25    DUAL BED ION EXCHANGE
REGENERATION-OPTIMIZATION FOR HIGH PURITY
WATER SYSTEMS
James A. Mueller, Professor
Environmental Engineering and Science
Manhattan College
Bronx, New York 10471
Warren Riznychok, Senior Associate Chemist
Gordon Bie, Senior Operator
IBM Thomas J. Watson Research Center
Yorktown Heights, New York 10598
INTRODUCTION
The Thomas J. Watson Research Center in Yorktown Heights, New York, is International Business
Machines (IBM) basic and applied research division headquarters. Historically, wastewater generated
by the research activities has been treated by an Industrial Wastewater Treatment Facility and its
effluent recycled for reuse in laboratory sinks, as boiler makeup and feedwater to the sites deionized
water systems. In January 1984 a newly constructed High Purity Water System (HPW) was brought
on-line and also received recycled industrial waste as a source of makeup water. High purity water,
used primarily in semiconductor research at the Center, can have a significant impact on research and
development if it does not meet required ionic, organic, and 6 quality specifications.
Due to upgrading of the industrial wastewater treatment plant, the HPW began to use city water
directly in January 1985, and by March 1985 the two bed ion exchange process, heart of the HPW
system, showed significant reductions in throughput volumes and quality. High pH and conductivity
focused attention to the cation unit as the problem. The body of this paper will discuss in detail the
steps taken to quickly recover cation bed capacity and to optimize regeneration efficiency.
PROCESS DESCRIPTION
A total water flow scheme is illustrated in Figure 1. Industrial waste characterization in 1982 of the
daytime (7:30 A.M.-7:30 P.M.) and nighttime waste demonstrated feasibility of segregation of the
waste stream into separate holding tanks, enhancing process operation. Daytime waste undergoes
neutralization, biological treatment with rotating biological contactors, settling, disinfection with
chlorine, and air stripping. Air stripper effluent quality determines if the pretreated day waste will be
discharged to the Westchester County Sewer System or undergo further treatment.
The dilute night waste, which contains 40% deionized water, or pretreated day waste, is further
treated by dual media filtration, activated carbon adsorption and two bed ion exchange present in the
nighttime waste process flow scheme. Provisions are also in place to pretreat city water through this
process area to assure adequate supply for makeup and users. Figure 2 indicates process flow and
water treatment possibilities.
High purity water is produced using dual media filtration for gross particulate removal, activated
carbon adsorption for removal of organics and chlorine, UV sterilization, two bed ion exchange,
mixed bed ion exchange, UV sterilization, 0.6 micron and 0.2 micron membrane filtration (Figure 3).
This high quality point of distribution effluent is pumped to the research center where it is repolished
by two separate stations. Water that is not required for makeup at the two polishing stations is
returned to intermediate storage in the main processing plant.
The polishing station servicing the Advanced Silicon Technology Laboratory and Aisles 1-6 repuri-
fies the water with nonregenerable mixed beds UV sterilization and 0.1 micron filtration. The second
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