OVERVIEW

The degree of instrumentation and automation in today s water treatment plants varies significantly. Many plants are fully automated and are staffed only during a day shift. Others employ minimal technology and rely on manual operation. Increasingly, automation is part of the design philosophy for new plants and upgrades of older plants. Some of the business reasons driving this change include

• A need for improved treatment quality. Modern automation and control allows coser and more consistent water treatment than is practical using manual control. The control system can be designed to alarm the operator whenever abnormal conditions require operator intervention.

• Tighter regulatory requirements. Increased regulatory requirements lead to a heavier dependence upon automation and instrumentation. Most regulations require grab samples for compliance testing. As the sampling intervals and record keeping increase, significant labor savings can result from adding on-line instrumentation and data collection. For example, the recent Interim Enhanced Surface Water Treatment Rule requires turbidity reporting at 15-min intervals. This makes on-line monitoring economically attractive.

• A need to reduce costs. There are many areas for cost savings through automation. This can be done through reduced chemical usage, reduced equipment wear and tear, and optimized energy usage. A few examples are sequencing pumps to minimize energy use; backwash turbidimeters to reduce energy and washwater use by terminating backwash cycles based on turbidity levels; and optimizing chemical control loops to minimize chemical costs.

• Improved labor efficiency. Labor savings can be achieved...