There are several methods to measure total suspended solids in water. They all give similar results for small to medium particles. The methods are; 1) USEPA method 160.2, 2) APHA 2540 D, 3) ASTM D-3977. The ASTM method is the most accurate, regardless of particle size.
All three methods filter water through filter paper that is weighed before and after with the solids are dried.
Typical water quality to minimize corrosion is to have the pH between 5.5 and 8.0, chlorides less than 50 ppm, oxygen content less than 20 ppb. I have seen H2S content in the cutting water tank at 5 ppm. Lower is better. Iron content should be less than 1 ppm, but the trends are the important data. If the iron content is 5 ppm for several weeks and then increases to 10 ppm, that is an indication of a change in corrosion in the water system. There should be a correlation between NH3 and H2S. If the ammonia is high, then the H2S will be high as well. Again, the trends are the important part.