CE 170:  Water Quality and Supply Engineering

Lab 3:  Measurement of Total Suspended Solids

Purpose of Lab

The purpose of this lab is become familiar with the standard measurement of total suspended solids (TSS) and the relative precision of that measurement.

Procedures

1.	The filters you will be using have been washed and dried.  You are going to weigh them on the analytical balance, so handle them with tongs or tweezers at all times.

2.	Remove three aluminum boats and three filters from the desiccater.  Note the markings on the boats.

3.	Using the analytical balance, weight the aluminum boats and filters.  Record those weights.

4.	Place the filter on the suction apparatus as directed by the instructor.  Wet filter with a small amount of deionized water to seat it.

5.	Filter 50 mL of the sample (or another volume as directed by the instructor).  Use care that you deliver exactly the volume specified and that your sample is well-mixed.

6.	Wash the filter with three successive 10 mL washings of distilled water while continuing suction.  Wait 3 min. between washings.  (If some solids have been caught in your glassware, rinse them out with these washings.)

7.	Turn off the suction and, using tweezers, place the filter in its boat.

8.	Repeat steps 4-7 for the other two filters.

9.	Place the all the aluminum boats and filters in the drying oven for at least one hour.

10.	Remove the aluminum boats and filters from the oven and place in the desiccater for at least 15 minutes.

11.	Weight the aluminum boats and filters.  Record those values.

Data Analysis

1.	Calculate the TSS values for your samples in mg/L.

2.	Exchange data with the other groups and record all the TSS values.

3.	For the complete class data set, calculate the mean, sample standard deviation, coefficient of variation, and 95% confidence interval about the mean.

Discussion Questions

1.	Compare the precision of the suspended solids data with that of the volume measurements of the previous week's lab.  (Use the COV as your measure of precision.)  Comment on possible reasons for the difference.  

2.	Why are there no calculations or discussions of relative error or accuracy in this lab?