This is a common problem in environmental microbiology. Often
the media is turbid, and prevents measurement of bacterial
concetration by checking the turbidity. Go with a direct
count. Centrifuge a sample, resuspend the pellet, and check
the concentration of cells in a counting chamber or hemocytometer.
Alternatively, you could try making a solid media for plate
counts. It might be easier if the turbidity of your media is
such that direct counting would be difficult.
Dept. Microbiology and Biochemistry
Rutgers University Cook College
New Brunswick, NJ. USA.