Direct Filtration: Polymer Wanted

Direct Filtration: DESCRIPTION

Direct filtration provides an alternative treatment process to coagulation and settling of low turbidity waters. The primary objectives for using a direct filtration treatment in municipal plants is to obtain quality water, at minimum coagulation dosage, without sacrificing filter production capacity. Higher filter capacity is achieved by obtaining a more uniform solids loading distribution and by utilizing as much as 80% of the media bed. Direct filtration differs from conventional treatment in that it does not provide for solids removal by settling but does allow for mixing of coagulant chemicals prior to filtration.

Direct Filtration: PRODUCT FEATURES

  • Variety of cationic polymers available
  • Multiple molecular weights available
  • Multiple charge densities available
  • Liquid and granular products, easy to feed
  • Readily soluble
  • Effective over broad pH range
  • Unaffected by chlorine

Direct Filtration: BENEFITS

  • Length of filter runs are increased
  • Post-precipitation of inorganic sludge is eliminated
  • Volume of solids applied to filters is significantly decreased
  • Lower chemical, storage and handling costs

Direct Filtration: APPLICATION

In many municipal water facility, inorganic coagulants are used to treat raw waters containing very low levels of turbidity. These coagulants, when applied directly to a filter, often cause shortening of the filter runs and, in some instances, may pass through the plant’s filters resulting in post precipitation and the formation of a chemical sludge in service mains. This sludge can be eliminated and filter runs extended by using polymers to treat the raw water prior to filtration. Tramfloc® polymers, when added to the raw water, act to neutralize solids and form small microflocs which are easily filtered. They do not form the large gelatinous flocs (associated with inorganic chemicals) that reduce filtering capacity.

In some instances, polymers also can be applied directly to the filter media. They then act to coat each filter particle with a neutralizing charge that interacts with the solids in the raw water and removes these solids as they pass through the filter. By using this technique, a much greater filter media depth can be utilized for filtration.

Direct Filtration: METHOD

In typical direction filtration operations, coagulants bearing a cationic charge are most often used. Tramfloc® polymers are accepted by the EPA and NSF for use in potable water and used for direct filtration are the Tramfloc® series of liquid, water soluble, cationic polymers. These are usually applied to an area of turbulence ahead of the filters for proper dispersion and contact with raw water solids. Dosages most often encountered in a typical application would be in the range of 0.2-2.0 mg/L.

Direct Filtration: EVALUATION

Tramfloc’s knowledge of polymer chemistry and other water treatment chemicals is based on years of experience correcting water treatment problems. Tramfloc’s specialists are well equipped to select the proper and most economical polymer treatment for your direct filtration application. Our knowledge of regional water characteristics and firsthand operating experience enables us to support on-site tests to help determine which Tramfloc® polymer will be the most effective in a given application.

 

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