Chemistry in Industry- water treatment

In summary, the water treatment process involves injecting chlorine into the water to kill the pathogens. If there is no residual of chlorine when the water leaves the last reaction vessel, this is an indication that the pathogens were killed. Chloramine is less effective than free chlorine but it is still used because it has less of an effect on taste and odor.
  • #1
leah3000
43
0
hello

I'm studying industry and the environment as part of my chemistry A level course. Water and water treatment falls under this.

I'm having trouble understanding what exactly is meant by a disinfectant residual in the treatment of water. Can someone please explain this.

Also why are chloramines more widely used as a disinfectant if it causes the growth of bacteria? I thought the point of disinfecting was to eliminate the bacteria.
 
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  • #2
Let's say you are using chlorine to disinfect waste-water. You inject chlorine (in some form) into the waste stream and the waste spends some time in a reaction vessel or a series of reaction vessels so that the chlorine has time to kill pathogens. If there is not a residual of chlorine in the waste-water when it leaves the last reaction vessel, that is an indication that all the chlorine was taken up, and you might not have killed all the pathogens. If there is a residual of free chlorine in the waste-water leaving the reaction vessel, that is a sign that you have done a thorough job killing the organisms that can take up chlorine. This is a rough guideline, and wastewater treatment plant operators fine-tune the required residual by running biological tests (typically E Coli tests) on the effluent. If E Coli is still present at a given chlorine residual, it will be necessary to increase the feed rate of the disinfectant.

That stage of treatment is usually called primary treatment. Secondary treatment generally involves running the treated effluent through an aeration tank of some kind, where aerobic bacteria can continue to break down the waste. For this reason, you don't want to send waste to the secondary stage with a very high concentration of disinfectant - you don't want to kill off too many of the "good" bugs.
 
  • #3
leah3000 said:
...Also why are chloramines more widely used as a disinfectant if it causes the growth of bacteria?...

Here's where you logic is wrong. Chloramines don't cause the growth of bacteria. It is somewhat less effective than free chlorine but it certainly doesn't cause the growth of bacteria.
 
  • #4
this explanation helps alot...thank you:approve:
 
  • #5
chemisttree said:
Here's where you logic is wrong. Chloramines don't cause the growth of bacteria. It is somewhat less effective than free chlorine but it certainly doesn't cause the growth of bacteria.

I think I phrased it incorrectly. What I'm questioning is the ammonia part...isn't that a nutrient that aids in the growth of bacteria?
 
  • #6
leah3000 said:
I think I phrased it incorrectly. What I'm questioning is the ammonia part...isn't that a nutrient that aids in the growth of bacteria?

3 ppm isn't going to grow many bacteria. If there is residual present, no growth is possible since they've been effectively killed.
 
  • #7
ok thank you for your help
 
  • #8
Not to be contrary, but I thought the microbe they usually tested for was cryptosporidium, because it easily incubates (right word...?) if things in the treatment plant are not operating correctly, and is a very dangerous contaminant.
 
  • #9
clustro said:
Not to be contrary, but I thought the microbe they usually tested for was cryptosporidium, because it easily incubates (right word...?) if things in the treatment plant are not operating correctly, and is a very dangerous contaminant.
Things may have changed since I let my license lapse ~25 years ago. We tested for coliforms then. It's a simple test and VERY sensitive.
 
  • #10
The Chloramine is used widely because he has a less effect on taste and odor in water.
 
  • #11
nhfs49 said:
The Chloramine is used widely because he has a less effect on taste and odor in water.

I believe it is used because chlorine reacts with stuff to produce carcinogens. This doesn't happen with the chloramine. http://www.epa.gov/ogwdw000/mdbp/pdf/alter/chapt_6.pdf
 
Last edited by a moderator:

1. What is water treatment in the context of industrial chemistry?

Water treatment in industry refers to the process of purifying and conditioning water for various industrial applications. This includes removing impurities, such as bacteria and chemicals, and adjusting the water's pH and mineral content to meet specific quality standards.

2. Why is water treatment important in industry?

Water treatment is crucial in industry to ensure the quality and safety of water used in various processes. Impurities in water can have negative effects on equipment, products, and the environment. Additionally, some industries, such as pharmaceuticals and food production, have strict regulations for the quality of water used in their processes.

3. What are the different methods used in water treatment for industrial purposes?

There are several methods used in water treatment for industrial purposes, including filtration, disinfection, coagulation and flocculation, and ion exchange. Filtration involves passing water through a physical barrier to remove impurities. Disinfection uses chemicals or UV light to kill bacteria and other microorganisms. Coagulation and flocculation involve adding chemicals to clump together small particles, making them easier to remove. Ion exchange involves using resins to remove specific ions from the water.

4. How does water treatment impact the environment?

Water treatment can have both positive and negative impacts on the environment. On one hand, it helps remove harmful pollutants from water, preventing them from entering natural water sources and harming ecosystems. On the other hand, the chemicals used in water treatment can also have negative environmental impacts if not properly managed. Additionally, the energy and resources required for water treatment can contribute to carbon emissions and other environmental issues.

5. What are some challenges in water treatment for industrial use?

Some challenges in water treatment for industrial use include the high cost of equipment and chemicals, the varying quality and sources of water, and strict regulations for water quality. Additionally, different industries may have specific needs and requirements for water treatment, making it a complex and specialized process.

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