Test samples
Once the test sample has been prepared correctly, there are a range of tests to complete when testing sedimentation and clarification processes.
Turbidity, pH and temperature are monitored closely throughout the sedimentation and clarification processes. Residual coagulant level is also measured at the end of the process in some plants.
Testing throughout the sedimentation and clarification process
Rollover the process to investigate the various tests and where they are usually carried out:
Sludge solids volume analysis
The main test on sludge is the sludge solids volume analysis. Solids volume analysis tests the sludge density. This aims to determine the weight of a sample of sludge compared to its volume and solid concentration (% w/v). This is similar to doing a 'total solids' test.
Step 1: Weigh an evaporating dish and record the weight.
Step 2: Place a volume of water into the dish.
Step 3: Place in a drying oven for 1 hr at 105° C
Step 4: When the water has evaporated, remove the evaporating dish.
Step 5: Weigh the evaporating dish with the remaining
solids.
Sludge solids = dry weight of the sample x 100%
volume of the sample
Sludge solids (w/v) % = dry weight of the sample x 100%
volume
of the sample
For example
The following extract from a Lab logbook gives an example of the calculations required
Volume of sample filtered 1000mL (1L)
Weight evaporating dish (before
test) 1,000
Weight evaporating dish (after test) 20g
Weight dissolved solid = Weight evaporating dish
(after test) - weight
of evaporating dish before test
Weight dissolved solid = 20 - 10
=
10g
Sludge solids = dry weight of the sample x 100%
volume
of the sample
Sludge solids = 10 x 100%
1000
Sludge solids = 1%
Workplace Project
Use the worksheet to answer questions about testing in your workplace.
Worksheet - Testing samples (Word doc 260 kb)