Gravimetric analysis or, simply, weighing:
Analytical balances routinely used for gravimetric analysis are sensitive to one tenth of a milligram, or one ten-thousandth of a gram. Most laboratories use electronic balances with direct digital readouts.
For a measurement of the milligrams per liter of solids in the water, a measured volume of sample can be dried in a tared (pre-weighed) dish; the dish plus solids are weighed after the water has evaporated off; the weight of solids is calculated by subtraction, and the concentration figured by dividing the weight of solids by the volume of the sample.
For a filtered sample, the tared filter itself is dried along with the solids it captured, a
nd the suspended solids (those captured on the filter) calculated in the same way. In some chemical analyses, a precipitate is formed by reacting the analyte of interest with another chemical reagent (reacting chemical); then the precipitate can be filtered, dried, and weighed as a suspended solid. This type of analysis is more common with water solutions that are more concentrated than environmental samples, though, such as chemicals purchased for use in water or wastewater treatment.
nd the suspended solids (those captured on the filter) calculated in the same way. In some chemical analyses, a precipitate is formed by reacting the analyte of interest with another chemical reagent (reacting chemical); then the precipitate can be filtered, dried, and weighed as a suspended solid. This type of analysis is more common with water solutions that are more concentrated than environmental samples, though, such as chemicals purchased for use in water or wastewater treatment. 
