Evaluation of methods for assessment of eco-toxicological risk due to complex effluent discharge

Sponsor: Water Research Commission
Leader: Dr NJ Griffin
Staff: Dr WJ Muller, Mr AK Gordon, Ms NP Gola, Ms N Ketse, Mr TJ Human
Collaborators: Ms H Pearson (Toxsolutions Kits and Services)
Duration: April 2007-March 2008


Aims and Objectives
The Department of Water Affairs and Forestry (DWAF) have acknowledged that substance-specific methods are not able to fully assess the ecological hazard posed by discharge of complex effluents. The introduction of the Direct Estimation of Ecological Effect Potential (DEEEP) as a more realistic environmental management approach assesses the ecological hazard of complex effluents on freshwater systems. The basis of the DEEEP approach is a series of tests, with lethal and sub-lethal endpoint toxicity tests included, using cultured standard laboratory species as test organisms.


Implementation of the DEEEP at an industrial level brings into question some uncertainties that need further consideration. There is a lack in South Africa of trained staff and accredited laboratories able to complete ecotoxicity tests. Quality assurance of endpoints is however crucial for legally defensible decisions relating to effluent control, and ISO standardisation particularly for international trade. The introduction of toxicity kits developed in Europe (based on standard laboratory organisms, reported to be easy to use and able to produce reasonably infallible, defensible endpoints) may alleviate many problems with the DEEEP including cost effectiveness, the need to maintain cultures, ease of handling, and possibilities of questionable quality assurance.


DWAF however have called for revision of the water quality guidelines with ecologically sensitive species relevant to South Africa. With the lack of dilution potential, Ecological Classes are defined in terms of sensitivity of organisms, with site specific water quality management also being considered. The ecological hazard of complex effluents is notoriously difficult to define because of variability in complexity both over time, and within and between industries, with toxic effects mostly seen at the sub-lethal level. Standard laboratory organisms may not give applicable ecologically protective endpoints.


This project aims to compare toxicological assessment of complex industrial and sewage effluents using commercially available toxicity test kits with tests using a range of indigenous species. Specific objectives are as follows:

•     Production of complete cost analyses of the use of toxicity test kits versus indigenous species and the recommended DEEEP methodologies.
•     Assessment of the applicability of hazard assessment based on a literature review of ecotoxicological endpoints obtained from the use of toxicity kits versus standard laboratory organisms versus South African    indigenous organisms.
•     Assessing the sensitivities of the different test methods using four complex effluents from a range of sources.
•     Assessment of the ecological relevance, usefulness and ease of implementation of the kits versus standard laboratory organisms versus indigenous organisms for implementation of the DEEEP.
•     Capacity building and awareness with technical staff of the municipality and industries from whom the samples were taken, with regards the DEEEP, toxicity test results, and implications of the resulting endpoints.

Last Modified: Fri, 14 Aug 2015 11:21:30 SAST