6 replies to this topic

[bdabhi]

Ours is a natural gas processing company having cooling tower & drinking water plant, Disinfection is required in both water cooling tower circualting water & drinking water. Liquid chlorine is used for disinfection but recent study shows that chlorine dioxide generator is used in Cooling tower to disinfect insteead of chlorine but Chlorine dioxide is still not reportedly found to be a disinfectent for drinking water in india. i have discussed this metter so many people & gone through lots of material avaiable on internet chlorine, dioxide is found to be used in USA for threatment of drinknig water not any where else.we want to eliminate the hazard of chlorine gas leak. As alternate solution , chlorine dioxide is thought about but unconverted chlorate& chlorite present in water are harmful so can any body suggest other alternative of disinfection which is economical

[kkala]

I think http://www.pdhengine...s/en/C-2008.pdf can help a bit. It shows advantages & disadvantages of each method. Chlorination is used in Athens, chlorine smell was sensed from time to time in the past, but not in the recent past. It depends on chlorine distribution, which should be in multiple points close to consumption. Otherwise you have to introduce excess chlorine for "safety" concerning disinfection, resulting in much unreacted chlorine at the consumtion points.
Local bottled water (never caught smelling Chlorine) is desinfected by UV radiation or ozone, according to my information. Desinfection is valid for a whole year, as understood from expiration date; but of course this bottled water does not contact impurities, bacteria, air, as potable water of public network does.

[kkala]

It is also noted that chlorine dioxide is used as potable water desinfectant not only in USA, but also in Brussels (Belgium) and probably in other countries. See http://en.wikipedia....hlorine_dioxide, chapter "uses", where drinking water pretreatment prior to chlorination is also mentioned.

Edited by kkala, 12 August 2011 - 07:46 AM.

[bdabhi]

Thanks for reply KKala

I have gone trough the PDH Engineer file sent by you which gives comparision between Chlorine & Sodium hypochlorite treatment . that is a alternative for chlorine dioxide but regarding residual chlorite & chlorate present in water is health hazard .is it true .kindly throw some light on it.

thamks in advance.

[tarafdar]

You may go through WHO reports related to drinking water,specifically chlorite ,chlorate & chlorine-dioxide related articles.One of these is "Chlorite & Chlorate in drinking water,WHO 2005.You also may study articles by "Health Canada".

[kkala]

Water centrally chlorinated -- then passed through an active carbon filter at any consumption point, is applied here in a few appartments and houses as an effective and rather healthy purification method. But this is an expensive way, while you would want an economical disinfection.
On the other hand UV radiation has no residuals, but leaves no residual disinfection, so it looks not proper (if applied alone) on water distributed through pipes (http://www.nesc.wvu....b/ot_tb_f00.pdf).
Some comparative information on water disinfection methods can be found in http://www.lenntech....CFZwz3wodfUoF8w.
You seem to want a scheme cheap & safe enough at the same time. Even if I knew your plant in detail, I would not have had the experience / knowledge for such a selection.
I would probably first look into same method as the one used for cooling water, trying to limit its draw backs to the extent possible. You can also contact suppliers of water disinfection, in addition to the search for literature mentioned by tarafdar.

Edited by kkala, 19 August 2011 - 03:28 PM.

[garycallachan]

In the UK, DWI (Drinking Water Inspectorate) limits are set at 0.5 mg/l (ppm) in the drinking water as combined chlorine dioxide, chlorite and chlorate.

With traditional chlorite/acid chemistries, the following stoichiometry is used:

5NaClO2 + 4HCl ==> 4ClO2 + 5NaCl + 2H2O

Chlorite will be left over due to the molar imbalances, as will some excess acid. The reaction proceeds best at pH 2.

Chlorate is present in very small DBP quantities. The reactor efficiency will determine the chlorite concentration - which should be low, given sound reactor design.