1. 
   Prechlorination
   The addition of chlorine at the headworks of a treatment plant prior to other treatment processes. Done mainly for disinfection and control of tastes, odors, and aquatic growths, and to aid in coagulation and settling,
   Found op http://www.epa.gov/OCEPAterms/
   
   
2. 
   prechlorination
   [n] - chlorination prior to another chemical process
   Found op http://www.webdictionary.co.uk/definition.php?query=prechlorination
   
   
3. 
   Prechlorination
   chlorination of water prior to filtration, or chlorination of sewage prior to treatment.
   Found op http://www.chemicalglossary.net/definition/1244-Prechlorination
   
   
4. 
   prechlorination
   noun chlorination prior to another chemical process
   Found op http://wordnetweb.princeton.edu/perl/webwn?s=prechlorination
   
   
5. 
   prechlorination
   1) Chlorination
   Found op http://www.mijnwoordenboek.nl/EN/crossword-dictionary/prechlorination/1
   
   

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