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EverythingAboutWater — Dr. H2O
Q. In water treatment, what are chelating agents?
Sunil Makarand, Thane
Chelating agents remove heavy metal ions from industrial water, thereby preventing scaling. Important chelating chemicals include citric acid, glutonic acid, organophosphates and other organic chemicals.
Chelating agents are also called sequestering or complexing agents.
Q. What are advantages of multimedia filtration over a sand filter?
V.K. Ranade, Ratnagiri
The design of a graded media in a multimedia filter allows a depth filtering process. Most single media beds accumulate a “cake” of contaminant on the bed surface. This tends to increase flow restriction (pressure drop) relatively soon. The graded media allows the finer particles to migrate further in the bed before being trapped.
This tends to ensure longer service runs between backwashes. Due to the graded media filters, the backwash flow rate is typically lower than a sand filter.
Q. I have heard of the contamination of drinking water with cryptosporidium? How is it harmful ?
Roshni, Chandigarh
Cryptosporidium is a microscopic organism that is naturally present in water bodies. Swallowing these tiny organisms can cause an intestinal illness known as cryptosporidiosis. Some people infected with cryptosporidium, however do not get ill.
The symptoms of the disease include diarrhea, stomach cramps and upset stomach. For most healthy people, the disease runs into course over a few weeks without any serious consequences. However for the elderly, infants and people with reduced immunity system, it can be life-threatening. Common disinfection methods like UV, ozonation and reverse osmosis can prevent the disease.
Q. If one uses ozone in a swimming pool, does one still need to add chlorine?
Harmit Singh, New Delhi
Ozone is a very effective disinfectant in swimming pools. However due to the low dosage that is normally used as well as ozone’s short life span, there is very little residue of ozone in the swimming pool water. Therefore, a 1 ppm residual chlorine level can be recommended for use, also to prevent algae problems.
By using ozone, the chlorine consumption can be reduced by 60 to 90 percent. The reduced chemical usage also ensures less bleaching, no dry skin and no red / irritated eyes in the pool.
Q. How efficient is the Indian paper industry in terms of water usage and consumption ?
Dr. Hasan, Chandrapur
We had to do some research for this question. Despite significant reduction in water consumption from 200 cubic metres per tonne of product in 1998 to about 135 cubic metres in 2001, the Indian paper industry is still a water guzzler. We still consume about 5 times as much as the best achievable limits in the developed world.
Fresh water averages in continental Europe and United Kingdom is about 40 cubic metres. Environmental concerns and regulatory legislations are putting the pressure in India also now.
TO GET ANSWER TO ALL YOUR WATER-RELATED QUESTIONS, ASK DR.H2O,
EMAIL TO - drh2o@eawater.com
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