Wireless Control of PH Level

The Problem:

Wastewater from a Textile Mill is dumped into a municipality’s sewer system.  The municipality requires that the Mill controls the PH level of the wastewater.  Three PH sensors are installed just down stream from each of the main mill discharge points.  These sensors are spread out along a single 4000 ft long wastewater line.  The sensors output a 4/20 mADC signal proportional to the PH level of the wastewater.   A control valve is used to inject lime and fresh water into the wastewater just before the water enters the municipality's sewer system.    Without a wireless solution six signal wire runs of 200 ft to 4000 ft would be required at a cost of $40 to $50 per ft.

The Solution:

Three DR9051 Wireless Transmitters were installed at the PH sensor locations.  The wireless transmitters required 24 VDC power, that was also available for the sensor.  Using a 7 inch omni-directional antenna the outputs of the PH sensors are transmitted to a single DR9050 installed along with a PLC at the Lime/Fresh Water Injection point.  The DR9050 is controlled via a small PLC that uses Modbus® commands to query data from each of the measurement points.  The data is then used to determine the amount of lime and fresh water to inject into the wastewater line.  An alarm is used to notify operations when the PH level reaches a set point.

Total Cost of Wireless Installation

$2,600.00 (List Including Wireless Transmitters/Receivers and Antennas)

Estimated Cost of Wire Runs (Without Wireless)

$45.00/ft x 4000 ft = $18,000.00