1 Remote Monitoring and I Control of Hazardous Waste

Remediation Activities Barry L. Shirk

With increaSrnglysWngent fe&aI, statel and local regulations, relrclble operation of envimnmental m d i a t i o n systems is crstical. Most envimn- mentalsystemsare requited to operatecontinuouslpnight and shy-and to be clwly monitored forperfonname and reporting. For the ownen of these systems, the cost associated with their long-term oMration and monitoring is a growing cotztm. This article desctlbes a cm-eflective solution to contd and monitor thesesystans, both local& andJFom m o t e locations. Ttvo case studies arepmvided.

Burry L S h k is a Projcd manager witb R

W.gbth-.&,&s, Middktown, PA

State-of-the-art, micro-processor based controls are used for attended or unattended processes. These systems can be controlled and monitored locally or remotely via public phone lines. Typical applications include air and water treatment systems with pumps, tanks, and blowers, and water or air quality monitoring systems. Programmable logic controllers are used to control the process and to collect data from the various sensors. The data are then displayed on custom-developed graphic screens utilizing a personal computer. These "real-time" data can also be displayed in text form for operational summary report. Reports can be formatted to provide the information required by the governing environmental agency. This technology allows for unattended operations and communication between multiple systems on the same site.

Modems can be used for monitoring these same sites via public phone lines connected to the owners' personal computer. This method of off-site monitoring and control provides all the same capabilities of the computer located at the site. Figure 1 illustrates the remote control monitoring process. Process control components can be enabled and disabled, and control setpoints can be changed, greatly reducing the need for costly site visits by highly paid technical personnel.

MONITORING THE REMEDIATION ACTIVTI[IES Remediation of environmental contamination requires not only analyz-

ing the problem and providing the client with recommendations, but also long-term monitoring of the selected alternative, once it is implemented. This often requires fully automated, unmanned systems. Existing technologies are constantly being refined-and new technologies are continually being

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The impetue for the development of these multi-faceted systems came fiom constantly changing federal, state, and local environmental regulations.

developed-in order to assist environmental managers in complying with new environmental regulations. Remote monitoring systems can be an invaluable aid in reducing the cost of remediating a contaminated site; they also provide assurance to management of the effectiveness of the remediation process and compliance with federal, state, and local envi- ronmental regulations.

This article will discuss the necessity for monitoring and controlling the equipment used at hazardous waste sites, and the methods and technologies employed to achieve this control. It is clear that, in the future, the sophistication and durability of these systems will continue to advance in keeping with trends in the field of hazardous waste remediation. New developments in hardware may include features such as user-oriented operator interfaces, universal programming devices, communication be- tween different brands of controllers, advanced fiber optic communication links, and faster, more flexible scan times.

The impetus for the development of these multi-faceted systems came from constantly changing federal, state, and local environmental regula- tions. These laws demand more accountability from the individuals responsible for the remediation of hazardous waste sites. With the constant increase in the number of contaminated sites, it is no longer cost-effective for these individuals to travel to each site on a daily basis to monitor operations. Remote monitoring systems provide an answer to these needs.

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of the following methods: Remote monitoring and control can be implemented via one or more

Automatic Telephone Dialers Automatic telephone dialers provide comprehensive remote-site moni-

toring and alarm notification. They maintain constant surveillance of various site conditions or parameters (determined by the operator) and automatically telephone pre-programmed numbers to deliver a clear message to the operator when an emergency occurs. In addition, the operator has the option of calling the automatic telephone dialer at any time to learn the current status of all points being monitored. Typically, these dialers utilize a digitally recorded voice, monitor discrete and analog inputs, store u p to eight telephone numbers, and provide for output control of up to four devices.

Central Monitoring System The Central Monitoring System (CMS) is appropriate for individuals who

have many sites potentially requiring immediate response under alarm conditions. The system usually consists of a software program running on a dedicated computer with a dedicated telephone line. The automatic telephone dialers used in conjunction with the C M S are then programmed to call the CMS fmt to document the alarm notification. The C M S can be programmed to acknowledge the receipt of the alarm. If the alarm is not

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acknowledged, the automatic dialer will continue to call pre-programmed numbers until an acknowledgment is received.

Generally, providing a complete range of system engineering services requires software and programming strategies for programmable controller and computer systems. The newest monitoring systems provide real-time animated graphic representations of the process being monitored. The software custom-developed for such systems obtains control data from programmable controllers, and displays it on a computer screen so that an individual can monitor an entire system from one location. In addition, an individual responsible for several sites at different location has the capability of monitoring these from a central ofice. An ideal application for the CMS is by the firm providing service contract work on site- remediation equipment.

The newest monitoring system provide real-time cmimutedgraphic representafions of the process being monitored.

ptocess ControlSystem A process control system consists of electrical/electronic measuring

devices that input information to a control system, and output devices that cause the system to operate. The system used to assemble these inputs and direct the outputs is generally a Programmable Logic Controller (PLC). The National Electrical Manufacturers Association (NEMA) defines a pro- grammable logic controller as "a digital electronic apparatus with a programmable memory for storing instructions to implement specific functions, such as logic, sequencing, timing, counting, and arithmetic, to control machines and processes." This is a computer-controlled system containing a microprocessor

programmed by a personal computer. The PLC is dedicated to receiving input signals and sending output signals in response to the program logic. Because the PLC is programmed with a computer, it can also be monitored with a computer, either locally or from a remote location. Remote monitoring is accomplished using modems and public telephone lines. This permits information to be reviewed as raw data, or to be used to animate graphic process screens. Drawings developed using Computer Aided Drafting (CAD) can actually "come to life" when animated from a programmable controller system, allowing the operator to view the actual system processes, and trouble-shoot potential problems before they occur.

THEPRA~CALAFPROACXETWOCASEH3(sTORIES It is clear that remote monitoring and control systems are capable of

adding significantly to the cost-effectiveness and efficiency ofsite remediation efforts. The following case studies describe the successful application of remote monitoring and control systems to manage groundwater collection and treatment systems at two sites.

Remediatkm of VoCContaminated Groundwater For a Fortune 500 client, R. E. Wright Associates, Inc. (REWAI) was

called upon to investigate and remediate an industrial site where volatile organic compounds (VOCs) had contaminated the groundwater. An investigation that took place from 1986 to 1389 culminated in the design,

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The treatment Byatem features four air- stripping towers and a 12,000-pound carbon unit, and is capable ofpumping up to 500 gallons per minute (gpm).

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construction, and start-up of a collection and treatment system for the contaminated groundwater.

Initially, a temporary groundwater recovery system was designed, complete with eight automated pumping locations with flowmeters, electrical wiring, and headers. Recovered groundwater was pumped to equalization tanks and through carbon units.

After additional investigation, RFiWAI designed the permanent ground- water collection and treatment system; managed and inspected its con- struction; and provided system startup, balancing, testing, and debugging. The collection system consists of 2,100 feet of groundwater interceptor trench and 3,400 feet of storm sewer replacement underdrain. The treatment system features four air-stripping towers and a 12,000-pound carbonunit, and is capable of pumpingup to 500 gallons per minute (gpm). After treatment, water is discharged in accordance with NPDES permit requirements .

REWAI designed and implemented a computer link to the final system using a Programmable Logic Controller CPLC) and REWAI's PC network. This link enables REWAI to monitor the system from our corporate headquarters, over 500 miles from the site. The system is also monitored by the operator, located approximately 50 miles from the site, and by the owner, who is 500 miles from the site.

REWAI is currently preparing the Operation and Maintenance (O&M) manual for the entire treatment system-including the remote monitoring system-delineating basic operations, maintenance procedures, and troubleshooting instructions.

Remediation of Groundwater Contaminated with TCE and TCA For another client, REWAI was retained to provide, install, and test a

treatment system for trichloroethene (TCE) and l,l,l-trichloroethane (TCA) contamination in the groundwater at their facility. This project, recently completed, required REWAI to provide all components and materials necessary to construct this groundwater collection and treatment system. When finished, this 25-gpm system will feature a single submersible pump installed in an existing 6-inch recovery well; 31-foot Air Stripping Tower (AST) with a 3-horsepower blower; a series of two vapor-phase carbon units to treat AST off-gas; and an electrical system that will accommodate both the proposed AST and another AST, in the event that a second one becomes necessary. Also included in this project will be the installation of 500 feet of overhead and underground electrical service line, 300 feet of 4-inch gravity discharge effluent line to a National Pollutant Discharge Elimination System (NPDES) permitted discharge point.

The finished system will include a number of devices to modify system operations in emergency situations, such as a differential pressure switch to prevent untreated water from being discharged in the event of a blower malfunction, and warning lights to alext system operators of a problem.

REWAI will complete detailed system component tests, and will staxt up the constructed system. As a result of the testing, REWAI will ascertain the operational capabilities of the system. Following start-up, REWAI will

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collect samples of influent and effluent of the system to verify the operating performance of the AST and vapor-phase carbon units. REWAI will train client personnel to operate the system, and will provide both an 0- manual with trouble-shooting instructions, and as-built drawings.

BENEFITS OF APPLICATION In the cases shown above, using a computer to monitor groundwater

collection and treatment systems proved an invaluable aid in complying with environmental cleanup regulations. Features that enhanced the usefulness of this technology include the following:

Flexibility: The parameters to be monitored could be changed quickly and easily. Simplicity: The control process was graphically represented, allowing lay operators to assess system status, without intimate knowledge of computer functions. Documentation: These systems provide not only verbal alarms, but also historical data logging and trending of selected system variables. Customized reports are also a part of the system package, to be used for determining overall system performance and for presenting documentation of remedial activities to appropriate regulatory agencies. Ease of maintenance: The system itself provides detailed, chrono- logical reports of all system malfunctions and alarms.

CONCLUSION Remote monitoring and control systems allow individuals responsible

for cleanup of contaminated sites to monitor site remediation in compli- ance with federal, state, and local regulations easily and cost-effectively. As illustrated by the case histories above, these systems are equally effective when used on-site, or 500 miles from the site; for temporary or permanent systems; and for systems treating 25 gpm or 500 gpm. Versatile enough to be adaptable to any situation, and effective enough to all but eliminate the need for technicians on-site, these systems promise to be a permanent fixture in the future of environmental remediation. H

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