PLC 22 WETLANDS & NITRIFYING BIO TOWERS SCADA SYSTEM OPERATION MANUAL. Revision 1.0 May 30, 2006

Transcription

1 PLC 22 WETLANDS & NITRIFYING BIO TOWERS SCADA SYSTEM OPERATION MANUAL Revision 1.0 May 30, 2006

2 PLC 22 WETLANDS & NITRIFYING BIO TOWERS SCADA SYSTEM OPERATION MANUAL Revision 1.0 May 30, 2006 Table of Contents 1 Introduction Revision History PLC System Overview Conventions Set Points and Process Values Equipment Colors Line sizes and colors Instrument Bubbles New Control Strategies PLC 22 Wetlands Pump Station Wetlands Flow Control Wetland Pump Station Biotowers Recycle Pump Station Nitrifying Biotowers Dewatering Pumps Effluent Turbidity Alum Mixer Alum Feed Tank Alum Pumps Chlorination System Sample SCADA Screens Wetlands Inlet Modulating Valve Typical Transmitter May 30, 2006 Rev. 1.0 PLC 22 Wetlands & Nitrifying Bio Towers SCADA System Operation Manual Page 1

3 6.4 Wetland Set Points Wetlands Pump Station Variable Speed Pump Wetland Pump Station Control Set Points Wetland Pump Station Flow and Level Alarms Nitrifying Biotowers Overview Nitrifying Biotower Recycle Pump Station Recycle Set Points Recycle Alarm Set Points Biotowers Effluent Dewatering Pump Pop Up Alum Dose Set Points Turbidity and Alum Level Set Points Chlorination Chlorinator Chlorine Dose Set Points Sample Panel View (OIT) Screens Wetlands Inlet Modulating Valve Typical Transmitter Wetlands Pump Station Variable Speed Pump Wetland Pump Station Control Set Points May 30, 2006 Rev. 1.0 PLC 22 Wetlands & Nitrifying Bio Towers SCADA System Operation Manual Page 2

4 PLC 22 WETLANDS & NITRIFYING BIO TOWERS SCADA SYSTEM OPERATION MANUAL Revision 1.0 May 30, Introduction This document presents sample SCADA screens and control logic for the Wetlands, Wetland Pump Station at the Tertiary Treatment Plant of the Stockton Regional Wastewater Control Facility. 2 Revision History The table below shows the history of revisions to this document. Rev. Description By Date 1.0 Issued for customer training Max Hanson/ 30-May-06 Imran Saeed 3 PLC System Overview PLC22 controls the operation of the Wetlands, Wetland Pump Station, Nitrifying Biotowers, Chlorination and Alum Feed System as shown in the Fig-1 below. A touch-screen Operator Interface Terminal (OIT) is connected to one of the Ethernet channels (CH1) on the main PLC rack, for allowing the plant operator to monitor and control the process locally and the same Ethernet channel (CH1) is also communicating to RIO22.1 and RIO22.2 (remote I/O racks) over the fiber optic cable. This PLC is also communicating to the plant main SCADA system fiber optic Ethernet network, through its second Ethernet channel (CH2). Process instrumentation such as pressure, level and flow transmitters and control signals for valves are wired to the digital and analog I/O channels of the PLC. The PLC monitors the process values from its analog and digital input channels. When the control mode is in AUTO, the PLC determines the necessary control outputs for achieving the desired process conditions according to the process set points entered by the operator. In Manual mode the plant operator can control the process by manually entering the values through OIT. PLC22 operation is further explained by the block diagram below (Fig-1). May 30, 2006 Rev. 1.0 PLC 22 Wetlands & Nitrifying Bio Towers SCADA System Operation Manual Page 3

5 RIO Wetlands (Allen Bradley Control Logix - Remote I/O Rack) RIO Chlorination Building (Allen Bradley Control Logix - Remote I/O Rack) PLC 22 Wetlands and Biotower System (Allen Bradley Control Logix - Main PLC Rack) Ethernet Network Communication. Digital I/O Channels Analog I/O Channels Ethernet Network Communication. Digital I/O Channels Analog I/O Channels CPU (Control Logic Processing) Ethernet Network Communicati on. CH1 Ethernet Network Communicati on. CH2 Digital I/O Channels Analog I/O Channels Ethernet (RJ45) Ethernet (RJ45) Ethernet (RJ45) Fiber/Copper Converter FC Fiber optic Fiber/Copper Converter FC Fiber optic OIT (Operator Interface Terminal) Ethernet (RJ45) FC Fiber/Copper Converter Fiber optic Ethernet (RJ45) ETHERNET Switch FC Fiber/Copper Converter Ethernet (RJ45) Ethernet (RJ45) Ethernet (RJ45) Fiber/Copper Converter FC FC Plant Central SCADA Fiber optic ENET Switch ENET Switch VFD VFD VFD Ethernet (RJ45) Ethernet (RJ45) VFD VFD VFD VFD VFD VFD Fig-1; PLC-22 Operation Block Diagram May 30, 2006 Rev. 1.0 PLC 22 Wetlands & Nitrifying Bio Towers SCADA System Operation Manual Page 4

6 4 Conventions 4.1 Set Points and Process Values Set points appear with a black background inset field and white text. Process values will show an inset field with a white background and blue text. Status indicators also have the white inset field, but the foreground color may change depending upon the conditions and the background will turn yellow for abnormal situations. Status Indicator Text Colors: Text Background Meaning Dark Red White Not called, inactive, off Dark Green White Called, active, on Gray White Not ready, unavailable for PLC control Black Yellow Alarm, abnormal condition 4.2 Equipment Colors Symbols for motor-driven equipment are animated with colors to reflect status. Valves symbols are also color-coded. Foreground Red Green Gray Yellow Foreground Red Green Gray Yellow Meaning Not called, inactive, off Called, active, on Not ready, unavailable for PLC control Alarm, abnormal condition Meaning Closed Opened (or called to open if no feedback) Position is uncertain or mid travel Alarm, abnormal condition 4.3 Line sizes and colors Where appropriate, major process lines are shown with 3D pipe symbols and are animated to show when fluid is flowing. Minor process lines are shown with a dark gray background and an animated foreground color. Minor process lines do not have 3D appearance and are smaller. May 30, 2006 Rev. 1.0 PLC 22 Wetlands & Nitrifying Bio Towers SCADA System Operation Manual Page 5

7 Foreground Gray Blue Cyan Yellow Light Green Magenta Pink Light Brown Teal White Dark Brown Meaning No flow is present Plant water Miscellaneous minor process (e.g., scrubbant) Sulfur dioxide Chlorine or sodium hypochlorite Ferric Chloride Polymer Wastewater Storm water Air Sludge 4.4 Instrument Bubbles Many screens will be arranged to show process flow similar to a Process and Instrumentation Diagram (P&ID). Instrument bubbles will show tag names and will have the relevant process value displayed. These bubbles are animated and will turn yellow when an alarm is present at the instrument represented by the bubble. Clicking on the instrument bubble will open the appropriate pop-up screen (note that these symbols are not used for some existing instruments as the PLC logic does not include all the features necessary to support the pop up screen). Note also that bubble type symbols are reserved for transmitters, which have a host of alarm set points associated with them. Discrete devices (e.g., pressure switches) that simply generate a single alarm will trigger a visible alarm indicator when tripped, but do not have a bubble that is visible all the time. 5 New Control Strategies PLCs #22 is new controller that will control operation of new processes at the Tertiary Plant. 5.1 PLC 22 Wetlands Pump Station Wetlands Flow Control Two valves are used to control flow into each wetland. Valves FV and 102 are modulating valves that will actuate to achieve a desired flow rate into each wetland. Each valve s position is controlled by a 4-20mA signal from the PLC. The PLC receives signals from a remote switch and a position feedback transmitter. Valves FV and 112 are open / close valves that are used when the desired flow rate is too great for the modulating valve. These valves feature limit switches to indicate fully opened or fully closed status. In the discussions below, x in a tag name will be 1 for the north wetland and 2 for the south wetland. May 30, 2006 Rev. 1.0 PLC 22 Wetlands & Nitrifying Bio Towers SCADA System Operation Manual Page 6

8 Flow Measurement An ultrasonic flow meter, FIT-40-10x, will measure the influent flow rate to each wetland. The PLC will receive this measurement in the form of a 4-20mA signal. High-high, high, low and low-low alarms are provided with adjustable set points. The low and low-low alarms will only be enabled when an inlet valve is open. A transmitter fail alarm is posted when the signal is out of range. All these alarms have a common delay set point. All alarms for the instrument are disabled by a common disable selector. A resettable flow total is calculated by the PLC in millions of gallons Flow Control Loop A proportional and integral (PI) loop will be used to control the inlet flow rate for each wetland. The output from the algorithm will be used to control the modulating valve, FV-40-10x. The loop may also be placed in manual control so that a fixed output can be used. If the desired flow rate is too high for the modulating valve, the full-flow valve, FV-40-11x, will be manually opened from the SCADA and the modulating valve will continue to control the flow rate by varying the amount added to the fluid flowing through the full flow valve Flow Control Valves Operating Modes MANUAL the operator enters the valve position command. AUTOMATIC The valves modulate to maintain the desired flow rate into each wetland Monitoring SCADA and OIT displays will show local / remote, ready, limit switch and position status information. A valve fail to open alarm will be posted if a valve does not respond to an open command for a delay period. Similarly a fail to close alarm will be posted when a valve fails to respond to a close command. A valve is considered READY if it is in remote mode and has no failure alarms active. Alarms for each valve may be disabled Level Measurement A submersible level transmitter, LIT-40-20x, will measure the water level in each wetland. The PLC will receive this level in the form of a 4-20mA signal. High-high, high, low and low-low alarms are provided with adjustable set points. A transmitter fail alarm is posted when the signal is out of range. All these alarms have a common delay set point. A common disable selector disables all alarms for the instrument Interlocks A high high level alarm in either wetland will cause the inlet valves for that wetland to close. May 30, 2006 Rev. 1.0 PLC 22 Wetlands & Nitrifying Bio Towers SCADA System Operation Manual Page 7

9 5.1.2 Wetland Pump Station The wetland pump station has three pumps that move water from the wetlands to the biotowers. An x in a tag name signifies 1 or 2 in the discussion below Manual Valves and Modes Four manual valves are used to control the destination of the discharge for the pumps. Since the PLC does not receive feedback from these valves, it is necessary for the operator to select the proper mode and inform the PLC of valve positions. Each pump may be selected to feed either biotower, but independent operation is not possible Level Measurement A pair of ultrasonic level transmitters, LIT and LIT , measures the water level in the wetwell. The PLC receives these levels in the form of a 4-20mA signal. High-high, high, low and low-low alarms are provided with adjustable set points. A transmitter fail alarm is posted when the signal is out of range. All these alarms have a common delay set point. A common disable selector disables all alarms for the instrument. Each level instrument has an independent set of alarms and set points. A selector allows an operator to choose which transmitter will be used for control. If the selected transmitter fails, the alarms from the backup transmitter will protect the pumps Flow Measurement A magnetic flow meter, FIT-42-30x, measures the discharge flow rate to each biotower. The PLC receives this measurement in the form of a 4-20mA signal. High-high, high, low and low-low alarms are provided with adjustable set points. The low and low-low alarms will only be enabled when a pump is running and feeding that biotower. A transmitter fail alarm is posted when the signal is out of range. All these alarms have a common delay set point. A common selector disables all alarms for the instrument. A resettable flow total is calculated by the PLC in millions of gallons Flow Control Flow Target MGD = 1 + ( Level - Desired ) in Max. Trim % 2 in x 100 x ( FI FI ) MGD Pump Control The operator selects the active wetland pumps by selecting a mode for each pump. The applicable modes are: May 30, 2006 Rev. 1.0 PLC 22 Wetlands & Nitrifying Bio Towers SCADA System Operation Manual Page 8

10 Offline Feeds Biotower 1 Feeds Biotower 2 Feeds both Biotowers Operating Modes MANUAL The pump starts and stops in response to pushbuttons. Speed may be set from the operator interface. AUTOMATIC The pump starts and stops in response to system operating conditions. Speed is controlled by the level/flow control loop Monitoring The following status points are monitored and displayed on the operator interface. REMOTE VFD is set for remote (PLC) control rather than local keypad control. READY Pump is ready for PLC control (in remote and not failed) FAULT VFD is reporting a fault condition. FAIL Either a fault has been present for a delay time or the VFD did not return a running status after being called for a delay period. RUNNING Motor is running. CALLED VFD is called to run by the PLC. SPEED COMMAND The speed requested by the PLC (%). SPEED Actual speed at which the VFD is operating (%). CURRENT Current output of the VFD to the motor (Amps). RUNTIME Reported in tenths of an hour Interlocks In automatic mode, the selected wetland pumps will start when the selected level exceeds a start set point for a time delay. They will continue to run until the level falls below a stop set point for the same delay period. A low low level alarm for either transmitter will stop the pumps. A pump failure alarm is triggered if a VFD faults or fails to run when called to do so. This alarm latches until reset by an operator. A pump will not be called if it has failed Biotowers Recycle Pump Station The recycle pump station includes 4 pumps and two wetwells. Although the wetwells may be joined by operating a manual gate, each wetwell and pair of pumps is generally associated with one biotower. In the discussions below, an x in a tag number represents the number of the biotower. May 30, 2006 Rev. 1.0 PLC 22 Wetlands & Nitrifying Bio Towers SCADA System Operation Manual Page 9

11 Manual Valves and Modes Three manual valves are used to control the destination of the discharge for the pumps. Five manual gates connect the biotower effluent and recycle wetwells. Since the PLC does not receive feedback from these valves and gates, it is necessary for the operator to select the proper mode and inform the PLC of valve positions Parallel Operation In normal operation, the biotowers function in parallel. A gate isolates the two recycle wetwells and the effluent channels are connected to the recycle wetwells. Effluent gates for both towers are open. Manual valves are aligned so that flow from each pair of recycle pumps goes to the associated biotower. In automatic mode, recycle pump speeds will vary to maintain a minimum total hydraulic loading for each biotower Series Operation In series operation, effluent from one biotower is fed into the other. The gate between the recycle wetwells is opened and one of the two level transmitters is selected for control. The second will act as a backup for alarms. The effluent gate for the lead biotower is closed so that all of its effluent flows into the recycle wetwell. The recycle gate for the lag biotower is closed so that all of its effluent goes to the Raw Water Pump Station. Manual valves are aligned so that the discharge from all 4 recycle pumps flows to the lag tower. All four pumps may be required to keep up with the larger wetland pumps. Recycle pump speeds vary to hold a level set point in the combined recycle wetwell Level Measurement A pair of ultrasonic level transmitters, LIT-45-20x, will measure the water levels in the wetwells. The PLC will receive these levels in the form of 4-20mA signals. High-high, high, low and low-low alarms are provided with adjustable set points. A transmitter fail alarm is posted when the signal is out of range. All these alarms have a common delay set point. A common disable selector disables all alarms for the instrument. Each level instrument has an independent set of alarms and set points. A selector allows an operator to choose which transmitter will be used for control when the biotowers are operating in series mode. If the selected transmitter fails, the alarms from the backup transmitter will protect the pumps Flow Control The recycle flow rates are controlled by varying the speed of the operating recycle pumps. Note that recycle flow rates are not measured directly; the total influent flow rate to each tower is used to control the recycle pumps Parallel Mode In parallel mode, each pair of recycle pumps is dedicated to its associated tower. The active pump(s), selected by the operator, will start when the wetland pump station flow rate to the biotower falls below an adjustable set point for a delay period. The pump(s) will run until this flow rate May 30, 2006 Rev. 1.0 PLC 22 Wetlands & Nitrifying Bio Towers SCADA System Operation Manual Page 10

12 exceeds a stop set point for the delay period. While operating, pump speed will vary to maintain a minimum total hydraulic loading (THL) for the tower. This THL set point is adjustable. THL gpm sf x 6889π sf Flow Target MGD = gpm MGD Flow Target MGD = THL x Series Mode In series mode, all the active recycle pumps will vary theirs speeds to maintain a level set point in the wetwell Pump Control The operator selects the active recycle pumps Operating Modes MANUAL The pump starts and stops in response to pushbuttons. Speed may be set from the operator interface. AUTOMATIC The pump starts and stops in response to system operating conditions. Speed is controlled by the flow or level control loop Monitoring The following status points are monitored and displayed on the operator interface. REMOTE VFD is set for remote (PLC) control rather than local keypad control. READY Pump is ready for PLC control (in remote and not failed) FAULT VFD is reporting a fault condition. FAIL Either a fault has been present for a delay time or the VFD did not return a running status after being called for a delay period. RUNNING Motor is running. CALLED VFD is called to run by the PLC. SPEED COMMAND The speed requested by the PLC (%). SPEED Actual speed at which the VFD is operating (%). CURRENT Current output of the VFD to the motor (Amps). RUNTIME Reported in tenths of an hour. May 30, 2006 Rev. 1.0 PLC 22 Wetlands & Nitrifying Bio Towers SCADA System Operation Manual Page 11

13 Interlocks In automatic mode, the active recycle pumps will start when the level exceeds a start set point for a time delay. They will continue to run until the level falls below a stop set point for the same delay period. A low low level alarm will stop the pumps. A pump failure alarm is triggered if a VFD faults or fails to run when called to do so. This alarm latches until reset by an operator. A pump will not be called if it has failed Nitrifying Biotowers The biotowers feature mechanical rotary distributors and four fans. The distributors are variable speed and can be used to maintain a desired instantaneous hydraulic application rate (SpülKraft or SK factor), calculated in inches per pass. Each biotower is controlled by an individual On/Off button. Once a tower is selected to run, the fans will start sequentially and the distributor will begin turning. In the discussion below, an x in a tag number refers to the number of the biotower Flow Measurement A magnetic flow meter, FIT-45-31x, will measure the influent flow rate to each biotower. The PLC will receive this measurement in the form of a 4-20mA signal. High-high, high, low and low-low alarms are provided with adjustable set points. The low and low-low alarms will only be enabled when a pump is running and feeding that biotower. A transmitter fail alarm is posted when the signal is out of range. All these alarms have a common delay set point. A common selector disables all alarms for the instrument. A resettable flow total is calculated by the PLC in millions of gallons Rotary Distributor The rotary distributor spreads influent water over the top of the biotower packing. In automatic mode, the speed of the distributor varies to maintain the instantaneous hydraulic application rate, or SK factor. Distributor speed is displayed in minutes per revolution. The operator enters two target SK factors. The normal value should be lower than the flush value. The flushing SK factor is used for a brief flushing period during which the distributor slows down and the media is exposed to a higher shear force. This is intended to slough off excess biofilm. The tower will flush for an operator-entered duration in minutes on an operator-entered interval measured in hours. FI-45-31x MGD x Speed min SK in pass = rev x gpm MGD 4 x 6889π sf x in 1 gal sf May 30, 2006 Rev. 1.0 PLC 22 Wetlands & Nitrifying Bio Towers SCADA System Operation Manual Page 12

14 Distributor Control SK in pass = FI-45-31x x Speed Target Speed min rev = Target SK x FI-45-31x Operating Modes MANUAL The distributor starts and stops in response to pushbuttons. Speed may be set from the operator interface. AUTOMATIC The distributor starts and stops in response to tower operating conditions. Speed is controlled by the SK control loop Monitoring The following status points are monitored and displayed on the operator interface. REMOTE VFD is set for remote (PLC) control rather than local keypad control. READY Distributor is ready for PLC control (in remote and not failed) FAULT VFD is reporting a fault condition. FAIL Either a fault has been present for a delay time or the VFD did not return a running status after being called for a delay period. RUNNING Motor is running. CALLED VFD is called to run by the PLC. SPEED COMMAND The speed requested by the PLC (%). SPEED Actual speed at which the VFD is operating (%). CURRENT Current output of the VFD to the motor (Amps). RUNTIME Reported in tenths of an hour Fan Control The process air fans operate whenever the biotower is running Operating Modes MANUAL The fan starts and stops in response to pushbuttons. AUTOMATIC The fan starts and stops in response to tower operating conditions. May 30, 2006 Rev. 1.0 PLC 22 Wetlands & Nitrifying Bio Towers SCADA System Operation Manual Page 13

15 Monitoring The following status points are monitored and displayed on the operator interface. REMOTE Starter is set for remote (PLC) control rather than local switch control. READY Fan is ready for PLC control (in remote and not failed) FAIL The starter did not return a running status after being called for a delay period. RUNNING Motor is running. CALLED Starter RUNTIME Reported in tenths of an hour Interlocks A motor failure alarm is triggered if a VFD faults or fails to run when called to do so. This alarm latches until reset by an operator. A motor will not be called if it has failed Dewatering Pumps The dewatering pumps are used to drain the effluent wetwell for biotower maintenance Level Control A low level switch serves to stop the dewatering pump Pump Control Operating Modes MANUAL The pump starts and stops in response to pushbuttons. A low level alarm will also stop it. There is no automatic mode Monitoring The following status points are monitored and displayed on the operator interface. REMOTE On/Off/Remote switch is set for remote (PLC) control. READY Pump is ready for PLC control (in remote and not failed) FAIL The starter did not return a running status after being called for a delay period. RUNNING Motor is running. CALLED Starter is called to run. RUNTIME Reported in tenths of an hour. May 30, 2006 Rev. 1.0 PLC 22 Wetlands & Nitrifying Bio Towers SCADA System Operation Manual Page 14

16 Interlocks A pump failure alarm is triggered if a starter fails to run when called to do so. This alarm latches until reset by an operator. A pump will not be called if it has failed. A level switch monitors level in the effluent wetwell. A pump will stop in the event of a low level alarm Effluent Turbidity Sample Pump The sample pump is not controlled by the PLC, however, the PLC receives a run signal from it; status is displayed on the SCADA system. Runtime is also calculated for the pump Turbidity Measurement A turbidimeter, AIT , will measure the effluent turbidity. The PLC will receive this measurement in the form of a 4-20mA signal. Highhigh, high, low and low-low alarms are provided with adjustable set points. A transmitter fail alarm is posted when the signal is out of range. All these alarms have a common delay set point. A common selector disables all alarms for the instrument Alum Mixer The mixer, ME45-801, blends alum into the effluent of the nitrifying biotowers Operating Modes MANUAL The mixer starts and stops in response to pushbuttons. AUTO The mixer starts when the alum pumps are required to run Monitoring The following status points are monitored and displayed on the operator interface. REMOTE On/Off/Remote switch is set for remote (PLC) control. READY Pump is ready for PLC control (in remote and not failed). FAIL The starter did not return a running status after being called for a delay period. RUNNING Motor is running. CALLED Starter called to run. RUNTIME Reported in tenths of an hour. May 30, 2006 Rev. 1.0 PLC 22 Wetlands & Nitrifying Bio Towers SCADA System Operation Manual Page 15

17 Interlocks A motor failure alarm is triggered if a starter fails to run when called to do so. This alarm latches until reset by an operator. A motor will not be called if it has failed Alum Feed Tank Level Measurement An ultrasonic level transmitter, LIT , will measure the alum level in the feed tank. The PLC will receive this level in the form of a 4-20mA signal. High-high, high, low and low-low alarms are provided with adjustable set points. A transmitter fail alarm is posted when the signal is out of range. All these alarms have a common delay set point. A common disable selector disables all alarms for the instrument Feed Tank Fill Control When the level in the feed tank falls below a start fill set point for a time delay, the fill valve will open. It will remain open until the level exceeds a stop fill set point for the time delay Alum Feed Valve Operating Modes MANUAL The valve opens and closes in response to pushbuttons. AUTOMATIC The valve opens and closes in response to tank fill control needs Monitoring The following status points are monitored and displayed on the operator interface. REMOTE Local/Remote switch is set for remote (PLC) control. READY Valve is ready for PLC control (in remote and not failed) FAIL The valve did not respond to an open or close command for a delay period. POSITION Opened, Closed or Middle according to limit switch signals. CALLED Called to open or called to close Alum Pumps Variable-speed chemical pumps are used to dose the biotower effluent upstream of the dual media filters. May 30, 2006 Rev. 1.0 PLC 22 Wetlands & Nitrifying Bio Towers SCADA System Operation Manual Page 16

18 Dose Calculation The operator enters a desired alum dosage in mg/l. The operator also enters the concentration and specific gravity of the alum solution in the feed tank. The dose rate is calculated by flow pacing based on the total wetland pump station discharge flow rate. Dose mg L x ( FI FI ) MGD Total Target Alum Flow gpm = 14.4 x Concentration % x Specific Gravity The total target chemical flow is divided by the number of pumps that are operating to determine a target for each pump. The target chemical flow is converted to a speed command by linear interpolation over a 5-point calibration curve. Calibration values for each pump are entered at the Panelview Operator Interface Pump Control Typically only one pump is required. Any pump that is in automatic will run when the wetland pumps are running. If two alum pumps are operating, the chemical flow will be split between them Operating Modes MANUAL The pump starts and stops in response to pushbuttons. Speed may be set from the operator interface. AUTOMATIC The pump starts and stops in response to system operating conditions. Speed is controlled by the dose control loop Monitoring The following status points are monitored and displayed on the operator interface. REMOTE SCR is set for remote (PLC) control rather than local control. READY Pump is ready for PLC control (in remote and not failed) FAULT SCR is reporting a fault condition. FAIL Either a fault has been present for a delay time or the SCR did not return a running status after being called for a delay period. RUNNING Motor is running. CALLED Pump is called to run by the PLC. SPEED COMMAND The speed requested by the PLC (%). SPEED Actual speed at which the SCR is operating (%). RUNTIME Reported in tenths of an hour. May 30, 2006 Rev. 1.0 PLC 22 Wetlands & Nitrifying Bio Towers SCADA System Operation Manual Page 17

19 Chlorination System Chlorine is introduced to the treated wastewater in the chlorine contact channel for disinfection purposes. Existing gas chlorinators are used to control the rate of chlorination. These existing devices will be wired to PLC 22 and controlled by logic in PLC 23. Output commands will be relayed between the PLCs over the fiber Ethernet network Chlorine Dose Chlorine dose rate is controlled by a compound loop. The primary loop is flow pacing based on the total wetland pump station flow rate. A trim factor adjusts the output of the flow pacing loop as a PID controller tries to control the residual chlorine in the contact channel. Flow Pacing: Chlorine Feed Rate lbs day = lb x L mg x MG Residual Chlorine Controller Trim: Trim factor = 1 + Final Target Chlorine Feed Rate: Max Trim % 100 x ( ) x Dose mg L PID Output 50 % 50 MG x (FI FI ) day Final Target Chlorine Feed Rate lbs day = Flow Pacing Chlorine Feed Rate lbs day x Trim Factor Chlorinator Control The chlorinators accept a 4-20mA signal to control the position of a variable orifice used to regulate chlorine gas flow. They also transmit a 4-20mA signal proportional to the actual gas flow rate. The PLC does not receive any signals that indicate if a chlorinator is online or not. The PLC needs this information in order to calculate the correct target flow rate for each chlorinator. An operator must click pushbuttons on the SCADA or operator interface to indicate which chlorinators are in service. The PLC will then divide the final target chlorine feed rate by the number of chlorinators in service and use the resulting feed rate for each. AUTOMATIC The operator clicks the On/Off control to indicate the chlorinator is in service. The PLC uses a PI controller to vary orifice position in order to control the feed rate to the calculated target. MANUAL FLOW If the flow target is placed in manual, the PLC will continue to use control the valve position, but the operator enters the target feed rate for the chlorinator directly. May 30, 2006 Rev. 1.0 PLC 22 Wetlands & Nitrifying Bio Towers SCADA System Operation Manual Page 18

20 MANUAL POSITION If position control is placed in manual, the operator can control the orifice position command directly. 6 Sample SCADA Screens Sample screens for PLC 22 follow. These are the screens that will appear on the plant SCADA system. Screens with similar function and design are configured on the local Panelview operator interface and are shown in section 7 of this document. Please note that no process data was present when these screens were generated. This means that process values will show zero and it is operating scenarios that are not actually possible may be shown. May 30, 2006 Rev. 1.0 PLC 22 Wetlands & Nitrifying Bio Towers SCADA System Operation Manual Page 19

21 6.1 Wetlands Inlet The Wetlands Screen presents data about the flow and level in the wetlands influent structure. Flow rate is reported for each wetland and status is shown for the valves that control the flows. May 30, 2006 Rev. 1.0 PLC 22 Wetlands & Nitrifying Bio Towers SCADA System Operation Manual Page 20

22 6.2 Modulating Valve This is an example pop up display for a modulating valve without limit switches and with analog position feedback. In manual mode, the operator can adjust the position command. May 30, 2006 Rev. 1.0 PLC 22 Wetlands & Nitrifying Bio Towers SCADA System Operation Manual Page 21

23 6.3 Typical Transmitter Clicking an instrument bubble opens a transmitter Pop Up. This screen presents alarm set points and status. May 30, 2006 Rev. 1.0 PLC 22 Wetlands & Nitrifying Bio Towers SCADA System Operation Manual Page 22

24 6.4 Wetland Set Points This screen presents alarm and control set points for the wetlands. May 30, 2006 Rev. 1.0 PLC 22 Wetlands & Nitrifying Bio Towers SCADA System Operation Manual Page 23

25 6.5 Wetlands Pump Station This screen shows the wetland pump station that feeds the biotowers. Status for the 3 pumps is shown graphically and in the table at the bottom. Status indication for the manual valves follows pump discharge destination selections. May 30, 2006 Rev. 1.0 PLC 22 Wetlands & Nitrifying Bio Towers SCADA System Operation Manual Page 24

26 6.6 Variable Speed Pump Clicking the status box for a wetland pump opens the variable speed pump pop up. In manual mode, the operator starts and stops the pump and controls the speed directly. May 30, 2006 Rev. 1.0 PLC 22 Wetlands & Nitrifying Bio Towers SCADA System Operation Manual Page 25

27 6.7 Wetland Pump Station Control Set Points This screen presents some control set points for the wetland pump station. The cascade loop that controls pump speed is spelled out here. Both contributing loops can be placed in manual. Near the bottom of the screen is the place where an operator enters the modes for the pumps. These modes are related to the position of the manual valves. The manual valve indicators are just used for display purposes. The modes are used to control the pumps. Any pump that is assigned to a tower will run when the tower is on. In normal operation, one of the three pumps will be set to offline. May 30, 2006 Rev. 1.0 PLC 22 Wetlands & Nitrifying Bio Towers SCADA System Operation Manual Page 26

28 6.8 Wetland Pump Station Flow and Level Alarms This screen presents flow and level set points. It includes alarm set points as well as start and stop levels. The active level transmitter is selected from this screen. May 30, 2006 Rev. 1.0 PLC 22 Wetlands & Nitrifying Bio Towers SCADA System Operation Manual Page 27

29 6.9 Nitrifying Biotowers Overview This screen presents an overview of the biotowers. It shows status for the wetland pumps, recycle pumps, biotowers, alum pumps and sample pump. May 30, 2006 Rev. 1.0 PLC 22 Wetlands & Nitrifying Bio Towers SCADA System Operation Manual Page 28

30 6.10 Nitrifying Biotower This screen presents set points and status for a biotower. Status is shown for all four fans and the rotary distributor. Set points for the SK factor, flush interval and duration and minimum THL are presented on the right. The biotower may be turned on or off from the button at the lower right. The system mode for the pair of biotowers is also set here. May 30, 2006 Rev. 1.0 PLC 22 Wetlands & Nitrifying Bio Towers SCADA System Operation Manual Page 29

31 6.11 Recycle Pump Station The recycle pump station shows the two wetwells and four pumps. May 30, 2006 Rev. 1.0 PLC 22 Wetlands & Nitrifying Bio Towers SCADA System Operation Manual Page 30

32 6.12 Recycle Set Points The recycle set points screen presents set points for control of the recycle pumps. When the biotowers are in parallel mode, recycle pump start and stop and speed control is based on the flow rate. When the biotowers are in series mode, recycle pumps start and stop and vary speed in response to wetwell level. Active pumps are selected at the bottom of the screen. All active pumps will run when required. May 30, 2006 Rev. 1.0 PLC 22 Wetlands & Nitrifying Bio Towers SCADA System Operation Manual Page 31

33 6.13 Recycle Alarm Set Points This screen shows level set points for the recycle pump station. It also allows selection of the active level transmitter for series operation. May 30, 2006 Rev. 1.0 PLC 22 Wetlands & Nitrifying Bio Towers SCADA System Operation Manual Page 32

34 6.14 Biotowers Effluent This screen shows the status of the nitrifying biotowers effluent systems. May 30, 2006 Rev. 1.0 PLC 22 Wetlands & Nitrifying Bio Towers SCADA System Operation Manual Page 33

35 6.15 Dewatering Pump Pop Up The dewatering pumps are manually operated. Note that NO3 is used as a shorthand abbreviation for Nitrifying in some descriptions. May 30, 2006 Rev. 1.0 PLC 22 Wetlands & Nitrifying Bio Towers SCADA System Operation Manual Page 34

36 6.16 Alum Dose Set Points The flow rate of alum is calculated from a desired dose and the teritary plant flow rate (total wetland pump station flow rate). May 30, 2006 Rev. 1.0 PLC 22 Wetlands & Nitrifying Bio Towers SCADA System Operation Manual Page 35

37 6.17 Turbidity and Alum Level Set Points This screen presents turbidity alarm set points and alum level set points. May 30, 2006 Rev. 1.0 PLC 22 Wetlands & Nitrifying Bio Towers SCADA System Operation Manual Page 36

38 6.18 Chlorination This screen shows a block diagram of the chlorinators. May 30, 2006 Rev. 1.0 PLC 22 Wetlands & Nitrifying Bio Towers SCADA System Operation Manual Page 37

39 6.19 Chlorinator This is a pop up window for a chlorinator. In this example, the chlorinator is active and it is in manual flow mode and automatic position mode. May 30, 2006 Rev. 1.0 PLC 22 Wetlands & Nitrifying Bio Towers SCADA System Operation Manual Page 38

40 6.20 Chlorine Dose Set Points The chlorine dosing screen allows an operator to change parameters used to calculate the chlorine feed rate. May 30, 2006 Rev. 1.0 PLC 22 Wetlands & Nitrifying Bio Towers SCADA System Operation Manual Page 39

41 7 Sample Panel View (OIT) Screens Sample screens for local Panel view operator interface for the Wetlands Pump Station follow. The function of these screens is exactly similar to the SCADA screens explained above in section 6. These are the screens that will appear at the plant Operator Interface Terminal (OIT) at PLC #22. Please note that no process data is present in these screens and these were generated during the offline development. May 30, 2006 Rev. 1.0 PLC 22 Wetlands & Nitrifying Bio Towers SCADA System Operation Manual Page 40

42 7.1 Wetlands Inlet The North Wetland Screen presents data about the flow and level in the north wetlands influent structure. Its function is similar to the SCADA screen explained in section 6.1. May 30, 2006 Rev. 1.0 PLC 22 Wetlands & Nitrifying Bio Towers SCADA System Operation Manual Page 41

43 7.2 Modulating Valve This is an example pop up display for a modulating valve without limit switches and with analog position feedback. In manual mode, the operator can adjust the position command. Its function is similar to the SCADA screen explained in section 6.2. May 30, 2006 Rev. 1.0 PLC 22 Wetlands & Nitrifying Bio Towers SCADA System Operation Manual Page 42

44 7.3 Typical Transmitter Pressing an instrument status display opens a transmitter Pop Up. This screen presents alarm set points and status. Its function is similar to the SCADA screen explained in section 6.3. May 30, 2006 Rev. 1.0 PLC 22 Wetlands & Nitrifying Bio Towers SCADA System Operation Manual Page 43

45 7.4 Wetlands Pump Station This screen shows the wetland pump station that feeds the biotowers. Status for the 3 pumps is shown graphically and in the table at the bottom. Clicking on one of the manual valves allows an operator to change the indicator for that valve. Its function is similar to the SCADA screen explained in section 6.5. May 30, 2006 Rev. 1.0 PLC 22 Wetlands & Nitrifying Bio Towers SCADA System Operation Manual Page 44

46 7.5 Variable Speed Pump Pressing the status box for a wetland pump opens the variable speed pump pop up. In manual mode, the operator starts and stops the pump and controls the speed directly. Its function is similar to the SCADA screen explained in section 6.6. May 30, 2006 Rev. 1.0 PLC 22 Wetlands & Nitrifying Bio Towers SCADA System Operation Manual Page 45

47 7.6 Wetland Pump Station Control Set Points This screen presents some control set points for the wetland pump station. The cascade loop that controls pump speed is spelled out here. Both contributing loops can be placed in manual. Near the bottom of the screen is the place where an operator enters the modes for the pumps. These modes are related to the position of the manual valves. May 30, 2006 Rev. 1.0 PLC 22 Wetlands & Nitrifying Bio Towers SCADA System Operation Manual Page 46