Chemistry Reference
In-Depth Information
Table 18.3
Concentration of orthophosphate in settled sewage samples, filtered and
unfiltered, with different preservatives, analysed at different times
Orthophosphate as P mg L
−1
after storage
Sample
0
1 day
3 days
6 days
Mean
Settled
unfiltered
5.26
5.96
6.33
6.63
-
Sewage
filtered
4.28
4.20
4.48
4.74
4.43
D.M.
a
−0.15 −0.23
+0.05
+0.31
Settled
unfiltered
4.19
5.35
6.04
6.44
-
Sewage
filtered
4.19
4.03
4.14
4.59
4.24
D.M.
a
pH 10
−0.05 −0.21
−0.10
+0.35
Settled
unfiltered
4.89
4.77
5.34
5.85
-
Sewage
filtered
4.09
4.16
4.14
4.24
4.16
HgCl
2
D.M.
a
−0.07
0.00
−0.2
+0.06
Settled
unfiltered
5.11
5.24
5.49
5.53
-
Sewage
filtered
3.56
3.54
3.76
3.90
3.69
HgCl
2+
pH 10
D.M.a
−0.13 −0.15
+0.07
+0.21
Settled
unfiltered
5.00
5.52
6.20
6.48
-
Sewage
filtered
4.15
4.16
4.54
4.74
4.40
D.M.
a
Formaldehyde
−0.25 −0.24
+0.14
+0.34
Settled
unfiltered
5.11
5.43
5.43
5.46
-
Sewage
filtered
3.84
4.09
4.04
4.00
4.00
Formaldehyde
pH 10
D.M.
a
−0.16
+0.09
+0.04
0.00
a
D.M.=deviation from the mean concentration in filtered samples
Source: Reproduced with permission from Sulpher Ltd., Chiswick, UK [16]
18.6
Sulphide
Samples for sulphide determination must always be fixed immediately after sampling.
Any sized bottle can be taken, but normally a 200ml bottle is convenient. As the
stabilised sample is a glutinous suspension and the use of the whole sample is
recommended, it is best to measure the volume of sample poured into the bottle. The
bottle neck should be sufficiently wide to allow for adequate policing (not with rubber) if
necessary. When stoppered, it should be airtight. If multiple determinations are made to
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