One of Loy Instrument customers had been struggling for a while trying to control their plant effluent pH in their waste water which flows back to the city water department. The city required this food processing customer to keep the pH control between 6 and 10 pH. This was especially tough when the flow would rapidly change from the plant or if a large rain storm entered the area. When the customer went outside of this pH they would be charged by the city for every half hour they were outside these limits.
The old system had a paper circular chart recorder for pH in the plant and city drain. It also had a paper chart recorder for the plant water flow. The system was controlled by a single loop pH controller which was independent of the flow control.
In this situation the pH controller would never see the flow changing and would be too late to react with chemical injection to bring the pH under control. This also resulted in an increase cost on chemicals purchased to control the pH.
We updated the customer’s controls and recording feature to include paperless data retrieval which cut down cost on consumable of paper and pens while also reducing the time involved in putting together monthly report for the city on total flow and pH recording. We tailored a report for this customer using a customized SCADA package which would give the customer instantaneous flow, totalized flow, pH and any alarms which might be present. With the new pH controller the customer’s system could predict when the flow was changing and adapt the control system to start adding chemicals before the large inrush on water flow. This reduced the amount of chemicals they used while keeping them within the specified tolerance of 6 to 10pH.
We used the Honeywell Hybrid Control HC900 for pH control and the UDA2182 pH analyzer with the Durafet Probes. The recording system consisted of the Specview SCADA software running on a plant PC communicating to the HC900 for data collection. This software package allowed the plant manager to be able to view his data 24 hours a day seven days a week using remote monitoring. In the past the plant manager would have to make a separate trip into the plant during off shift hours to evaluate the system. Now the plant manager can relax at his home and pull up the system on his home PC to view the control system.
Loy Instrument engineered the new control cabinet along with custom programming and delivered a solution wrapped around the customer needs. We typically ask the customer what keeps them up in the middle of the night. The plant manager’s response was easy……bad effluent water pH control!
The results for this project were less money spent on chemicals, less money spent in fines from the city, less money spent on paper, less headaches spent looking for the data and the most important thing of all was a fully rested and worry free plant manager!
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