Abstract

The management of wastewater effluents in South Africa has to date been based on physico-chemical standards although recently the assimilative capacity of the receiving stream has been included but not widely implemented. Very few assessments of the success of these management practices in protecting the downstream aquatic environment have been done. Bioassessments using benthic macro invertebrates were conducted up and down stream of a number of wastewater works to measure the degree of impact that the works were having on the stream ecosystems. A significant deterioration in the benthic invertebrate fauna downstream of most of the wastewater works was observed. This was particularly noticeable where the receiving stream was of good quality while there was little change in poor quality receiving streams. This was confirmed using ordination techniques. The ordination diagrams displayed how community composition varied with important environmental variables although some of these may be surrogates for other unmeasured variables. It was revealed that river flow and the dilution of the effluent were the most important of the measured variables explaining the variability in the biota. Escherichia coli and soluble phosphorus were also shown to be important with suspended solids also significant. Most of the wastewater works, in the month prior to the biological investigation, had complied with their permit requirements. The exceptions, found on infrequent occasions at different works, were soluble phosphorus, chlorine, E. coli and conductivity. One permit requirement that was consistently ignored was a statement forming part of the effluent standards permit system which states that the effluent should not contain constituents that are poisonous or injurious to animal (including aquatic) life. No systems for monitoring this criterion were in place. Despite the general compliance with regulations governing wastewater treatment a lack of adequate effluent dilution appeared to be the major cause of degradation of the downstream biota. These wastewater works are found in a region that does not have an abundant supply of water for dilution so treatment of the effluent to a condition that is not injurious to aquatic life becomes a necessity. Thus it appears that the physico-chemical standards used to characterise and manage wastewater treatment in South Africa are inadequate to protect the downstream environment in the vicinity below many wastewater works.

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References

Bascietto, J., Hinckley, D., Plafkin, J. and Slimak, M.
1990
.
Ecotoxicology and ecological risk assessment
.
Environ. Sci. Technol.
,
24
:
10
16
.
Cairns, J.
1976
. “
Estimating the assimilative capacity of water ecosystems
”. In
The biological significance of environmental impacts
, Edited by: Sharma, R.K., Buffington, J.D. and McFadden, J.T.
173
189
.
Springfield, VA
:
National Technical Information Service
.
In:
Cairns, J.
1995
. “
Chemical versus biological pollution monitoring
”. In
Pollution and biomonitoring
, Edited by: Rana, B.C.
7
25
.
New Delhi
:
Tata McGraw-Hill
.
In:
Chesters, R.K.
1980
.
Biological Monitoring Working Party. The 1978 national testing exercise. Department of the Environment (UK), Water Data Unit
.
Technical Memorandum
,
19
:
1
37
.
Chutter, F.M.
The rapid biological assessment of stream and river water quality by means of macroinvertebrate communities in South Africa
.
Proceedings of a joint South African/Australian workshop
.
February 7–12
,
Cape Town.
Classification of rivers and environmental health indicators
, Edited by: Uys, M.C. pp.
217
234
.
South Africa
:
Water Research Commission
.
In:
Chutter, F.M.
1995
.
Research on the rapid biological assessment of water quality impacts in streams and rivers
South Africa
Draft final report to the Water Research Commission
Dallas, H.F. and Day, J.A.
1993
.
The effect of water quality variables on riverine ecosystems: a review
,
Report No. TT 61/93
South Africa
:
Water Research Commission
.
DWAF (Department of Water Affairs and Forestry)
.
May
1984
.
Requirements for the purification of waste water or effluent
,
May
,
South Africa
:
Government Gazette
.
1984.
Hart, B.T., Campbell, I.C., Angehrn-Bettinazzi, C. and Jones, M.J.
1993
.
Australian water quality guidelines: a new approach for protecting ecosystem health
.
J. Aquat. Ecosyst. Health
,
2
:
151
163
.
Hill, M.O.
1979
.
DECORANA — A FORTRAN program for detrended correspondence analysis and reciprocal averaging. Ecology and Systematics
,
Ithaca, NY
:
Cornell University
.
ISO/IEC
.
1990
.
International organisation for standardization/international electrotechnical commission
Geneva
Guide 25
Jongman, R.H.G., ter Braak, C.J.F. and van Tongeren, O.F.R.
1987
.
Data analysis in community and landscape ecology
,
Wageningen
:
Pudoc
.
Norris, R.H. and Georges, A.
1993
. “
Analysis and interpretation of benthic macroinvertebrate surveys
”. In
Freshwater biomonitoring and benthic macro-invertebrates
, Edited by: Rosenberg, D.M. and Resh, V.H.
234
286
.
New York
:
Chapman and Hall
.
In:
Quinn, J.M. and Hickey, C.W.
1993
.
Effects of sewage waste stabilisation lagoon effluent on stream invertebrates
.
J. Aquat. Ecosyst. Health
,
2
:
205
219
.
Roux, D.J.
1994
.
The use of toxicity testing in effluent regulation and control: A new dimension to assessment and management of water quality in South Africa
.
Sth. Afr. J. Aquat. Sci.
,
20
(
1/2
):
62
78
.
Roux, D.J., van Vliet, H.R. and van Veelen, M.
1993
.
Towards integrated water quality monitoring: Assessment of ecosystem health
.
Water SA
,
19
(
4
):
275
280
.
SABS 0259
.
1990
. “
South African Bureau of Standards Code of Practice
”. In
General requirements for the competence of calibration and testing laboratories
Pretoria, , South Africa
(Equivalent to ISO/IEC Guide 25:1990)
Standard Methods
.
1989
.
Standard methods for the examination of water and wastewaster
, 16th ed.,
Washington, DC
:
APHA, AWWA and APCF Joint Publication
.
ter Braak, C.J.F.
1986
.
Canonical correspondence analysis: a new eigenvector technique for multivariate direct gradient analysis
.
Ecology
,
67
:
1167
1179
.
ter Braak, C.J.F.
1987–1992
.
CANOCO a FORTRAN program for Canonical Community Ordination
,
Ithaca, NY
:
Microcomputer Power
.
USEPA (US Environmental Protection Agency)
.
1991
.
Technical support document for water quality-based toxics control
Washington, DC
EPA/505/2-90-001