needs. He adds, 'We are going to go to these delineated basins which have been prioritized based upon inflow and infiltration rates. Weâll be breaking the basin down into 50-75 homes per sub-basin metering site. Because there will be lower flows, the Flo-Darâs will be used because itâs a better application for them versus our meters with submerged sensors. The decision to use the Flo-Dar meters would eliminate the possibility of data errors due to sensor fouling as well as the effects of the wave in front of the submerged sensors that causes data errors.ä

In addition to utilizing the Flo-Dar meters for their studies, the city also purchased a Marsh-McBirney Flo-Mate Portable Flowmeter in 2005 to use in their flow monitoring tasks. The Flo-Mate was used for velocity spot-check measurements and to assist in flow monitoring site pre-qualification. Additionally, the meter is used as Îdouble-checkâ of other instrument readings as part of their quality check program. 'We had some earlier flow monitoring done in the late 80âs, early 90âs and we wanted to utilize the same monitoring points so we used the Flo-Mate instrument to pre-qualify the sites.ä

Despite an increase in wastewater demands in the region, wastewater flows have actually decreased at the City of Fairfield largely due to the efforts of the personnel of the Cityâs Wastewater Division. Real progress is seen in the fact that the Cityâs flow rates are down to 5.3 mgd for average dry weather flow which is what is was back in 1991 despite a population increase of 15,000. Proficiency in their flow monitoring tasks including the use of innovative and accurate flow monitoring devices such as the Flo-Dar meters have really paid off. By utilizing their collected flow data, personnel have been able to locate, correct and prevent stormwater infiltration into their wastewater system and in turn reduce their operating costs for wastewater treatment.