Storm Water Turbidity Problem--Chitosan not working

[Ecorp]

We are treating turbid storm water with chitosan and then sending it through a sand filter. Unfortunately, the suspended particles(clay/silt not really sure) are not being neutralized by the chitosan. This is the first time that chitosan has not worked for reducing turbidity on any storm water treatment during construction. Without having to test the water by a laboratory, to see exactly what the suspended solid is, is there another way (hopefully not more expensive than chitosan) of treating this water to reduce turbidity and still meet water quality. I can only that the charge on the soil particles(+) is reverse of what is normally experienced(-) and therefor chitosan(+) is not working.

Could anyone please help me with this challenging problem and your help is greatly appreciated.

 

[bhwtam]

Ecorp,

Just some suggestions for you to consider.

1. Check the pH of the water and see whether it is within the operation range of the chemical "chitosan"

2. You may contact some chemical suppliers for water treatment (i.e. a polymer supplier), they are always willing to offer help. They have their own laboratory and can match the best chemical to suit your needs.

 

[Muggle]

Just a thought here - but we found that running the water through an electrolytic field will increase/speed the chitosan flocculation. Had to do it for industrial textile water. Since your not trying to "treat" the water, but only change polarities - a simple one or two pass through the electrode flow chamber, probably in series, would suffice. Also works where you ahve "floating clay" particles. Pulls them out of suspension like now!

 

[Ecorp]

The manufacturer/distributor of liquid chitosan recommended treating storm water with turbidity problems for pH as low as 6.5 and as high as 8.5. The storm water that was being treated at the site had a natural pH of approximately 8.0. Since this pH value was within the recommended range it was assumed that the chitosan should work to remove colloidal clay suspended particles.

Once the pH of the stormwater was lowered to 7.0, by adding muriatic acid to the sample the chitosan was able to induce flocculation and turbidity of the sample was greatly reduced to me water quality standards. Citric Acid will now be used to lower the pH of treated stormwater which will then be treated with liquid chitosan.

I would like to thank Mike Chase of "Rain for Rent" for helping me solve this problem. I would also like to thank everyone else who replied with other ideas and suggestions to solve more persistent turbidity problems.