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The Project was submitted to Parallax by Ernie Adsett, P. Eng.
Wastewater Management Control systems must consider the two prominent “E"s, (Environment and Energy). Saint John’s new control system for the Lancaster aerated lagoon does just that. By controlling accurately the wastewater oxygen content and at the same time reducing the number and loading of the blowers, both conditions are being met. Over $46,000 in energy costs were saved in the first year of operation.
The system was designed by Advanced Monitoring Technologies (AMT) of Fredericton, New Brunswick, Canada. Extensive use was made of AMT’s monitoring and control EnT board along with their own integrated computer graphics software (REM). Each EnT board housed at least one Parallax BASIC Stamp® module or SX chip. The chips contained the intelligence to operate all equipment.
 The Lancaster Lagoon can require an electric load as high as 1 MW (1,000 horsepower) and is therefore a prime candidate for energy savings. Each of the five blowers is rated at 200 H.P. Energy costs can be reduced by minimizing the number of blowers operating as well as by controlling the air flow through the blowers. Fewer active blowers means less consumption (kWh) as well as a lower demand charge (kW). As an example, unnecessarily operating an extra blower for only 15 minutes in a month can cause a new peak electrical demand and add $1,000 or more to the energy bill.
REM's Energy Screen
The control system maintains a more accurate level of dissolved oxygen (DO) by utilizing a modified proportional/ integral (PI) algorithm. DO and temperature readings are taken by means of an analyzer located on the lagoon. These signals are sent via wireless to the central controller. Air flow is modulated and the blowers activated based upon the difference between the DO set point and its actual value.
AMT’s PC-based monitoring and control program REM (Remote Equipment Monitoring) receives data from the controllers and determines the operation of each component. This allows the city operators to review trends, respond to alarming, change set points, and thus fine tune the system for optimum operation and savings. All parameters are logged and stored in a Microsoft compatible database for later review and analysis. Blower priorities can be changed and runtime values are determined in order to schedule maintenance and equalize the operation times of all units. Distributed control by means of the Parallax operated boards means the remainder of the system will continue to function as designed if a controller or the central computer is out of service for a time. As well, all BASIC Stamp source code applicable to this control system is available to the City and can be changed by the City’s personnel if so desired.
REM's Operator Screen
 AMT distributes the EnT controller board at a reasonable price. It is an attractive alternative to conventional PLCs costing much more. It can accommodate up to two Parallax BASIC Stamp modules or SX chips and has eight onboard relays as well as provision for digital and analog I/O.
The flexibility and cost of the Parallax chip made this system cost effective, efficient and reliable.
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