BALLINA WEST INTERIM UPGRADE DAF EFFLUENT TREATMENT PLANT

Transcription

1 BALLINA WEST INTERIM UPGRADE DAF EFFLUENT TREATMENT PLANT FUNCTIONAL SPECIFICATION Issued: February 2007

2 ABBREVIATIONS: A/L ASV CAS DAF HMI MCC MSA NTU P&ID PID PLC R/L SCADA SEPA SP TSS USO UPS UV VFD Air/Liquid Air saturation Vessel Compressed Air System Dissolved Air Floatation Human Machine Interface Motor Control Cabinet Metal Salt Acid Nephelometric Transfer Unit Process & Instrumentation Diagram Proportional Integral Derivative Process logic Control Recycle/Liquid Supervisory Control and Data Acquisition SEPA Waste Water Treatment Pty Ltd Set Point Total Suspended Solids Unless Stated Otherwise Uninterrupted Power Supply Ultra Violet Variable Frequency Device Page 2 of 25

3 1 PREAMBLE 1.1 INTRODUCTION This Functional Specification is for a 100 to 300 m3/hr DAF that was supplied by SEPA Waste Water Pty. Ltd. and completed by the Principal, Ballina Shire Council. 1.2 SUPPORTING DOCUMENTATION This Functional Specification is to be read in conjunction with the following documents: Technical Specification SEPA P&ID DWG s: 7275-P1-001 to 010 Rev N ALLDOS P&ID DWG s: SE2167-P01 Rev A & SE2167-P02 Rev C Valve schedule Data sheets Item schedule Pump schedule Instrument schedule 1.3 ELECTRICAL & CONTROL Electrical Supply is: 415V, 50Hz USO 1.4 ASSUMPTIONS & PRECONDITIONS It has been assumed that the following applies: Values and SP settings stated herein are mostly for clarity of communication. They are the initial settings during commissioning and therefore subject to review/change. Page 3 of 25

4 1.5 DESIGN CRITERIA The following design criteria have been adopted: Material of Construction As Specified, if NS then Material Compatibility Tables All control via PLC and SCADA All flow switches designated FS xxx will have PLC timed delay of no less than 3 seconds. They are intended to prevent premature trips. The values given on the P&ID s are suggested values for start-up/commissioning and my need to be re-considered. All solenoid valves have manual by-pass valves. 1.6 SCADA System SCOPE Remote monitoring of the Waste Water Treatment process from Amenities building at site; with mimic screens, alarms and trends. (DAF plant HMI is equipped with additional features in setting process variables and trouble shooting). Starting of the DAF plant from SCADA. This SCADA is run on a computer that is part of the fibre optic plant network. SYSTEM ARCHITECTURE Citect SCADA interacts with the DAF plant Omron PLC to monitor or perform limited control of the DAF. Citect Version 6.0 runs in the computer at the Amenities building for the SCADA task. SCADA SCREENS The following mimic screens are designed: Lagoon Reaction Tank DAF Chemical Dosing MSA System Page 4 of 25

5 Recycle System Sludge System Treated Water UV Plant RTU Utilities The following trend screens are designed: DAF Chemical use Recycle Reuse The following alarm screens are designed: Current alarms Alarm summary Hardware alarms Other screens are for the following: Reports Login Logout Citect SCADA (overall Citect main menu screen) Navigation top the relevant screen is possible from the screen being viewed. SCADA MIMIC SCREEN OBJECT DEFINITIONS Object like motors, pumps have the following interpretation for the graphic displays: Green running Blue stopped Red Fault Analog instrument values are displayed in the process mimic screens. TREND SCREENS The trend screens are multi pen trend recordings. Range of the pen is displayed when selected. Digital display of the selected pen is possible at the time pointed by the vertical cursor line. Adjustment is possible for the time scale. Page 5 of 25

6 ALARM SCREENS Hardware alarm is on the network and communications. Current alarms are against date and time stamping. Following is the colour coding in the alarm messages: White Blue - Existing alarms - Acknowledged alarms Alarm summary are again against date and time stamping. Date and time of arrival of alarm, date and time of alarm acknowledgement, date and time when alarm condition become normal are shown in the alarm summary screen. Acknowledged alarms are shown in green colour. FEATURES Icons in the left help in selecting the screens, to visit the previous screens etc. To alert presence of unacknowledged alarms, the top most entry of alarm is displayed in a common top area viewable from any screen LOGIN AND LOGOUT User name and password are required. If logged in with the required security level, then can acknowledge the alarms. Access to the utilities screen is restricted. 1.7 UPS Configuration The UPS supplies power to the SCADA System and all communications. It is alarmed to notify of the following events: - loss of incoming power - internal fault - bypass mode - battery failure Page 6 of 25

7 1.8 Overall System Alarms To be provided Page 7 of 25

8 2 CONTROL OVERVIEW The primary control requirement is lagoon level to a tolerance of ±30 mm. Variable speed pumps, P101/102 facilitate this via control loop 101. Flow meter FE201 measures the resulting flow for flow paced doing of MSA, polymer & surfactant. ph control is achieved by acid and caustic dosing in accordance with readings from ph probes AE202 & AE203 respectively. FE201 also initiates for Plant wide interlocking for shut down. The surfactant and acid dosing systems utilise the same infrastructure, hence only one of these can be operational at a given time. Acid dosing is unlikely to be used with the current chemistry but has been retained from the initial design to allow for added flexibility. The process control strategy for the DAF recycle is unusually complex, but is necessitated by the continuous turndown demands of the Specification, specifically: DAF flow range from 100 to 300 m3/hr DAF recycle flow~60 to 80m3/hr CAS flows to suit Set Pointed A/L ratio at constant pressure. Sludge pumping is controlled by simple on/off level control All duty/standby pump sets operate on an alternate start up basis. When a selector switch for a pump or motor is in the manual position there is no process protection, only overload protection. Page 8 of 25

9 3 PRE-DAF OPERATIONS Refer to DWG No P1-003/N P&ID LAGOON PUMPING STATION 3.1 LAGOON Treated sewage effluent is discharged to the lagoon. Lagoon water is then treated by the DAF system described in this Functional Specification. 3.2 T101 PUMPWELL T101 Pumpwell is located on the lagoon embankment within 15m of the DAF, which is adjacent to the existing UV Plant. T101 Pumpwell is fitted with a baffle and one manually cleaned mesh screen designed to help prevent ingress of macro-fauna. V309 manual isolation valve provides the sole point of ingress of lagoon water to T101 Pumpwell. T101 Pumpwell is fitted with two variable speed submersible pumps, P101 & P102. They pump lagoon water to the DAF and operate as duty/standby. As with all duty/standby pump sets in this plant they alternately operate on start up. The flow range is from 100 to 300 m3/hr Lagoon Level Control Under normal operating conditions submersible pressure transducer LE101 via LIC101 provides continuous PID control of lagoon level within a tolerance of ±30mm. To negate the effects of waves and ripples on the lagoon surface the PLC will provide appropriate filtering of the transducer signal. Pumpwell pumps P101 & kw motor, 415V, 50Hz, 3phase, VFD Duty Selector Selector for Auto/Off/Test at DAF MCC Mode Selection OFF: No Pumps running TEST: Operates under Maintenance staff control AUTO: The operator will be able to choose from the following AUTO run modes at the HMI: Page 9 of 25

10 Manual Flow an operator set fixed flow set-point entered. VFD s are controlled to achieve the flow value Manual Level An operator set pond level is entered. The VFD s are controlled to maintain this level. Auto DRY flow DAY A set point for flow is set if the pond level is below the DRY level set-point and the current time is specified as DAY Auto DRY flow NIGHT - A set-point for flow is set if the pond level is below the DRY level set point and the current time is specified as NIGHT Auto WET flow DAY A set point for flow is set if the pond level is below the WET level set-point and the current time is specified as DAY Auto WET flow NIGHT A set point for flow is set if the pond level is below the WET level set point and the current time is specified as NIGHT Low low level if the pond level falls below a minimum value the pump speed will be set to zero and the DAF will enter the cleaning phase High high level if the pond level rises above a maximum value the pump speed will be set at 100%. The control will remain in dry flow until the pond level rises above the wet level setpoint when the wet flow will be selected The control will remain in the wet flow until the pond level falls below the dry level set-point when dry flow will be selected. Night shall be defined as between a start time and a finish time as defined by a 24 hour clock. If it is not night it will be day. Manual level will be subject to dead-band about the level set-point to minimise flow variation in the DAF flow. The VFD s will be subjected to a speed ramp of 10 minutes (0-100%). PI104 & PI105 provides local indication of pump performance The following conditions stop the pumps when in AUTO mode: Motor control fuse failure Low level in pumpwell via LSL102 Low level in lagoon via LIC101 No flow signal via FS106 VFD fault Page 10 of 25

11 MCC stop activated Local Isolator in OFF position FAULT CONDITIONS: The following conditions illuminate the fault light when motor is in Auto mode: Motor failure to start or stop Local isolator in OFF position Influent flow meter FIC201 This flow meter monitors the flow through the treatment process from the pumpwell and provides for flow totalisation and signal transmission to the PLC. FIC 201 provides: PID control for: flow paced control of MSA dosing via VFD127/128 flow paced control of the polymer dosing flow paced control of the surfactant dosing Auto mode operation of pumpwell pumps DAF sludge scraper speed via VFD105 DAF recycle water flow rates Pumpwell pumps when in flow control mode Immediate ON/OFF control [i.e. interlock for shut down] of: S108 Stirrer All chemical dosing pumps 20 minute delayed shut down via KC201 for: DAF recycle and aeration system DAF scraper. The 20 minute delay allows for the DAF to shut down in a clean state. This will limit the amount of solids re-suspension that can cause a temporary/immediate TSS spike in DAF effluent upon start-up. Page 11 of 25

12 4 DAF Refer to DWG 7275-P1-004A/N P&ID DAF & REACTION TANK & DWG 7275-P1-004B/N P&ID DAF RECYCLE Reaction Tank Mixer S108 The reaction tank mixer operates on an on/off basis depending on flow detection by flow meter FE kw, 415V, 50Hz, 3phase Duty Selector Selector for Auto/Off/Test at DAF MCC OFF: Motor is off TEST: Operates under Maintenance staff control AUTO: Stirrer starts/stops on signal from flow meter FE201 FAULT CONDITIONS: The following conditions illuminate the fault light when motor is in Auto/Manual mode: Motor failure to start or stop Local isolator in OFF position DAF sludge scraper It has been assumed that higher flows to the DAF will increase sludge production. Accordingly The DAF is fitted with a variable speed scraper. The scraper speed is controlled via FIC201 & implemented by.vfd105 i.e. speed paced. The SP is HMI adjustable. Duty selector Selector for Auto/Off/Manual at DAF MCC OFF: Motor is off TEST: Operates under Maintenance staff control AUTO: Starts when flow is detected in flow meter FE201 Page 12 of 25

13 Continues to operate for 20 minutes (HMI definable) after main feed pumps have been given signal to stop as part of main shutdown i.e. no flow detected in FE201 and signal for shutdown given to rest of plant. FAULT CONDITIONS: The following conditions illuminate the fault light when scraper is in AUTO/MANUAL mode: Motor failure to start or stop Local isolator in OFF position 4.1 DAF recycle P103/104 DAF Recycle Pumps operate as duty/standby. The recycle rate is operator defined via HMI and will typically range from 60 to 80 m3/hr (nominally). The recycle rate SP can be set as flow in m3/hr via FIC207. Note: YA201A enunciates after a 60 second delay when the recycle flow deviates by more than 5% of the Set Point. The delay is operator adjustable via the HMI. FE207 is a mag flow meter. It furnishes the feedback signal for FIC207/FIC201A to provide real-time flow indication [as m3/hr] PID control for the modulating valve V026 to adjust for the required recycle flow. V026 is a motorised modulating butterfly valve. DAF Recycle pumps P103 & P kw motor, 415V, 50Hz, 3phase Duty selector Selector for Auto/Off/Manual at DAF MCC OFF: Motor is off TEST: Operates under Maintenance staff control AUTO: Starts when flow is detected in flow meter FE201 Continues to operate for 20 minutes (HMI definable) after main plant shutdown Immediately stop if high high pressure detected in ASV FAULT CONDITIONS: The following conditions illuminate the fault light when pumps are in Auto/Manual mode: Page 13 of 25

14 Motor failure to start or stop Local isolator in OFF position 4.2 Aeration System Compressed air service (CAS) is provided by 2 compressors, AC106 & AC107. Their operation is controlled by high & low pressure settings within the compressor program. The Compressed air is stored in T204 Air Receiver. The pressure in this vessel can be locally monitored by PI218. A safety pressure relief valve V425 is provided. An automated solenoid drain valve V038 is providing for draining of condensed water and oil. The flow of compressed air to the ASV is controlled by Solenoid valve V040. When V040 closes, after KC minute delayed initiation after plant shutdown, air flow will immediately cease but the air compressor will continue operating i.e. the air compressors work independently of all other systems. To prevent cyclic CAS delivery pressure that would compromise smooth airflow to the ASV, a regulator valve V428 is provided. Its setting is done locally via HC428. Operator defined SP air flow in N.m3/hr is provided via HMI. FE208 is a rotameter that furnishes the feedback signal to FIC208 for modulation of V043. V043 controls the required airflow within a % of ± 10%. This valve is an initial valve suitable for start-up at commissioning. It determination is based on a combination of expected system hystereses, of (approx.) ±3 to 4%, plus (approx.)± 3% for the rotameter measurement with the remaining 3 to 4 % used as a safety factor. Note, it is expected that the large volume of the ASV will attenuate residual oscillations that maybe inherent to the commissioned control strategy. Thereby making the control system s dynamics invisible to the user/operator. 4.3 ASV ASV Pressure Control The operating pressure inside T203 ASV is operator defined via HMI. It is measured by PE209 and controlled by PIC209 via modulating valve V045. If the operating pressure of the ASV exceeds 8 bar the recycle pumps will shut down immediately and an alarm will be raised. Page 14 of 25

15 4.3.2 Multiple ASV & DAF inlets Due to the range in recycle flow the ASV is equipped with 3 inlets. The first one is feed by line 413. It will operate for all flows. When the flow increases above 33m3/hr but less than 66 m3/hr then V047 opens so that line 412 operates in parallel with line 413. When the flow is >66 m3/hr all three lines 413, 412 & 413 are operational. The same control philosophy applies to the aerated recycle streams entering the spin-mixer in the DAF. For flows < 33m3/hr motorised valves V166 & V168 are closed and only line 415 is operational. V166 opens at flows >33m3/hr and V168 at flow >66m3/hr. External limit switches are provided on Valves V046, V047, V166 & V168 to confirm that they have opened and closed to their full limit. There is a 30 second delay to before enunciation of a failed valve position. This is a priority 1 alarm DAF Effluent As partially discussed in section 4.4 Analysis of Turbidity, DAF effluent can be diverted either to the UV Plant via line 403-FPW or the Lagoon if it is noncompliant via 404-WW When effluent quality compliance is met, closing of motorised valve V021 and opening of motorised valve V024, FS 211 initiates a 30 second timed conformation of flow to the UV Plant. Effluent compliance involves meeting both the HMI definable set points for ph (measured by AE204) and turbidity (measured by AE205). Turbidity and ph readings will need to be within the acceptable range for a period of 5 minutes (HMI definable) prior to valve changeover redirecting the stream to the UV plant. If both valves V021 & V024 are in the closed position or either is in fault condition, the main feed pumps are signalled to stop and the plant begins shutdown. Page 15 of 25

16 4.4 Analysis of turbidity DAF effluent turbidity is measured by AE205. A low turbidity event initiates AIC205 to the open V024 and close of V021. This configuration facilitates gravity flow of DAF effluent to the existing UV Plant. A high turbidity event will: Enunciate by AAH205 as a priority 1 alarm. Initiate AIC205 to divert DAF effluent to the Lagoon by opening V021 first & closing V024 second. Performing the operation in this order prevents DAF flooding in the event of a valve failing to open/close correctly. The reverse order applies when compliant effluent is re-established i.e. good-to-go to the UV Plant. Table 1 Typical Turbidity Correlation to TSS (for information only) TSS (mg/l) Turbidity (NTU) comment 10 FIO: < 5 Good quality effluent from DAF Discharge to UV Plant 20 FIO: 5-10 Acceptable quality effluent from DAF Discharge to UV Plant 50 FIO: > 10 Poor quality effluent from DAF. Discharge to Lagoon NB: It is impossible to equate turbidity (NTU) with TSS because we are measuring two completely different things. Notwithstanding, it is still possible to attain useful a correlation that will be subject to varying particle & colour characteristics of the test sample. Accordingly re-calibration needs to be performed as frequently as these characteristics change. Page 16 of 25

17 5 CHEMICAL FACILITIES 5.1 MSA bulk storage Refer to DWG 7275-P1-007/N P&ID MSA BULK STORAGE & TRANSFER T501 MSA Storage tank is located away from the DAF plant. It has three separate/independent level measurement systems/devices: Ultra sonic level measurement via level element LE500 and pump permissive signal for P123/124 via control loop 500. LSHHH506, a hard wired interlock, which provides the third level of protection for MSA storage tank overfilling from the tanker filling point by cutting power to delivery tanker pump. LSLL501 & LSHH501 for on/off control of P123/124 MSA Transfer Pumps in the event of failure of loop 500. Should such an event occur and loop 501 is activated for P123/124 pump control, either YALL501 or YAHH501 will be enunciated as a priority 2 alarm. P123/124 MSA Transfer Pumps have on/off control firstly by loop 500. If that fails loop 501 activates. P123/124 operate on a duty/standby basis with changeover on start-up Pressure relief valves, V712 & V713 provide over-pressure protection of P123/124 pumps. FS504/5 via YC504/5 provide for low flow protection of P123/124 MSA Transfer Pumps. The anti siphon loops in lines 711 & 712-MSA-15-uPVC eliminate the possibility of back-flow to the MSA bulk storage tank. Leak detection in MSA transfer lines Leakage of MSA from the transfer lines can be detected visually in the inspection pits. MSA transfer pumps P123 & P kw motor, 415V, 50Hz, 3phase Duty selector Selector for Auto/Off/Manual at Bulk Storage MCC Page 17 of 25

18 OFF: Motor is off TEST: Operates under Maintenance staff control AUTO: Start when low level in MSA dosing tank, T304, is signalled via LE702 or LSL703 Stop when high level in T304 is signalled via LE 702 or LSH703 Stop when low level in MSA storage tank, T501, is signalled via LE500 or LSLL 501 Stop on no flow signal from FS504 FAULT CONDITIONS: The following conditions illuminate the fault light when pumps are in Auto/Manual mode: Motor failure to start or stop Local isolator in OFF position 5.2 MSA Dosing Refer to DWG 7275-P1-009/N P&ID MSA & ACID DOSING MSA solution will be flow paced dosed from T304 MSA Dosing Tank via P127/128 MSA Dosing pumps utilise internal speed control. FIC201 provides the PID algorithm for automated pump speed control. HC127/128 sets the dose rate manually. Accordingly, for maximum operational flexibility these pumps are best set at the mid-range for stroke. The dose rate is set and controlled by FICQ700. This is HMI definable. The flow is also totalised. P127/128 MSA Doing Pump calibration is achieved via the adjacent calibration cylinder, L705. The Pressure relief valve, V911, in the event of upstream blockage or accidental valve closure, provides for over-pressure pump protection and drains back into tank T304. MSA dosing pumps P127/ kw motor, 415V, 50Hz, 3 phase Duty selector Selector for Auto/Off/Manual at DAF building MCC Page 18 of 25

19 OFF: Motor is off TEST: Operates under Maintenance staff control AUTO: Start when flow is detected by FIC201 Stop when low low level is reached in MSA dosing tank, initiated in the first instance by LE702 with LSLL703 providing backup Stop when no flow is detected in flow meter FM 700, 3 sec delay after pump start 5.3 Surfactant Dosing or Acid Dosing Refer to DWG 7275-P1-009/N P&ID MSA & ACID DOSING Mineral acid can be used for attaining the required ph for coagulation. It will be dosed directly into line 303-WW The dose rate will be controlled by AIC202. Out of range ph will be enunciated by AAL202 & AAH202 for the low & high scenario respectively. The identical above mentioned infrastructure is used for flow paced dosing of the surfactant. Comments given in Section 5.2 MSA Dosing for pump control & protection similarly apply here. Surfactant/Acid dosing pumps P129/ kw motor, 415V, 50Hz, 3 phase Duty selector Selector for Auto/Off/Manual at DAF building MCC OFF: Motor is off TEST: Operates under Maintenance staff control AUTO: Start when signalled by ph meter AE202 or FE201 in the case of the surfactant Stop when low low level is reached in acid/surfactant pallecon, initiated by LSLL704 Stop when no flow is detected in flow meter FM 701, 3 sec delay after pump start initiated Page 19 of 25

20 5.4 Caustic Dosing Caustic will be dosed into the latter part of the reaction tank. It will correct the ph to a value between 6.5 and 8.5. The dose rate will be controlled by AIC203. Out of range ph will be enunciated by AAL203 & AAH203 for the low & high scenario respectively. Comments given in Section 5.2 MSA Dosing for pump control & protection similarly apply here. Caustic dosing pumps P129/ kw motor, 415V, 50Hz, 3 phase Duty selector Selector for Auto/Off/Manual at DAF building MCC OFF: Motor is off TEST: Operates under Maintenance staff control AUTO: Start when signalled by ph meter AE203 Stop when low low level is reached in caustic pallecon, initiated by LSLL801 Stop when no flow is detected in flow meter FM 800, 3 sec delay after pump start initiated ph probe wash system All 3 ph probes will be washed by: timer initiation by KC103 via V161, or out of range event detected by any ph probe and initiated by YC103. This wash cycle will be enunciated by the alarm associated with the ph probe that detects the out of range event. A priority 1 alarm applies. T204 Air Receiver supplies the air power for P133 ph Wash Pump that pumps the wash water to all 3 ph probes. Page 20 of 25

21 5.5 Polymer Facilities Refer to DWG 7275-P1-005N P&ID POLYMER FACILITIES And Alldos DWG s SE2167-P01/A & SE2167-P02/C The Polymer Facilities comprise of: Polymer powder handling & storage Polymer powder dispensing Polymer preparation & aging Polymer transfer to Day Tank Polymer dosing The system is supplied as a complete package by Alldos with process control supplied through the PLC. The polymer dosing pumps are flow paced according to the main influent flow rate via FIC201 The three outputs relayed to the PLC are, polymer system is running, product is available and a fault condition has arisen. Page 21 of 25

22 6 SLUDGE FACILITIES Refer to DWG No P1-006/N SLUDGE TRANSFER Sludge gravitates from T202 DAF Tank to T401 Sludge Tank via pipe 405-SLUD Inside T401 Sludge Tank the sludge is periodically agitated via KC402/KC402A timed controllers. These on/off timer settings are operator defined from HMI. Sludge from the tank is pumped via P120 & P121 Sludge Pumps to either Sludge pond No.1 or Sludge pond No Controls Level control The Ultra Sonic sensor LT403 measures sludge level in T401 Sludge Tank. LSL403 initiates YCL403 to trip P120/121 Sludge Pumps in the event of the tank nearing empty. LSH 403 furnishes a pump start signal for P120/121 sludge pumps. In the event of both pumps being non-operational eg pipe blockage occurs in lines 606-SLUD-DN63-PE and 607-SLUD-DN63-PE, the main feed pumps to the DAF are shut down once the high high alarms have been triggered Stirrer The same signal via YCL403 that trip P120/121 Sludge Pump also trips the operation of S119 Stirrer via the interlock. KC402/A controls the on/off operation of S119 Stirrer. Both run and stop duration are operator defined via HMI Pumps P120/121 Sludge Pumps are protected from line blockage via pressure relief valves V611 & V612. PI404/5 monitors P120 Sludge Pump performance. A pressure build up implies immanent line blockage, flushing/dilution of sludge is required. Similar comment for PI406/7. FQR402 totalises sludge flow and records it. Page 22 of 25

23 6.1.2 Line flushing UV water via P125 RE Water Pump is used for flushing. Selection of sludge pump to aid in the line flushing process and which line is to be flushed is manually determined via Valve V606, V607, V615 & V616 operation Pond selection Selection of the sludge pond No.1 or No.2, for transference of sludge is done manually via valves V605, V608, V615, & V Tank Draining The sludge tank can be drained via line 612-SLUD-100-PVC to floor sump A. Sludge pumps P120 & P kw motor, 415V, 50Hz, 3 phase Duty selector Selector for Auto/Off/Manual at DAF building MCC OFF: Motor is off TEST: Operates under Maintenance staff control AUTO: Start/Stop sinal from ultrasonic level controller 403, level control loop 401 acts as backup Stop when no flow is detected via FM 401, 3 seconds delay from pump start up request Sludge pumps alternate on start up, if one fails the other automatically starts, if both fail a Priority 1 alarm is raised. Sludge tank stirrer S kw motor, 415V, 50Hz, 3 phase Duty selector Selector for Auto/Off/Manual at DAF building MCC OFF: Motor is off TEST: Operates under Maintenance staff control Page 23 of 25

24 AUTO: Start when sludge pump is on Start on 5 min on/ 5 min off basis, HMI definable Page 24 of 25

25 7 RECYCLED WATER FROM UV PLANT Refer to DWG 7275-P1-008/N UV SERVICE WATER Recycled water from the UV plant is stored in tank T205 RE Water Tank. Its level is maintained full by floating ball type valve, V802. P125 RE Water Pump: Performance is monitored via PI601 & PI602 local pressure gauges Pump protection is provided for by Pressure switch PS603 which also initiates pump start once pressure drop has been detected in the line due to opening of Valves downstream. Pressure Accumulator PA606 is an 80litre storage vessel to minimise pump on/off cycling. The UV Makeup Water is used in providing for Polymer dosing line Sludge lines Various non-potable water wash points RE water pump P kw motor, 415V, 50Hz, 3 phase Duty selector Selector for Auto/Off/Manual at DAF building MCC OFF: Motor is off TEST: Operates under Maintenance staff control AUTO: Start when pressure drop has been detected by pressure switch PS603 Stops when pressure reestablishment has been detected by PS603 Stops when LSL 600 has been activated In the event where low level has been detected in the RE water tank the pump will stop and alarm YAL600 will be raised. The start permissive signal to P125 will only be given when YAL600 has been physically reset by the operator. Page 25 of 25