Pollution from human and animal faecal waste is a major cause of deteriorating water
quality and increased nutrient loads in coastal and inland waterways. Management of
this problem depends on knowing which sources of faecal matter are the cause and
what is the degree and extent of the pollution. Bacterial indicator organisms have long
been the principal method used to test water samples for faecal contamination.
However, none of the currently used bacterial indicators on their own are source
specific enough to distinguish different sources of faecal matter. The use of faecal
sterol biomarkers in conjunction with existing bacterial indicators offers a new way to
distinguish sources of faecal contamination.
This study investigates the sources of faecal sterols, the relationship of coprostanol to
existing bacterial indicators of faecal pollution, the degradation of faecal sterols and the
problem of determining the sources of faecal contamination and the distribution of
faecal contamination using faecal sterol biomarkers. 5p-Stanols (i.e. faecal sterols)
were found to be significant constituents of human, herbivore (i.e. cows, sheep etc.)
and pig and cat faeces. Human faeces contained 73 ± 4% coprostanol in relation to
the sum of coprostanol and 24-ethylcoprostanol and primary treated effluent contained
86 ± 0.4% coprostanol. Herbivore faeces contained 38 ± 4% coprostanol and 62 ±
4% 24-ethylcoprostanol whereas pig faeces contained 50 � 5% of each compound.
Both birds and dogs faeces contained either trace amounts of 5B-stanols or they could
not be detected. Notable differences were observed in the abundance of Closthdium
perfringens spores between the faeces of birds and domestic pets such as cats and
dogs. The above differences were subsequently exploited to distinguish faecal
contamination in Lake Tuggerah. An examination of the relationships between
coprostanol and bacterial indicator concentrations from several environments revealed
that 60 and 400 ng L of coprostanol corresponded to currently defined primary and
secondary contact limits for bacteria measured as either thermotolerant coliforms or
enterococci in the environment.
Four degradation experiments showed faecal sterols and related sterols such as
cholesterol decay at similar rates. An induction period was observed in all
experiments which meant that simple exponential equations to describe the rate of
decay of coprostanol were inadequate; a complimentary log - log transformation of the
data was used and the equation:
Y = l-Exp(-Exp(time x -0.01 + temp x -0.158 + 3.33)) x 100
was derived where Y equals the predicted percentage of coprostanol remaining over
time at a given temperature. In terms of persistence in the environment, Clostridium
perfringens spores > coprostanol > enterococci > thermotolerant coliforms.
Two field studies were undertaken to highlight the use of faecal sterols. In the Lake
Tuggerah study, the results indicated that faecal contamination of receiving waters in
the Tuggerah Lakes during rain events was significant, but was not derived from
human faecal matter; rather it appears to be principally derived from native birds and,
to a lesser extent, domestic pets. In the Derwent Estuary study, based on the
distribution of the faecal biomarker coprostanol, the mid estuary and parts of the upper
estuary (from Newtown Bay to Taroona), were found to be severely contaminated by
sewage. In summary, the use of faecal sterols to trace faecal contamination were found
to be an invaluable addition to the tools water managers use to investigate faecal
pollution.
| Identifer | oai:union.ndltd.org:ADTP/219121 |
| Date | January 1996 |
| Creators | Leeming, Rhys, n/a |
| Publisher | University of Canberra. School of Resource, Environmental & Heritage Sciences |
| Source Sets | Australiasian Digital Theses Program |
| Language | English |
| Detected Language | English |
| Rights | ), Copyright Rhys Leeming |
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