Suspended solids
For the total amount of solids, C,
C=S+X
(2.1)
In connection with chemical precipitation, particles up to and including O.lJlm can
be precipitated, and hence the determination of suspended solids by filtration
through an 0.1 Jlm filter may be a good idea.
The distribution of particles in wastewater is essential to separation and precipitation processes. Fig 2.2 shows how particles may be distributed. In spite of the
varying concentration of the wastewater at the three dates of sampling, a certain
pattern is seen in the appearance of the curve. The wastewater has its fingerprint.
Sometimes the solubility index, is used which is defined as
SIC
20.0
15.0
10.0
5.0
ml particles in each
size interval per m3 wastewater
(
/\
I \
1.0
\
\
\
\
\
\
2 .0
2915 - -
16/5 - - - 10 00
25/5 • • • • 7 00
..
.,. -
' '
. . . .
4 .0
Particle
diameter
8 .0 11 m
(2.2)
Fig 2.2
Distribution of particles in raw wastewater, from the Lundtofte tr eatment plant
(Denmark)/19/.
2.1.1 Settleable solids
Settleable solids are normally ascertained after 2 hours' settling. It is the difference
between the total content of solids in the untreated sample o f wastewater and in the
upper part of the water column after 2 h ours' settling.
38