Learning objective : to become familiar with basic functions of various physical, chemical and...
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![Page 1: Learning objective : to become familiar with basic functions of various physical, chemical and biological processes. Physical ~ screening and filtration,](https://reader030.fdocuments.in/reader030/viewer/2022020217/55151ae855034673228b4e20/html5/thumbnails/1.jpg)
Learning objective: to become familiar
with basic functions of various physical,
chemical and biological processes.
Ph
ysical ~
screening and filtration, sedimentation, flotation
Chemical ~ coagultation/flocculation, adsorption, precipitation, UV-radiation
Bio
log
ical
~
mic
robi
al d
ecom
posi
tion,
pre
datio
n, u
ptak
e in
pla
nts
4.6 Physical, biological and chemical treatment processes
What compounds can be removed from wastewater?
How can Nature assist or react?
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Treatment results for small and large
water utilities
More than 2,000 persons
Less than 2,000 persons
J-O Drangert, Linköping University, Sweden
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B: Physical processes
Possible combinations of physical processes
Jan-Olof Drangert, Linköping university, Sweden
screening forced micro- filtration
filtrationflotation and sedimentation
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Screening of debris and other solid items
Solids trapped by a screen in a city wastewater treatment plant
Organics from kitchen pipe sorted out in a plastic screen
Jan-Olof Drangert, Linköping university, Sweden
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Flotation and sedimentation processes
Inlet ofwastewater
Baffels
Outlet of treated water
Inspection hole
Floating grease, particles, organisms
Jan-Olof Drangert, Linköping university, Sweden
Sludge built up
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Filtration – mainly by gravity
Saturated flow of wastewaterPartially unsaturated flowJan-Olof Drangert, Linköping university, Sweden
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Forced micro-filtration
Manufactured porous material
Direction of filtered water flow
Appliedpressure
Jan-Olof Drangert, Linköping university, Sweden
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C: Chemical processes
Adsorption of charged particles
G. Jacks, Royal Institute of Technology, Stockholm
OHH2PO4- + Fe OH
OH H2PO4- + Al OH
Adsorption of phosphateon ferric hydroxide
Adsorption of phosphate on aluminium hydroxide particles
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The three important kinds of charged soil particles are:
1. Organic matter
RCOOH < > RCOO- + H+
(a negative pH-dependent charge)R is phenolic ring derived from lignite in residues of plants
2. Clay mineralsClay 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-
Organic ”overcoat” on a soil mineral
- -
K+ K
+ Mg
2+ -
- -
Cu 2+
OH
Fe(III) + HAsO4
-
OH
Adsorption of charged particles to soil medium
G Jacks, Royal Institute of Technology, Stockholm
Mineral grain
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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
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• 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
Precipitation and flocculation
+ -
-+
+-
- ++
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Source: Ubomba-Jaswa et al. 2009
http://www.sodis.ch/Text2002/T-TheMethod.htm
UV-radiation by sunlight
Inactivation of micro-organisms by UVA-radiation and increased temperature
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More diffuse stratification
Strong algal stratification
K Tonderski, Linköping University Sweden Courtesy of Duncan Mara, University of Leeds, UK
Vertical view of the pond
Shallow ponds with a dense population of algae
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Ozonation and chlorination
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D: Biological processes
Karin Tonderski, Linköping university, Sweden
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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:
+ oxygenUnsaturated soil profile Aerobic
bacteria
Jan-Olof Drangert,
Linköping university, Sweden
Organic matter
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Biological processes - without air
Many microorganisms can survive in environments with no oxygen and they use other compounds for their survival:
+ e.g. nitrate, sulphate or iron ions (Fe 3+ )
Organic matter in waste-water
CO2 + e.g. N2, S2-, Fe2+
Saturated soil profile with little or no oxygen
Anaerobic micro-organisms
Jan-Olof Drangert,
Linköping university, Sweden
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Microorganisms attached to surfaces are more stable than those suspended in water
Grain particle
Jan-Olof Drangert, Linköping university, Sweden
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O2 H2O (oxygenisation)
NO3- N2, N2O (denitrification)
MnO2 Mn2+
Fe(OH)3 Fe2+
SO42- H2S (sulphate-reduction)
CO2 CH4 (methanogenesis)
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
Gunnar Jacks, Royal Institute of Technology, Stockholm
“Redox-ladder”
Decrease in oxygen
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Gunnar Jacks, Royal Institute of Technology, Stockholm
Changes in concentrations of electron acceptors when organic matter (TOC) decomposes
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What happens in the root zone?
O 2, sugars, proteins,
etc
Jan-Olof Drangert, Linköping university, Sweden
Water, nutrients, heavy metals, gases (e.g. CO2)
Organic matter, O2, NO3
- , SO4
2-, CO2 etc
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Predation on microorganisms stimulates decomposition
Courtesy of Frida Lögdberg, Linköping university
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Soil organisms vary tremendously in size and numbers
Modified from Sylvia, D. et al. 2004. Principles and applications of soil microbiology
A teaspoon soil ~ one gram
Microbial group
Example Size (µm)
Numbers (per gram soil)
Biomass (g wet mass per m2 soil)
Bacteria Pseudomonas 0.5 – 1.5 108 - 109 30 – 300
Fungi Mucor 8 (hyphae diameter)
105 – 106 50 - 500
Protozoa Euglena 15 * 50 103 - 105 0.5 – 20
Nematodes Pratylenchus 1000 10 – 102 0.1 – 10
Earthworms Lumbricus 100 000 1 - 100
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Organic matter is decomposed most efficiently in the top soil
Million organisms per gram soil
106
106
De
pth
in m
ete
rAnaerobic bacteria
Aerobic bacteria
0.5 m
Courtesy of G. Jacks, Royal Institute of Technology, Stockholm
Soil surface
0