Rank Brimar use about 5m3 /h of high purity (>15MΩ
.cm) water in the production of their cathode ray tubes. The
original system consisted of two-bed deionisers with sub-micron
cartridge filtration and a ring main with mixed bed polishing.
The introduction of new, higher specification products demanded
improved treated water purity and this lead to the addition of
ultrafiltration. Seasonal variation in mains water quality caused
membrane fouling resulting in extended down time and high maintenance
costs. Whitewater was commissioned to investigate the problem
and recommend a cost-effective solution.
Site investigation, implementation of pilot plant trials, system
design and specification.
Site investigations including water analyses, SDI monitoring
and SEM examination showed that the principal problem was one
of colloidal silica associated with seasonal algal activity in
the reservoir. A pilot scale colloid adsorbing resin unit was
installed and run in parallel with the ultrafiltration unit and
demonstrated good removal of colloidal silica and significant
improvements in SDI.
A full scale colloid adsorber was added to the treatment train
upstream of the membrane ultrafiltration units. The result was
increased ultrafilter throughput, reduced downtime for cleaning
and extended membrane life. At the same time, the existing equipment
was refurbished, the process route rationalised and a new control
system added. The investment showed payback within two years.