Water & Wastewater Asia May/June 2022

FOCUS
AUTOMATIC SCRAPER
STRAINERS PROTECT
critical membrane systems
Automated scraper strainers pre-filter water and wastewater to protect
fragile membrane systems from damage caused by large, suspended
particles, reducing maintenance and replacement costs.
By Del Williams
Automatic scraper strainers
are motorised and designed to
continually remove suspended
particulates in industrial
process water and wastewater
to the specific size required
down to 0.003 inches
For industrial process facilities,
membrane filtration is a valuable,
commonly used means of filtering
water and wastewater. The challenge
is that membrane systems are
delicate and can be easily damaged
by large particulates in the water. A
pre-filtration step eliminates this risk
by removing oversized suspended
solids to prevent damage, eliminate
unnecessary maintenance, and
reduce the cost of premature
membrane replacement.
Among the pre-filtering options
available, automatic self-cleaning
scraper strainers are increasingly
popular because they are affordable,
require very minimal maintenance
or attention, and can remove solids
down to 75µm. The strainers allow
for continuous, uninterrupted flows
even during blowdown cycles.
When compared to filters that
must be manually cleaned or even
conventional backwash systems,
automatic scraper strainers can save
substantial costs on maintenance and
membrane replacement.
INDUSTRIAL WATER TREATMENT
AND MEMBRANE SYSTEMS
Although various filtration methods
use membranes, the most mature is
pressure-driven membrane filtration,
which relies on a liquid being forced
through a filter membrane with a
large surface area. Depending on
the size and type of the particles
involved, the process could be
categorised as reverse osmosis
(RO), nanofiltration, ultrafiltration or
microfiltration.
In general, RO is used to produce
potable water or deionised water.
Nanofiltration is used in wastewater
treatment as well as by the
petrochemical industry to purify
gas condensates and the chemical
industry for solvent recovery.
Ultrafiltration and microfiltration
are increasingly used in water and
wastewater treatments.
Numerous industries have high
water usage that can require
further treatment of water, including
automotive, aerospace, oil and gas
extraction, refining, textiles, and pulp
and paper mills. Ultrapure water,
which must meet strict limits of
certain constituents in the water such
as suspended and dissolved solids,
dissolved gases, organic carbon
and biological organisms, is utilised
in electronics and pharmaceutical
manufacturing processes.
WATER & WASTEWATER ASIA | MAY/JUNE 2022 41