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What are the minimum chlorine levels that are acceptable in potable water?


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#1 Rudra

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Posted 17 February 2020 - 04:42 AM

Dear all,

I read many posts on water safety here and they are indeed very interesting. I got a minor non conformity during my recent HACCP meeting:

NC: "It was noted that Central Water Authority (CWA) potable water was used for the production activities, cleaning programme & personal hygiene. However, the following discrepancies were noted at time of audit:
-The free chlorine test carried out at time of audit indicated a free chlorine level of less than 0.2ppm at point of use & control measure was not defined in case of deviations from the acceptable limit or during periods of heavy rainfall (for example, additional chlorination)"
Please note that out of 6 tests done at 6 different hand washing points, only 1 test was <0.2ppm. The others were 0.5-0.6 ppm. This is the first time since past 3 years that we have got such a low result. Can you please help me to tackle this issue?
Many thanks and Regards,
Shakti


#2 pHruit

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Posted 17 February 2020 - 09:26 AM

It might be useful if you can provide a bit of further clarification on exactly what has gone wrong, what potential risk that poses, and what in a practical sense you're actually able to do about it?
Do I infer correctly that the "Central Water Authority" is a municipal supply of potable mains? Are they the ones adding the chlorine, and do you top it up on site to achieve a specific level?
What is the water used for - do you actually need the specific level of chlorination for specific processes?

 



#3 Rudra

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Posted 17 February 2020 - 11:19 AM

Let me clarify. CWA is the supplier of water across the country (government) and is responsible for water treatment and purification (addition of chlorine etc..). This water is used in our company to prepare at 100 degrees and also for drinking purposes and hand washing. WHO sets a chlorine range of 0.2 - 1.0 ppm in portable water. We auditor tested for level of chlorine in water which we use to clean our hands, it was <0.2 ppm. She argues that low Cl level = high risk of bacteria. Since heat treatment destroys possible bacteria, there might be a cross contamination during handwashing. we dont have any chlorination process. 



#4 Charles.C

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Posted 17 February 2020 - 02:06 PM

Hi Rudra,

 

You omitted to mention the product/process. I deduce you are cooking something.

I also deduce you currently do not internally increase the free Cl2 ppm level or routinely monitor the input supply.

Does <0.2 ppm mean undetected ?

Allowable increased internal Cl2 levels sometimes depends on the product/customer/specific Cl2 generator in addition to local regulatory factors.

 

If yr auditor was generally correct, thousands of factories would probably be out of business. However I partially agree with yr auditor that if you are working with materials of significantly high micro.levels then IMEX boosting the Cl2 ppm level internally to a few ppm may reduce the overall baseline micro. level prior to applying routine cleaning/sanitizing.

 

Measured Internal free Cl2 levels will depend on (a) the input, (b) the distribution network inside the plant, © the sampling points, (d) the method of sampling, (e) method of analysis.

 

One obvious comment is that it is advantageous to monitor the micro levels (eg APC, coliforms, generic E.coli) of supply water / internal water at appropriate points on a random basis.

 

IMEX 1-3 ppm free Cl2 in main internal input assures negligible APC/coliform counts at internal sub-distribution points as long as an appropriate residence time is used at input + clean/non-excessively long internal pipelines.

 

Clearly, if the input Cl2 level varies on a daily basis, so will the internal levels.

 

IMo need some data / information on (b-e) to probably say much more.


Kind Regards,

 

Charles.C


#5 Rudra

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Posted 18 February 2020 - 03:39 AM

Dear Charles,
Many thanks for this detailed answer. Our scope of production of instant dry noodles: water is used during mixing, steaming steps. Same water is used for drinking and hand wash.
We use apparatus Cl DPD to monitor Cl level in water on a daily basis. As per WHO Cl level in portable water should be between 0.2 - 1.0 ppm. At time of audit, only one point, auditor got a result of <0.2 ppm (sampling point is hand wash basin). The other hand washing points, Cl level was 0.6 ppm.

- We don't add chlorine to our water tank neither do we want to add it. 

- There are 4 water tanks and water is distributed from any one of them

- Sampling point : tap

- Sampling method: just fill in the apparatus directly form the tap (image attached)

Results of Cl in water at same point where auditor did the test taken at 3 time a day (intervals of 3 hours):

9:30 am : < 0.2 ppm

12:30 pm : 0.6 ppm

15:30 pm : 0.6 ppm

Thanks,

Rudra



#6 Charles.C

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Posted 18 February 2020 - 05:19 AM

Dear Charles,
Many thanks for this detailed answer. Our scope of production of instant dry noodles: water is used during mixing, steaming steps. Same water is used for drinking and hand wash.
We use apparatus Cl DPD to monitor Cl level in water on a daily basis. As per WHO Cl level in portable water should be between 0.2 - 1.0 ppm. At time of audit, only one point, auditor got a result of <0.2 ppm (sampling point is hand wash basin). The other hand washing points, Cl level was 0.6 ppm.

- We don't add chlorine to our water tank neither do we want to add it. 

- There are 4 water tanks and water is distributed from any one of them

- Sampling point : tap

- Sampling method: just fill in the apparatus directly form the tap (image attached)

Results of Cl in water at same point where auditor did the test taken at 3 time a day (intervals of 3 hours):

9:30 am : < 0.2 ppm

12:30 pm : 0.6 ppm

15:30 pm : 0.6 ppm

Thanks,

Rudra

 

Hi Rudra,

 

Thks above. But no image attached.

 

Afai can see, the main input Cl2 level is not in yr control, regardless of WHO preferences. :smile:

 

I deduce all audit measurements were on different tanks ?.

 

I hope you adequately  flushed the tap/line prior to sampling.

 

I assume all the tanks are similar size, material, cleanliness, distances, and indoors.

 

IMEX DPD is used with Lovibond meter. There should be a visible colour for a detectable Cl2 level so I anticipate that <0.2ppm meant some colour but weaker than the (usually lowest available) 0.2 ppm standard.

 

Maybe the <0.2ppm  audited tank was stagnant prior to  test ? Just speculating. Are all the tanks in use all the time ? (and prior to 0930 hrs ?)

 

Assuming that all 4 tanks are (somehow) filled from one main line you need to (a) monitor the main input as in (b) and (b) repeat the audit procedure on all 4 tanks (at "same"  time)  for a few days. Ideally more frequently than the audit.

 

A typical correction procedure could be to boost the Cl2 level  if reading <0.2ppm however this relies on yr main line being significantly greater.


Kind Regards,

 

Charles.C


#7 Rudra

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Posted 24 February 2020 - 06:06 AM

Hello Charles,

Thanks for your prompt reply. Below are the answers of your query:

- The main input Cl2 level is not in yr control (Yes)

I deduce all audit measurements were on different tanks ? (NO- out of 3 points, only 1 point was tested by the auditor and found to be non conformed. This point is used few times per day while the other 2 points are used more frequently. The 2 points were tested by our lab technician and the Cl level was 0.6 ppm )

I hope you adequately  flushed the tap/line prior to sampling (No flushed - how many secs do you propose to flush prior to sampling?)

I assume all the tanks are similar size, material, cleanliness, distances, and indoors.(YES)

Maybe the <0.2ppm  audited tank was stagnant prior to  test ? Just speculating. Are all the tanks in use all the time ? (and prior to 0930 hrs ?) YES - water remained stagnant for 2 days. Not all tanks used at same time

 

A typical correction procedure could be to boost the Cl2 level  if reading <0.2ppm however this relies on yr main line being significantly greater: we found 2 points with correct Cl level and only one point with <0.2ppm. I was thinking of a probable contamination in one specific water distribution pipe may be?

I need to answer my auditor and for the time being I don't want to commit by adding Cl in water. i think I shall answer my auditor like this: " we shall perform several tests at the different points and based on the results we shall put in place an action plan. We shall write a procedure for Cl testing and monitoring"

please comment.

many thanks



#8 Charles.C

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Posted 24 February 2020 - 09:07 PM

Hello Charles,

Thanks for your prompt reply. Below are the answers of your query:

- The main input Cl2 level is not in yr control (Yes)

I deduce all audit measurements were on different tanks ? (NO- out of 3 points, only 1 point was tested by the auditor and found to be non conformed. This point is used few times per day while the other 2 points are used more frequently. The 2 points were tested by our lab technician and the Cl level was 0.6 ppm )

I hope you adequately  flushed the tap/line prior to sampling (No flushed - how many secs do you propose to flush prior to sampling?)

I assume all the tanks are similar size, material, cleanliness, distances, and indoors.(YES)

Maybe the <0.2ppm  audited tank was stagnant prior to  test ? Just speculating. Are all the tanks in use all the time ? (and prior to 0930 hrs ?) YES - water remained stagnant for 2 days. Not all tanks used at same time

 

A typical correction procedure could be to boost the Cl2 level  if reading <0.2ppm however this relies on yr main line being significantly greater: we found 2 points with correct Cl level and only one point with <0.2ppm. I was thinking of a probable contamination in one specific water distribution pipe may be?

I need to answer my auditor and for the time being I don't want to commit by adding Cl in water. i think I shall answer my auditor like this: " we shall perform several tests at the different points and based on the results we shall put in place an action plan. We shall write a procedure for Cl testing and monitoring"

please comment.

many thanks

 

Hi Rudra,

 

TBH I'm surprised that yr auditor didn't complain about yr (I deduce) not having any monitoring data for yr tap water.

 

Flush for 2-3 minutes. Also remove/clean/replace any strainers if used inside the tap.

 

Yr immediate priority IMO is to get some tap data vs time of day + some data for the input supply. Especially if any points are stagnant.

 

May depend on what you are producing but control might be easier if you only used one large internal supply tank + installed an automatic Cl2  doser.


Kind Regards,

 

Charles.C


#9 carine

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Posted 25 February 2020 - 08:20 AM

HI Rudra, 

 

Basically we are encounter same problem as you, hard to maintaining the Cl2 level in our raw material and finished product where, standard CL2 level for potable water and bottled drinking water is the same; min 0.2ppm. 

 

We are bottled drinking water manufacturer, our main raw material is potable where supplied by local water authorities here.  As you all know CL2 level will be slowly reduced along the process due to the evaporation characteristics. Furthermore, water will pass through filtration treatment prior to bottling and this even escalate the evaporation of Cl2. 

 

Appreciate had this issue before , your input is much appreciated. Thanks in advance



#10 Charles.C

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Posted 25 February 2020 - 01:15 PM

HI Rudra, 

 

Basically we are encounter same problem as you, hard to maintaining the Cl2 level in our raw material and finished product where, standard CL2 level for potable water and bottled drinking water is the same; min 0.2ppm. 

 

We are bottled drinking water manufacturer, our main raw material is potable where supplied by local water authorities here.  As you all know CL2 level will be slowly reduced along the process due to the evaporation characteristics. Furthermore, water will pass through filtration treatment prior to bottling and this even escalate the evaporation of Cl2. 

 

Appreciate had this issue before , your input is much appreciated. Thanks in advance

 

Same suggestion as Post 8

 

Invest in an appropriately designed main input / distribution system which includes a  "chlorine"  injector pump (or pumps) equipped with a feedback loop control function.


Kind Regards,

 

Charles.C


#11 Rudra

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Posted 28 February 2020 - 08:13 AM

Dear all,

many thanks for your comments. I am doing tests to monitor it. will revert back soon.

thanks






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