Solids are categorized based on particle size and characterization as:
– Total Suspended Solids (TSS)
– Total Dissolved Solids (TDS)
– Volatile Suspended Solids (VSS)
– Total Solids (TS)
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 the amount of total suspended solids in mg/l of sample.
TDS are those solids that pass through a filter with a pore size of 2.0
micron 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.
VSS are those solids lost on ignition (heating to 550 degrees C.) They give
a rough approximation of the amount of organic matter present in the
solid fraction of wastewater, activated sludge and industrial wastes
TS are the total of all solids in a water sample. They include the total
suspended solids, total dissolved solids, and volatile suspended solids.
A water sample is filtered through a standard
glass-fiber filter, and the filtrate liquid is
evaporated to dryness in a weighed dish and dried
to constant weight at 180°C. The increase in dish
weight represents the total dissolved solids
– Glass-fiber filter disks
– Membrane filter funnel
– Gooch crucible, 25-mL to 40-mL capacity
– Suction flask
– Drying oven, for operation at 180 ± 2°C.
Preparation of evaporating dish: If volatile solids are to be measured, ignite cleaned
evaporating dish at 550°C for 1 h in a muffle furnace. If only total dissolved solids are to
be measured, heat clean dish to 180 ± 2°C for 1 h in an oven. Store in desiccator until
needed. Weigh immediately before use.
Sample analysis: Stir sample with a magnetic stirrer and pipet a measured volume onto a
glass-fiber filter with applied vacuum. Wash with three successive 10-mL volumes of
reagent-grade water, allowing complete drainage between washings, and continue
suction for about 3 min after filtration is complete. Transfer total filtrate (with
washings) to a weighed evaporating dish and evaporate to dryness in a drying oven.
Dry evaporated sample for at least 1 h in an oven at 180 ± 2°C, cool in a desiccator to
balance temperature, and weigh.
TDS [mg/L] = (A – B) X 1000 / (sample volume [mL])
A = weight of dried residue + dish, mg, and
B = weight of dish, mg.
TDS and electrical conductivity are in a close
connection. The more salts are dissolved in the
water, the higher is the value of the electric
The majority of solids, which remain in the water
after filtration are dissolved ions. Sodium chloride
for example is found in water as Na+ and Cl-
High purity water is the ideal case only in H2O
without salts or minerals and has a very low
Temperature affects conductivity so that its value
increases from 2 up to 3 % per 1 degree Celsius.
Conductivity is a measure of the ability of water to pass an
electrical current. Conductivity in water is affected by the
presence of inorganic dissolved solids such as chloride,
nitrate, sulfate, and phosphate anions (ions that carry a
negative charge) or sodium, magnesium, calcium, iron, and
aluminum cations (ions that carry a positive charge).
Organic compounds like oil, phenol, alcohol, and sugar do
not conduct electrical current very well and therefore have a
low conductivity when in water.
Conductivity is also affected by temperature: the warmer
the water, the higher the conductivity. For this reason,
conductivity is reported as conductivity at 25 degrees
Celsius (25° C).
Affected by geology. Streams that run through areas
with granite bedrock tend to have lower conductivity
because granite is composed of more inert materials
that do not ionize (dissolve into ionic components)
when washed into the water. On the other hand,
streams that run through areas with clay soils tend to
have higher conductivity because of the presence of
materials that ionize when washed into the water.
Ground water inflows can have the same effects
depending on the bedrock they flow through.
Discharges to streams can change the conductivity
depending on their make-up. A failing sewage system
would raise the conductivity because of the presence of
chloride, phosphate, and nitrate; an oil spill would
lower the conductivity.
Conductivity meters are typically calibrated
using a 0.01 N KCl solution, which has a
specific conductance of 1413 µS at 25°C
(conductivity of solutions increases with temp).
Specific conductivity is commonly used in
water analyses to rapidly estimate total
dissolved solids (TDS) content:
Water type Spec. Cond. (µS) TDS (mg/L)
DI water 0.5 – 3.0 0.3 – 1.7
water 50 - 1500 30 – 850
Seawater 53,000 – 62,000 30,000 – 35,000
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Where A = weight of dried residue + dish (mg)
B = weight of dish (mg)
TSS are solid materials, including organic and inorganic, that are suspended in the
water. These would include silt, plankton and industrial wastes.
High concentrations of suspended solids can lower water quality by absorbing light.
Waters then become warmer and lessen the ability of the water to hold oxygen necessary
for aquatic life. Because aquatic plants also receive less light, photosynthesis decreases
and less oxygen is
Suspended solids can clog fish gills, reduce growth rates, decrease resistance to disease,
and prevent egg and larval development. Particles that settle out can smother fish eggs
and those of aquatic insects. The material that settles also fills the spaces between rocks
and makes these microhabitats unsuitable for various aquatic insects, such as mayfly
nymphs, stonefly nymphs and caddisfly larva.
Suspended solids can result from erosion from urban runoff and agricultural land,
industrial wastes, bank erosion, bottom feeders (such as carp), algae growth or
A well-mixed sample is filtered through a standard GF/F glass
fiber filter, and the residue retained on the filter is dried to
constant weight at 103-105C
Glass microfiber filters discs, 5.5 cm, without organic binder,
Whatman type GF/F (0.7 Fm)
Disposable aluminum dishes
Suction flask, 1000 mL
47 mm glass microanalysis filter holder (funnel, clamp, and base)
Drying oven for operation at 103-105°C
Muffle furnace for operation at 550 ± 50°C
Analytical balance, capable of weighing to 0.1 mg
Reagent grade water (ASTM Type I water)
Insert the filter disk onto the base and clamp on funnel. While vacuum is
applied, wash the disk with three successive 20 mL volumes of reagent
grade water. Remove all traces of water by continuing to apply vacuum
after water has passed through.
Remove funnel from base and place filter in the aluminum dish and ignite
in the muffle furnace at 550°C ± 50°C for 30 minutes. Rewash the filter
with an additional three successive 20 mL volumes of reagent water, and
dry in an oven at 103-105°C for one hour. When needed, remove dish
from the oven, desiccate, and weigh.
Select a sample volume (max. of 200 mL) that will yield no more than 200
mg of total suspended solids.
Place the filter on the base and clamp on funnel and apply vacuum. Wet
the filter with a small volume of lab grade water to seal the filter against
Shake the sample vigorously and quantitatively transfer the sample to the
filter using a large orifice, volumetric pipet. Remove all traces of water by
continuing to apply vacuum after sample has passed through.
Rinse the pipet and funnel onto the filter with small
volume of reagent grade water. Remove all traces of
water by continuing to apply vacuum after water has
Carefully remove the and filter from the base. Dry at
least one hour at 103-105°C. Cool in a desiccator and
Total Suspended Solids, mg/L = (A-B) x 1,000/C
– Where: A = weight of filter and dish + residue in mg
– B = weight of filter and dish in mg
– C = volume of sample filtered in mL
If volatile suspended solids is desired retain the sample
in the dish for subsequent ignition at 550°C (see next
After determining the final weight in the total
suspended solids analysis, place the filter and dish
in the muffle furnace and ignite at 550°C ± 50°C for
Allow to partially air cool, desiccate and weigh.
Volatile Suspended Solids, mg/L = (A-B) x 1,000/C
Where: A = weight of residue + filter and crucible in
mg from TSS test
Total Suspended Solids test
B = weight of residue + filter and crucible in mg after
C = volume of sample filtered in mL
TDS 442: A mixture of sodium sulfate (40%),
sodium bicarbonate (40%) and sodium chloride
(20%). The 442 mixture is designed to mimic the
ions often present in natural fresh water systems.