pyrolox filter 2

[Bogdanaquasys]

I have the fallow application:
Pyrolox / sand filter with 2000 mm tank diameter. I fill the tank with 420 kg of quartz 2-4 mm on base. After that I put, in the succesive layer, 2360 kg of quartz 0.8-2 mm and 2120 kg pyrolox 8x20.
Work condition is: filtering flow is 40 mc/h, backwash flow is 192 mc/h, backwash daily with 30 min duration.
Water contain 0.385 mg/l manganesse and 0.08 mg/l iron. pH is arround the 7.0.
I put the filter in service and the concentration of manganesse in the filtered water not decrease below 0.130 mg/l.
Please help me with a advice, because I don't know is happen and where I wrong.

Thank in advance.
Bogdan

 

[ashtree]

Your feed rate looks okay and the pH is within the recommendations.
A couple of questions.
Does the water contain high levels of tannins , sulphur or chlorides?
How are you measuring the manganese?
How long after a backwash are you testing the water?
Have you tried injecting chlorine before the filter?


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

 

[bimr]

The pH needs to be above 9. If the pH is below 9, a oxidation of manganese will not be satisfactorily and you will not be able to filter the manganese out.

 

[Bogdanaquasys]

Thank you Ashtree for your response.

So,my answer for your question is:

Does the water contain high levels of tannins , sulphur or chlorides?
no tannins, no sulfur and chlorides is around 100 mg/l

How are you measuring the manganese?
two methods: 1 - in site with Hach Lange DR900 colorimeter, 2 - in the lab

How long after a backwash are you testing the water?
Testing the water 30 min after backwash.

Have you tried injecting chlorine before the filter?
Yes. I have gas chlorine in the front of filter. The dose is around 15 g/h.

Thanks.
Bogdan

 

[ashtree]

There is no doubt that the performance will definitely be better at 9 pH or above as bimr suggests.
The manufacturers claim that anything above 6.5 will work well but i would suggest that at the lower end you should allow for a slower process rate , longer contact time and more media to achieve the manganese removal to a low level. This will particularly apply below 8 pH
Its likely that much of the manganese removal is being achieved by the chlorine dose applied. Based on the amount of chlorine applied assuming there is no other chlorine demand the manganese should be at around 0.08mg/l. But there will be other demands which will reduce the amount of chlorine available for the oxidation of the manganese.

So you could try reducing the flow rate, or increasing the pH and check if the removal improves.

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