Abstract:In the context of control systems for water and wastewater unit processes, the authors define Automation as the ability of a Control System to react (without human intervention) to upstream and downstream variations of a unit process to maintain a reference standard that defines good performance. This is in contrast to monitoring, which merely displays information for use by the operator, who then needs to take corrective action.
With the research data generated during the 1990s regarding the mechanisms of solids dewatering, controls experts were enabled to design enhanced control protocols for these unit processes. In addition, Fig 1 illustrates that during this period there were major developments in the area of operator interface, microprocessor based control, field sensors, and sampling equipment. The charts provide an indicator regarding the functionality, and reliability of the four major elements of an automation system.
The authors will describe the evolution of these elements, and their current status. Since there is a historic concern regarding the reliability of sensors, there will be data from independent agencies on proven sensor technologies that are now installed at numerous locations.
They will then describe how these concepts are being applied to current dewatering and thickening automation projects. Included will be information on Mass Flow Control Systems which utilize feed forward information from upstream process, and feedback information from downstream processes.
There will also be a section on developments in the field of Manual Automation, which was first recommended in WERF Optimizing Thickening and Dewatering Operations Through Automation 98-REM-3. This concept puts decision making into the hands of the operators, with modern control technology providing them with the pertinent data in a user-friendly format. This provides the operator with a “feel” for the function that the variables perform in a control algorithm. When the operator becomes familiar with effect of changing these variables, and their interplay, they can confidently select the variables appropriate for his facility. They will also be more comfortable to put the unit process into full automation mode when it suits them.
Document Type: Research Article
Publication date: January 1, 2005
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