Having an eﬀ ective, durable pretreatment system in advance of ion exchange produced-water softening systems is the ﬁ rst, most critical line of defense – ensuring smooth, more troublefree performance downstream.
It’s especially true when dealing with today’s ion exchange technologies, which require TSS (total suspended solids) of 0.1-0.5
mg/L and turbidities of 0.1-1 NTU (nephelometric turbidity units).
Most suppliers of ion exchange resin would advise removal of
suspended solids to at least 1 mg/l or better through some form
of pretreatment and that some, but not all, of the residual solids
that accumulate within resin beds be removed by periodic backwashing of the resin. If allowed to accumulate, these solids can adversely impact water and regenerant chemical distribution,
will ultimately increase pressure drop, and degrade water quality
Furthermore, longer term fouling by solids and residual oil can make subsequent resin cleaning much more diﬃ cult, if not
With the ongoing trend towards packed bed ion exchange systems, the sensitivity to solids fouling has increased even more. In these systems there is little or no freeboard space within the resin column making it much more diﬃ cult and, in some cases, impossible to backwash the resin to remove the accumulated dirt. This means resin must routinely be removed from the column and washed, with typical cleanings reported to be one to two times per year.
What Makes Sense?
So what makes the most sense, given the various options available? There is of course no such thing as a standard pretreatment process. In the past, the most prevalent ion exchange pretreatment options have been direct (depth) media ﬁltration using a layer of granular media such as sand, and/or anthracite with coagulation...
Considering the various positives and negatives behind today’s pretreatment options, striking a strong balance makes sense – in other words, maintaining the low capital and operating cost of
conventional dual media ﬁlters while addressing limitations and boosting ﬁltration eﬃciency to levels once only achievable with membranes.
In recent years, multi-media ﬁltration has advanced considerably – now boasting superior ﬁltration relative to conventional media ﬁlters and ﬁltration eﬃciency approaching levels similar to ultra ﬁlters
and micro ﬁlters. Combining greater ﬁltration eﬃciency with the durable – basically indestructible – nature of media ﬁltration means a signiﬁcant reduction in cleanings, overall downtime, and many other related costs for plants.
For several years, design and manufacturing ﬁrm Eco-Tec, Inc. has been delivering a strong preﬁltration solution through its advanced
media conﬁguration known as Spectrum Micro Media, basically a
two-layer depth media ﬁlter with a number of features that depart from conventional designs; namely, a coarse media (either anthracite or nutshells) upper layer, a ﬁne micro-media lower
layer, and high service ﬂow rates.