Modern DCS Helps Convert Wastewater to Safe Water

The central California city of Monterey is located along the state’s rugged coastline, with expansive views of the Monterey Bay. The area’s moderate climate makes it ideal for agriculture, earning it the nickname the “Salad Bowl of the Nation,” with major farming productions providing a range of fruits, vegetables and even grapes for wine production. Monterey Regional Water Pollution Control Agency (MRWPCA) processes more than 18.5 million gallons of wastewater each day for the region’s nine cities.  

After completing an extensive research project in 1998, the agency determined that recycled water was safe for use on various crops. As a result, the area decided to implement wastewater recycling programs to help support the local crop irrigation needs. The agency also provides recycled water for 12,000 acres of high-value food crops.

The program’s recycled wastewater is pulled in from more than 10 collection points for fresh, edible food crops, including artichokes, celery, broccoli, lettuce and cauliflower. This vast system includes the Salinas Valley Reclamation Project (SVRP) water recycling plant and the Castroville Seawater Intrusion Project (CSIP) distribution system.

The gathered wastewater is cleaned through an extensive process-control system, which requires tight control over water-quality analysis, level control, chemical additions and distribution.

After almost 15 years in operation, the control system running the process was nearing obsolescence. The dated Windows^® XP-based human-machine interface (HMI) software had no backup power in case of a shutdown or emergency. Communications from the various, disparate collection points often were delayed and irregular, leading to falsified communication status. Additionally, production data was logged manually, a time-sensitive and error-prone process that also made data transfer unreliable.

The system operators were unable to quickly gather data and trend reports critical for good decision-making. For example, if an engineer put in a request for flow estimates, the data might not be available for weeks.

After a review of the entire supervisory control and data acquisition (SCADA) and IT system’s master plan with Kennedy Jenks Consultants, the agency decided it was time to upgrade its control and information system to assist in providing better operational control of irrigation demands, improve reliability and reduce risk.

Refreshing the System

The agency wanted a thorough understanding of the current SCADA system’s operational performance and turned to Rockwell Automation for a complete Installed Base Evaluation^™ assessment. This process provided MRWPCA with a baseline understanding of its most critical assets and obsolescence risks.

The agency decided to rebuild the network and control infrastructure and implement a PlantPAx^® distributed control system (DCS) from Rockwell Automation.

Starting from the ground up at the SVRP facility, MRWPCA needed to lay new fiber optic runs to help support the newly virtualized system. The old programmable logic controller (PLC) code was easily converted to the new PlantPAx system, helping to ease setup and programming during commissioning. The virtualized system also would allow staff to start operations with a backup server in case the primary server failed, reducing the risk of interrupting recycled water deliveries.

The system was built using EtherNet/IP^™-based network communications standards to help streamline control and information flow and allow real-time diagnostics and electronic documentation for the water treatment process.

Conversion to nine Ethernet I/O modules reduced installed I/O by an entire rack and increased the system’s speed. This allowed MRWPCA to physically move the PLC off the plant floor and into an administrative building.

A Rockwell Automation field service engineer was on-site to help install the software and provide hands-on training for the agency staff.

Improving the new DCS’ information-enabled functionalities included redundant historian capabilities to provide real-time and historical water trends, such as system demands, levels and storage. The system collects, tracks and records key process data from about 2,300 historian tags to pinpoint water trends.

The new HMI was converted directly from the old software and implemented on redundant virtual servers, which has increased reliability and speed — all with improved screen aesthetics.

To ease process and regulatory reporting, MRWPCA also implemented a FactoryTalk^® VantagePoint enterprise manufacturing intelligence (EMI) system from Rockwell Automation, which aggregates water treatment information from the historian and other assets. Operators can use the EMI system to access various instrument and report tags in real time and generate specific reports for process management and regulatory purposes.

Improvements Across the Board

The new DCS has helped MRWPCA collect and access data that is crucial to the water treatment process. Now operators can access data reliably from any of the disparate locations in real time.

Better visibility and access to data have helped improve control over chemical usage. Because the treatment processes use upward of 5,000 lbs. of chlorine each day, achieving tighter control meant major cost savings. MRWPCA since has been able to save $25,000 per year in chemical costs. These cost savings were not anticipated initially, but were an added benefit that, in turn, provided a full return on investment (ROI) on the HMI upgrade in just five years.

An energy audit yielded no further energy-saving suggestions — drives were running more efficiently, and the system was fully optimized for energy savings. This was a huge win for the agency, as energy consumption often is one of the highest operating costs associated with water treatment.

MRWPCA also was operating a booster station affected with a pressure problem, leading to multiple burst pipes, breaking valves and several other unresolved issues. Before upgrading to the DCS, the county couldn’t determine the issue’s cause, but the data collection and trending capabilities helped operators pinpoint and resolve the problem. The DCS prevented the county from having to modify the booster system by putting in variable-frequency drives (VFDs), saving almost $3 million.

The agency also worked with Rockwell Automation Encompass™ Product Partner OSIsoft to use its open data infrastructure PI System^™ to build dashboards of publicly facing data. The data is migrated from the SCADA system up to the enterprise system. Then it’s pushed up to Microsoft^® Azure^™ cloud, where dashboards show users water quality in real time.

Advanced reporting capabilities within the new DCS also allowed for easy regulatory reporting. The process, which used to take up to three days, now is done through the click of a button.

And Now, a New Initiative

MRWPCA is taking the lessons learned from the SVRP and CSIP projects and applying them to a critical new initiative — groundwater replenishment. The Pure Water Monterey project will make use of a PlantPAx system and aims to provide safe, reliable and sustainable drinking water.

^{The Journal From Rockwell Automation and Our PartnerNetwork™ is published by Putman Media, Inc.}