Membrane technology for color removal

Nanofiltration systems are used for a wide variety of applications, including color removal from surface water sources including removal of disinfection pre-cursors. They operate at lower pressures than reverse osmosis so when they apply to any particular application, energy costs are lower than the equivalent reverse osmosis systems.

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Membrane technology for color removal

Membranes selectively remove dissolved species from a variety of sources including:

  • Surface water
  • Rinse water from fabric dyeing
  • Industrial wastewater
  • Landfill leachate

 

Demands for development of membranes with specific performance continue to increase as water quality requirements tighten and water treatment system designs become more complex. Such demands lead to development of new reverse osmosis (RO) and nanofiltration (NF) membranes with higher rejection characteristics for better dissolved salts and boron removal.

New applications have developed which require selective removal of certain dissolved species such as:

  • hardness
  • natural organic matter (NOM)
  • pesticides
  • Organic material which causes color

 

Engineers desire high removal of specific contaminants in these applications, but at the same time want to maintain some level of salts in the water so it does not become aggressive, which can cause corrosion problems with piping in the distribution network.

Nanofiltration (NF) membranes have good selectivity for removal of naturally occurring organic compounds as well as iron. Organic material can be found in groundwater sources which have surface water intrusion, or groundwater sources which are influenced by decomposing vegetative materials. The contamination of these waters is measured in terms of color units.

Treated water from landfill leachate is another source of color in wastewater. When this wastewater is discharged to a municipal treatment plant (POTW), color and the presence of certain organic acids affect the performance of the final ultraviolet treatment step, causing the receiving facility to require that these components be reduced or eliminated.

Dynatec has developed a number of options for color and organic acid removal. Since each project requires different levels of removal and has different treatment requirements, treatability work is typically carried out to establish the required treatment process steps. Typically, treatment requirements not only include color removal, but may also require the removal of COD, BOD, oil and grease, metals, etc. The treatment steps may include:

  • metals and/or free floating oil
  • settleable materials removal
  • ultrafiltration for removal of suspended colloidal materials
  • nanofiltration using several options that are available, depending on the requirements of the particular application
  • reverse osmosis for the removal of color, dissolved solids and organics

 

Finally, some color removal can be accomplished with ion exchange resins specially developed for color removal.

Dynatec will carry out treatability work at their treatment lab or will provide small-scale pilot equipment that is shipped to the project site where longer term studies can be carried out.

 

The Dynatec Difference

Nanofiltration systems are typically used for:

  • Color removal from surface water sources including removal of disinfection pre-cursors
  • Retention of humic and fulvic acids in landfill leachate to improve UV transmissivity
  • Pharmaceutical solvent recovery and management
  • Removal of tar compounds in petroleum industry
  • Separation of blood compounds in medicine
  • Water softening

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