1. 4.6 Physical, biological and chemical treatment processes
microbial decomposition, predation, uptake in plants
Biological ~
Physical ~
screening and filtration, sedimentation, flotation
Learning objective: to become familiar with basic functions of various physical, chemical and biological processes.
Chemical ~
coagultation/flocculation, adsorption, precipitation, UV-radiation
What compounds can be removed from wastewater?
How can Nature assist or react?

2. Treatment results for small and large water utilities
More than 2,000 persons
Treatment results for small and large water utilities
Less than 2,000 persons
J-O Drangert, Linköping University, Sweden 2

3. Possible combinations of physical processes
B: Physical processes
flotation and sedimentation
screening
filtration
forced micro-
filtration
Possible combinations of physical processes
Jan-Olof Drangert, Linköping university, Sweden 3

4. Screening of debris and other solid items
Organics from kitchen pipe sorted out in a plastic screen
Solids trapped by a screen in a city wastewater treatment plant
Jan-Olof Drangert, Linköping university, Sweden 4

5. Flotation and sedimentation processes
Inspection hole
Baffels
Inlet of
wastewater
Outlet of treated water
Floating grease, particles, organisms
Sludge built up
Jan-Olof Drangert, Linköping university, Sweden

6. Filtration – mainly by gravity
Partially unsaturated flow
Saturated flow of wastewater
Jan-Olof Drangert, Linköping university, Sweden 6

7. Forced micro-filtration
Manufactured porous material
Applied
pressure
Direction of filtered water flow
Jan-Olof Drangert, Linköping university, Sweden

8. C: Chemical processes Adsorption of charged particles
Adsorption of phosphate
on ferric hydroxide OH
H2PO Fe OH
H2PO Al
Adsorption of phosphate on aluminium hydroxide particles
G. Jacks, Royal Institute of Technology, Stockholm 8

9. Adsorption of charged particles to soil medium
The three important kinds of charged soil particles are:
Organic matter
RCOOH < > RCOO- + H+
(a negative pH-dependent charge)
R is phenolic ring derived from
lignite in residues of plants
2. Clay minerals
Clay mineral consist of Al-Si-sheets
with different cations (Na+, K+ etc.)
in between the sheets. There is a
negative charge on sides and edges:
3. Ferric hydroxides Fe(OH)3 < > Fe(OH)2- + H+
(a pH-dependent positive charge)
R-COO Pb 2+
R-COO-
Mineral
grain
Organic ”overcoat” on a soil mineral
Cu 2+
K+ K Mg OH
Fe(III) HAsO4-
G Jacks, Royal Institute of Technology, Stockholm 9

10. Adsorption of chemical compounds differ
Copper (Cu) and Zink (Zn) are positively charged, and adsorb easily on organic matter and clays when the pH > 7
Arsenic (As) is negatively charged and adsorbs easily on ferric hydroxides when pH < 7
G Jacks, Royal Institute of Technology, Stockholm 10

11. Precipitation and flocculation
Precipitation – a chemical reaction between dissolved compounds to form solids
Flocculation - an aggregation process (or processes) leading to the formation of larger particles from smaller particles
+ -
- + - + +
G. Jacks, Royal Institute of Technology, Stockholm 11

12. UV-radiation by sunlight
Inactivation of micro-organisms by UVA-radiation and increased temperature
Source: Ubomba-Jaswa et al. 2009

13. Vertical view of the pond
Shallow ponds with a dense population of algae
More diffuse stratification
Vertical view of the pond
Strong algal stratification
Courtesy of Duncan Mara, University of Leeds, UK
K Tonderski, Linköping University Sweden

14. Ozonation and chlorination

15. D: Biological processes
Karin Tonderski, Linköping university, Sweden 15

16. Biological processes - with air
Oxygen is vital for most living organisms, including bacteria and viruses. When oxygen is present, organic matter (measured as BOD) is efficiently decomposed by organisms into CO2 + water:
Unsaturated soil profile
Organic
matter
Aerobic bacteria
+ oxygen
Jan-Olof Drangert,
Linköping university, Sweden 16

17. Biological processes - without air
Many microorganisms can survive in environments with no oxygen and they use other compounds for their survival:
Organic matter in waste-water
+ e.g. nitrate, sulphate or iron ions (Fe 3+ )
Anaerobic micro-organisms
Saturated soil profile with little or no oxygen
CO2 + e.g. N2, S2-, Fe2+
Jan-Olof Drangert,
Linköping university, Sweden 17

18. Microorganisms attached to surfaces are more stable than those suspended in water
wastewater flow
anaerobic biofilm
Biofilm o
aerobic biofilm
Grain particle
Jan-Olof Drangert, Linköping university, Sweden

19. “Redox-ladder”
When microorganisms descend the redox-ladder they first use O2 as an electron acceptor, then nitrate NO3, and further down other compounds as electron acceptors. The blue arrow indicates a reaction with energy-rich organic substances (electron donors) in
the wastewater
O H2O (oxygenisation)
NO N2, N2O (denitrification)
MnO Mn2+
Fe(OH) Fe2+
SO H2S (sulphate-reduction)
CO CH4 (methanogenesis)
Decrease in oxygen
Gunnar Jacks, Royal Institute of Technology, Stockholm 19

20. Changes in concentrations of electron acceptors when organic matter (TOC) decomposes
Exemplet från soptipp
Gunnar Jacks, Royal Institute of Technology, Stockholm

21. What happens in the root zone?
Water,
nutrients,
heavy metals, gases (e.g. CO2)
O2, sugars, proteins, etc
Organic matter, O2, NO3- , SO42-, CO2 etc
Jan-Olof Drangert, Linköping university, Sweden 21

22. Predation on microorganisms stimulates decomposition
Courtesy of Frida Lögdberg, Linköping university

23. Soil organisms vary tremendously in size and numbers
A teaspoon soil ~ one gram
Modified from Sylvia, D. et al Principles and applications of soil microbiology

24. Organic matter is decomposed most efficiently in the top soil
Million organisms per gram soil
Anaerobic bacteria
Aerobic bacteria
Soil surface
106
106
Depth in meter
0.5 m
Courtesy of G. Jacks, Royal Institute of Technology, Stockholm 24