Research Results

Bacterial Hazards 

Most common bacteria: Camplyobacter

• size: minimum below .45 microns (can pass through)
• prevalence: extremely common, even in developed world
• effects: diarrhea for a week or longer, not usually lethal

Most deadly bacteria (untreated): Vibrio cholerae

• size: 1 micron (small dimension)
• prevalence: rare, but can cause epidemics
• effects: diarrhea, nausea, vomiting, shock, death, usually lethal if untreated

E. coli:

• size: .5 microns (small dimension)
• prevalence: extremely common, but pathogenic strains rare
• effects: haemolytic uraemic syndrome, death, deadly strains rare

Shigella:

• size: .5 micron (small dimension)
• prevalence: less common, mainly in children of developing countries
• effects: dysentery, death, not usually lethal
• death is rare for majority

Protozoa:

• typically >2 microns

Chemical Hazards (removable by filtration)

Aldrin and dieldrin

• require coagulation
• chlorinated pesticides
• highly toxic

Arsenic

• generally requires coagulation
• can be deadly

Atrazine

• can be removed by bankside filtration and nanofiltration
• herbicide
• can cause reproductive and immune problems

Chlorpyrifos

• requires coagulation
• insecticide
• inhibition of cholinesterase activity

Chromium

• requires coagulation
• carcinogen

DDT

• requires coagulation
• pesticide
• hazardous

Mercury

• coagulation
• from electronics, industrial waste
• highly toxic

Nickel

• coagulation
• potential allergic reaction

Polynuclear aromatic hydrocarbons

• coagulation
• industrial
• uranium
• coagulation
• radioactive

References

Rollins, David M. "Campylobacter Summary." Life.umd.edu. N.p., Aug. 2000. Web. 07 May 2013. <http://www.life.umd.edu/classroom/bsci424/pathogendescriptions/Campylobacter.htm>.

Formadi, Herman. "Vibrio Cholerae." Cv.vbi.vt.edu. N.p., 5 July 2007. Web. 07 May 2013. <http://ci.vbi.vt.edu/pathinfo/pathogens/V_cholerae_2.html>.

"Shigella." Cdc.gov. Centers for Disease Control and Prevention, 9 Feb. 2011. Web. 07 May 2013. <http://www.cdc.gov/pulsenet/pathogens_pages/shigella.htm>.

"Guidelines for Drinking-water Quality, Fourth Edition." WHO. N.p., n.d. Web. 07 May 2013. <http://www.who.int/water_sanitation_health/publications/2011/dwq_guidelines/en/index.html>.




Additional Research


Optimal Biofilm Growth Conditions

• higher temperature is better, as long as it is not too high to kill the microbes
• optimal hyduaulic loading ~3m/h
• *note, figures for sand filter
• **3 m/h is for testing, corresponds to ~900 ml/h flow rate

Filter Dimensions and the Use of Iron

According to one study, this group used 5kg iron nails to remove arsenic in a filter of 30'' diameter and 61 cm height. They put the iron nails in the top of the filter separated in a 'diffusion box'

Relative to our dimensions we would need ~7g scaled for radius and height. Scaled for only radius we need 6g - a study later showed the iron did not propagate very far through the filter, accounting for the full height may be unnecessary 

References

Fengbing Tang, et al. "Effects of Bio-Sand Filter on Improving the Bio-Stability and Health Security of Drinking Water". Mechanic Automation and Control Engineering (MACE), 2010 International Conference on. 2010. 1878-1881. Print.

"Effects of Bio-Sand Filter on Improving the Bio-Stability and Health Security of Drinking Water". Mechanic Automation and Control Engineering (MACE), 2010 International Conference on. 2010. 1878-1881. Print.

Ngai, Tommy, and Sophie Walewijk. "THE ARSENIC BIOSAND FILTER (ABF) PROJECT: DESIGN OF AN APPROPRIATE HOUSEHOLD DRINKING WATER FILTER FOR RURAL NEPAL." N.p., 2003. Web. 8 May 2013. <http://web.mit.edu/watsan/Docs/Other%20Documents/KAF/NgaiWalewijk-%20ABF%20Report2003.pdf>.