220 Organic compounds in soils, sediments & sludges
Typical chromatograms are shown in Figure 10.2. Figure 10.2A represents a standard injection of a mixture of 20 mg/L for each volatile fatty acid while Figure 10.2B
shows a spiked volatile fatty acid-free added at a concentration of 20 mg/: of each
volatile fatty acid. Figure 10.2C shows a routine pig slurry analysis. The Supelogel
610H satisfactorily separated the volatile fatty acids within 34 minutes. A baseline
derivation observed on Figure 10.2B during the run did not affect the identification of
peaks. Unidentified peaks appeared in the sample chromatogram of spike volatile fatty
acids-free slurry, probably due to the volatile fatty acid removal aeration technique,
but these peaks did not affect the quantification of the acids added to the slurry. For
slurry analysis the major peak is acetic acid, and the minor peak is valeric acid. Three
peaks appeared 37.47, 41.64 and 44.20 minutes after the volatile fatty acid peaks with
no effect on analysis quality. These compounds were 2-methylvaleric, 4-methylvaleric
and 5-methyl valeric acids.
10.2.4 Phenols
Doetsch and Cook et al [45] reported that a common feature of acidophilic bacteria
was a resistance to copper ions. Growth of acidophilic bacteria occurs at pH2-5, the pH
range for the copper sulphate preservative. These facts make the use of copper sulphate
at pH4 suspect as a good preservative, especially if the samples are not stored at 4
◦ C.
The same sample with 2ml concentrated sulphuric acid per litre, which produces a
pH of about 1.5, at 25
◦ C, was stable for 8 days. Kushner et al [46] has reported that
far fewer microorganisms can tolerate pH1.5 than 4. Even at pH1.5 and 25
◦ C the
phenolic concentration decreased substantially. This observation indicates that while
neither acidification nor cold storage stabilises phenolic compounds in a waste water,
the combination does.
To evaluate the biological-induced degradation of phenolic compounds, Carter
and Huston et al [47] measured microbiological activity on a raw and secondarytreated sewage. Samples were preserved as indicated in Table 10.2 and total plate
counts taken after 1 hour (day 0), 8 and 20 days. The only secondary sewage aliquot
that showed any significant activity was the chemically unpreserved sample stored at
4
◦ C. The microbiological activity noted corresponds very closely with the chemical
stability of phenolics in treated sewage found by Carter and Huston et al [47]. The
enhanced stability of the samples preserved with the higher acid concentration is excellent evidence that the greatest cause of sample instability is microbiological activity,
not chemical activity.
Carter and Huston et al [47] have compared preservation of phenolic compounds
in waste water and sewage using copper sulphate and phosphoric acid with storage
at 4
◦ C. It was shown to be effective for 3–4 weeks, while other preservatives were
effective for only 8 days. Loss of phenolic compounds occurred rapidly unless the
preservative was added immediately after sampling. A correlation found between loss
of phenolic compounds and microbial activity suggests that the latter is dominant in
determining sample stability.
The stability of phenolics in three different waste waters preserved with copper
sulphate-phosphoric acid and stored at 4
◦ C was studied. The raw sewage was fairly
weak with a biological oxygen demand of only 955 mg L
−1 , and the treated sewage
Typical chromatograms are shown in Figure 10.2. Figure 10.2A represents a standard injection of a mixture of 20 mg/L for each volatile fatty acid while Figure 10.2B
shows a spiked volatile fatty acid-free added at a concentration of 20 mg/: of each
volatile fatty acid. Figure 10.2C shows a routine pig slurry analysis. The Supelogel
610H satisfactorily separated the volatile fatty acids within 34 minutes. A baseline
derivation observed on Figure 10.2B during the run did not affect the identification of
peaks. Unidentified peaks appeared in the sample chromatogram of spike volatile fatty
acids-free slurry, probably due to the volatile fatty acid removal aeration technique,
but these peaks did not affect the quantification of the acids added to the slurry. For
slurry analysis the major peak is acetic acid, and the minor peak is valeric acid. Three
peaks appeared 37.47, 41.64 and 44.20 minutes after the volatile fatty acid peaks with
no effect on analysis quality. These compounds were 2-methylvaleric, 4-methylvaleric
and 5-methyl valeric acids.
10.2.4 Phenols
Doetsch and Cook et al [45] reported that a common feature of acidophilic bacteria
was a resistance to copper ions. Growth of acidophilic bacteria occurs at pH2-5, the pH
range for the copper sulphate preservative. These facts make the use of copper sulphate
at pH4 suspect as a good preservative, especially if the samples are not stored at 4
◦ C.
The same sample with 2ml concentrated sulphuric acid per litre, which produces a
pH of about 1.5, at 25
◦ C, was stable for 8 days. Kushner et al [46] has reported that
far fewer microorganisms can tolerate pH1.5 than 4. Even at pH1.5 and 25
◦ C the
phenolic concentration decreased substantially. This observation indicates that while
neither acidification nor cold storage stabilises phenolic compounds in a waste water,
the combination does.
To evaluate the biological-induced degradation of phenolic compounds, Carter
and Huston et al [47] measured microbiological activity on a raw and secondarytreated sewage. Samples were preserved as indicated in Table 10.2 and total plate
counts taken after 1 hour (day 0), 8 and 20 days. The only secondary sewage aliquot
that showed any significant activity was the chemically unpreserved sample stored at
4
◦ C. The microbiological activity noted corresponds very closely with the chemical
stability of phenolics in treated sewage found by Carter and Huston et al [47]. The
enhanced stability of the samples preserved with the higher acid concentration is excellent evidence that the greatest cause of sample instability is microbiological activity,
not chemical activity.
Carter and Huston et al [47] have compared preservation of phenolic compounds
in waste water and sewage using copper sulphate and phosphoric acid with storage
at 4
◦ C. It was shown to be effective for 3–4 weeks, while other preservatives were
effective for only 8 days. Loss of phenolic compounds occurred rapidly unless the
preservative was added immediately after sampling. A correlation found between loss
of phenolic compounds and microbial activity suggests that the latter is dominant in
determining sample stability.
The stability of phenolics in three different waste waters preserved with copper
sulphate-phosphoric acid and stored at 4
◦ C was studied. The raw sewage was fairly
weak with a biological oxygen demand of only 955 mg L
−1 , and the treated sewage