Abstract: This paper uses the Forcecon SCADA software and the pSpace real-time historical database as system platforms, combined with the process requirements of leachate treatment in landfill waste disposal, to achieve real-time monitoring of leachate treatment, remote deployment and management of treatment equipment, and seamless integration of environmental data with environmental management departments.
Keywords : landfill, leachate treatment, eForcecon SCADA software, real-time historical database, pSpace
1. Overview
Currently, waste treatment methods both domestically and internationally mainly include incineration, landfill, composting, and comprehensive utilization. Among these, sanitary landfill has become the most widely adopted method in my country due to its relatively low cost, mature technology, and convenient management. During the process of urban waste sanitary landfilling, leachate is generated due to the combined effects of waste decomposition, precipitation, surface water, groundwater infiltration, irrigation, and liquid waste. To prevent secondary pollution of the environment by leachate, it must be treated before discharge. Because the quality and quantity of leachate are complex and variable, seeking technically and economically reasonable treatment methods, processes, and technologies tailored to specific circumstances is particularly important today, given the increasing volume of urban waste and the increasingly urgent task of sanitary landfill disposal.
2. Introduction to Landfill Leachate Treatment Process
Currently, there are various leachate treatment processes both domestically and internationally, including biological treatment, physicochemical treatment, and land treatment. Generally, a reasonable combination of two or more treatment technologies is necessary to ensure that the treated leachate meets discharge standards. The table below shows commonly used landfill leachate treatment processes.
3. Design of Real-time Monitoring System for Landfill Leachate Treatment
3.1 System Requirements
A modern real-time monitoring system for landfill leachate treatment needs to integrate management and control, and achieve office automation. The control system not only has a good interface with lower-level control equipment, but also an interface for integration with upper-level management systems, and is scalable.
The dynamic and smooth on-site process display allows on-site personnel to monitor real-time data on various aspects of the landfill leachate treatment process, including water quality, influent and effluent conductivity, pH value, liquid level, flow rate, pressure, temperature, and the operating status of each piece of equipment. It also possesses powerful data processing capabilities, featuring fault alarms, event handling, and user access control mechanisms. The monitoring system also includes remote management functionality for on-site equipment.
The entire system possesses reliable redundancy and fault tolerance capabilities, enhancing its reliability and enabling long-term, trouble-free operation. Furthermore, all data can be uploaded to the higher-level environmental protection center for data aggregation and archiving.
3.2 System Architecture
Based on the above requirements, the system can be divided into an on-site data acquisition and monitoring layer, a data aggregation layer at the environmental monitoring center, and a remote equipment management layer. The system architecture diagram is shown in Figure 1.
Figure 1 System Architecture Diagram
3.3 On-site data collection and monitoring layer
Based on the process flow and monitoring requirements, each substation PLC requires a total of 128 input points, including 98 digital inputs, 30 analog inputs, and 28 digital outputs, totaling 156 points. The lower-level PLC, serving as the control host, utilizes the Modicon TSX Premium series mid-range PLC, comprising two 64-point digital input modules, two 16-point analog input modules, and one 32-point digital output module. Accordingly, an 8-slot, non-expansion rack (with power supply) was selected for the system. This series of PLCs features a modular structure, offering flexible system configuration, powerful functionality, and easy expansion, fully meeting the control requirements.
Modicon TSX Premium is Schneider Electric's next-generation PLC, combining its experience in industrial communication with the latest TCP/IP technology. It features a revolutionary distributed architecture, allowing a single unit to control up to 2048 I/O points. The I/O method utilizes a revolutionary distributed architecture—the BUS-X bus—supporting multiple controllers. Communication methods are simple yet powerful, supporting TCP/IP Ethernet, Unitelway, Modbus, Modbus Plus, Fipway, and more. It also features a complete hot standby system.
The acquisition of on-site data and the display of monitoring screens utilize ForceControl 6.1, a general-purpose SCADA software. ForceControl 6.1 interacts with the Modicon PLC via a redundant Ethernet network, ensuring data integrity. The ForceControl software analyzes and processes the acquired real-time data and displays it in the form of dynamic screens or curve reports according to process requirements.
ForceControl 6.1 supports communication with over 1000 mainstream devices from various manufacturers, including DCS, PLC, DDC, fieldbus, and smart meters; it supports data acquisition from most environmental protection instruments and provides historical storage of relevant pollution source data for easy retrieval; and it supports uploading to the Environmental Protection Standard 212.
Figure 2. Plant layout plan
Figure 3. Process flow chart of combined anaerobic treatment
Figure 4 MBR processing flow diagram
Figure 5. Nanofiltration process flow chart
Figure 6 Report display screen
Figure 7 Trend Curve Screen
3.4 Data aggregation and remote device management layer
Environmental data typically needs to be stored for at least three years for future reference. Currently, most environmental information centers use relational databases like SQL Server and Oracle, coupled with disk arrays for storage. When the data volume is small, the drawbacks are not very noticeable. However, once the data volume reaches a certain level, the drawbacks become apparent, such as large disk space consumption and slow query speeds, often proving intolerable. To address these issues, the environmental center has equipped itself with ForceControl pSpace 5.0 enterprise-level real-time historical database as its data aggregation platform. ForceControl pSpace is a high-performance, high-speed, high-throughput, highly reliable, cross-platform, open real-time historical database system. The product features a fully distributed architecture, allowing for flexible application configurations and supporting both C/S and B/S applications. It provides a rich set of enterprise-level information system client applications and tools; it offers large-capacity support for enterprise applications, internally achieves high data compression rates, enables massive storage of historical data, and its flexible scalability meets various needs, while also providing extensive security and traceability.
The data platform supports remote deployment, allows online parameter modification, and is suitable for collaborative development by multiple users to build typical distributed applications. It can simultaneously build various application modes such as historical data servers, event servers, and alarm servers. It is specifically equipped with remote deployment server and remote deployment client tools.
Remote deployment function
This platform enables the collection and uploading of operational data from field equipment, variable monitoring, and parameter setting. It also provides a database for storing historical operational data. Administrators can view the operational status and historical data of field equipment via a web interface and generate various analytical reports. Furthermore, the platform supports providing operational data in a specified storage format to the monitoring center's maintenance and analysis workstations for data analysis and processing, and can simultaneously support unified access and management of thousands of TCP connections.
4. Summary
Using the Forcecon SCADA software and the pSpace real-time historical database as system platforms, combined with the process requirements of leachate treatment in landfill waste disposal, the system achieves real-time monitoring of landfill leachate treatment, remote deployment and management of treatment equipment, and seamless integration of environmental data with environmental management departments, thereby reducing the production, maintenance and management costs in the landfill leachate treatment process.
