1. Sustainable Agricultural Use of Municipal Wastewater Sludge
Eyob Habte Tesfamariam
Department of Plant and Soil Science
University of Pretoria
19 September 2018

2. How do we perceive wastewater sludge?
As nuisance by product?
As a product as is?
As a raw material with high value with further processing?

3. How…?
The perception of Arthur C. Clarke during the launch of Apollo 13 was different than most of us:
“There is no such thing as waste, there are only resources we are too stupid to know how to use.”
Quoted from a mars society convention presentation (12 August 2005)

4. Nutrient cycling in human food chain
Non renewable nutrients K P N
Renewable resources
Residue
Crop production
Energy generation
Bricks etc… ?
Loss of non-renewable resources
Non agricultural beneficial use ?
Landfills, Incineration, Disposal (land and marine)
Environmental pollution
06/04/2019

5. Do we perceive the role a processed municipal sludge could play
Liquid & Solution
Solid
Source of water and crop nutrients (recycling)
SDG 6 (Clean water and sanitation)
SDG 1 (Zero hunger)
SDG 3 (Good health and well being)
SDG 15 (Life and land)
Restoration of degraded lands
SDG 12 (Responsible consumption and production)
SDG 13 (Climate action)
C sink (climate change mitigation)

6. Challenges and opportunities
Sustainable beneficial agricultural use of sewage sludge in South Africa
Challenges and opportunities

7. Current and Future focus
Resource recovery
Fertilizer recovery
Water reuse
Carbon sequestration
Carbon footprint/ GHG emissions
Reduced footprint
Zero carbon footprint
Carbon neutral thru offsets

8. Current South African sludge guideline for agricultural use
Microbiological class
A B C
Stability class
Pollutant class
a b c

9. Current South African sludge guideline regulation for agricultural use
The current South African sludge guideline recommends:
Sludge to be assessed if it qualifies for use in agricultural lands.
Sludges to be applied according to crop nutrient requirement (upper limit: 10 t ha-1 yr-1).
Assess potential environmental impacts from sludge use in agricultural lands.

10. SARA model development
SARA model was developed to assist the implementation of SA guideline by providing:
The sludge class and its suitability for use in agricultural lands,
Site and crop specific sludge recommendation rates,
Economic value of sludge using commercial inorganic fertilizer as bench mark,
Potential trace metal accumulation from sludge application in agricultural lands.

11. SARA model – flow diagram
SLUDGE CLASSIFICATION
Does the sludge qualify for safe use in agricultural lands? No
Yes
Farm parameterization
Location of farm:
Province, nearest weather station,
Sludge parametrization
Crop nutrient requirements – site specific
(per unit area)
Nutrient availability – site specific
(per unit mass of sludge)
Soil parameterization
Crop parameterization
Sludge recommendation
Economic analyses
(using commercial inorganic fertilizer as bench mark)
Long-term trace metal accumulation

12. Sludge Classification Interface
Sara model

13. SARA Model – sludge classification interface

14. Site, Crop And Soil Parameterization
Sara model

15. SARA model – Site, Crop And Soil Parameterization

16. Sludge Parameterization
Sara model

17. SARA model – sludge parameterization

18. Sludge Recommendation
Sara model

19. SARA model – Sludge recommendation rate
per field
Potassium recommendation (for optimal crop growth)
Total sludge recommendation for the farm

20. Cost Benefit Analyzer
Sara model

21. SARA model – Cost benefit analyser
Cost benefit analyses using commercial fertilizer as bench mark

22. Trace Metal Accumulation
Sara model

23. SARA model – Trace metal accumulation
Years to reach threshold level

24. THANK YOU ACKNOWLEDGMENTS