Sierra's Thermal Meters Give Municipalities Precise Air Measurements to Aeration Basins
For municipalities around the country, running an efficient, safe, cost-effective waste water treatment plant is paramount.  In the critical secondary stage of waste water treatment, blowers aerate the basins, removing about 85% of the organic matter by making use of the bacteria living within it.  And municipalities need mass flow measurement instrumentation to bubble the precise amount of air into these aeration basins.

In the 1980s, many municipalities used differential pressure devices to measure the mass flow rate of air delivered to these aeration basins. These devices, however, proved to be expensive to maintain, clogged easily, measured only volumetric flow, and required a separate pressure and temperature transducer, and flow computer in order to deliver true mass flow.  Because of these pitfalls, in the 1990's, municipalities began searching for an alternative to these costly and inefficient DP devices.  Moving to thermal technology was their answer.  With thermal technology, cities around the country measure true mass flow directly with one thermal instrument, have great turn down, improved accuracy, and a lower-cost of ownership.                         

In 1999 Glen Coblentz, Sierra's Regional Sales Manager, began educating a large western city on the benefits of Sierra’s thermal meters.  And in 2003, Glen secured an account to retrofit their aeration basins with Sierra's 640S thermal insertion mass flow meters.

640S Steel-Mass Measures Exact Dissolved Oxygen Content
Since 2003, this city has installed Sierra’s 640S rugged Steel-Mass on their headers and airlines to accurately monitor and adjust the mass flow rate of air, hence oxygen, bubbling into their aeration tanks to control the critical dissolved oxygen levels.  According to Scott Rouse, Sierra's Industrial Product Manager, "the micro-organisms that 'eat' the waste need an exact amount of oxygen to survive." If the mass flow controller is not accurate, the culture will be destroyed, inadequately treating effluent discharge, leading to potential fines, environmental damage, and even human illness due to untreated sewage."

Glen Coblentz reports that they have been very pleased with Sierra’s performance, especially the accuracy.

Unique to the Industry:  Dry-Sensor Technology and In-House Closed Loop Calibration 
Sierra differentiates itself in the industry with its patented Dry-Sensor Technology.  Unlike other thermal companies, Sierra's FR sensor uses no organic fillers or cements, which can crack over time, changing the "skin resistance" of the thermal sensor, causing drift or outright failure.  So by design, Sierra's sensors are extremely accurate, stable over time, and hold their calibration much longer. 

Sierra also calibrates each meter in a closed loop calibration system, located at the factory, exactly matching the customer's temperature, pressure, and flow rates.  This virtually customizes every meter, ensures better calibration and that the meter will read correctly from its initial installation. 

Municipalities Can Save Up to 50,000 a Year with Steel-Mass
Controlling the precise dissolved oxygen content in the secondary stage of waste water treatment saves cities money.  Typically, the electricity required to run the blowers for their aeration systems make up 45-50% of the typical operating cost of a waste water treatment plant. Carefully monitoring the mass flow rate of air to these basins with only the required airflow can substantially reduce electricity costs—thus saving cities money.

Scott Rouse reports in one case study that his customer automated their aeration dissolved oxygen system with the 640S as a key input into the control loop in a 7.8-mgd plant that treats both industrial and domestic wastewater.  In doing so, the company saved approximately $50,000 a year in aeration costs and reduced chlorination and pH adjustment costs as an added benefit. Nearly total nitrogen removal was accomplished and resulted in improved effluent suspended solids as well.  By choosing Sierra's thermal meters, cities get incredible sensor stability, true mass flow with one device and a single pipe penetration, dramatically reducing installation costs and cost-of-ownership. 

Other cities around the country have also decided to use Sierra's 640S™ Steel-Mass over other thermal products.

When Efficiency Matters. Gas Metering by Steel-Mass.