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Water disinfection: the chlorine dilemma

  • Water disinfection: the chlorine dilemma

About the blog

John Mmbaga
PhD (Chemistry) student at the University of Nairobi with an interest in ag nutrient and metal recovery from water. Currently researching on materials for recovery of phosphates and nitrates for reuse as controlled release fertilizers.
ACCIONA
Idrica

Irresponsible human activity never leaves our environment the same.

Though man-made, synthetic chemicals useful in industry, agriculture and medicine have made our lives better, they have adversely impacted on the quality of water we drink.

Perhaps that’s why most of us are obsessed with treating our water using chlorine before drinking it.

Chlorine is not the panacea to all water contamination challenges.

Infact, if not handled correctly, it might just inject impurities which end up making our water riskier than we ever thought.

Disinfection by-products (DBPs)

Though chlorine has revolutionized water disinfection, it’s use has tagged along a fair share of disadvantages among which disinfection by-products are the most conspicuous.

Whether we bubble chlorine gas through water, use chloramination or sodium hypochlorite, chlorine is one sure way of getting rid of many forms of bacteria that thrive in water.

Even though some hardened microorganisms e.g protists such as cryptoporidium and giardia seem to escape this bleach purge, chlorine in many ways is the golden standard for water disinfection.

It’s effectiveness originates from its ability to exist as a ‘radical’ ion (one that scavenges for electrons) thereby capable of destroying bacterial coatings in order to render the water safe for drinking.

But what happens when other organic contaminants exist in the water as well?

Because of it’s reactivity, chlorine forms compounds with these substances which are referred to as disinfection by-products most of which are not outrightly classified as carcinogenic but have been associated with instances of tumor development.

Though their presence in drinking water is not thought of as much of a risk, reputable organizations such as the US Environmental Protection Agency (USEPA) have gone to the extent of tabulating their cancer potency factors in relation to their daily intake.

Since disinfection by-products are as a result of organic contaminants in water, effective filtration of drinking water before chlorination is key in reducing their presence.

Besides, their presence also signifies a total reduction of residual chlorine useful in continuous disinfection of water when especially delivered through a piping system.

In conclusion

Though disinfection By-Products (DBPs) may arouse less interest today, the increased use of chlorine in water treatment is bound to increase their levels in water.

Water filtration techniques such as the use of activated carbon, coconut shells and ion exchangers is essential before chlorination to guard against the presence of DBPs.

However, more research needs to be carried out to determine the effects of exposure to DBP levels over the long-haul since the use of chlorine in water disinfection is cheap and accessible to the most economically disadvantaged.

Originally posted on John Mmbaga's Blog

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