Feature Waste management & recycling
Monitoring systems help landfill operators manage leachate levels
System Devices UK provides automation systems and support to customers in the United Kingdom and Ireland. The company’s expertise covers automation and monitoring systems, SCADA and robotics. In recent years, the company has provided control systems to landfill operators that not only meet their immediate needs, but are so flexible, they allow for future expansion without having to change hardware or software later in the system’s life cycle
urrently, the vast majority of municipal waste in the UK (over 85 per cent) is sent to landfills. Local governments across the UK provide land for the establishment of landfills and the disposal of household and other types of waste. But these sites don’t remain landfills forever. Typically, landfills operate for 15 years, after which the site must be returned in good condition. This requires the col- lection, treatment, and discharge of leachate, which is created when mois- ture and rain water permeate the waste deposited in a landfill. As this water mixes within the solid waste, it picks up contaminates (organic and inorganic chemicals, metals, biological wastes) and becomes leachate.
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Containment and treatment of leachate before it reaches groundwater or public sewer systems is critical, not only for maintaining the environmen- tal integrity of the landfill, but also for compliance with regulatory guide- lines, such as the Deposit of Poisonous Wastes Act of 1975. Failure to adhere to these guidelines usually results in substantial financial penalties. As a result, automation and control profes- sionals working on landfill projects must treat the leachate and ensure that none is discharged outside of the established discharge parameters.
System Devices
According to System Devices’ Darren Weissenborn, these leachate manage- ment systems use Opto 22 SNAP PAC programmable automation controllers and I/O as the key components that let landfill operator customers connect to, continuously control and acquire data from pumps, valves, and other equip- ment at outstations, ponds, control cen- ters, and all over their individual sites.
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Specifically, at one landfill located in Lancashire, System Devices has imple- mented a leachate management system that uses a rack-mounted PAC as its cen- tral controller. This controller is Ethernet-enabled, allowing it to exist on a network that supports both wired and wireless connectivity for powerful and comprehensive monitoring and man- agement. The system also includes approximately 128 digital and 36 analog I/O points. Digital inputs include inter- faces to conductivity sensors and float switches that detect the presence and level of water across the site.
HMI and Alarming According to Weissenborn, if conditions at the landfill ever deviate out of their prescribed operating ranges, it’s impor- tant that the control system contains the fault and reports it immediately. Therefore, System Devices’ leachate management system has been config- ured to alarm on low chemical levels, improper valve and pump states, pump failures and dangerous pH, methane, and ammonia levels. The entire system and all alarms are viewable via HMI screens running on the site’s SCADA PC in the Site Control Cabin. Any alarm states detected by the system are reported on the computer screen so the issue can be acknowledged and recti- fied. For off-site notification, the Opto 22 SNAP PAC controller sends SMS alerts (i.e., text messages) to designated individuals’ cell phones whenever the site experiences crises like power losses or electrical contactor failures. There are also alarms for pump failures and low chemical levels.
Data Archiving
All well conditions are monitored 24/7 via secure wired and wireless Ethernet
Analog and digital I/O communicated wirelessly via Modbus/TCP to a network switch that then passes
acquired data to the controller
connections that encompass the entire site. All gathered data is logged and stored on the SCADA PC’s hard drive for historical archiving and compli- ance reporting. To better enable this, System Devices designed a network architecture that takes full advantage of the SNAP PAC’s dual Ethernet inter- faces. “We’ve successfully segmented our network and use one of the con- trollers’ Ethernet ports exclusively for monitoring and control, and the other for communicating to PCs and data- bases,” says Weissenborn. “This design offers better management of network traffic and lowers risk by establishing a built-in firewall that shields and safe- guards landfill operations from viruses or other threats.”
Containment and treatment of
leachate before it reaches groundwa- ter or public sewer systems is critical, not only for main- taining the environ- mental integrity of the landfill site
Remote Access
System Devices UK T: 01928 571977
systemdevices.co.uk Enter 333
Landfill operators must be sure that their automation systems not only optimally manage the processing of leachate, but that they also aggregate data confirming that the criteria for elimination and dispersal of contami- nants has been met and no discharge into the public sewer system took place during any period of non-com- pliance. And because landfill sites are usually far removed from most of the population, these same automation systems must offer secure, remote access to the individuals responsible for the site. To accommodate this, System Devices designed its system to notify off-site personnel of problems via SMS, and then allow remote access via secure virtual network computing software. This way, respondents are able to confirm problems, identify the causes, and initiate corrective actions from wherever they may be.
MARCH 2011 Factory Equipment
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