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7.5 Turbidity
Turbidity is usually caused by particles so fine that the filter cannot retain them. Enhancement can be
achieved on sand filters by addition of a suitable flocking agent, i.e. a flocking layer on the filter bed
holds back even fine turbidity-inducing particles. A flocking agent which is effective regardless of the
pH value is particularly suitable for this purpose.
7.6 Causes of unsatisfactory water condition
If the water is still not clear despite circulating filtration, the cause may lie in the following:
7. The pH value is incorrect and therefore added chlorine remains almost ineffective.
8. Inadequate disinfection of the water (excessively wide intervals, insufficient dosing) does not
maintain microorganism development within the necessary limits.
9. The filtration system is of too small a scale.
10. The filtration system has not been backwashed for too long a period.
11. The filtration times of the filter are calculated too short and therefore only a portion of the
water can be filtered, with the remaining portion remaining unfiltered.
12. The chosen dimension of the suction and pressure lines may be too small. This inevitably
results in insufficient circulation efficiency, which may likewise result in water turbidity.
