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Research on Sewage Treatment System by Configuration Software and PLC [Sensors & Transducers (Canada)](Sensors & Transducers (Canada) Via Acquire Media NewsEdge) Abstract: The automation products have been applied in various industries, especially in the water disposing industry. This paper describes the design of the hardware and the software of the monitoring system of sewage treatment which is based on S7-300 PLC (Programmable Logic Controller) and the Profibus bus technology. The hardware of PLC includes the power supply, CPU (Central Processing Unit), analogdigital conversion module. Through the management of the configuration software MCGS (Monitor and Control Generated System), the system realizes the main functions, such as the multi analog signals' testing, the control of the driving output, the display of the digital information collection, the parameters enactment, the manual debugging control, etc. Then, the monitoring and management of the disposing of sewage plant is completed. Copyright © 2014 IFSA Publishing, S. L. Keywords: Sewage treatment, PLC, Profibus, MCGS, Industrial Ethernet. (ProQuest: ... denotes formulae omitted.) 1. Introduction With the rapid development of modem control technology and computer technology, the control technology has been widely applied in sewage treatment plants. In order to ensure the sewage treatment technology and the equipment can run safely and reliably for a long time, we adopt Siemens S7-300 programmable controller and intelligent instrument to constitute the lower computer and realize the monitoring of field devices. The sewage treatment system can improve the level of the sewage treatment operation maintenance with the advantages of high reliability, superior control performance, perfect management function, etc. It is important to guide the normal operation of the process and equipment and improve the level of automation control and management [1], 2. Sewage Treatment Process The pretreatment of sewage treatment plant adopts the grid with rotational flow grit process to removes impurities and sediment. The biological treatment adopts Orbal oxidation ditch sewage treatment process. The sludge treatment adopts dosing and belt type filter press compression dewatering process [2], The flow chart of the process is shown as Fig. 1. 3. Structure of Sewage Treatment Control System The structure of the control system is mainly composed of three parts. There are industrial PC, PLC and the peripheral circuit board and the panel of the analog switches input and output control. The structure diagram of the sewage treatment control system is shown in Fig. 2. 3.1. Hardware of PLC Control According to the requirements of the actual electrical wiring diagram, the configuration of the PLC control is consisted of PS307 power supply, CPU315-2DP, the analog input module AI8xl2Bit, the digital input module DI32xDC24V and DI16xDC24V, the digital output module D016x, the digital relay output module AC 120V and the analog output module A04xl2V. 3.2. Control Functions of PLC Control The device control mode is divided into two kinds, the central control and the local control. Local control device are respectively arranged in the vicinity of each unit. Through field (manual / automatic) switches to manual mode, the field switches directly control equipment. This is the highest priority control in this mode. PLC is only used to monitor the running state. When the field (manual / automatic) switches to automatic mode, it becomes central control mode. In the running program of PLC, the upper computer control mode and PLC control mode is set. When the mode switches to the upper machine mode, the PLC receives instructions from the upper computer, controls the field devices directly through the computer remote, such as start or stop the various types of pumps, blower, valve, mixer, etc. When the upper computer control mode switches to the PLC mode, according to the parameters of the measurement of liquid level, the preset flow rate and the dissolved oxygen, PLC operates the pump and the fan, and monitors the operation status of the equipment [3]. The sewage treatment requires the constant pressure, the constant flow rate and dynamic saving a large amount of data. If the control of the pressure and flow is adopted manual, the process is not only tedious but also has large errors, and the energy wastes. The system adopts PC, PLC, frequency converter and MCGS configuration software to constitute the sewage treatment control system [4], This control system takes PLC as the locale control unit. The system which takes PLC as the layered sewage treatment process of the control unit has the following characteristics, such as function distribution, PLC, the operator station, dispatching station respectively as the field control, operation control, data management, reasonable task allocation, strong control function and high reliability. 4. Control System Software Design The software design quality is directly related to the quality of the control system and the safety of the equipment and person, so the development of a set of perfect function and high reliability software is very important. Based on the system of the actual situation, the software design of the user is also divided into the upper computer configuration software and the lower computer processor program. 4.1. Lower Computer PLC Step 7 has mainly three kinds of programming methods, there are the linear programming, the distributed programming and the modular programming. According to the actual situation of the control equipment, the modular programming method divides the whole wastewater treatment process into a number of flows, and each flow corresponds to a function or a function block. The function blocks of PLC program mainly realize the motor start-stop control, automatic control, manual control, sewage treatment and sewage sludge functions, etc. The compiled ladder diagram program can be downloaded to the PLC through a dedicated communication cable. The pumping station pump is mainly used to promote the water out of the coarse grid to the fine grid. In the promoting field, the three lifting pumps running status and their start and stop are needed to measure and control. The lift pump control schematic is shown as Fig. 3. Three lift pumps can be controlled manually or automatically by a switch. The automatic control process in described as followed. Through the PC set the starting level of each pump, if the level is relatively low, then only a lift pump is enabled to make the water level maintain in the water, and when the water level rose to the second starting level, the second lift pump is enabled. If the water level continues to rise and the starting level exceeds than the third setting, the third lift pump is enabled. It also can be set high and low level alarm, when the liquid level is lower or higher than the normal value, the alarm works. To detect the lift pump water level, the ultrasonic level meter is installed before the ascension pump, and its detection water level range is 0 ~ 10 meters, 4 ~ 20 mA output analog current signal. After the further process in PLC, the signals are transmitted to the central monitoring of the upper computer through the Ethernet [7]. The ultrasonic liquid level meter adopts the principle of time travel by emit ultrasonic wave to the surface, and the echo of the object can be received by the sensor. The pulse transmitting and receiving time T is calculated, and then the sound velocity C is used to calculate the distance between the probe and the surface of the liquid level. The formula is shown as followed. ...(1) According to the pool depth E set by the user, the liquid level is gained. ...(2) 4.2. Upper Computer Program Design S7-300 has a variety of different communication interfaces. There are a variety of communication processors used to connect the industrial Ethernet with PROFIBUS interface system, communication processors used to join point to point communication systems, multi-point interface (MPI) integrated in the CPU is used for connection the programming with PC and man-machine interface system and other SIMATIC S7 / M7 / C7 automation control systems. CPU31x - 2 DP used in the paper is refers to the integration interface profibus-dp s7-300 CPU, i.e. CPU315-2 DP [9]. PROFIBUS-DP system consists of a DP master station and a smart DP slave station. The configuration intelligence slave station includes the new S7 project, hardware configuration and DP mode selection and defines the compiling configuration and slave station communication interface area. Then the configuration main station connects to the slave station, and the communication interface area is compiled [5]. The PC adopts the Yanhua 610 industrial computer with the sewage treatment software. The software adopts configuration software MCGS development environment [6]. There are 5 parts in the MCGS development environment, equipment window, main control window, real-time database, the user window and operation strategy, which are shown in Fig. 4 Master window is the main window or main frame engineering. In the main window, a device window and multiple user windows are placed. The master window is responsible for schedule and management of open or close of the window. Equipment windows is the working environment of connect and driver the external devices. This window consists of configuration data acquisition, output devices control, device driver register and data variables definition to connect and drive the equipment. The sewage treatment using the MCGS software to support the above characteristics of the hardware drive, can read or write ADAM module signals and the registers associated with PLC. So ADAM module controls water pump and the speed of the peristaltic pump and reads the COD (Chemical Oxygen Demand) values. It makes each individual equipment unity under the management of the software. When the software runs, the device window is not visible [8]. User window is mainly used for setting project in the human-computer interaction interface, such as the generation of the various animation display, alarm output, data and the curve chart, and so on. The sewage treatment automatic control system is established in the user window main interface. In and out of the water COD, the dosage of PAC (Polyaluminium Chloride) and PAM (Polyacrylamide), the water flow rate of each variable such as day, month and year change curve are also established. The window is the man-machine interface of this system. The operation of the main window in sewage treatment automatic control system is completed, and the relevant curves and data can be browsed in other windows. Real-time database window is the data exchange and process of each part of the engineering center and make the MCGS engineering parts connect into an organic whole. Run policy window is the main operational process of complete engineering control. Including write control program and choose a variety of functional components, such as data extraction, history curve, timer, formulation and multimedia output operation. 4. Conclusions Through the analysis of the technological process and control requirements of the sewage treatment process, the system use STEP7 software to complete the field of PLC control program and realize the automatic control field device. The PLC technology in sewage treatment control system is not only to simplify the system and improve the reliability, but also to reduce the labor intensity and obtain the good social benefit, economic benefit and environmental benefit. Reference [1] . Gao Jinggeng, Design of control system of sewage treatment based on PLC and Profibus, Industrial Instrumentation & Automation, Vol. 4, 2013, pp.82-84. [2] . Liu bin, On application of Orbal oxidation ditch in wastewater treatment plant, Shanxi Architecture, Vol. 38, Issue 11,2012, pp. 126-127. [3] . Su Dongsheng, The Design of Sewage Treatment Control System Based on PLC, Mechanical & Electrical Engineering Technology, Vol. 4, 2013, pp. 65-68. [4] . Zhang Fen, Research into teaching innovation of PLC practice based on configuration software MCGS, International Electronic Elements, Vol. 20, Issue 10,2012, pp. 162-164. [5] . Zhang Yu, Managing Countermeasures for Sourceseparated Sewage Treatment and Recycling in Campus, Journal of Anhui Agricultural Sciences, Vol. 23,2009. [6] . Chen Jin, The development of sewage treatment system based on MCGS, Industrial Instrumentation ¿Automation, 2009, pp. 61-63. [7] . Ullah Irfan, Ullah Qurban, Ullah Furqan, Shin Seoyong, Sensor-Based Autonomous Robot Navigation with Distance Control, Journal of Computational Intelligence and Electronic Systems, Vol. 2, Issue 1,2012, pp. 161-168. [8] . Yun She, J. Mechatron, Output Feedback Control of Electronic Throttle Valve, Journal of Mechatronics, Vol. 2,2013, pp. 161-168. [9] . Wang, Yong, Typical Circuit Performance Analysis of Multi-Station Tunnel Drilling Machine's Hydraulic System, Journal of Mechatronics, Vol. 38 December 2013, pp. 73-79. 1 Yu Guoqing,2 Du Libo, 3 Chen Shuwang Institute of Information Science & Engineering, He Bei University of Science and Technology, Yuxiang Street, No.26, Shi Jia Zhuang City, He Bei Province, China, 050000 2 Tel: 15690325956, 2E-mail: [email protected] Received: 2 April 2014 /Accepted: 31 July 2014 /Published: 31 August 2014 (c) 2014 IFSA Publishing, S.L. |