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Contact Flocculation Water Treatment Plants

Application and Benefits of Contact Flocculation

Contact Flocculation is a direct filtration process used to treat bore and surface water to potable water quality.

Contact Flocculation is a different water treatment process than conventional rapid sand filtration.

For a typical rapid sand filtration water treatment system, the water treatment coagulant is dosed a sufficient distance in front of the filter for flocculation to occur before the filter. This floc is filtered out of the water flow by the filter, with most of the filtration occurring in the top layer of the filter.

With contact flocculation, the water treatment coagulant is dosed close to the inlet of the first filter and flocculation occurs within the filter media of the first filter.

The floc sludge formed is stored in the volume of voids in the filter media. Because flocculation is occurring within the media, the full volume of voids within the filter media can be used for the storage of the floc sludge formed.

Any floc leakage from the first filter is captured by the second filter.

This feature allows for longer filtration runs, than those provided by a traditional rapid sand filter. Also, because of the close contact between the suspended solid and the organic particle in the water, with the coagulant, contact flocculation uses less coagulant, than conventional water treatment technology.

The contact flocculation process produces very clean treated water, at a very economical price.

Contact flocculation water treatment systems are used to treat surface catchment and bore waters with high turbidity and/or organic dissolved matter.

For New Zealand surface water applications, (low turbidity and high dissolved organic matter), the CMWEL Contact Flocculation Water Treatment systems can cope with raw waters up to 150NTU.

For waters of high turbidities, the mixed tank diameter systems are recommended.

For these mixed tank systems, the filtration rate, (filter face velocity), is lower on the first filter. The larger first filter provides a larger volume of voids in the filter media, allowing a larger volume of sludge to be stored between back washes. This allows for longer filtration runs.

  • Fully automatic, backwashing on delta pressure and time inputs.
  • Multi-media configuration to allow long filter runs and low micron filtration.
  • Air scour used in the backwash process to ensure removal of floc particles from the filter media.

Process Schematic

Contact Flocculation water treatment plant schematic

System Specifications

  • Vessels: FRP.
  • Fully Automatic. Regenerates on delta pressure, turbidity break through and/or time. PLC Controller.
  • Electrically Safe: 240V; 50 Hz supply to Controller. 24VDC supply to pressure transducer and actuated valves.
  • Pressure: 210 – 825 kPa
  • Vacuum: Nil. (Use vacuum breaker if there is any potential for vacuum).

Contact flocculation water treatment plant models available

Contact Flocculation WTP Models – Technical Details
Model Tank Size
Flow Rates
Pipe Size
Diam. Height Recom. (mm)
CF450 450 1650 3.2 30
CF500 500 1800 3.9 40
CF530 530 1600 4.4 40
CF600 600 1800 5.7 40
CF750 750 1800 8.8 50
CF900 900 1800 12.7 80
CF1200 1200 2150 22.6 80
CF1400 1400 2150 30.8 100
CF1500 1500 2400 35.3 100
CF1575 1575 1675 39 100
CF1600 1600 2150 40.2 100
CF1800 1800 2800 50.9 150
CF2000 2000 3200 62.8 150
CF2200 2200 3200 76 150
CF530x450 See above tanks 3.3 40
CF600x530 See above tanks 4.2 40
CF750x600 See above tanks 6.6 50
CF900X750 See above tanks 9.5 80
CF1400x1200 See above tanks 23.1 100
CF1600x1400 See above tanks 26.5 100
CF1800x1575 See above tanks 38.2 150
CF2000x1800 See above tanks 47.1 150
CF2200x2000 See above tanks 57 150

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