水污染监测英文文献

1、The Besign of Oxidation Ditch Control System Based onPLC andKingviewJie SUCollege of Mechanical Engineering, Ningxia UniversityYinchuan, ChinaXuejun ZhuCollege of Mechanical Engineering, Ningxia UniversityYinchuan, ChinaAbstractWith the exhaustion of water resources, the urban sewage circulation pro

2、cessing has become an indispensable way for the construction of an environmental-friendly, energy-saving and sustainable society. The key is directly determined by the superiority of treatment process and automatic level of control system. For instance, there is a sewage treatment plant in Yinchuan

3、city, which has the sewage treatment capacity of 50,000 t/d and uses the oxidation ditch process. In this paper, we design an automatic control and monitoring system for the sewage treatment plant. In the system, Siemens S7-300 PLC is a slave station. It can be used to control field devices and coll

4、ect variable data from sensors, including DO, PH, liquid level, flow, and MLSS, etc. The upper computer uses KingVIEW software to exchange data with slave station, thereby realizing the centralized management. Keywords: Sewage treatment; oxidation ditch process; PLC; DCS;KingVIEWI、INTRODUCTIONWater

5、is a basis for the survival of human being, and is the foundation of all creatures. It plays an important role in regulating global climate. But with the rapid economic and social development and the further promotion of industrialization and urbanization, water resources have become an important fa

6、ctor of restricting economic development1. By the end of 2010, Chinese urban wastewater quantity is 133.45 million m3 per day but urban sewage disposal capacity is only 102.62 million m3/d. The rate of urban sewage treatment is only 76.9%. The general situation of water resources is worsening, and i

7、mproving the capacity of sewage treatment is extremely urgent.In the sewage treatment process, oxidation ditch is the core of biological chemical method and influences the quality of effluent water directly. Using the PLC controller with a superior performance, a stable and reliable integrated autom

8、ation system for sewage treatment can be designed and has great significance. The configuration monitoring system can help the sewage treatment process to realize fully automatic control. KingVIEW with industry is leading HMI and object oriented environment with strong graphic network function, can

9、exchange data realtime with the machine and other computer application 2. Through the communication protocol conversion interface I/O Server, it is convenient to connect other industrial control equipment. Due to KingVIEW, we can create the oxidation ditch process section efficiently by using comput

10、er interface.II、INTRODUCTION TO THE OXIDATION DITCH PROCESS At present, biological chemical method is a way most frequently used in urban sewage treatment. Compared with chemical treatment, biological treatment method for the sewage processing is more economical, efficient and mature. It is to absor

11、b and transform the harmful substances in sewage water by the metabolism of microorganism. The oxidation ditch process is typical in biological treatment method. It is a kind of connections between the front and the cycle flow aeration ditch. It can also be called continuous circulating aeration whi

12、ch is a kind of activated sludge variant 3. Considering the stability of sewage water and its treatment capacity between 30000 to 100000 m3 per day, we choose the Carrousel-3000 oxidation ditch. It can fully embody the good treatment effect and its energy-saving characteristic of oxidation ditch pro

13、cess 4, 5. It has a thick grid, sewage pump room, ascension grid, aeration heavy fine sand pool, choose pool, anaerobic pool, oxidation ditch, eventually pond, contact disinfection pool, backflow sludge pump room, the sludge regulation ponds and sludge dewatering, etc. The Carrousel-3000 oxidation d

14、itch process section is shown in figure 1 and its flow diagram type in figure 2. After primary treatment, urban sewage water flows into oxidation ditch with decomposition purification and finally gets to the stage of mud water processing. The oxidation ditch process section is the place for biologic

15、al treatment, where waste water and the biological sludge are mixed; table aeration machine provides suitable dissolved oxygen levels for bacteria metabolism, help form alternately good oxygen, lack of oxygen and anaerobic conditions in the trench and undertakes the main task of biochemicaltreatment

16、. Figure 1Carrouse-3000l oxidation ditch process section Figure 2Carrousel-3000 oxidation ditch process flow Figure 3DCS control system structure based on PLC and the KingVIEWIII、THE OVERALL DESIGN OF CONTROL SYSTEMAs an object for control, the demand for oxidation ditchprocess section mainly center

17、s on data collection and its orderand logic control. Thus, PLC is chosen as the slave stationinautomatic control system 6. The system needs to realizemonitoring and automatic control of the biochemical treatmentprocess, which mainly includes the control of table aerationmachine, propeller and water

18、electric weir. The DO value ismonitored and by the use of soft measurement technology,BOD is estimated and the flow of water is monitored based onthe value of DO, PH, ORP. Table aeration machine realizes itscontrol by taking dissolved oxygen aeration as a controlvariable; propeller adopts switch con

19、trol; water electric weirtakes BOD as a variable to realize its control. According to thecharacteristics of the Carrousel-3000 oxidation ditch processand its controlling requirements, we can design a DCS controlsystem in line with the idea of "separate control and integratedmanagement", wh

20、ich is based on PLC and KingVIEW 7. Asis shown in figure 3, the first level is Site layer, mainlyincluding inspection instruments, the I/O interface device, andthe local control cabinet; The second layer is PLCprogrammable controller, which can realize logic control basedon the data collected from s

21、ite and the logic relationship ofequipment operation; The third layer is the remote monitoring(scheduling center, mainly using industrial control computer(IPC to monitor the real time parameters of process sectionand the working condition of equipments, automatically adjustthe equipment operation an

22、d realize the functions of alarmingand interlocking. It can also display the dynamic real-time graph directly, make the trend analysis and show and print the historical monitoring data8. For the monitoring system, we use Yanhua industrial computer IPC as the master station. After installing the King

23、VIEW configuration software, we can set up a database. The SIMATIC S7-300 PLC is employed as a slave station. In the oxidation ditch process period, the logic control of table aeration machine, propeller and water electric weir is realized based on the data collected from site and the logic relation

24、ship of equipment operation. Touch screen will be fixed if needed, mainly used to display the field of process parameters and configure control parameters, which can realize the manual operation. The central processing unit chooses CPU315-2 DP. It has strong processing capacity and adopts modular de

25、sign structure which has an easy configuration and is convenient for future expansion. Equipped with CPU module CPU315-2 DP, we need PS307 power supply module 1 piece, CP343-1 comunication module 1 piece, 2 pieces of 32 points SM321 DI module, 2 pieces of 32 points DO module, 1 piece of SM322 8 road

26、 SM331 AI module 9, SIMATICTP270-10 touch screen. The data transmission is mainly achieved through adopting an universal, open, high-speed and reliable industrial Ethernet betweenmaster-slave stand 10. By installing the distributed the I/O ET200, it makes possible communication between the machine w

27、ith the field under equipment and intelligent instrument, constituting the bottom profibus-DP. Figure 4, figure 5 and figure 6 are the wiring diagram between PLC and the equipment, instrument, which are DI module, DO module and the AI module of the wiring diagram respectively. Figure 4oxidation ditc

28、h process section digital input module wiring diagram Figure 5oxidation ditch process section digital output module wiring diagram Figure 6oxidation ditch process section analog input module wiring diagramNOTE:IFTAAMC:Industrialfrequency table aeration automatic machine conversion; IFTAMMC:Industria

29、l frequency table aeration machine manual conversion;IFTAMSR:Industrial frequency table aeration machine soft running;IFTAMMO:Industrial frequency table aeration machine motor overloaded;FCTAMAC:Frequency conversion table aeration machine automatic conversion; FCTAMSR:Frequency conversion table aera

30、tion machine soft running;FCTAMMC:Frequency conversion table aeration machine manual conversion; FCTAMMO:Frequency conversion table aeration machine motor overloaded;1 #PO:1 #Propeller operation ; 1 #PMO:1 # Propeller motor overloaded;1 #PCC:1 #Propeller control conversion; 2#PO:2# Propeller operati

31、on;2#PMO:2#Propeller motor overloaded; 2#PCC:2# Propeller control conversion;3#PO:3# Propeller operation; 3#PMO:3# Propeller motor overloaded;3#PCC:3# Propeller control conversion; 4#PO:4#Propeller operation;4#PMO:4#Propeller motor overloaded; 4#PCC:4#Propeller control conversion;WEWL:Water electric

32、 weir lower; WEWC:Water electric weir cap;EWCC:Electric weir control conversion ; EWMO:Electric weir motor overloaded;1#PAC:1#Propeller automatic control; 2#PAC:2#Propeller automatic control;3#PAC:3#Propeller automatic control; 4#PAC:4#Propeller automatic control;WEWR:Water electric weir rise; WEWD:

33、Water electric weir down;IFTAMSAC:Industrial frequency table aeration machine soft and automatic control;30HZFCTAMSAC:30HZ frequency conversion table aeration machine soft and automatic control; ORP MI:ORP Measuring instrument;40HZFCTAMSAC40HZ frequency conversion table aeration machine soft and aut

34、omatic control; DO MI:DO Measuring instrument;30HZFCTAMSAC:30HZ frequency conversion table aeration machine soft and automatic control; PH MI:PH Measuring instrument;FMI:Flow measuring instrument; LMI:Level measuring instrument;MLSS MI:MLSS Measuring instrument;IV、THE SOFTWARE DESIGN OF OXIDATION DI

35、TCH PROCESS SECTION PLC CONTROL STATIONIn the oxidation ditch process, the control station is mainly responsible for data acquisition and monitoring of table aeration machine, propeller, water electric weir and apparatus.In the oxidation ditch process, we install two table aeration machines, one of

36、which adopts Frequency conversion control, four propellers and a water electric weir. All devices can realize local control, remote control and automatic control. We install DO meter, PH meter and ORP meter, whose data are sent to the PLC in the form of the 4-20 mA standard signal. The oxidation dit

37、ch process is to absorb and decompose the matter in the sewage through the metabolism ofmicroorganism. Since the concentration of dissolved oxygen hasdirect influence on biological activity, it is of great importance to keep an appropriate dissolved oxygen level of the filter ditch. According to pre

38、vious experience, when the dissolved oxygen level remains at 1.0 -2.0 mg/L, the biological activity is the largest and the treatment effect is the best 11. DO meter transmits the dissolved oxygen to PLC in the form of standard electrical signal. Based on DO value, PLC adjusts the speed of the table

39、aerator machine by regulating the frequency of inverter, thereby controlling the concentration of dissolved oxygen in oxidation ditch 12. The DO control flow chart of Frequency conversion table aeration machine is shown in figure7. Figure 7frequency conversion table aeration machine DO value control

40、 flow chart wayFlow meter transmits the flow of water to PLC in theform of standard electrical signal and based on the flow data,PLC controls the start/stop of the propeller so as to keep thevelocity above 0.3 m/s.V、THE DESIGN AND REALIZATION OF KING VIEW MONITORING SYSTEMWith the technology of soft

41、 measurement, data measured by DO meter, PH meter and ORP meter are sent to PLC in the form of standard electrical signal, and then PLC will control the rise and fall of water electric weir based on the estimation of BOD5. After confirming the framework of control system and the scheme of hardware c

42、onfiguration in the stage of craft, the human-machine interface used to monitor the real time device status and parameters of Oxidation Ditch craft section is designed by the use of KingVIEW6.53 developmentenvironment, combined with the technology of database, command language, equipment, and system

43、 configuration. Its specific functions include: oxidation ditch process interface, operating parameters and settings, real-time and historical data query, alarm, operating authority, etc. Operators can not only learn the device operating parameters, status, alarms, real-time data display directly th

44、rough interface, but also can set up and operate parameters for the locale equipment.VI、CONCLUSIONSWith this design of the control system, it can make water index meet the demand of the second level of China's sewage discharge standard stably, guarantee devices operate stably and reliably. Meanw

45、hile, the system can be used easily and maintained conveniently. It greatly reduce the workload and labor intensity of operators, improve the utilization efficiency of energy and equipment, solve the problem that equipments in the sewage treatment plant are distributed, complex and difficult to cont

46、rol, achieve energy conservation and reduce energy consumption as well; which provides a theoretical reference for the design of urban sewage treatment system inthe future. Wastewater treatment process is a complex, nonlinear, uncertain and time-varying process, so the real-time on-line detection of

47、 water quality parameters has increasingly become a prominent problem. The use of soft measurement technology for real-time on-line detection can be a good way to solve this problem 1314. In order to overcome the errors caused by inaccurate model, uses the advanced intelligent control system will be

48、come effective means. PLC is a controller in the DCS, it plays the role of Upload issued, the FieldBus-coexist and the locale equipments are supported different agreement to make the interchangeability poor. The PLC communication module will be attached more and more importance by automation manufac

49、turers 15. With the rapid development of network technology and enterprise's request for the interchangeability of locale equipment, we must cater to the market. Therefore, in the future development of DCS, Ethernet technology extension into the industrial control field device layer will become

50、the trend 16.REFERENCES1 Bin Chen, Yuannong Li. Yang ling vocational technology collegeJ.Journal of shallow city the rationaluse of water resources and management,2009(3:28-29.2Yakun technology KingVIEW 6.53.3 Kaijun Wang, LiminJia.Wastewater treatment new technology development and application M.Beiji