surface water treatment systems

As previously noted, groundwater sources “influenced by surface water” must also be included in this category.

Figures 1 and 2 respectively, group the basic treatment stages applicable primarily in water pre-treatment and then in the water’s complete treatment and, if applicable, its polishing.

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It is clear that many potential solutions to producing the desired water quality are available and that these have to be implemented subject to a certain number of simple rules that consider, separately, the removal efficiency of the various contaminants at the different stages of the treatment train, based on:

• the state in which they are present in the water:
  • floating;
  • suspension (settling naturally);
  • colloidal (settling after coagulation);
  • dissolved;
  • ion;

• their respective size (in the case of suspended solids):
  • 150 µ: micro-screening and/or grit removal;
  • 150-10 µ: desludging (micro-screening in exceptional cases);
  • < 10 µ: clarification;

• their specific properties:
  • colloidal (coagulation-flocculation and /or membrane filtration);
  • dissolved matter (oxidation and/or adsorption and/or biological degradation);
  • ion (precipitation and/or desalination membrane);
  • pathogenic micro-organisms (chemical disinfection or irradiation or membrane filtration).

Finally, it must be confirmed that the n stages arranged in the overall treatment system enable the water quality objectives (standards, reliability…) to be achieved in the most cost-effective manner.