GORMAN-RUPP VG3B3-B, Инструкция по установке, эксплуатации и обслуживанию

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Process Specification UF 1(2012-05) E inge
Page 3
Subject to modifications and errors ▪ © 2012 inge GmbH ▪ All rights reserved
1 Process description
Basically, the UF process consists of three key processes:
1. Pretreatment
2. Filtration
3. Backwash/Chemical Enhanced Backwash (CEB)
The water to be treated first passes through an optional pre-treatment stage before it is
filtered by the UF membrane. During the pressure-driven filtration process, the pressure at
the membrane steadily increases due to the accumulation of fouling on the membrane
feed side. To clean the membrane, filtered water is held in a filtrate reservoir and made
available for backwashing. Backwashing serves to remove the accumulated fouling from
the membrane and return the admission pressure to its initial level. The option is also
available to boost the effects of the backwash by adding various different cleaning
chemicals.
1.1 Pretreatment
Before the water to be filtered reaches the UF membrane system, rough dirt particles are
removed by a screen prefilter. This prefilter offers automatic backwashing capabilities and
must be equipped with filter cartridges with wire mesh screens and a mesh size of less
than 300 µm.
1.1.1 Coagulation
Coagulation is an effective pre-treatment process employed in many applications that
make use of ultrafiltration technology. Its main effect is to reduce organic fouling by
incorporating dissolved organic compounds in ferric or aluminum flocs and by forming a
porous fouling layer on the membrane surface which encourages a stable filtration process
and ensures high backwash efficiency.
Proper implementation of the coagulation process can reduce the concentration of
dissolved organic carbon (DOC) by up to 60 percent. Optimized coagulation can also
improve filtrate quality by reducing SDI, DOC concentration and colloidal matter. The
coagulant metal residuals in the filtrate should not exceed more than 1 percent of the
added metal concentration.
If the type of coagulant and the raw water quality mean that pH adjustment is necessary,
acid or caustic must be added to ensure the optimum pH value for coagulation. To
optimize the coagulation process, it is important to adjust the chemical contact time to
reflect the feed water quality (e.g. temperature) in order to achieve the required UF
filtrate quality (e.g. DOC, Al or Fe residual).