Transcript ppt - Sustainable Sanitation

What compounds can be removed
from wastewater?
How can Nature assist or react?
Chemical ~
coagultation/flocculation, adsorption, precipitation, UV-radiation
Physical ~
screening and filtration, sedimentation, flotation
Biological ~
microbial decomposition, predation, uptake in plants
4.6 Physical, biological and chemical treatment
processes
More than 2,000 persons
Treatment results
for small and large
water utilities
Less than 2,000 persons
J-O Drangert, Linköping University, Sweden
B: Physical processes
screening
flotation and
sedimentation
filtration
forced microfiltration
Possible combinations of physical processes
Jan-Olof Drangert, Linköping university, Sweden
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
Flotation and sedimentation processes
Inspection
hole
Baffels
Inlet of
wastewater
Outlet of
treated water
Floating grease,
particles, organisms
Jan-Olof Drangert, Linköping university, Sweden
Filtration – mainly by gravity
Partially unsaturated flow
Saturated flow of wastewater
Jan-Olof Drangert, Linköping university, Sweden
Forced micro-filtration
Applied
pressure
Manufactured
porous material
Direction of filtered water flow
Jan-Olof Drangert, Linköping university, Sweden
C: Chemical processes
Adsorption of charged particles
Adsorption
of phosphate
OH
on ferric H PO - +
2
4
hydroxide
OH
OH
H2PO4- +
OH
Fe
Al
Adsorption of phosphate on
aluminium hydroxide particles
G. Jacks, Royal Institute of Technology, Stockholm
Adsorption of charged particles to soil medium
The three important kinds of charged soil particles are:
1. Organic matter
-
-
R-COO
R-COO
+
RCOOH < > RCOO + H
(a negative pH-dependent charge)
R is phenolic ring derived from
lignite in residues of plants
OH
Fe(III) +
OH
Organic ”overcoat”
on a soil mineral
Cu
2+
-
+
K
-
+
K
Mg
2+
-
-
3. Ferric hydroxides
-
HAsO4
2+
Mineral
grain
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:
Pb
Fe(OH)3 <
> Fe(OH)
2-
+H
+
(a pH-dependent positive charge)
G Jacks, Royal Institute of Technology, Stockholm
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
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
UV-radiation by sunlight
Inactivation of microorganisms by UVAradiation and increased
temperature
http://www.sodis.ch/Text2002/TTheMethod.htm
Source: Ubomba-Jaswa et al. 2009
Shallow ponds with a dense population of algae
More diffuse stratification
Vertical view
of the pond
Strong algal stratification
K Tonderski, Linköping University Sweden
Courtesy of Duncan Mara, University of Leeds, UK
Ozonation and chlorination
D: Biological processes
Karin Tonderski, Linköping university, Sweden
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
+ oxygen
Aerobic
bacteria
Jan-Olof Drangert,
Linköping university, Sweden
Biological processes - without air
Many microorganisms can survive in environments with no
oxygen and they use other compounds for their survival:
Organic + e.g. nitrate, sulphate
matter in or iron ions (Fe 3+ )
wastewater
Anaerobic
microorganisms
Saturated
soil profile
with little or
no oxygen
CO2 + e.g.
N2, S2-, Fe2+
Jan-Olof Drangert,
Linköping university, Sweden
Microorganisms attached to surfaces are
more stable than those suspended in water
Grain particle
Jan-Olof Drangert, Linköping university, Sweden
“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
O2
H2O (oxygenisation)
NO3N2, N2O (denitrification)
MnO2
Mn2+
Fe(OH)3
Fe2+
SO42H2S (sulphate-reduction)
CO2
CH4 (methanogenesis)
Gunnar Jacks, Royal Institute of Technology, Stockholm
Changes in concentrations of electron acceptors
when organic matter (TOC) decomposes
Gunnar Jacks, Royal Institute of Technology, Stockholm
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
Predation on microorganisms stimulates
decomposition
Courtesy of Frida Lögdberg, Linköping university
Soil organisms vary tremendously in size
and numbers
A teaspoon soil ~ one gram
Microbial
group
Example
Size
(µm)
Numbers
Biomass
(per gram soil) (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
Modified from Sylvia, D. et al. 2004. Principles and applications of soil microbiology
Organic matter is decomposed most
efficiently in the top soil
Million organisms per gram soil
Anaerobic bacteria
0
Aerobic bacteria
Soil
surface
Depth in meter
106
106
0.5 m
Courtesy of G. Jacks, Royal Institute of Technology, Stockholm