WSP10769

• File Number: 8220.105
• Description: Colorado River-Water Projects-Navajo
• State: CO
• Basin: Colorado Mainstem
• Water Division: 5
• Date: 7/1/2001
• Author: BOR
• Title: Revised Draft Environmental Assessment for the Jicarilla Apache Nation Water Subcontract-aka USBR/PNM Water Contract Renewal and Extension
• Water Supply Pro - Doc Type: Report/Study

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5.2

Sulfur Dioxide Removal Equipment

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The flue gas desulfurization (FGD) system in operation at SJGS includes the following processes:

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. Limestone preparation and feed area
. Absorber ceils - three per unit
. Gypsum filter and load-out area

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In 1996. after a detailed engineering analysis, PNM made the decision to replace the existing Wellman-
Lord sulfur dioxide (SO,) removal system with a limestone SO, removal system. After the existing air
permits were modified by the New Mexico Environment Department, PNM started construction of the
limestone system in April 1997. Full operation began in 1999. Unlike Ihe Wellman-Lord system, the
limestone system is not a regenerative system. The limestone removal process produces gypsum as a final
byproduct. Presently. there is no market for gypsum. The gypsum is being trucked to the mine and used as
fill material. The water requirements for the limestone system are equivalent to the Wellman-Lord
system.

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5.3 Zero Discharge Wastewater Treatment

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The management of water at SJGS involves a series of complex processes that make it possible to use this
resource as efficiently as possible. Water is reused, some as much as 100 times, before it is ultimately
evaporated either as part of the plant cooling system, FGD process, or from the series of zero liquid
discharge ponds used to manage the process wastewater generated by SJGS. Zero liquid discharge refers
to the fact that no process wastewaters are discharged off site from SJGS.

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SJGS has operated as a zero liquid discharge facility since 1983. All wastewater streams generated at
SJGS, both sanitary and process, are collected in a system of drains. Depending on the source of the
wastewater, these drains divert the wastewater to one of several high density polyethylene-lined holding
and settling ponds, from where it is pumped to the wastewater treatment system. Following treatment, the
water is returned for reuse in various SJGS water systems. The wastewater treatment system at SJGS
treats and allows for reuse of approximately 400 million gallons (about 1,371 AF) of wastewater
annually.

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The wastewater treatment system was installed to handle the wastewater that is generated by the operating
units, towers. and the limestone areas. This wastewater treatment consists of two brine concentrators
(BCs) rated at 500 gpm and 350 gpm. The product from these syst~ms is also used for demineralizer and
cooling tower makeup water. The final wastes from the system are routed to one of the solar evaporation
ponds that have a total area of approximately 75 surface acres. Each pond is lined with high density
polyethylene and has a leak detection system (Figure 5).

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5.4 SJGS Unit Number 3 Cooling Tower Retrofit

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The cooling towers for units 1,2 and 4 are wet systems which rely on the evaporation of water to provide
the required cooling capacity. The unit 3 cooling tower was originally built as a hybrid wet/dry system
designed to minimize the amount of water lost through evaporation while running the generating unit.
Two of the ten cooling cells which make up unit 3 cooling tower have been converted to wet systems.
This has been necessitated by limitations of the hybrid wet/dry cells to provide adequate cooling at unit
generating capacities now being achieved. This has especially been a limitation to generation during the

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