Revision: 1 1/3/14 Turk Pond Treatment System Description Page 1 of 64

Transcription

1 Revision: 1 1/3/14 Turk Pond Treatment System Description Page 1 of 64

2 Revision: 1 1/3/14 Turk Pond Treatment System Description Page 2 of 64

3 Figure 1 - Pond Treatment System Basic Flow Reference Diagram Revision: 1 1/3/14 Turk Pond Treatment System Description Page 3 of 64

4 Turk Pond Water Treatment System Description NOTE: Figure 1 can be referenced to provide an elementary flow path for the Pond Water Treatment System. Additionally the following flow diagrams can be referenced for specific information: Flow Diagram 1-51WW WW PW SW QW QW QW QW QW QW QW QW QW019 Description COAL PILE RUNOFF POND PROCESS WATER POND POTABLE WATER SERVICE WATER LAMELLA SETTLERS THICKENER, FILTER PRESS EFFLUENT TANK, PUMPS BACKWASH, RINSE WATER TANK BACKWASH AND RINSE PIPING MULTI MEDIA FILTERS MULTI MEDIA FILTERS MULTI MEDIA FILTERS FLOCCULENT PUMPS 1. Introduction 1.1. Purpose The coal pile run-off pond (CPRP) and process water pond (PWP) discharge water treatment system is intended to reduce total suspended solids (TSS) to the levels required for discharging to internal outfalls 201 and 101 respectively. This is accomplished through supplemental treatment to achieve the required TSS reductions and simultaneously manage water inventory. The CPRP discharge treatment system consists of coagulation, flocculation, settling through a Lamella clarifier, and finally filtration. The PWP discharge treatment system consists of filtration only. Typical operation of the CPRP is to provide storage (surge) capacity during rain events, such that the treatment system is not overburdened. Routine management of CPRP water levels are to ensure that free storage volume is readily available to hold run-off water from major rain events. Thus CPRP levels must be maintained at as low a level as possible (ideally empty) at all times (when practical) by discharging to the PWP, or when necessary to outfall 201. Therefore utilization of the treatment system at the start of all significant / measurable rain events, providing the required TSS reduction, must be implemented to ensure that the CPRP provides Revision: 1 1/3/14 Turk Pond Treatment System Description Page 4 of 64

5 ample retention for subsequent major rain events and prevents the need for any potential discharge to outfall 002 or exceedences of outfall 201 s TSS limits. Typical operation of the PWP is to supply and store water to and from plant process water users / contributors as needed. The PWP also provides surge capacity, though it is intended to operate as a net consumer of water, without the need for surplus discharge to control pond levels. However should excess PWP influent(s) ultimately require discharge to outfall 101 to manage pond levels; this flow is treated with multi-media filtration (MMF) for TSS removal to prevent exceedences of outfall 101 s TSS limits. The treatment system for both internal outfalls (101 and 201) is combined and share common multi-media filtration equipment that can only be used for treatment of one pond waters at a time. The options to manage CPRP and/or PWP discharge within the treatment system are determined / selected based on several operational factors and provide the functionality to support the three following scenarios: 1) Treatment of CPRP discharge only 2) Treatment of PWP discharge only 3) Simultaneous treatment of both CPRP and PWP discharge Additionally, within these three treatment scenarios, subsequent options exist for the treated effluent location of the pond(s) discharge and/or processing steps. These include the following: Treatment of CPRP discharge only A) For routine management of CPRP levels, CPRP discharge is sent through the Lamella clarifiers followed by multi-media filtration, with the final treated effluent directed into the PWP. This provides a high quality effluent for supplemental PWP make-up while managing CPRP levels. This option is available provided the PWP levels are low enough to accept this effluent. Based upon the overall system design (subsequently described) this treatment option is suggested for CPRP discharge flow rates ranging from 100 to 400 gpm. B) For CPRP discharge treatment rates greater than 400 gpm that are used to supply supplemental make-up water to the PWP; the option available is to send the Lamella effluent directly to the PWP. This is accomplished by a controlled overflow of the Lamella effluent storage tank, which is directed into the PWP. This also provides a relatively high quality make-up water to the PWP, though it may be slightly higher in TSS than a filtered effluent. C) If the level in the PWP becomes/is too high to accept treated CPRP discharge or if a decision is made to select this effluent destination, the treated water can be directed into the make-up water pond (MWP) through outfall 201 to control CPRP levels. With this option the CPRP discharge is treated through the Lamella clarifiers, then the following options are available to send the Lamella effluent to the MWP: a. Further treatment with multi-media filtration, provided the filters are not treating PWP discharge and are available, sending the filtered effluent to outfall 201. This is the recommended treatment for flow rates up to 550 gpm. b. Directing the Lamella effluent storage tank into outfall 201. This option is available if the multi-media filters are unavailable and/or when flow rates exceed 550 gpm. Revision: 1 1/3/14 Turk Pond Treatment System Description Page 5 of 64

6 c. Any flow rate combinations of the two previously described options (a. and/or b.), depending on equipment availability (filters) and/or the total CPRP discharge flow rates required to manage CPRP levels. The two treated effluents are combined prior to the 201 outfall and sent to the MWP. Treatment of PWP discharge only Treatment of surplus PWP discharge is accomplished by multi-media filtration only. A portion of the PWP sump pump discharge is directed through the multi-media filters at a nominal designed flow rate of 300 gpm. Filtered effluent is combined with cooling tower blowdown through outfall 101 and ultimately sent into the waste water pond (WWP). Simultaneous treatment of both CPRP and PWP discharge With simultaneous treatment of both pond discharges; the multi-media filters can only treat discharge from the PWP. Therefore, PWP treatment proceeds as previously summarized, through the multi-media filters into internal outfall 101. Discharge from the CPRP is treated thought the Lamella clarifiers and is pumped from the Lamella effluent storage tank to the MWP through internal outfall 201. The pond treatment system is sized based on historic rain event data to provide an adequate treatment rate, storage volume for routine rain events, and historically frequent major rain events. However, atypical high frequency major rain events may exceed the design flow of the treatment system. These rare instances are outside of the design basis and in order to quickly regain the surge capacity of the CPRP and prevent a discharge to external outfall 002, the CPRP is pumped directly to the MWP, thought internal outfall 201, via the (treatment system) bypass line. If bypassing the CPRP discharge treatment system is necessary, the TSS could be in excess of outfall 201 s permit limits, though a discharge to outfall 002 would be avoided. 2. Design Basis 2.1. CPRP Design Basis and Operation The CPRP is sized to provide storage of rain water run-off from a 25 year rain event, approximately 9 million gallons of water. In order to maintain and restore the pond s storage capacity from routine rain events, two sets of pumps are employed. Normal operation is with two 100% low-flow pumps each rated at approximately 200 gpm, pumping to the treatment system and into the PWP. For management of extreme rain events or emergency circumstances, two 50% high-flow pumps each rated at 3,350 gpm discharges into the plant s MWP via a dedicated 20-inch line. To protect the integrity of the pond walls, the pond also employs an overflow weir that discharges to Bridge Creek (waters of the State), through external outfall 002. NOTE: Any operation of the high flow pumps, bypassing the treatment system and discharging to the MWP, and/or weir overflows to outfall 002 are only employed to manage extreme and/or emergency situations. These are not anticipated to occur and are not considered standard operation. Revision: 1 1/3/14 Turk Pond Treatment System Description Page 6 of 64

7 2.2. TSS Management PWP and CPRP The objective of the pond treatment system is to reduce the TSS levels in the CPRP and PWP discharge water to less than 30 mg/l. This level of TSS ensures that the permit limit for both internal outfalls, which is 30 mg/l monthly average, and 50 mg/l daily maximum, are met. Empirical testing has demonstrated that the required TSS reduction of the CPRP discharge is achieved by a combination Lamella clarifier followed by a multi-media filter (MMF) system. Similarly, multi-media filtration alone has demonstrated the required TSS reduction for treatment of PWP discharge Water Treatment System Capacity Evaluations of historical rainfall data for the region assessed the likely outcomes of varying capacities of CPRP discharge treatment systems. The analysis assumed that at the onset of a significant / measureable / typical rainfall event, defined as a rain event with rainfall totals below the 25 year rain event, plant personnel would initiate operation of the CPRP water treatment system, discharging to the PWP or when necessary to outfall 201. This is to ensure adequate pond inventory for storage of major rain event(s) run-off water, defined as a rain event with rainfall totals up to the 25 year rain event. Continuing/continuous and/or increasing rainfall in excess of the 25 year rain event and/or with events occurring at un-historically high frequencies, the design basis of the CPRP discharge treatment system s pond inventory management capacity would be exceeded. In these instances where the CPRP level would reach six inches below the overflow weir to outfall 002, the existing high flow pumps would be placed in service thus bypassing the water treatment system. This condition is termed a Bypass Event, and under such a situation the 6,700 gpm high-flow pumping system, discharging to the MWP, would keep the pond from overflowing into outfall 002. This prevents a CPRP discharge to an external outfall. However the TSS levels in the bypass line exceeding the plant s discharge permit limits, established for internal outfall 201, would be a highly probable outcome. Additionally, despite the designed capacity of the high-flow pumps to prevent weir overflows, extreme rainfall events, beyond what can be anticipated based on the available historical rainfall data analyzed, may not preclude a weir overflow (discharge to 002). Given the pond s poor settling characteristics, in such an extreme situation, external outfall 002 would most certainly experience a permit TSS exceedence. Based on this prefaced design philosophy and historical rain fall data analysis, a nominal 800 gpm Lamella clarification system, which is the main component for suspended solids removal in the CPRP discharge, was selected. This design treatment rate, based on the historical data analysis, would prevent CPRP weir overflow events; provided extreme rainfall events are not encountered. Two 50% capacity Lamella clarifiers (each rated at a nominal flow of 400 gpm) provide treatment of CPRP discharge to meet the nominal 800 gpm design criteria. The MMF is provided based upon the filtration capacity needs for the PWP as part of a prior engineering study. As such, the MMF is a 3 x 50% triplex system, designed to treat a nominal 300 gpm (each filter is rated at a 150 gpm nominal capacity) with a maximum of 550 gpm. The triplex filtration system allows for one filter vessel to be backwashed online while maintaining a nominal flow of 300 gpm through the other two vessels. When the MMF is configured for CPRP treatment where it provides final polishing of the Lamella effluent, the total effluent flow from the Lamella can/will be in excess of the designed nominal filter capacity. Under these conditions, the excess Lamella effluent flow is combined Revision: 1 1/3/14 Turk Pond Treatment System Description Page 7 of 64

8 with the filtered water. The TSS of the combined waters is anticipated to be below the 201 outfall limit, though it will be tested to confirm this prior to discharging to the 201 outfall. Additional capacity may be available within the MMF system that may allow the treatment system to operate without a direct flow of Lamella effluent to the 201 outfall; however it will depend on the effluent quality of the Lamella as well as further onsite testing to confirm higher flow rates through the MMF will be acceptable. In either case when the MMF is utilized for CPRP treatment the designed filtration system redundancy is compromised. 3. Equipment Descriptions 3.1. Coal Pile Runoff Pond Pumping and Piping to Lamella Influent Mix Tanks / Clarifiers The CPRP low flow pumps (1PP-WW0210/WW0220) are each rated at 200 gpm at 130 TDH with a maximum flow capability of 395 gpm at 85 TDH. This allows for approximately 790 gpm of total influent flow to the Lamella clarifiers The low flow pumps are direct drive utilizing a nominal 20 HP motor The low flow pump discharge feeds are re-directed to the 20-inch high flow pump (1PP- WW0110/WW0120) discharge line which is branched off via an 8-inch line to the inlet of the Lamella influent mix tanks. The low flow pump discharge also feeds an alternate line for coal yard water users (a future installation/usage based on plant assessment) At the take-off location of the 8-inch feed line to the Lamella influent mix tanks a 20-inch isolation valve (1HV-WW4403) is placed just downstream to prevent untreated flow from going to the MWP (201 outfall). The associated 8-inch return line (treated water) from the CPRP treatment system is tied back into the same 20-inch line just downstream of the 20-inch isolation valve. The official 201 outfall TSS sample location (1HV- WW4603) is on the 8-inch return line, inside the pond treatment building, downstream of the 8-inch MMF common outlet line and Lamella effluent feed tie point A pressure transmitter (1PIT-WW9400) is located on the CPRP low flow pump common discharge header Two vee-ball style control valves (1RV-QW0112/1RV-QW0122) controls the flow independently to each Lamella clarifier trains. This allows for independent Lamella clarifier train operation The CPRP low flow pumps are operated as follows One pump is in service with the second pump in automatic standby The flow control valves to each Lamella clarifier train are automatically adjusted to maintain a flow rate set point based on feedback from each trains inlet flow transmitter (1FIT-QW0112/1FIT-QW0122). Each flow control valve controlling flow to the Lamella train fail/trip in the closed position The flow transmitters signal to the Lamella trains also controls the speed of the coagulant and flocculent chemical injection pumps to maintain respective dosage set points. Revision: 1 1/3/14 Turk Pond Treatment System Description Page 8 of 64

9 Due to high velocities expected when the low flow pump is operated at the end of its curve, mitigation of this potential is accomplished by starting the standby pump when the total Lamella clarifier influent flow rate set point is above 300 gpm or when header pressure drops below 40 psig Provision are incorporated in the plant DCS logic to allow the use of one high flow pump (1PP-WW0110/1PP-WW0120) in place of the low flow pumps at total Lamella clarifier influent flow rates greater than 550 gpm Coagulant Feed (1SK-QW4100) A coagulant feed, common to both Lamella trains, is injected upstream of two inline static mixers in the common 8-inch influent line prior to branching off to each individual influent mix tank. The total flow signal from both Lamella train flow transmitters is added to provide the total inlet flow signal that is used to pace the coagulant feed for the CPRP treatment system. There are 2 x 100% coagulant injection pumps, one duty and one standby. Estimated (average) dosage is approximately 50 ppm of an aluminum based coagulant. PLC values used for flow pacing of the coagulant feed are: User input values at PLC HMI Coagulant dose (ppm) Coagulant specific gravity (no units) Coagulant percent solution (%) Dosing pump output at 100% speed (ml/min) Reference Variable C_D C_SG C_P C_MX PLC Values From Instrumentation Lamella Train 1 Influent Flow (gpm) Lamella Train 2 Influent Flow (gpm) LT1_Q LT2_Q Dosing Equation [C_Q], (% speed): (LT1_Q LT2_Q C_D % C_SG C_P C_MX Sample points with manual isolation valves are located upstream of the coagulant injection point (1HV-QW0100) and downstream of the static mixers on each Lamella train influent line (1HV-QW0510/1HV-QW0520) Lamella Influent Mix Tanks (1TK-QW3010/1TK-QW3020) The Lamella influent mix tanks are each a 108-inch diameter by 120-inch high open top baffled mixing tank. The tanks are equipped with a 1.5 HP, 100 rpm constant speed, Revision: 1 1/3/14 Turk Pond Treatment System Description Page 9 of 64

10 variable drive, top mounted mixer used for dispersion and mixing of the flocculent with the influent water. Flocculent is added into each individual Lamella influent mix tank influent line at approximately 1.5 ppm as product. The flocculent is activated in a solution tank through a mix chamber with dilution water provided from the potable water header. Each flocculent feed system consists of 1 neat flocculent feed pump, 1 mixing chamber, 1 prepared solution day tank, and 1 solution (prepared flocculent) feed pump. Each Lamella inlet flow transmitter provides the signal to an individual flocculent solution feed pump to pace the flocculent feed to each Lamella train independently. There are 2 x 100% flocculent solution feed systems, one dedicated to each Lamella train and one common 1 x 100% cold standby, that is a shared standby system with the thickener/filter press flocculent feed skid. PLC values used for flow pacing of the Lamella flocculent feed are: User input values at PLC HMI Flocculent dose (ppm) Flocculent percent solution (%) Dosing pump output at 100% speed (ml/min) Reference Variable F*_D F*_P F*_MX PLC Values From Instrumentation Lamella Train 1 Influent Flow (1FIT-QW0112, gpm) Lamella Train 2 Influent Flow (1FIT-QW0122, gpm) LT1_Q LT2_Q (*) = 1 or 2 depending on Lamella train Dosing Equation [F*_Q], (% speed example for Lamella train 1): LT1_Q F1_D % F1_P F1_MX 3.3. Lamella Clarifiers (1TK-QW3110/1TK-QW3120) The Lamella clarification process is utilized for the removal of the suspended material (TSS) in the CPRP discharge water. Clarification in general is designed to bind the smaller particles (i.e. coal fines) in the raw (CPRP) water together to produce larger Revision: 1 1/3/14 Turk Pond Treatment System Description Page 10 of 64

11 particles through coagulation and flocculation. This is accomplished by charge neutralization of the suspended particles through the reaction between the coagulant and the influent water and subsequent agglomeration of these particles together with the addition/aid of a flocculent. With proper contact time and mixing, the influent (smaller) particles will combine in this physical-chemical process to form larger particles with a mass high enough that it will drop out in the clarifier s settling basin by gravity. The clarified water ( clear overflow) should have a significant portion of the influent TSS removed in this process and the suspended material drops out in the settling basin ( sludge underflow) for disposal. The Lamella clarification process also utilizes inclined plates within the settling basin to provide a significant increase in surface area compared to traditional clarifiers to enhance settling. The inclined plates decreases the particulate settling distance that needs to occur in the settling basin, allowing for a Lamella clarifier to operate at higher rise rates (velocities) and with a consequential footprint reduction than traditional clarifiers The Lamella clarifiers have a nominal minimum flow capacity of 100 gpm and a maximum total flow capacity of 800 gpm (400 gpm per train). Individual Lamella clarifier operating values are: Nominal Flow (gpm) 400 Maximum Influent TSS (mg/l) 1000 Nominal Effluent TSS (mg/l) Nominal Underflow Solids (%) Surface Rise Rate (gpm/ft 2 ) 1.7 Plate Area (ft 2 ) 1884 Plate Area Rise Rate (gpm/ft 2 ) 0.21 Settling Basin Length (ft) Settling Basin Width (ft) Nominal Sludge Removal (gpm) 50 Maximum Sludge Removal (gpm) The Lamella clarifier treatment system is supplied as a 2 x 50% (2 x 400 gpm) train configuration and consists of 2 inlet flow control valves, 2 inlet flow meters/transmitters, 2 influent (flocculent) mixing tanks, 2 effluent turbidity meters, 2 inclined FRP plate Lamella clarifiers, eight (8) ¾-inch settling basin sludge sample valves, and 4 underflow sludge transfer pumps (each train has a 2 x 100% (2 x 50 gpm) pump configuration) Effluent discharge from the Lamella clarifier will gravity feed to the Lamella effluent storage tank or the backwash / rinse water storage tank An automatic control option for the Lamella effluent destination can be done utilizing the online turbidity meter analysis. A high-high turbidity alarm would provide an option for the PLC to automatically shut the block valve feeding the effluent storage tank and open the block valve in the line feeding the backwash / rinse water storage tank. Revision: 1 1/3/14 Turk Pond Treatment System Description Page 11 of 64

12 The Lamella sludge transfer pumps (sludge underflow) (1PP-QW3111/3112/3121/3122) are each rated at 50 gpm. Each Lamella train has 2 x 100% capacity pumps (total sludge pumping capacity per Lamella train is 100 gpm, system total is 200 gpm). Sludge transfer from the Lamella to the thickener will be done on a timed duration and frequency basis (time the pump is on and time the pump is off) with all parameters adjustable through the PLC HMI. Sludge transfer will depend on the influent solids loading to the Lamella trains and will require operator interaction to optimize and manage this inventory A single biocide chemical addition skid (1 x 100% pump) is used for manual, intermittent treatment with biocide (initially sodium hypochlorite) to the flocculent mix tanks to prevent microbiological growth within the system. Treatment with biocide may be done online or offline as necessary Lamella Effluent Storage Tank (1TK-QW3400) and Pump Skid (1PP-QW3410/1PP-QW3420) The primary function of the Lamella effluent storage tank is to provide storage for MMF backwash influent and rinse water to prevent cross-contamination of PWP water into CPRP water when the MMFs are used for treating Lamella effluent Tank capacity is a nominal 30,000 gallons, which supplies the required volume to backwash and rinse one MMF vessel (anticipated backwash volume of 20,250 gallons) without any influent flow to the tank Tank level transmitter (1LIT-QW1102) provides the signal for: Permissive to start MMF backwash sequence (set point level above grade, default of 9-feet) When discharge from this tank is directed to the MMFs, the tank level is automatically maintained at 9-feet above grade to ensure adequate volume for MMF backwashing Permissive for Lamella effluent transfer pump operation (minimum set point level above grade) Provide a bias for the Lamella influent flow control valves to prevent a tank overflow by reducing flow rates should tank levels exceed 9-feet above grade Discharge pumping consists of 2 x 100% pumps, each rated at 1365 gpm Pumps are capable of supplying 900 gpm backwash and concurrent influent flow to two MMFs at 400 gpm (one MMF backwashing, two MMFs online processing 400 gpm) Pump minimum flow protection is accomplished using an orifice plate providing sufficient flow, approximately 65 gpm, to prevent the pump(s) from overheating There is a turbidity monitor (1AIT-QW1302) on the pump discharge upstream of the recirculation tap-off point. Revision: 1 1/3/14 Turk Pond Treatment System Description Page 12 of 64

13 Turbidity values can be used to direct flow to the backwash / rinse water storage tank on a high-high turbidity alarm Direct discharge into the PWP is accomplished through the 10-inch tank overflow line (1QW160) Discharge into the MMFs is controlled by the MMF outlet flow control valve (1RV- QW0105) Direct discharge to outfall 201 from the Lamella effluent transfer pumps (through 1RV- QW1802), is only possible provided the TSS sample analysis obtained from sample valve (1HV-QW4600) indicate this is acceptable Discharge to the backwash / rinse water storage tank or to the coal pile run-off pond can be done during Lamella startups, to control Lamella effluent storage tank level, or to purge the Lamella effluent storage tank if contaminated Multi Media Filters (MMFs) (1SK-QW3500) Three (3) 84-inch diameter, 225 psi ASME code stamped MMF vessels provide solids removal for PWP discharge or Lamella clarifier effluent from the CPRP. The MMF system design basis is to treat a nominal 300 gpm of PWP water prior to discharging into the 101 outfall. However due to the anticipated infrequent usage of these filters for this service, they are also set up to provide supplemental TSS removal for the Lamella effluent; providing downstream filtration during periods of un-steady state / transitional conditions, which has been found to be necessary to consistently meet discharge TSS levels for the 201 outfall. The MMF vessels contain filter media to remove the suspended solids. The media depths in each vessel are 18-inches of anthracite, 12-inches of filter sand, and 6-inches of garnet. MMFs provide deep bed filtration of the suspended solids allowing for staged filtration as each of the media layers provide finer particle filtration as flow moves vertically down the bed. As such, the design of the MMF allows for relatively high filtration rates with less pressure decay than typical single or dual media filtration systems. Solids that accumulate within the media produce head loss (pressure drop/decay from the filter inlet line to the filter outlet line) across the filter bed. Once the head loss through the media is high enough, the filter must be backwashed (reverse flow) at a relatively high rate to remove the accumulated solids and restore the media Normal operation, when treating PWP discharge - influent comes from the PWP sump pumps discharge, MMF outlet (filtered discharge) is sent to outfall 101, backwash and rinse water influent is supplied by the PWP sump pumps discharge, and backwash waste and rinse water outlet is sent back to the PWP. A MMF skid outlet turbidity meter is used for indication of outlet quality and should these levels trigger a high-high turbidity alarm during operation, the MMF discharge is automatically directed back to the PWP Normal operation, when treating Lamella clarifier effluent - influent comes from the Lamella effluent storage tank transfer pumps, MMF outlet (filtered discharge) is sent to the PWP or when necessary (typically during high PWP levels) discharged to outfall 201, backwash and rinse water influent is supplied from the Lamella effluent storage tank transfer pumps, and backwash waste and rinse water outlet is sent to the backwash / rinse Revision: 1 1/3/14 Turk Pond Treatment System Description Page 13 of 64

14 water storage tank. A MMF skid outlet turbidity meter is used for indication of outlet quality and should these levels trigger a high-high turbidity alarm when discharging to outfall 201, the MMF discharge is automatically directed to the backwash / rinse water storage tank System design uses manual double block and bleed isolation philosophy of the MMF outlet water to maintain isolation of PWP water from CPRP water discharge to outfalls 101 or 201 respectively Valve position indication provides permissives for each mode of operation and transitional usage of the MMF system Chemical Feed Systems A ½- inch female NPT tap is installed in the filter inlet line for provisions to accommodate a future chemical feed (filter aid) inlet/injection point should it be necessary Disinfection Periodic disinfection with a sodium hypochlorite soak and backwashing can be performed if needed. A ¾-inch female NPT connection on the backwash inlet line to each filter vessel is provided to accommodate a periodic injection of sodium hypochlorite. Should disinfection be necessary, the Lamella sodium hypochlorite dosing skid can feed to the injection point. The dosing skid will feed to the injection point by portable hose connections. Once chemicals have been added the vessel can be air mixed, soaked (as/if needed), and backwashed. This is all a manual operation controlled by the User Backwash / Rinse Water Storage Tank (1TK-QW3600) and Pump Skid (1PP-QW3610/1PP- QW3620) The purpose of the backwash / rinse water storage tank is primarily to temporarily hold the MMF backwash and rinse water when filtering Lamella effluent to prevent solids accumulation in the PWP; the initially designed location for backwash waste. The tank also provides temporary storage for Lamella effluent during upset conditions. This tank provides the normal means of returning waste / upset waters back to the CPRP Tank capacity is a nominal 40,000 gallons providing volume to hold 2 MMF vessel backwashes / rinse cycles without effluent flow from the tank. Normal operation with 300 gpm effluent from the tank provides storage capacity for typical MMF backwashing as needed Tank level transmitter will provide signal for: Permissive to MMF skid for backwash sequencing of one vessel (set point level above grade, default value of 1-foot 8-inches) Permissive for discharge pump operation (1-foot 6-inches above grade pump trip, 1-foot 8-inches above grade reset). Revision: 1 1/3/14 Turk Pond Treatment System Description Page 14 of 64

15 Level control in the tank is accomplished by a defined set point in the PLC HMI to start and stop the discharge pumps to ensure a maximum free inventory in the tank at all times as practical. Discharge pumps will start at the defined level set point, initially 2-feet 6-inches and will continue to run until the low level set point, initially1-foot 8-inches is achieved. Pumps will remain in automatic standby when discharge flow is not required and will start when the set point value is achieved. PLC automatically will define the Lead/Lag pump operation or can be designated by the User Auto start and stop of the Lag pump will occur at tank levels of 7-feet 6-inches and 4-feet respectively Provide an override to close the Lamella influent flow control valves to stop influent flow should the high level alarm be active for a specified amount of time when the system is running in 1 st Stage Startup Provide a bias for the Lamella Effluent Tank to Backwash Tank flow control valve (1RV-QW1902) to prevent a tank overflow by reducing flow rates should tank levels exceed the high level set point for a specified amount of time When the tank is receiving MMF backwash outlet flow (up to 900 gpm) the Lead pump will start when the level in the tank reaches 1-foot 6-inches (low level trip point) Discharge pumping consists of 2 x 100% pumps each rated at 315 gpm Minimum flow protection is achieved by a manual recirculation with an orifice plate Lamella Sludge Thickener (1TK-QW3200) Partially thickened sludge from the Lamella underflow is sent to the sludge thickener for holding and the continuing thickening necessary prior to feeding the sludge filter press for ultimate disposal / re-application to the coal pile. The sludge thickener is essentially a traditional clarifier without upstream coagulation of the influent. The low rise rates (settling velocities) and high detention time provided in the sludge thickener vessel allow for settling and further thickening of the Lamella sludge to acceptable concentrations for filter press operation. If gravity settling alone does not provide acceptable settling, provisions for a flocculent feed are provided and can be implemented when/if necessary. The solids that settle to the bottom of the thickener vessel are collected in the center, ultimately through a sludge scraper mechanism, and are pumped to the sludge filter press. Overflow from the thickener is sent to the online Lamella influent mix tank(s) or if overflow solids concentrations are excessive to the PWP The sludge thickener vessel is a 30-foot diameter, nominal 84,964 gallon steel tank with a 2 x 12 sloped bottom floor used to collect and thicken the settled sludge from the Lamella clarifiers FUTURE Sludge scraper mechanism x 100% (2 x 50 gpm) air operated diaphragm sludge transfer pumps send settled sludge from each Lamella train underflow to the sludge thickener (4 total pumps, maximum Revision: 1 1/3/14 Turk Pond Treatment System Description Page 15 of 64

16 sludge pumping capacity is 200 gpm). Sludge concentrations entering the thickener are assumed to be approximately % solids. Overflow from the sludge thickener is assumed to be less than 50 mg/l TSS. Underflow from the thickener vessels is assumed to be 2 5% solids The air operated diaphragm pumps are controlled by User adjustable PLC HMI set points defining the pumping duration (minutes pump is on) and dwell/deadband time (minutes pump is off) During normal Lamella clarifier operation, the air operated diaphragm pumps are staged such that only one (total) pump is in operation at a time. Should solids management in the Lamella clarifier settling basin become inadequate with this restriction, an option on the PLC HMI is available to override this and put the Lamella in high solids mode, allowing up to 100 gpm of sludge flow out of each Lamella Four sample locations are provided on the bottom side shell of the thickener vessel to assess sludge concentrations and bed level Sludge level indication instrumentation (1LIT-QW0702) is provided to estimate sludge volume in the thickener vessel Flocculent addition is provided if needed to enhance settling. The flocculent is activated in a solution tank through a mix chamber with dilution water provided from the potable water header. Each flocculent feed system consists of 1 neat flocculent feed pump, 1 mixing chamber, 1 prepared solution day tank, and 1 solution (prepared flocculent) feed pump. Operational feedback from the Lamella sludge transfer pumps (number of pumps in operation and Lamella train pumping to the thickener) provides the signal to the flocculent solution feed pump to pace the flocculent feed to the thickener and opens the appropriate feed inlet valve. The flocculent feed is provided by a 1 x 100% flocculent solution feed system and one common 1 x 100% cold standby that is a shared standby system with the Lamella trains flocculent feeds. The flocculent system feed piping branches off to the outlet line from each Lamella train sludge transfer pump discharge. The feed line also has a second branch off to provide flocculent for a potential future use to the filter press inlet. PLC values used for flow pacing of the thickener flocculent feed are: PLC user input values at the HMI Flocculent dose (ppm) Flocculent percent solution (%) Dosing pump output at 100% speed (ml/min) Reference Variable FT_D FT_P FT_MX PLC Values Revision: 1 1/3/14 Turk Pond Treatment System Description Page 16 of 64

17 Lamella Train 1, Transfer Pumps in Operation Lamella Train 2, Transfer Pumps in Operation Sludge flow per pump (gpm) LT1_STP_ON LT2_STP_ON S_Q (50 Normal) (100 High Solids Mode) Dosing Equation [FT_Q], (% speed example for Lamella train 1): (LT1_STP_ON S_Q FT_D % FT_P FT_MX 3.8. Sludge Filter Press (1FL-QW3000) A sludge filter press is utilized to de-water the pre-thickened sludge from the thickener for ultimate disposal / re-application on the coal pile. The filter press will provide the means to transform the sludge slurry into a friable solid suitable for transport. The filter cake produced from the filter press is discharged to a roll-off dumpster and filtrate (overflow water) is sent to the effluent storage tank or the PWP. Operation of the filter press is largely accomplished through relays provided in the Siemens control cabinet located on the filter press mezzanine. The User will determine when a filter press run is necessary and will initiate the press sequencing through the PLC HMI. Detailed operating and system descriptions for the filter press are found in the Siemens vendor manuals The filter press has a 95 cubic foot capacity and produces approximately 3,200 pounds of a 20% moisture filter cake per run Filter press feed pump skid has 2 x 100 % air operated diaphragm pumps each rated from 25 to 175 gpm depending on discharge head pumping thickened sludge (underflow) from the thickener to the press. The PLC controls the operation of these pumps when the press is in operation Until the sludge scraper mechanism is installed in the thickener, the interim operation of the filter press feed pumps will be automated to continuously recycle sludge within the thickener tank to prevent solids accumulation at potential dead zones in the tank when sludge is not being transferred from the thickener to the filter press Filtrate water will typically be sent to the Lamella effluent storage tank, though a manual option is available to route filtrate to the PWP A pressure transmitter (1PIT-QW0302) on the filter press inlet line provides a signal to pace a future flocculent feed (if found necessary) and provide operation information to the User to evaluate filter press operation A locally mounted high pressure washer is available to clean filter press as needed Dumping of filter cake is into a roll-off dumpster. Revision: 1 1/3/14 Turk Pond Treatment System Description Page 17 of 64

18 Center core blow back is sent to the roll-off dumpster A provision for a future flocculent addition is provided to improve sludge press operation, should the sludge characteristics change and/or other future operational issues reveal that this may be necessary. The proposed automated flocculent addition would only feed when the filter press sequence is in stage 1. Should an additional flocculent feed be necessary past the stage 1 sequence, operations would need to set up the flocculent system for a manual addition. The flocculent is activated in a solution tank through a mix chamber with dilution water provided from the potable water header. Each flocculent feed system consists of 1 neat flocculent feed pump, 1 mixing chamber, 1 prepared solution day tank, and 1 solution (prepared flocculent) feed pump. Operational feedback from the filter press feed pumps (discharge pressure) provides the signal to the flocculent solution feed pump to pace the flocculent feed to filter press. The flocculent feed is provided by a 1 x 100% flocculent solution feed system, that is shared with the thickener flocculent feed application, and one common 1 x 100% cold standby that is a shared standby system with the Lamella trains flocculent feeds PLC values needed for flow pacing of the flocculent are: PLC user input values at HMI Flocculent dose (ppm) Flocculent percent solution (%) Dosing pump output at 100% speed (ml/min) Reference Variable FT_D FT_P FT_MX PLC Values Discharge Pressure (1PIT-QW0302, psig) PR_FPF (Proposed) Dosing Equation [FT_Q], (% speed): (-PR_FPF FT_D % FT_P FT_MX Revision: 1 1/3/14 Turk Pond Treatment System Description Page 18 of 64

19 4. Operation NOTE: In this section User refers to either plant laboratory or operations personnel 4.1. When flow is anticipated and/or required to discharge from the CPRP and/or PWP to control pond levels, the User begins the process of bringing the treatment system online through the PLC control system interface (HMI) 4.2. User checks the PLC HMI for alarms and/or other issues that would prevent a startup of the system. User clears alarms and/or addresses issues and then begins the process of starting up the system Alarms and/or issues that cannot be resolved are communicated to the plant laboratory staff and/or plant management as appropriate and the process to address these items is initiated User designates the treatment mode on PLC HMI Main Page from the following options CPRP treatment PWP treatment Dual treatment (treatment of both CPRP and PWP waters) 4.4. Once a treatment system mode is designated the User then has the option to select the treatment scheme for each mode. The options available are: CPRP Treatment MMF treatment discharging to the PWP MMF treatment discharging to outfall MMF treatment and Lamella effluent combined discharge to outfall Lamella effluent direct discharge to PWP PWP Treatment Discharge to outfall This is the only option for this treatment mode and is automatically selected when this mode of operation is designated by the User Dual treatment CPRP discharging to outfall 201, PWP discharging to outfall CPRP discharging to PWP, PWP discharging to outfall CPRP Treatment Revision: 1 1/3/14 Turk Pond Treatment System Description Page 19 of 64

20 Selecting this option puts the system into CPRP treatment mode The PLC HMI displays selections buttons for the User to select one of the following on the Main Page to designate the treatment system option: (1) MMF treatment discharging to the PWP (2) MMF treatment discharging to outfall 201 (3) MMF treatment and Lamella effluent combined discharge to outfall 201 (4) Lamella effluent direct discharge to PWP NOTE: For discharge of the Lamella effluent tank directly to outfall 201 the User can select the third option and input a MMF maximum outlet flow rate set point (on the HMI Set Points screen) to 0 gpm. NOTE: Prior to a direct discharge of the Lamella effluent tank to outfall 201 a TSS sample analysis is required from the effluent transfer pump discharge sample valve (1HV-QW4600) indicating that the TSS levels are acceptable to discharge to outfall 201. These results must be logged prior to a 201 outfall discharge Once a treatment option has been designated by the User, the startup process for the Lamella clarifiers can be initiated Initial Startup User checks PLC HMI Main Page once a treatment option is selected. If the system displays Ready this allows User to walk down the system and line-up / confirm any valves, equipment, etc. necessary to bring flow into the treatment system as appropriate for the option selected. System valve line-up for the options presented in section is provided in section 5.1. The following process permissives are necessary to display the Ready status on the PLC HMI for initial startup in CPRP treatment mode: Description Tag Number Position/Status CPRP High Flow Bypass Block Valve 1HV-QW4403 Closed CPRP Supply to Treatment System Block Valve Treatment System Return to Outfall 201 Header Block Valve 1HV-WW4303 1HV-QW4503 Open Open Coagulant Feed System 1SK-QW4100 Ready Flocculent Feed System 1SK-QW4000 Ready PWP Sump Discharge to MMF Double Block A 1HV-QW8000 Closed Revision: 1 1/3/14 Turk Pond Treatment System Description Page 20 of 64

21 Description Tag Number Position/Status PWP Sump Discharge to MMF Double Block B MMF Outlet to 101 Outfall Double Block A MMF Outlet to 101 Outfall Double Block B 1HV-QW8200 1HV-QW7400 1HV-QW7600 Closed Closed Closed PREREQUISITE: System turbidity meter online, cleaned, calibrated, and ready for service Once the correct flow path (valving) and equipment status is confirmed and logged by the User, the chemical feed systems are checked and the appropriate set points and dosages for coagulant and flocculent are input into the PLC HMI in the Chemical Feed page The User can input a total Lamella clarifier influent flow rate set point or specify individual Lamella train influent set points, in gpm into the PLC HMI in the Lamella page Inputting a total Lamella clarifier influent flow rate set point, the number of Lamella trains in service is controlled by the PLC under the following ranges: Flow Range (gpm) Initial Operation Required # of Lamella Trains in Service Train-1 Train Lead Standby Lead Lag The PLC will cycle Lamella trains lead-lag-standby designation following each shutdown or they can be designated at the discretion of the User Inputting individual Lamella train influent flow rate set points, each Lamella can operate independently at the flow rates designated by the User Once the User inputs a Lamella influent flow rate set point greater than 100 gpm, the PLC then moves the system from Ready to 1 st Stage Startup. When the system is in 1 st Stage Startup : Lamella clarifier effluent water is automatically routed to the backwash / rinse water storage tank Discharge from the backwash / rinse water storage tank is directed to the CPRP. Revision: 1 1/3/14 Turk Pond Treatment System Description Page 21 of 64

22 The PLC HMI will display an option to Move Into 2 nd Stage Startup Once the User determines that the Lamella clarifier(s) effluent turbidity values (or TSS sample results) observed/obtained from the 8-inch Lamella train overflow lines (Lamella train 1 and 2 turbidity meters and sample point locations 1AIT-QW0512 and 1HV-QW1610, 1AIT-QW0522 and 1HV-QW1620 respectively) indicate it is acceptable to send water to the Lamella effluent storage tank, the User will select Move Into 2 nd Stage Startup. Initially the User will monitor this process and determine when acceptable turbidity values are achieved and makes the decision to direct flow to the Lamella effluent storage tank. An option for automatic routing of Lamella effluent based on turbidity values is available on the PLC HMI, but should not be implemented until sufficient operation experience with the system is obtained to confirm the turbidity values are acceptable to support this operation If unacceptable Lamella clarifier(s) effluent turbidity continues to where backwash / rinse water storage tank levels continue to increase up to the high level alarm point, this information needs to be communicated to the plant laboratory supervisor and/or plant management as appropriate. If acceptable effluent turbidity values cannot be obtained within a reasonable period of time (such that CPRP levels are at risk of not providing sufficient run-off water volume storage), these individual(s) must then make a decision to continue with treatment or bypass the TSS removal system to manage CPRP levels Once the system has moved into 2 nd Stage Startup : Effluent/overflow water from the Lamella clarifier(s) is sent to the Lamella effluent storage tank Discharge from Lamella effluent storage tank is routed to the backwash / rinse water storage tank or directly to the CPRP depending on the level in the backwash / rinse water storage tank or at the discretion of the User Since flow is not monitored from the Lamella effluent transfer pumps when discharging through the 8-inch line to the backwash / rinse water storage tank, control of these pumps will be based on level control in the Lamella effluent storage tank. The pump will start at a specified tank level and stop at a specified tank level The PLC HMI Main Page will display the selection button Startup Complete Proceed with Discharge Treatment Option * (*) = One of the options presented in section To be able to select Startup Complete Proceed with Discharge Treatment Option * the following must be determined and/or confirmed by the User depending on the treatment option selected: For CPRP discharge treatment options (1), (2), or (4) presented in section 4.5.2: User determines that stable operations and turbidity readings observed from the effluent transfer pump discharge turbidity meter (1AIT-QW1302) and/or bench top Revision: 1 1/3/14 Turk Pond Treatment System Description Page 22 of 64

23 turbidity analysis have been achieved and are acceptable to complete the startup process. The User logs the operational values (turbidity, flow, etc.) as appropriate and proceeds with one of these operational options For CPRP discharge treatment option (3) presented in section 4.5.2: A TSS sample must be obtained and analyzed from the effluent transfer pump discharge sample valve (1HV-QW4600). The results of the TSS analysis must show acceptable levels for continuous discharge into outfall 201; as the MMF system will startup in Alternate Outlet to PWP/Recirculation mode such that a combination of MMF outlet flow with the Lamella effluent will not be possible until the MMF system moves from Alternate Outlet to PWP/Recirculation to Discharge mode. These results are logged and communicated with the plant laboratory supervisor and/or plant management. Once this communication has taken place, the authoritative plant personnel can determine that the system can continue with this treatment option or if alterative operation is needed. If a decision to proceed with alternate operation is made, the User logs this communication and alternate operation is determined by the plant staff as appropriate MMF treatment discharging to the PWP: MMF treatment to the PWP is to be the default treatment method utilized for routine CPRP level management. This mode of operation however is constrained by what flow rate the system can continuously manage as the Lamella clarifiers treatment rate could potentially exceed the MMFs treatment capacity, and that pond and tank level management is limited based on the discharge flow rate (return to the CPRP) of the backwash / rinse water transfer pumps. As such, this mode of operation is suggested when routine CRPP level management can be successfully obtained with discharge flow rates (total Lamella influent flow) of less than 400 gpm. Therefore if higher flow rates are necessary to where high pond or tank levels or unacceptable MMF performance is observed at the flow rates necessary for CPRP level management, an alternate treatment mode must be selected. This option can also be used if the Lamella effluent turbidity levels are too high for direct continues discharge to the PWP where accumulation of solids and/or unacceptable water quality would ultimately be detrimental to PWP operation In this mode of operation: The Lamella effluent transfer pumps discharge is directed to the MMFs to supply MMF inlet, backwash inlet, and rinse water. Pump discharge is also directed to the backwash / rinse water storage tank when necessary to maintain the flow path through the Lamella clarifier(s) should the MMF outlet flow rate required to maintain the PWP level set point (automatically reduced MMF outlet flow rate) result in high Lamella effluent storage tank levels. MMF outlet water is directed into the PWP. MMF backwash outlet and rinse water is directed to the backwash / rinse water storage tank. The backwash / rinse water storage tank effluent is directed back to the CPRP to Revision: 1 1/3/14 Turk Pond Treatment System Description Page 23 of 64