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MICROBIAL ACTIVITY IN BLOCKING COMPOSTS. 3. DEGRADATION OF UREAFORMALDEHYDE.
Chemical (nutrient) analyses of composts, especially of NH4-N and NO3-N, were carried out during the investigations.
Blocking media sterilised and ‘inoculated’ with media which contained ureaformaldehyde, as well as unsterilised media were used in these studies.
Initially, ATP concentrations were very much lower in sterilised, inoculated media than in unsterilised media.
Three days from the start of the experiment, ATP contents increased in sterilised, inoculated media to around 1.25 μg ATP cm-3, compared with concentrations of 0.5 μg ATP cm-3 in unsterilised media.
This was most probably due to a flush of microbial growth involving the degradation and assimilation of the constituents of organisms killed during the sterilisation process.
At the same time that increases in ATP occurred; CO2 evolution and O2 consumption also increased.
Ureaformaldehyde breakdown began almost immediately in unsterilised media and proceeded gradually over a period of 70 days.
The degradation of ureaformaldehyde in sterilised media initially proceeded at a very slow rate.
This was probably due to the loss of microorganisms responsible for breakdown of ureaformaldehyde.
These organisms must have been reintroduced from the stored compost since, at about 40 days from the start of the experiment, ureaformaldehyde breakdown was proceeding at the same rate as in unsterilised media.
No major changes in ATP concentrations, CO2 evolution or O2 consumption were evident in the later stages of ureaformaldehyde breakdown.
It is likely that the fraction of the microbial population responsible for ureaformaldehyde degradation and transformation to ammoniacal and nitrate nitrogen was very small.
The analytical techniques were probably not sufficiently sensitive to monitor changes in populations of microorganisms responsible for ureaformaldehyde degradation.