WSP07913

• File Number: 8277.400.200
• Description: Lower Virgin River Project
• State: NV
• Basin: Colorado Mainstem
• Date: 11/1/1986
• Title: Study of Saline Water Use at the Harry Allen Generating Station - Final Report - November 1986
• Water Supply Pro - Doc Type: Report/Study

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Section 3

WATER SUPPLY DESCRIPTION

The study compares the use of two alternate water supplies for total makeup to
the power plant. The base case water supply Is secondary treated sewage ef-
fluent from the Clark County, Nevada Advanced Wastewater Treatment (AWT)
Plant. The alternate water source for this study Is from the Lower Virgin
River Unit, which Is a saline water source under study by the Bureau of
Reclamation and Is comprised of both ground and surface water.

SECONDARY SEWAGE EFFLUENT

The Clark County AWT plant provides continuous secondary sewage effluent
treatment and periodic tertiary treatment to meet discharge requirements.
Secondary sewage effluent quality was assumed In the study because of the con-
tinuous data base. Water quality analyses for the secondary treated sewage
effluent for 1985 were obtained from the laboratory at the AWT plant In Las
Vegas. Additional data on the quality of secondary effluent were obtained
from the City of Las Vegas. The Colorado River Commission provided future
projections of wel I water to Colorado River ratios for Las Vegas and Reclama-
tion provided data on the future projections for salinity of the Colorado
River at Lake Mead. The projected quality of the secondary sewage effluent
based on these data Is shown on Table 3-1. SupportIng analytical data are
shown In Appendix B-1. For the plant design, no changes In water quality In
the pipeline between the AWl plant source and the power plant are assumed.

TABLE 3-1

LAS VEGAS SECONDARY SEWAGE EFFLUENT WATER QUALITY
(mg/I as Ion)

Ion Average High Average
Na 187 216
Ca 132 151
Mg 55 62
HC03 66 94
CI 239 264
. S04 550 626
N03 2 2
P04 3 3
SI02 16 16
TDS 1250 1434

Water quality data Is from the Clark County Advanced Wastewater Treatment
Plant for the period of December, 1984 to January, 1986. High Average water
quality Is one standard deviation above the mean. Sodium Is used at the
balancing Ion.

3-1