Field Methods of Monitoring
Aquatic Systems
Unit 3 – Suspended and
Dissolved Solids
Copyright © 2006 by DBS
Title
Total dissolved solids is a good measure of the
concentration of ionic substances in water
Solids
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Solids are categorized into several groups based on particle size and
characterization
– Total Suspended Solids (TSS)
– Total Dissolved Solids (TDS)
– Volatile Suspended Solids (VSS)
– Total Solids (TS)
Consist of an inorganic fraction (silts, clays, etc.) and an organic
fraction (algae, zooplankton, bacteria, and detritus)
Inorganic portion >>> organic
Contribute to turbidity of the water
High sediment loads are obvious because of their "muddy" appearance
Drinking water limit 500 mg L-1 (secondary standard)
Total Suspended SolidsCategories
TSS are the amount of filterable solids in a water sample.
Samples are filtered through a glass fiber filter. The filters are
dried and weighed to determine total suspended solids in mg L-1
Total Dissolved Solids
TDS are those solids (inorganic+organic) that pass through a
filter of 2.0 μm or smaller. They are said to be non-filterable.
After filtration the filtrate (liquid) is dried and the remaining
residue is weighed and calculated as mg/l of Total Dissolved
Solids
Volatile Suspended Solids
Volatile solids are those solids lost on ignition (heating to 550
°C.) They give a rough approximation of the amount of organic
matter present in the solid fraction
Total Solids
TS are the total of all solids in a water sample. Can be
measured by evaporation - problems with water retention and
decomposition of OM
TS = TSS + TDS + VSS
Question
What physical problems may be caused by suspended
particles?
Cut down light transmission and lower the rate
of photosynthesis
Clog fish gills
In less turbulent parts of rivers and particularly
in lakes particles sediment out (siltation)
smothering the bottom dwellers
Also affect temperature and DO (heat capacity)
Sources of Error
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Sampling, subsampling, pipeting 3-phase smples
Keep homogeneous during transfer – do not pipet from vortex!
Mix small samples with magnetic sampler
Pipet SS with wide-bore pipet
Analyze at least 10% samples in duplicate
(should agree ± 5% average weight)
• Dry to constant weight (or change is < 4% previous or 0.5 mg)
• Record variations in procedures
Sampling
• Sample size needed will vary depending on turbidity
– Choose sample volume to yield 2.5 - 200 mg dried residue
– If longer than 10 min for filtration increase filter size or
decrease sample volume
• Store in the dark at 4 °C to minimize MO decomposition
(for up to 7 days)
• Analyze ASAP due to impracticality of preserving sample
(preferably no longer than 24 h)
• Bring to room temperature prior to analysis
Analysis for TSS
• Analysis via filtration and weighing
– Hartley funnel or magnetic
funnel
– Glass fiber disc with membrane
filter
Hartley Funnel
Magnetic Funnel
Analysis for TSS
Remove sample from refrigerator ~30 mins prior to analysis
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Prepare a 0.45 micron filter using wash-dry-cool cycle
Seat filter with DI water prior to filtration
Pipet a measured volume into filtration apparatus from stirred
sample
Wash filter with 3 x 10 mL washings DI water
Apply suction for 3 mins after washing
Transfer to aluminum dish for support
Dry in the oven at 103-105 °C overnight (should be 1 h)
Place in a dessicator to cool to room temperature, reweigh to
the nearest 0.1 mg
Calculate TSS in mg L-1
Analysis for TDS
Remove sample from refrigerator ~30 mins prior to analysis
1. Dry a clean dry beaker at 103-105 °C for at least 1 hour
2. Dessicate until cool and weigh to nearest 0.1 mg
3. Filter 50.0 mL through a 0.45 μm filter paper into clean dry beaker using
technique described above
4. Heat the sample to just below boiling and reduce the volume to 10 mL
DO NOT ALLOW TO BOIL OVER OR SPLATTER
5. Allow the beaker to cool and dry in the oven at 103-105 °C overnight
6. Remove the beaker and place in a dessicator to cool to room
temperature, reweigh to the nearest 0.1 mg
7. Calculate TDS in mg L-1
Question
Why is it necessary to wash filter with 3 x 10 mL washings of
DI water?
If water contains an appreciable amount of dissolved
substances these will add to the weight of the filter as it is
dried
TDS Meter
• Conductivity meter ‘in disguise’
• Only detects ions
• Do not detect neutral species
– Organics
– Marcoscopic particles
• Not really TDS
• +/- 10% accuracy compared to
TDS
Turbidity
• Turbidity - cloudiness or haziness of water caused by individual
particles that are too small to be seen without magnification
• In water quality monitoring situations, a series of more labor
intensive TSS measurements will be paired with measurements
from a nephalometer to develop a site-specific correlation
Text Books
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Rump, H.H. (2000) Laboratory Manual for the Examination of Water, Waste Water and Soil.
Wiley-VCH.
Nollet, L.M. and Nollet, M.L. (2000) Handbook of Water Analysis. Marcel Dekker.
Keith, L.H. and Keith, K.H. (1996) Compilation of Epa's Sampling and Analysis Methods.
CRC Press.
Van der Leeden, F., Troise, F.L., and Todd, D.K. (1991) The Water Encyclopedia. Lewis
Publishers.
Kegley, S.E. and Andrews, J. (1998) The Chemistry of Water. University Science Books.
Narayanan, P. (2003) Analysis of environmental pollutants : principles and quantitative
methods. Taylor & Francis.
Reeve, R.N. (2002) Introduction to environmental analysis. Wiley.
Clesceri, L.S., Greenberg, A.E., and Eaton, A.D., eds. (1998) Standard Methods for the
Examination of Water and Wastewater, 20th Edition. Published by American Public Health
Association, American Water Works Association and Water Environment Federation.