Dual flocculation

Optimization of water purification by dual flocculation

General

The use of anionic polymeric flocculants for cleaning wash waters in gravel and sand washing has become the state of the art method in recent years. The operational reliability of the separation process and the quality of the clear water phase depend on the properties of the raw material as well the water temperature. Often, falling ambient temperatures lead to a measurable deterioration in the separation performance. Reliable operation of the water cleaning process can be ensured only by significantly higher polymer dosage amounts.

Problem

Positive and negative charges are distributed on the surface of the suspended particles. The total charge of the particles results from the larger number of positive point charges. The smaller this excess of positive surface charges, the weaker the reaction is between suspended particles and oppositely charged polymer molecules. Therefore, fine particle don’t react easily with the much larger chains of flocculants and remain as residual turbidity in clear water. This effect strengthens with falling water temperatures and the simultaneously increasing viscosity and density of the water.

 

dual-flocculation-foto-vergleich_engl

Solution

The organic coagulant GoFloc® C 592–1 is a special in-house development of HeGo Biotec GmbH for use in the sand and gravel industry. The ready to use solution contains short, highly cationically charged polymers, which react with the negative particle charges on the slurry surface. Thereby, a more defined charge on the suspended particles is generated which causes rapid and complete flocculation after addition of an anionic flocculant (see fig. 1).

Dosage of GoFloc® C 592-1

The dosing point of the organic coagulant GoFloc® C 592-1 should be behind the feed pump for the thickening unit. It is important to ensure sufficient reaction distance between the metering point for GoFloc® C 592-1 and the addition of the anionic flocculant. Here a combination of GoFloc® C 592-1 with GoFloc® A 515 has proven particularly effective.

.

Example of use

dual-flocculation-dosierschema_engl

Advantages at a glance

  • Ready-to-use solution with low viscosity
  • Dosage with progressive-cavity or diaphragm pump possible
  • Significantly improved quality of clarified water phase
  • Controlled flocculation allows targeted influence on sedimentation rate and packing density of flocculated sludge
  • Higher operational reliability ensures reduced downtime
  • Reduction of the risk of overdosing with anionic flocculant
  • Simultaneous reduction in the dosing quantity of anionic flocculant