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Instrumentation
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trol within the plant. It is essential that the digesters receive the proper flow of solids to maintain proper temperatures and sludge treatment times. Raw sludge pumping can be controlled by either time or by density control. The limita tion of time-based pumping is that it makes assumptions based on historical data. The better method of raw sludge pumping is density-based pumping. A crucial component of the densitypumping scheme is the maintenance of controlled primary blanket levels. It is important to maintain at least a mini mum sludge level in the tanks to ensure sufficient sludge density. When the blanket readings are provided by manual measurements it is quite possible to over pump the clarifier and send low level solids to the digesters. These low level solids create problems for the digestion process. The more constant the solids fed to digesters, the better the treatment
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Corrosion InhilDitors^^ ^ ] from ClearTech • Corrosion Control • Scale Control
-
- Membrane
- Lime Slurry • Fe/Mn Stabilization • Pb/Cu Corrosion Control
process.
While the total scope ofthe project is still in its infancy, the plant is able to use the online interface
level information to better control
the overall plant process. Finally, there is the problem of sep tic sludge and odour. As was discussed previously, there is the problem of offgassing and septic sludge. If the primary sludge is allowed to remain too long in the primary clarifier, it will go septic and start to biodegrade. This biological ac tivity produces odorous gases that give treatment plants their smell. One of the best ways of controlling primary sludge
The results you want! • More effective disinfection
• Fewer customer complaints • Aesthetically pleasing water • Reduced soluble lead
• Lower pumping energy costs
• Improved infrastructure life For more information, contact one of our sales offices:
Saskatoon:(306) 933-0177 Regina:(306) 721-7737 Calgary:(403) 279-1096 Vancouver:(604) 272-4000 Winnipeg:(204) 987-9777 Edmonton:(780) 452-6000
Toronto (Mississauga): Toll Free (800) 387-7503
is to know the levels on real-time bases,
which allow for proper distribution of the raw sludge before the odour occurs.
or visit us at
www.cleartech.ca
RESPONSIBLE DISTRIBUTION ■ OUR COMMITMENT -
Conclusion
While the total scope of the project is still in its infancy, the plant is able to
Head Office CiearTech Industries Inc. 2302 Hanselman Avenue
use the online interface level informa
Saskatoon, SK S7L 5Z3
CACD
tion to better control the overall plant
process. A project to control sludge pumping based on interface level will be looked at in the future. This project proved the feasibility of the use of ul trasonic interface detectors and digital radios and interfacing with an existing SCADA system. The plant has other moving bridge primary clarifiers and there are plans to automate in the same manner.
For more information,
circie repiy card No. 141 Environmental Science & Engineering, September 2001
For more information, circie repiy card No. 142 (See page 25)
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