Permeate after IRO constance contamination

[Pauzen]

Hello,

I have constance problem with contamination (P.Fluorensces, A.Ceafalis) on permeat after I RO between II RO stage. I chlorinate water on pretreatment 2ppm, dechlorination UV lamps. Cleaning (ultrasil73,110) and sanitization with biocide DBNPA, izothiazolin or oxonia active doesnt give any result. Rest of the treatment station is clear most time. Zero dedlegs, everything seems to be ok, but the result there are all the time TNTC. Do you have any idea what can be wrong? Weekly cleaning and sanitization give effect only for 2-3 days.

 

[ashtree]

Are you treating water for the food industry?
Just to be clear are you doing two passes (as in the permeate from one RO plant goes to another plant for further treatment) or do you have a 2 stage plant where the concentrate from one stage becomes the feed for the second stage.
What pretreatment do you have in front of the RO?

Regards
Ashtree
"Any water can be made potable if you filter it through enough money"

 

[Pauzen]

Pharma/cosmetic

We have two stages plant, chlorination->UV dechlorination->RO I stage-> degasser-> RO IIstage -> cEDI.. etc but we have constance contamination between permeate 1 stage and 2 stage, after 2 stage water is ok.

 

[quark]

Are you recirculating part of RO1 reject?

 

[Pauzen]

Yes, but i do extra recirculation pipe C&S

 

[ashtree]

Are you using a packed tower degasser?

If you are putting the DBNPA etc into the feedwater almost none of that chemical will pass through into the permeate, so there would be every chance that these bacteria are growing either in the peremeate side of the membrane or in the degasser. They are subsequently removed by the RO2 stage.
Chemicals such as the Ultrasil will do little to disinfect the membranes as they are primarily cleaners.

You may need to do a physical inspection on your degasser media. Also i would try a shock dose of DBNPA into the RO1 permeate stream and see if that improves the situation. You might get some fouling on RO2 for a while.

Regards
Ashtree
"Any water can be made potable if you filter it through enough money"

 

[quark]

Not a problem of C&S. RO systems are capable of filtering as well as passing microbes. If there is count in feed water, it gets concentrated at reject and subsequently can pass in to permeate. I suggest following steps.

1. Check TVC at feed to RO1, reject of RO1 and permeate of RO1.
2. In case of TNTC, one level serial dilution to check the actual count. Just leave it if it is still TNTC.
3. Neutralize sample before RO1 feed with SMBS and check whether you are getting any count. Sometimes, 2 ppm NaOCl may not kill bacteria but may keep them in sedentary mode.
4. Neutralize sample before RO and check the count. You need to do chlorine dosing based on actual viable count.
5. Check for the possibility of adding RO reject before chlorination.

Good luck,

 

[Pauzen]

Quark,

I checked everything and i think that i have problem with circulation pipe.
But i have also different question. What type of antiscalat do you use? I use RPI 7000 ropur but it is very contaminated with yeasts and molds (new package) is this normal situation or we have contamineted batch?

 

[quark]

It can be possible. Water system component and chemical manufacturers are not as strict as we are. I experienced sever contamination issues with multi grade medium, softener resin and also SMBS. Better to drain RO reject if you have problem with that. You have more water consumption but at least you will get output.

 

[ashtree]

Think of antiscalant as the oil for an engine. Would you put contaminated oil in an engine. Without knowing your water quality I cannot say if the antiscalant you are using is the most suitable for your application but f the product is contaminated i would try another product.

Regards
Ashtree
"Any water can be made potable if you filter it through enough money"

 

[Pauzen]

Can you recommend me a company that produces anti-scales with an emphasis on microbiological purity?

 

[ashtree]

Use Google to find a supplier in your area or Country. You will need a water quality analysis plus some performance detail of your RO so they can assess your requirements.

Regards
Ashtree
"Any water can be made potable if you filter it through enough money"

 

[quark]

Just filter that using 0.22 micron filter

 

[Pauzen]

Quark, thank you for this information I will try to do it. You use filter after dosing pump (i have grundfoss DDC) or before the pump?

 

[quark]

Any where is ok, if you want to do online. Alternately, filter the antiscalent separately and then use for dosing.

 

[ashtree]

The dose pump will never push through a 0.22 micron filter. In fact it will be quite difficult to filter any significant quantity of antiscalant with a filter of that size unless you have the appropriate equipment to do so.
I would suggest that you obtain a replacement batch.

Regards
Ashtree
"Any water can be made potable if you filter it through enough money"