Alum for water treatment?

[rhihn]

A friend mentioned the use of alum in standing water to reduce settling time of silt (specifically thinking of standing desert water in canyons). Does anyone (lawnsale?) have information or opinions on this method? Has anyone here actually tried it?

I found this article on the subject:

http://www.gcrg.org/bqr/7-4/water.htm

Thanks.