Challenges in discontinuous high rate direct filtration

I. Slavik*, Wahnbachtalsperrenverband, O. Hoyer, Germany; W. Uhl, Norwegian Institute for Water Research, Norway

In a surface water treatment plant special challenges have to be met to treat the water by direct filtration to reduce the phosphorous concentration to ≤ 10 µg/L. These challenges include (i) high concentration of manganese (0.3 to > 2 mg/L Mn2+), (II) varying phosphorous concentration (e. g. 27 – 388 µg P/L in 2015), (III) operation at maximum hydraulic capacity for a period of several weeks, (iv) rapid variation of volumetric flow from 70,000 to 403,200 m3/d, (v) operation for a few hours, out-of-operation intervals for several days, frequent start-up and shut-down, (vi) water temperatures of even low as 0 °C, (vii) high turbidity up to 100 mg/L of solids, (viii) removal of ≥ 99 % of the plankton and of inorganic turbidity, (ix) rapid and extensive variation of the coagulant dosage.

Full-scale and pilot-scale investigations were performed as a first step to optimise this discontinuous high rate direct filtration process. The investigations were triggered by recurring blockages of the filter material and the filter nozzles due to manganese deposition. The consequence was a greatly reduced filtration performance.

The results and findings so far include the development and installation of special filter nozzles, an optimised filter design and a modified backwash procedure. The optimisation was mainly focused on the direct filtration process with its objective to primarily remove as much phosphorous and turbidity from the surface water resource as possible. Besides the discontinuous operation of coagulation and filtration at high volumetric flow rates the requirement to minimise sludge production to limit disposal costs has to be taken into account....

Session: L15 - Depth Filtration I
Day: 13 October 2016
Time: 09:00 - 10:15 h

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