Design of Water Recovery System for the Hal C. Weaver Power Plant

Photo of Jacques Lesage, Jennifer McMahon, and Ben Taylor Students: Jacques Lesage, Jennifer McMahon, and Ben Taylor

Sponsor: University of Texas Utilities and Energy Management

Date: Fall 2008

Requirements:
The new design must have variable speed control of the pump to reduce on/off cycling. Sources to be recovered in the system must have a conductivity of 2100 micro-Siemens per centimeter or less. UT Utilities requires the project cost to be less than $5,000. This includes cost for any materials, such as new pumps, piping, valves, and the variable frequency drive (VFD).

Problem:
The purpose of this project is to improve an existing water recovery system and identify new water recovery opportunities at the UT Power Plant.

Solution:
Improvements to the existing system focused on resizing the existing pump and recovering new sources of waste water. The design team determined existing water recovery capacity to be 102 gpm, calculated by conservation of mass principles. This value, along with new recovery source data, was used to determine minimum and maximum capacities, 65 and 190 gpm, respectively. A consequent task was the evaluation of the existing recovery system. The pump's efficiency, 30.5%, and use of only a fraction of capable capacity indicate a poor fit to the existing system and need for improvement. After the identification, assessment of sources, and evaluation of the current recovery system, the team selected an improved water recovery system. The highest ranked configuration, a system with a single, new, VFD controlled pump and 3" discharge piping, was chosen. Variable speed control decreases pump energy consumption 75%, from 8.5 HP to 2 HP, by optimizing pump speed. The decrease in consumption translates to $1,817 in annual electricity savings. Total Power Plant water recovery is increased by 15.2 million gallons per year, translating to approximately $63,000 in yearly savings. Although small (only 2% of annual Power Plant usage) the recovered volume generates significant savings, and contributes towards UT's conservation efforts.

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