The Application of the SOS-Chromotest and the UMU-C assay to determine genotoxicity levels in Waste water effluents

Transcription

1 The Application of the SOS-Chromotest and the UMU-C assay to determine genotoxicity levels in Waste water effluents Presented By: Dr. Rahzia Hendricks Rand Water Analytical Services 12 October

2 Presentation Overview Why investigating genotoxicity in treatment plants (STPs) are important? sewage Different methods used in the study to determine genotoxicity in STP effluents. Results of study. Discussion of results. Conclusion and Recommendations. 2

3 Introduction Accelerating urbanization and industrialization = increase in water consumption Leads to increase in environmental problems especially water pollution To combat effects water re-use becomes an important factor to conserve this precious commodity Re-use of sewage effluents is often used for non-potable purposes such as irrigation 3

4 Introduction Re-use of sewage effluents comes with problems such as water-borne pathogens; presence of compounds that can result in toxicity Difference between mutagenicity and genotoxicity? Mutagenicity- referred to a permanent change of the nucleotide sequence of the genome of an organism. Progeny of the germ cells also having the same mutation. 4

5 Introduction Genotoxicity- broader term not necessarily associated with mutagenicity. Tests give an indication DNA damage but not mutagenicity. Effects of genotoxicity in water-dna damage, genetic mutation; chromosome aberration Current methods to test genotoxicity- Comet assay, AMES assay, Micronucleus test 5

6 Aim of study To apply the SOS and UMU-C assays or tests to determine the genotoxic potential of sewage treatment effluents from three different sewage treatment plants. 6

7 Study area Figure 1. Sewage treatment plants situated in the Vaal Triangle. 7

8 INFLUENT SAMPLING POINT Inflow Automated Primary Secondary Fine screen Settlement tank Settlement tank Chlorine contact chamber Rough screen Grit chamber Biological Nutrient Removal Reactor Sludge Maturation Pond System EFFLUENT SAMPLING POINT River System Figure 2. Influent and effluent sampling points at STPs 8

9 Manual Coarse Bar Screens Inlet Works Automated Mechanical Front Rake Fine Screens Channels into plant Grit Chambers Figure 3. Inlet works at the Sewage Treatment Plants 9

10 Primary Settlement Tank (PST) Biological Nutrient Removal (BNR) Reactor (aka Activated Sludge Process) Secondary Settlement Tank SST (aka Clarifier) Anaerobic Digesters Figure 4. Primary and Secondary Treatment of sewage influents. 10

11 Disinfection Chlorine contact channel Figure 5. Tertiary treatment of the sewage effluents at the sewage treatment plants. 11

12 Principle of SOS and UMU-C tests Figure 6. The Principle of the SOS-C and UMU-C tests. 12

13 SOS assay procedure Figure 7. SOS Chromotest procedure. 13

14 UMU-C assay procedure Figure 8. UMU-C assay procedure. 14

15 Calculation of Genotoxicity Results Table 1. Interpretation of Induction factor results. Induction factor (IF) Result < 1.5 Not genotoxic > 1.5 Genotoxic 15

16 Results of Physical and Chemical parameters Table 2. Average Physical and Chemical parameters for STP 1; STP2 and STP3 for STP effluent samples. Parameter Result Guideline for Effluents ph to 9.5 (NWA, 1998) Out of guideline limits Turbidity (NTU) <5 NTU (WHO, 2011 ) DO (mg/l) 6.56 > 4 mg/l Free chlorine (mg/l) Total Chlorine (mg/l) 0.18 <0.25 mg/l mg/l Temperature ( C) 16.6 <25 C (DWAF, 2005) 16

17 Induction Factor (IF) Induction Factor (IF) Induction Factor (IF) STP STP Weeks Weeks STP Weeks Influent Effluents Figure 9. Induction factors of STPs influents and effluents over the 4-week period using the SOS-Chromotest. 17

18 Induction Factor (IF) Induction Factor (IF) Induction Factor (IF) STP STP Weeks Weeks STP Weeks Influent Effluent Figure 10. Induction factors of the STPs influents and effluents over the 4 week period using the UMU-C test. 18

19 Parameters Discussion Composition of sample Nature of genotoxicity test Microbial degradation of compounds Sedimentation of compounds Genotoxicity 19

20 Discussion Design of STP to treat for nitrogen; phosphates Capacity of STP- increase in population 20

21 Discussion Which test kit is the best to use to determine the genotoxicity of effluents?? 21

22 Conclusions and Recommendations STPs important source of genotoxic compounds Can pose a health risk to aquatic and human health Variable results using SOS and UMU-C assays Investigate seasonal differences 22

23 Thank you 23