Chemistry Reference
In-Depth Information
Seasonal Pattern of NOM-Fractions in Lake Water
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Biopolymers
Humics
Building Blocks
LMW-Organics
Neutrals
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Figure 10.3 Seasonal changes in NOM fractions in the Lengg raw water taken from Lake
Zurich (at a depth of 30m) [10].(permission received).
10.2.6
Weesperkarspel Plant, Amsterdam, the Netherlands
In some countries, such as the Netherlands and Switzerland, drinking water is
produced without chlorine, and thus is distributed without disinfectant residual.
In such cases, it is particularly important that no easily degradable organic matter
should enter the water distribution system, as this could promote bacterial
re-growth. The operation of the Weesperkarspel treatment plant of Waternet (the
water cycle company for Amsterdam and surrounding areas) provides a good
example of this (Figure 10.4).
The treatment plant at Weesperkarspel receives pretreated water, as shown in
Figure 10.4 [11]. The pretreatment consists of an intake of seepage water from the
Bethune polder, sometimes mixed with Amsterdam-Rhine Canal water, and a
consecutive treatment of coagulation and sedimentation, self-purification in a lake-
water reservoir, and rapid sand filtration. The pretreated water is transported to the
Weesperkarspel treatment plant without chlorination. At this treatment plant,
the first process is ozonation to provide disinfection and oxidation of organic
matter, which results in an increase in the biodegradability of NOM.
After ozonation, pellet reactors are used for softening the water. This is followed
by BAC filtration, which is applied to remove NOM and organic micropollutants.
The last step in the treatment is slow sand filtration for nutrient removal and
reduction of suspended solids. This process is regarded as the second important
barrier in the treatment against pathogens, and is especially important for
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