Treatment Plant Calls Cell Phones with Alarms
Many small communities do not have the resources to staff all infrastructure services 24/7, so water and wastewater processing plants need the ability to run on auto-pilot when employees are not on site. Given the critical nature of these operations and potential for fines when things go wrong, control systems need to be able to page specific operators when necessary to alert them to equipment ...
Many small communities do not have the resources to staff all infrastructure services 24/7, so water and wastewater processing plants need the ability to run on auto-pilot when employees are not on site. Given the critical nature of these operations and potential for fines when things go wrong, control systems need to be able to page specific operators when necessary to alert them to equipment malfunctions or upset conditions.
Xenia is a municipality of 25,000 people in southern OH, halfway between Columbus and Cincinnati. It is unusual for a city its size in that it maintains two wastewater treatment plants: one at Ford Road and the other at Glady Run. These use an activated sludge process for wastewater treatment, where microbes convert carbon into cell tissue and oxidized end products that include carbon dioxide and water. In addition, a number of microorganisms in activated sludge obtain energy by oxidizing ammonium to nitrates in the process known as nitrification. The success of the activated-sludge process is dependent upon maintaining a mixed community of microorganisms that perform three critical functions:
Remove and consume organic waste material;
Aggregate and adhere the material in a process known as bioflocculation; and,
Settle it in such a manner as to produce a concentrated RAS (return activated sludge) for recycling.
During successful operation, there should be no interference with compacting and settling rates of the activated sludge prior to its recycling.
But stuff was being missed
The Xenia Water Reclamation Department consists of 10 people, and operates from 7:30 a.m. to 4 p.m. Before this project, operators used local instrumentation and indicators to check process status. The only part of the operation that was integrated or ran on computers was an automated billing process.
An external alarm system sounded only the existence of an alarm condition but gave no indication of the cause. After hours, the department had to rely upon the local police dispatcher to notify off-duty personnel of alarm conditions at the plants. This introduced obvious problems, and in one case an alarm was overlooked for more than 10 hours, raising the issue of violating regulatory compliance. EPA fines for violations can run up to $15,000 each, with multiple violations possible for each incident. In addition the department can be forced to pay for fish kills and damages to residents along waterways impacted by a violation incident. As one manager said, “Stuff was getting missed.”
In addition to complying with environmental regulations, a new solution had to meet these requirements:
System improvements had to be fully cost-justified because the municipal government maintains tight control on expenditures.
Avoid false alarms that might be caused by intermittent conditions such as power drops or temporary surges of waste inflow.
The wastewater division monitors five primary values:
Raw flow (incoming waste water);
Waste flow (treated output);
Wet well levels (overflow).
Management of the Xenia Water Reclamation Division determined that an appropriate solution would be to install a networked system that would provide remote electronic updates to the duty person every four hours and eliminate the need to drive in and check conditions in person. Initial research on Ethernet-based I/O options led to Sixnet, which in turn directed them to Kemper Controls.
Dean Norton of Kemper immediately recognized that he could resolve the situation with an InduSoft SCADA system and Sixnet I/O modules. The solution as integrated and delivered to Xenia involved two client PCs at each site and a server in the main control area running four Web sessions.
The system was built using browser-based operator displays, and Norton calls the application, “an ideal example of using InduSoft Web Studio with Web clients. Instead of paying thousands for each seat, the web clients only cost Xenia a couple of hundred dollars.”
Department managers can now call up status displays and check status from a PC anywhere in the city. Norton used the built-in InduSoft e-mail functions and scripting language to create a remote reporting function that sends selected key values from 24 I/O points to the duty person’s cell phone every four hours. These appear on the cell phone display as a brief text message and enable the operator to tell at a glance how the plant is functioning.
Equally important, the Xenia system includes a remote alert function for times when a significant alarm condition occurs. This incorporates a delay function for each alarm setting so that intermittent conditions do not result in the duty person being called when the problem has resolved itself. These delays can be configured during runtime so that they can be modified without shutting down the system and jeopardizing control of the treatment function. Up to 15 system conditions can be configured for alarms and the operator can enable, dispel, and set trip points as required.
'We sleep a lot better’
Since startup the system has virtually eliminated environmental violations. Next in line for Xenia is expansion of the system to include calculations that will enable it to pinpoint areas of the sewer system that need expansion, and installation of a similar system for the water treatment facility.
In the first year of operation, Xenia experienced unusually heavy rainfall. Heavy rain events bring surges of water into the system that can result in major problems. But this time there were no regulatory violations as a result of slow response to alarms. Avoiding one single violation more than pays for the cost of the new system, and department managers are delighted with the results. One of them remarked, “We all sleep a lot better at night.” By eliminating the human factor in reporting alarm conditions, the Xenia Water Reclamation Department improved its regulatory compliance, avoided expensive fines, reduced overtime costs, and, equally important to the personnel who work there, enabled them to get a good night’s sleep.
Jason Tincu is wastewater supervisor, Water Reclamation Division, Xenia, OH. Contact him at firstname.lastname@example.org
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