Transcript Alternative Coagulants

Point of Use Coagulation and
Flocculation
Turbidity
Terminators:
Morgan Rog
Shubha Bhar
Melanie Tan
Lindsay Ellis
Comparing Chemical Coagulants
Coagulant
Alum (aluminum
sulfate, etc.), alum
potash
Iron salts (ferric
chloride or sulfate)
Community/Household Use
Disadvantages
Difficult to optimize
without training and
equipment
Cost*
Yes/rare-moderate
Advantages
Community use
common; simple
technology
Yes/rare
Same as Alum
Same as Alum
Same as Alum; pH
control and
neutralization a
problem; hazardous
chemicals
Moderate
Proper use
requires skill
Proper use
requires skill
Moderate
to high
Softeners; not
applicable to
many waters
Lime (Ca(OH2)),
lime+soda ash
(Na2CO3), caustic soda
(NaOH)
Yes/rare-moderate
Same as Alum
Moderate
Comments
Alternative Coagulants: Plants
• Study done by Kenneth Yongabi, Tafawa
Balewa University, Bauchi Nigeria
• Medicinal plants could have coagulative
properties
Experiment:
–Samples from each plant were dried, ground and stored
–Alum was added to each sample
–Coagulation mixtures added to turbid water samples
–Alum was used as a control
–The samples sat for 24 hours
–Coagulative effect and bacterial counts were recorded
–Extracts were tested for E. coli as a fecal contamination indicator
Jatropha Curcas
• Common plant found in western and
southern Africa
• Roots and leaves highly medicinal
• Seeds dried and ground up to
determine coagulative properties
Results:
–Coagulated 60-80% of particles
–Decrease bacterial counts
–Less effective than Moringa, but still more
effective than Alum
Hibiscus subdariffa
• Plant cultivated in Northern Nigeria
• Contains red calyx extract dried and tested for coagulation
Results:
–Effective coagulation
–Effective disinfectant
•Reduced E. coli
and coliform
bacterial counts
better than Alum
–Leaves water tinted red
Pleurotus tuberregium
• Grown in Cameroon and parts
of Nigeria
• Mushrooms have medicinal
value
Results:
–Least effective coagulant
–No antimicrobial
properties
–Still just as effective as
Alum
Moringa oleifera
• Originally from India, found in tropics in Asia, S. America, and Africa
• Tough plant, easy to grow and cultivate
• Drumstick, use dried seeds from pods
• One tree cleans enough water for 5-6 people
• Also contains pterygospermin, antibacterial
Results:
–Coagulated 90% of particles
–Much better than treatment with just alum
–Antimicrobial properties
•Bacterial counts reduced from “Too
Numerous to count” to 2700 CFU
Preparation of Moringa Oleifera
Process:
• dry and crush seeds
• make into a paste
• filter
• add paste to turbid water
• stir fast for ½ minute
• stir slowly 5 minutes
• settle 1 hour
Dosage Demand:
< 50 NTU
10-50 mg/L
50-150 NTU 30-100 mg/L
>150 NTU 50-200 mg/L
Pros and Cons of Moringa Oleifera
Advantages:
• Cheap, readily available
• doesn’t alter pH, pH independent
• doesn’t change taste
• biodegradable sludge
Disadvantages
• still needs to be disinfected
• possibility of recontamination, no
residual
• needs to be fresh
POU Coagulation & Flocculation in
Guatemala
• diarrhea 2nd highest cause of death
• water generally kept in open containers
• use bleach to treat water
The Experiment, by Proctor and Gamble
– Households assigned home flocculation-disinfection system
– 4 controls using flocculation disinfectant and bleach
– Stir water 30 seconds quickly, stir 5 minutes slow, let sit ½ hour, filter
Effectiveness of Proctor and Gamble
Experiment
How it Works:
– Cheap flocculation disinfectant contained: ferric
sulfate, bentonite, sodium carbonate, chitosan,
polyacrylamide, potassium permanganate, and
calcium hypochlorite
– causes clumps to form and settle with stirring
– chlorine residual 3.5 mg/L
Results:
•Flocculation-disinfection
(top) reduced diarrhea by
24%
•Flocculation-disinfection with
special container reduced
diarrhea by 30%
Helpful Websites
http://www.blackwell-synergy.com/links/doi/10.1111/j.13652672.2004.02309.x/pdf
http://murungaexports.ebigchina.com/sdp/181012/4/cp1011556.html
http://www.treesforlife.org/project/moringa/uses/uses_water
_lgscale_article.en.asp
http://www.biotech.kth.se/iobb/news/kenneth04.doc
http://www.ajtmh.org/cgi/content/abstract/69/4/411