Turk Wastewater Outfall Discussion

Transcription

1 Turk Wastewater Outfall Discussion ADEQ s permit writer for the John W. Turk, Jr. (Turk) Plant NPDES permit recently indicated that he is contemplating designation of four internal outfalls for the purpose of wastewater monitoring, as shown on the attached markup of the facility wastewater schematic. These internal outfalls would consist of: 01A cooling tower blowdown discharge to the Wastewater 01B coal pile runoff pond discharge to the Process Water 01C low volume waste discharge to the Process Water 01D landfill leachate pond discharge to the Process Water AEP/SWEPCO notes that three of these four internal outfalls discharge to the Process Water. All water from the Process Water is consumed internally under any but the most atypical conditions. Essentially, there would need to be a storm event of sufficient magnitude to exceed the capacity of the Process Water, combined with an extended outage of the power plant wherein typical processes using this water (i.e., bottom ash cooling and FGD slurry preparation) are shut down. Under these circumstances, the Process Water excess will be transferred to the Wastewater. There will never be a discharge of the Process Water to surface water. The facility could easily operate for an entire permit cycle without encountering these conditions, which would mean that monitoring of proposed internal outfalls 01B, 01C, and 01D during this time would have served no purpose since these discharges would not have contributed to any discharge to surface water. Essentially, AEP contends that the water is not a waste (wastewater) until/unless it has been transferred out of the Process Water into the Wastewater for additional treatment prior to being discharged. The permit writer may be separating all identified categorical wastes (e.g., coal pile runoff, low volume wastes) entering the Process Water into individual streams that he believes must be monitored prior to being commingled and/or discharged. This may not necessarily be required in the case for Turk, as the monitoring requirements for coal pile runoff include the same parameters (TSS, ph) as do the monitoring requirements for Low Volume Wastes and Landfill Leachate (TSS, ph, oil & grease). The actual numerical TSS limitations, however, are different for the two types of wastes, as the numerical limitations for TSS for discharges of Low Volume Wastes are lower (30 mg/l) than the numerical limitations for TSS from Coal Pile Runoff (50 mg/l). SWEPCO has another facility in East Texas (Welsh Power Plant) that does not separate its Coal Pile Runoff from its Low Volume Wastes prior to monitoring and discharge. The rationale used by the permit writer in this case is that the numerical limits for Low Volume Wastes are much more stringent than the limits for Coal Pile Runoff, so they simply apply the limits for the Low Volume Wastes to the commingled combination of 1

2 the two wastes at the point of discharge (after treatment in retention ponds). The case at Turk is substantially similar, and AEP is requesting that the need for an internal monitoring point for the combination of categorical wastestreams be limited to that point at which the combination of wastes may be routed from the Process Water to the Wastewater for additional treatment prior to discharge. To require monitoring other than what has been proposed by AEP for the discharges entering the Process Water would essentially be pointless since the water contained in the Process Water is for internal reuse, and never actually gets discharged from that pond. In other words, there is no direct release (discharge) of water from the Process Water to Waters of the United States. In consideration of the aforementioned paragraphs, AEP contends that there should only be one internal monitoring point for the Process Water, and it should be designated at the point of discharge from the Process Water to the Wastewater. The effluent described as the waste being monitored at this location should be listed as a combination of Low Volume Wastes, Coal Pile Runoff, Landfill Leachate, and Storm Water, and the effluent limitations applied to the outfall should include the most stringent of the combination of these sources, or those that are typically applied for Low Volume Wastes. With respect to the fourth internal outfall being considered (01A), Cooling Tower Blowdown is the only source of wastewater to the Wastewater until/unless wastes are transferred from the Process Water to the Wastewater. This will only happen on an infrequent basis during episodes of extremely heavy precipitation during an extended plant outage, at which time the plant would not even be producing blowdown. Essentially, monitoring point 01A would be redundant with external outfall 001 except during rare circumstances, at which time the wastestream intended for monitoring will not be produced. In consideration of the previous paragraphs, there is no need to create a separate internal monitoring point for the cooling tower blowdown, as it will only be combined with the previously monitored wastes from the Process Water on an infrequent basis prior to being discharged from the facility s primary external wastewater outfall. AEP has another facility in Louisiana (Arsenal Hill Power Plant) that combines Low Volume Wastes as previously monitored wastes with Cooling Tower Blowdown prior to discharge. The permit for this facility does not require the two wastes to be monitored separately prior to discharge. The permit simply requires the Low Volume Wastes to be monitored prior to the commingling of the two wastes, which is what AEP is proposing to do in the case at Turk Power Plant (at the point of discharge from the Process Water to the Wastewater ). In addition, the Cooling Tower Blowdown will be routed to the Wastewater for additional treatment prior to ultimately being discharged. As such, the potential to exceed the maximum allowable concentration for chlorine (total residual, since continuous chlorination is being proposed) at the outfall will be mitigated by the additional retention time in the Wastewater. Designation of an internal monitoring 2

3 point for chlorine upstream of this planned treatment would not provide useful information. Consequently, AEP contends that the monitoring for Cooling Tower Blowdown should be limited to the point of discharge from the facility s primary external outfall. In consideration of these facts, there should be no need for an internal monitoring point for Cooling Tower Blowdown, and the facility would simply have one external outfall for the discharge of the previously monitored wastes from the Process Water and the Cooling Tower Blowdown. As such, the wastes described as being discharged from the facility s primary external outfall would simply be Cooling Tower Blowdown and previously monitored wastes. Your attention to these details is appreciated. 3

4 Little River Intake John W. Turk, Jr. Power Plant Wastewater Schematic (Page 1 of 2) INTERNAL 01A blowdown Make-up Water Pre-Treatment System Cooling Tower Basin Wastewater Outfall 001 To Little River overflow during extended outage (Outfall 101) Process Water Automated overflow from extreme event (Outfall 201) Monitoring Equipment Coal Handling Area Sumps Equipment washdown area Rotary car dumper area Yard reclaim tunnel areas Equipment storage building area Crusher house area Transfer tower area Service water tank overflow Landfill Bottom Ash FGD Waste Other Small-Volume Non-Hazardous Wastes Oil-Water Separator Coal Pile Landfill Leachate Coal Area Runoff INTERNAL 01B Emergency INTERNAL 01D spillway Outfall 002 to Unnamed Tributary 4

5 John W. Turk, Jr. Power Plant Wastewater Schematic (Page 2 of 2) Building Sumps: Boiler building Turbine building Air heater/blower building Fly ash exhaust building Oil-Water Separator INTERNAL 01C Overflows Landfill Leachate Coal Area Runoff Water Treatment Building Sump Filter Backwash from Demineralized Water System Reagent Prep Building Sump Baghouse Area Sump Process Water Wastewater Internal Use Bottom Ash Cooling and Pyrites Transport FGD Slurry Preparation Sanitary Waste Town of Fulton STP Drainage System s Evaporation/ Discharge to Ground 5