Low cost water purification systems
It has been estimated that millions of people do not have access to improved drinking water
sources. Consumption of unsafe water continues to be one of the major causes of the million
diarrhoeal disease deaths occurring annually, mostly in children. There is now conclusive
evidence that simple, acceptable, low-cost interventions at the household and community level
are capable of dramatically improving the microbial quality of household stored water as well as
for moving people and reducing the risks of diarrheal disease. In this review the candidate
technologies and approaches for household water treatment are examined on the basis of their
technical feasibility, practicality, availability and effectiveness in improving the microbiological
quality of water and reducing waterborne disease.
 Chlorine tablets (chlorine treatment): The tablets are convenient and portable.
Chlorine is the most affordable, easily and widely used agent. It is highly effective
against nearly all water borne pathogens with notable exception being cryptosporidium
parvum oocysts and mycobacteria species. At doses of a few mg/l an contact times of
about 30 minutes, free chlorine generally inactive great than 99.99% of enteric bacteria
and viruses. Water should be free of turbidity for effective chlorination. Advantage of
chlorine treatment are that, it is cheap and provides residual effect.
 Life straw: It is a lightweight water purifier which is portable to use. Can be used
to directly drink from sources of contaminated water. It removes parasites and bacteria.
The consumer sucks water directly from a contaminated source through the Life Straw.
Water passes through the hollow fiber membrane, which traps bacteria, parasites, and
particles. Clean water is delivered directly to the mouth of the consumer. Very effective
against bacteria (99.9999%) and parasites (99.9%). It also removes sediment and micro
plastics. However, it excludes viruses, chemicals, and dissolved salts from being filtered.
 Thermal treatment with solar radiation: Water can be heated to temperature of 55°c in
transparent bottles exposed to sunlight for several hours especially if the bottle is painted
black on one side or is lying on a dark surface that collects and radiates heat. A limitation
of this method is the availability of sunlight, which depends greatly with season and
geographic location. Another potential limitation of solar heating to disinfect water is the
determination of water temperature. Several simple low cost temperature indicator have
been devised. One of the simplest and most effective is a reusable water pasteurization
indicator based on the melting temperature of soybean wax.
 Solar Disinfection (SODIS): If cost is a bigger concern than time or convenience, the
cheapest way to treat water is to leave it in a plastic bottle in the sunlight. Leave clear
bottles in the sun for a few hours and UV radiation and heat kills the microbes that cause
diarrhea and other waterborne illness. The Sodis (for solar disinfection) method was
deployed in some parts of Haiti after the earthquake in 2010, and it is used in
emergencies and impoverished regions worldwide. The system would be employed to the
rural area of Malawi as well to purify the contaminated water to make it drinkable at a
house hold level and well as for people on the move.
“It is the combined effect of UV irradiation and high temperature that leads to antimicrobial
action,” according to a paper published in 2020 in the journal ACS Catalysis.
Reference:
https://www.engineeringforchange.org/news/ten-low-cost-ways-to-treat-water/
https://pmc.ncbi.nlm.nih.gov/articles/PMC4921383/