Point of Use Coagulation and Flocculation

Turbidity Terminators:

Morgan Rog

Shubha Bhar

Melanie Tan

Lindsay Ellis

Comparing Chemical Coagulants

Coagulant Community/Household Use Advantages Disadvantages Cost* Comments Alum (aluminum sulfate, etc.), alum potash Yes/rare-moderate

Community use common; simple technology

Difficult to optimize without training and equipment Moderate

Proper use requires skill

Iron salts (ferric chloride or sulfate) Yes/rare Same as Alum Same as Alum Moderate

Proper use requires skill

Lime (Ca(OH2)), lime+soda ash (Na2CO3), caustic soda (NaOH) Yes/rare-moderate Same as Alum

Same as Alum; pH control and neutralization a problem; hazardous chemicals

Moderate to high

Softeners; not applicable to many waters

                                  

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

Results:–Coagulated 60-80% of particles–Decrease bacterial counts–Less effective than Moringa, but still more effective than Alum

• Common plant found in western and southern Africa

• Roots and leaves highly medicinal

• Seeds dried and ground up to determine coagulative properties

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

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

• diarrhea 2nd highest cause of death

• water generally kept in open containers

• use bleach to treat water

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

Effectiveness of Proctor and Gamble Experiment

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.1365-2672.2004.02309.x/pdf

http://murungaexports.ebigchina.com/sdp/181012/4/cp-1011556.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