Storm Water Treatment-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 assume 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.

 

[KRSServices]

Up here, we are now being required to discharge relatively "clean" stormwater into the environment. One acceptable method is to construct a retention, or holding pond to settle out and fines prior to discharge. We also utilize chambers (big CB basins) to capture some debris as well. It has not yet come to the stage of using chemicals to floc the water. The ponds though, require a huge amount of space.

KRS Services

http://www.krs-services.com

 

[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.