Water Disinfection - Massive UV Source and Exposure System Design

Ozone treatment is well understood and more large-scale friendly method of doing just that. Not an expert but think an advantage is that it also oxidises the disinfection byproducts. And it's been aplied long enough that asociated costs are becoming reasonable. S.M.

CaptMoosie: "Frankly, I would NOT rely on UV to provide all your disinfection. There is no residual to incapacitate pathogens in the storage and distribution works."

Yes, UV exposure is for causing immediate damage and nothing goes with water after that in the form of any residual chemical. Left over pathogen sure again will start multiplying so water is to be used immediately within limited time.

Yes, it is assumed that filter and filtering process is applied to remove sediments and also excessive minerals. The last one is to kill the Pathogen as they remain in filtered water.

Both Chlorine and Ozone are well know and toxic agents. While Chlorine can kill, Ozone kills brain memory in inhaling through lungs. Both agents are good Pathogen killers.

UV of high energy 5eV to 12eV is perhaps an ideal source to kill Pathogen. Lamps are directly inserted into water flow to absorb almost all of the UV light. UV in water can't generate Ozone as Oxygen in water is very small. However it can directly kill the Pathogen on exposure. I think it also reduces multiplication of the Pathogen or slows down their multiplication after exposure.

It look that for drinking water UV is more safer than using Chlorine or Ozone. UV Lamps are expensive as they use Quartz window. Glass absorbs UV and Quartz permits UV up to 6.2eV (12400/200nm gives energy in eV or electron Volts) . For higher energy UV MgF2 window material to be used in UV lamps. I am working on this part of the design to see how we can let highest energy UV enter water to kill Pathogen effectively.

I agree if water is to be stored and used then it can have trapped Chlorine for some time which can come out only on heating the water. This gives longer time for disinfection. I will keep this point in mind. I some how dislike using Bleaching Power directly into water to generate Chlorine. Bleaching powder can have Calcium Hypochlorite (Ca(ClO)2) and other Chlorides like CaCl2 and Ca(OH)2 and these chemicals are directly mixed with water. We already have lots of Calcium in water and it also cause high Blood Pressure.

Sorry, I have to disagree firmly with paragraph #2.: that after UV, nothing remains....or some such.

Every oxydisation process, be it mediated by Fl, Cl, O2, O3, or UV leaves similar (organic) debris behind.

The advantage of UV, and say Cobalt gamma irradiation is the aggressive halogen components do not need to be dealt with. Only others.

On the other hand the halogens all leave halogen/organic debris behind. If that is in any significant amount, you need to deal with it. Research on municipal water systems are replete with it.

On the other hand -if you are accessible to it, that is - deep drilling may sidestep most of the concerns. I understand, that is an entirely different technology.

Look up "artesian wells". I used them without any further technology, and they are delightfully reliable and clean.

leveles: "Sorry, I have to disagree firmly with paragraph #2.: that after UV, nothing remains....or some such."

If your choice is between live Pathogen or their Debris then perhaps Debris can be considered OK to survive.

Irradiation by UV will also generate Radicals from what is there in water. We need to see their percentage and lifetime in water. Mostly UV irradiated water is used immediately.

Gamma Energies are not considered in the discussion as using nuclear facilities has many regulations requirements.

Some people also use Silver electrodes and Nitrates coated balls in the water filters to kill Pathogen and I think these can be comparable techniques but may leave small trace of chemicals.

Depp drilling or source of water is not a part of discussion. Avoid this from discussion. It is like searching free pure water for which all people do not have access so why to discuss here.

We are considering that we have water from some available source and want make it living Pathogen free. It is true that some dead Pathogen are more deadly than living one. Perhaps partially dead Pathogen may be a good idea. Just make them useless cells but not a toxic chemical Debris. This point is well taken.

You have started an interesting blog, that we all should really understand if possible, who knows what the future will bring.

With regard to your last very interesting post, I am of the opinion that although this comment is largely true "I agree if water is to be stored and used then it can have trapped Chlorine for some time which can come out only on heating the water." the "only" is wrong.

If the water is stored under pressure in the pipes leading to the user (disinfects the pipes etc at the same time, a "good" side effect of chlorine to my mind), yes, the chlorine is retained, but if the water is placed in an open vessel (Jug for example) and placed in a Refrigerator, the gas seeps away all on its own.....in my experience in the RN many years ago.

No need for boiling and wasting energy.

I personally dislike the smell of chlorine intensely, but like the "cleaning" effects.

In the UK, the water from the tap (and sometimes here too) can smell strongly of chlorine occasionally.......as its otherwise good water, the jug method works well.

As I have never had water tested myself, it could be that even though the smell/taste of chlorine is gone, a tiny amount stays, is that what you mean? I was always told that once the smell was gone, the water was safe to drink (RN again!).

If that is NOT true, then a lot of people are being slowly "poisoned" and not just in India......

What are the true facts about chlorine and local drinking water supplies folks???!!!

What should we know that we don't YET?

Whatever disinfection processes you may decide and settled on, bacterial growth continues. To minimize and control, specially for stored water in storage tanks, it will be wise and prudent to maintain a control on water temperature, acidity level (PH), and to have some provisions for a continued water recirculating process that will help slow down or minimize rapid bacterial pathogenic growth.

Andy Germany:
It is true that excessive amount of Chlorine starts popping out of water but lots of it remains with water for many hours as dissolved Choline. Remember that Chlorinated water from swimming pool may give you eye burn and remains in water for almost a complete swimming session.
When I said that heating water is the only way to get rid of Chlorine is true. Almost all or most of the Chlorine comes out of water once you boil the water. That is the only procedure available for the common men and women to get rid of trapped Chlorine to near zero level. Some Chlorine may react with minerals and can form Chlorides / Hypo-chlorides etc but in small quantity as minerals are in ppm concentration level. I keep mineral at 50 ppm level in my RO. Tap water often has 150ppm to 400ppm level of mineral.
Remember that Chlorine in small amount only bleaches your hair and cloths and gives eye burn but remains harmless to great extent or tolerant you can say. Flooded Chlorine can kill which is not possible for water based Chlorine to do so.
I have to see how Ozone and Chlorine compare to kill Pathogens. Ozone from my point of view is more toxic. It may not kill but can make a person totally dumb by killing neurons even at small ppm level exposure and this I did experience when I was working with UV experiments for my Ph.D. Research. I was generating UV by arc plasma. I felt that something I am starting to forget. I was having normal memory of many years even for small things. I then checked EPA norms for Ozone only to be shocked that less than 0.5ppm in air / hour exposure was allowed. I know that Ozone can easily kill Pathogens.
UV source automatically convert Oxygen into Ozone when Oxygen is ionized at high energy levels of UV in the range of 10eV. LED UV can't do so but fluorescent lamp UV can do so. We use quartz tube for UV lamps and no Lithium Fluoride white power on UV tubes. Mercury Lamps have a lot of UV at 250nm.
We can discuss other points also here. Ozone is also advocated to clean vegetables and there are some companies like Kent in India are selling these. I wonder what they are selling so will buy one to experiment with.

I agree that community or town water processing plants is a good idea. If you buy 1L mineral water bottle then in India it roughly costs you INR20 and if you buy a can of 20L then also it costs you INR20 as refilled water in larger quantity for home use. Production cost of the water need to be INR1/L to run the plant economically.

Small towns here have population of about 4000 to 5000 houses having 5 people on average in each house. Each house may need 20L purified drinking water daily and that means about 100000L of water to be processed in small plants.

Chlorinated water on an average 1000L per family is required.This means about 5ML of processed water is required for small town. Right now each family is paying INR300/m for municipal water which is about $5/month for each family which is almost free. Drinking water costs $10/month for same family. This makes $15/month in expenses for water right now and very soon this may double or triple to settle at about $50/month as this looks highly subsidized one.

Good source of infection is milk and vegetables. If this part is not addressed then this discussion will not be fruitful at all. People will remain sick even if they use clean drinking water as Pathogen attached to Vegetable skin are going to be very dangerous and milk can not be trusted as clean processes are not universal in India.

vsar;

I fully agree on this. You have a very valid point here. Water storage to be considered. Normally we process water for immediate use and not for storage. You store and process and immediately deliver each day. Bottled water sure is stored item and that is to be addressed from this storage point of view. Perhaps chill the bottle to keep the Bacterial growth at minimum. You can see a lot of stock of water bottles stored in open hot atmosphere and they are Bacteria breeding reactors.

I ignored this point earlier but now I think this was a serious mistake. Fact is that this one is most serious problem and to be addressed immediately. Once water is bottled, it must be stored chilled till not used and never exposed to heat or left in open for long. People in India chill only when they sell and keep the water at normal temperature otherwise is a serious problem I suppose.

Reference: AQUARAY® H2O 36 inch, a new inline cross flow UV reactor

http://workingwithwater.filtsep.com/view/897/ultraviolet-reactor-for-water-treatment/

If you want to avoid external chemical processes and chemical injection then UV reactors are good choice. It requires only electricity. This design is only for reference. I have very different highly efficient design for Massive UV Source.

What about filtration to remove suspended solids, then UV lamps, then OZONE treatment. The Ozone will release from the reaction tank where the water will be stored for ~ 1 hour before supplying to the network. Therefore, no residual ozone will be in the water. At this point, if Chlorine is added it will be only to maintain control of the patogens population, if any.

What will be the drawbacks here?

Do you have access to a reference study online that you can post me the weblink for, as what you say differs greatly from the official line from both the RN and my personal but limited experience.....also the W.H.O. (World Health Organization).

I hate the smell of chlorine in drinking water (but I know exactly why its there and accept that) and I react badly (can't drink it!!), so I would like to see a relevant study as to how long it takes to dissipate and what temperatures this happens.

Remembering that gases take longer to leave cold water than hot.....so putting the jug in the fridge would/should actually slow things down, but in my experience, after only a couple of hours, you have palatable, drinkable water with no smell.......

This is probably (I am guessing here) because Chlorine has a boiling point of -34.6°C, so not even the temperature of a fridge will prevent it leaving the water, not even freezing it in ice in a deep freeze will either, though it may slow it down slightly.....

I fully accept that some tiny part of the chlorine remains, the question is "Just how much?". The answer being about 0.2 -1% according to the W.H.O. in most drinking waters.

That level is not signaled by the W.H.O. as being dangerous.

Whether or not there are other chemicals that could react with chlorine is a a local problem maybe. Here in Germany these are "weeded out" in other ways before chlorine is used it would seem.

Treating a water with possible unknown substances in it using chlorine, that could react badly with the chlorine is a best stupid.....as I am sure you would agree.

Furthermore, in Germany, where they have a rule or a law for everything, THEY DO NOT SPECIFY TO:- "NOT DRINK WATER THAT STILL SMELLS OF CHLORINE".

The question is "Why not?", probably because it is safe to do so.....then why are you making so a "Song & Dance" about it....

I am sure that some poor person on the streets in India, is far less likely than even I to turn down a glass of water just because there is a faint small of chlorine.....

I base my comments on a W.H.O. document, which may be interesting to you as well. You will find a copy here:-

World Health Organization on Chlorine in Drinking water.pdf

This fits in completely with both my personal experience and the infos from the RN that I was issued when serving....

Thanks for you time and trouble for answering my questions, but your comments up to now do not either fit in with my layman's experience nor the information from the Royal Navy or W.H.O..

Sorry, but your comments about the levels of chlorine in a swimming pool being in some way similar to drinking water are at best laughable.

What has one to do with the other? I personally NEVER EVER drink from swimming pools, too much kiddy piss!!!! Surely you don't either?

In the WHO Document, it specifies the minimum levels for both tasting and smelling Chlorine in water.......it still does not say that even these levels are dangerous to drink.....

So my empirical method of that once the smell/taste of chlorine has gone, you are probably OK to drink it, is what I get from the W.H.O. document. At least where the other noted possibly dangerous chemicals (when mixed with chlorine) are also not present....

Have a great day, you know how sceptical (CR4 dictionary does not know this word!!) I am of statements made without a shred of evidence offered.

Your comments spiked my interest enough to go and find out the real story, so thanks for that!!! But I would rather believe the WHO than anyone else at this time....but if you can supply contrary evidence, please do, I am interested in everything....

LAA_Lucke:

Larger water processing plants often remove suspended matter by precipitation method and in larger tanks. Some chemicals are also added which have property of coagulation with suspended particles. Aerators are also used and slowly water is filtered in large tanks in which water is stirred for mixing chemicals and then allowed to form sediments.

In smaller system larger sediments are not injected or processed. If they exist then some crude filters are to be used and replaced each time they clog. There are several types of designs for sediment filtration.

Finally membrane filter is used to to remove mineral ions slowly at desired pressure under reverse Osmosis process.

These are modular processes so you use many in parallel to get more water processed by multiplication method.

Some filters can be cleaned by reverse flow method but some require frequent replacement. Cheaper materials like jute, sand, coal, active charcoal, synthetic membranes, membrane candles of many types are often employed in sediment filters. Some of these membranes actually breed Bacteria so require treatment.

Andy Germany:

Chlorine in water has its presence in different forms at different pH. Normally what you get as supply water may be at pH 7.5pH to 7.8pH slightly basic and not acidic. In this pH, Chlorine is in the form OCl- radical. Below 7.2pH (6.5pH - 7.3pH zone) it is more like HOCl and perhaps H2 may be getting out of water as Cl replaces one H atom from water molecule and binds with water. This is one reason it can't come out easily.

Decay coefficient with temperature is like diode characteristics - exponential and rapid between 0C to 45C. You apply more heat and more rapidly Chlorine leaves water. As it is a chemical processes it also has a time parameter for which I need to do some work to know. Best thing to do is to warm water for 15-30 minutes and then chill again in freezer for days stock and drink it as and when you need it. You can also make Ice cubes and then use them.

Our stomach has very low pH 1.5 to 3.5 very acidic due to HCl. This is what we use to digest tough food. Once digested, it is neutralized mainly by the bile juice from liver stored in gall bladder and then it is also mixed with Pancreatic juices before it crosses duodenum valve linked to small intestine. pH value in small intestine need to be above 7.0 plus or slightly basic. If Chlorine enters our body then in stomach it will become Cl2 molecule as there is enough HCl there. I think it is not going to be too much harmful there but may come out with some smell.

I think you can consider small amount of Chlorine in water not only safe but also helping one if water pH is above 7.5-7.7 and maximum up to 8.

"The answer being about 0.2 -1% according to the W.H.O. in most drinking waters."

Not percent, but milligram per litre, or parts per million.

Any more than 2ppm is deemed to be unsuitable for drinking.

Most UK water companies dose to 1 - 1.5ppm in the works as this allows for any losses between there and the end user. 40ppm is the maximum used for commissioning new pipework, and this is reduced to standard values then left for 24hrs before final testing: any result below 0.5ppm will result in failure, and a repeat of the chlorination process once the cause has been dealt with..

UV works relatively well in clean water. Its disinfection success is reduced greatly when the water is muddy as the suspended particles can shield bacterias and viruses from the light.

The quartz tubes have to be kept clean which is very difficult. Many automatic sweepers exist but few are reliable...

The UV lamps rarely last more than 12000h. This is not a long life for semi-continuous operation.

The main advantage of UV compared to Ozone is the lower capital cost but the operation costs are much higher. Large UV plants have technicians replacing tubes on a continuous basis. The lamps is where the manufacturers make their money...

Disposal of used lamps may be a problem as they are tainted with mercury.

Mercury is not required to generate UV. Plasma in N2 and O2 can produce high energy UV. UV glass windows are fragile and expensive.

Interesting notes, all.

However, it is worth to cast a wider view, to see, why is being done what is being done. And is it being done forced by circumstances only.?!? Or there is another way.

When I was a small kid, a crew came thru town, drilling for oil. They have not found any, but brought up artesian well water from 1km deep or thereabout. It was laced with minerals, including Iodine and Bromide, Chlorine. These chemicals kept the water clean for drinking, but gave a funny taste. As a young kid, I was to get it for my grandmother.

Additionally, a well of 10 meters was hand dug on their property in loess soil. Normally, the water level was at 6 meters. The city tested it, and found it clean enough for anything, but straight drinking. Washing, cooking after boiling was fine.

Surface water was never ever used for anything around the houses. That was allowed to collect in the local reed swamp (good for fishing, frogging and getting lost in, being at least 10km long). After passing thru that, locals deemed it safe for drinking. So much for factual and anecdotal evidence.

I have a reason for this detour into history. Our ancestors had keen eyes and good observational brain. They learned to use nature to their advantage, or else. What they were lacking, was technology, to put a honed edge on the knowledge. To acknowledge our limits, neither you nor I am Mr. Microsoft, able to try to force technological solutions all the way.

Public sanitation and good public habits did more to health and hygiene, than anything else in the Americas and Europa, where I am fairly knowledgeable. A century ago both malaria and e.coli infections were endemic up to the arctic circles, and plenty others. Yes, you read it right, up to the arctic circles. Then mosquito screens and screened outhouses were instituted, and both problems faded in two generations. DDT was not invented yet.

Why I am saying that? Because there was no targeted research on those matters as far as I know. Rather, the results came from not targeted research's side effects.

There is a compatriot of yours, a Professor of economics. He - by his own words - inadvertently lent some small sums of money. Microlending was born, and he got fame and a Noble Prize for this discovery. There is plenty to study in itself, and how it happened. But the bottom line is, that you have to leave yourself open to surprises.

Filtering is interesting. Unexpected things discovered are (Noble Prize) awesome.

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Our ancestors were blessed with keen eyes, and sharp intellect. They were lacking modern technology. Do you believe, that your sharp mind came from nowhere?!? Don't lose continuity and common sense, and you get someplace.

I wish you good luck doing it better than the real experts.

CaptMoosie;
I agree with the point that Chlorination is a good reliable process. Perhaps Gas circulation is a good idea with some risk at the plant side where massive Chlorine is generated or stored and used. It is a swimming pool model and has been in use.
What do you suggest for each home? If we can't trust municipal supply then what kind of system one has to use? In many cities in India, Lake water or river water is pumped and has many point broken in between mixing gutter water in the drinking water as both gutter and drinking water pipes run in parallel and both pipes are of ceramic or cement which get rotten over time and no replacement until you see water on the road puffing out.

What is that people themselves have to do now? They do not have space to put large processing plant as with their life time saving they can have some flat somewhere at best. Villages do not have proper water supply and if they have then it is directly well water pumped to you house.

In cities we get sediments, colored water which may contain anything and everything. It is for anything other than drinking.

For individuals, and also for small houses societies within a building complex a small sediment filtering plant and UV has been analyzed as water is processed and used immediately. No Sodium or Calcium Hypo can be used as water already has 200 ppm to 400 ppm mineral level. Municipal water here is never processed for mineral control and in fact they may add bleaching power (Hypo) as they don't have Chlorine plants.
I think picture is different in different countries and so the solution may also differ. I fully agree that if municipal water is properly processed and delivered through proper pipe lines then just Chlorination can retain the water quality. However, this is not happening and people have to live so they have to find ways and we have to think for them rather than asking Government to run properly for which we pay taxes. Either we keep beating the drums or do something to survive are only two choices. I think we need to survive even if we have to beat the drums. Isn't it true.

Many places in USA there were industrial poisoning and I think each country may have its story from its people. It is the strength of the people to find solution to be the fittest will also make them live longer.

While municipal model of collective sediment processing and Chlorination look very good one, I still feel that at terminal point sediment removal and UV exposure is a wise thing to do to assure that water if directly consumed will not bring in diseases. We all know here that those houses do not use RO with UV always have cold and cough and entire family run at low immunity. We don't accept if they offer us water. Does not this sound very unsocial? Country being populated by mainly poor population and for financial reasons even that $300 RO they can't install. I will sure consider some safe method of Chlorination which sounds good if it is feasible to implement safely at delivery point. I think Chlorine has to be in water for few hours to be effective.

I will like to thank you for advocating for Chlorination which is a good point. I still prefer UV at the terminal point as it is electricity operated. UV lamps are $0.5 only for 6W lamps and $2 for 40W lamp. Power consumption is also not very high. 40W lamp can process 1000L water in about 5 hours with total 200W power per day.

marcot: ;

I am planning to redesign the UV source and not to use ready made tube light models. I want to have more contact area and contact time with running water for much higher energy UV.

I am also looking at direct electric discharge model similar to ORP model but by using very high voltage of several kV for nano-seconds. This one to be used for food items like juices, cold drinks and many other things as well.

Similar to Gamma radiation UV exposure also helps vegetables and fruits from getting rotten. Fresh fruits can be directly exposed to UV before placing them in freezer. Vegetables perhaps can be washed in Chlorinated or Ozone water but fruits people don't wash before putting in refrigerators. UV exposed last longer and remain better.

We run five water treatment facilities (for drinking water) and there is one thing that must be understood. Each water source is different and requires development of a suitable treatment SYSTEM for that locality.

UV is only part of the possible treatment stream.

Shyam, I understand that you are specificallt looking at household treatment of whatever the household might receive from their water supplier.

The system will need multiple "barriers" and differnt systems require different sequences and combinations. We use a combination of Membrane filtration (Or floculation combined with sand filters) followed by Ozone (Or UV) followed by Activated charcoal (to remove odour/taste plus organic residues of killed bugs.) this creates our "clean" water. This water is then "preserved" by addition of Chlorine before we send it to our customers.

If you are talking of benchtop domestic units, then you would may not need the "preservative" action.

If you are using RO, then there is no pathogen small enough to be in the produced water and using UV would provide no benefit, while if you are using a simpler particulate filter, then pathogens could definatley pass that barrier.

For UV to be effective, then there is an irradiation intensity that is required to be achieved. Cloudy fluid will mean that the gaps between the light source elements will need to be smaller. (That is higher turbidity requires closer spacing).

The real challenge with any household treatment system is providing a means to determine that it is actually providing the benefit that it claims. A failed UV element, or one fouled by detritis may still draw current, but be totally ineffective in disinfection. The typical householder would be unable to determine those situations with the related health consequences.

To discuss UV without the context of the other barriers that are intended to be used is an incomplete scenario and one where many "sides" of the argument can all be correct in their own context.

Just an Engineer:

In our house hold system, we have sediment membrane, two more sediment filters and one with active charcoal and then reverse osmosis membrane filter and finally UV lamp. UV remains visible as inlet and outlet water pipes glow due to UV. If UV lamp fails then system gives an alarm. We have no Chlorine system at home.

Some people use just membrane filters and nothing else. Candle type. I discarded this system.

Some people boil the water. This also precipitates minerals.

Now, I need to think of how to use Chlorine in each house? Or do we do it for a community and then supply to them. This can be done only fro drinking water. People will still use unhygienic water for cleaning utensils, washing cloths, washing hands, brushing teeth and bathing. Perhaps I can consider it economical to have 5L purified water per person per day and 100L municipal water per person per day as it is supplied.

You are adjusting your statements after the event......not good.

Your statement in Post #3 was:-

"I agree if water is to be stored and used then it can have trapped Chlorine for some time which can come out only on heating the water."

This comment is wrong in several ways as 1) the gas will only remain in the water IF UNDER PRESSURE, storing it without pressure will allow it to leave the water. 2) It does not need to be heated, but then takes a bit longer to escape.

Go back and read your statements in your own posts.....CORRECT THEM HERE AND NOW PLEASE?

Everyone (well almost everyone) knows that gases leave a hot liquid faster, but you were saying before that basically "it had to be done or the chlorine would remain, obviously meaning, in quantities that could be harmful".

Simply not true. It will leave water of its own accord when the pressure is dropped, which is one of the MOST beneficial aspects of using chlorine to make water safe.

The quantities left in the water when not boiled are not considered harmful by the WHO. Or anyone else for that matter that has published on the web as far as I was able in a short search to find........

So please stop adjusting your statements after the event, you were wrong! You do not need to boil/heat the water to remove chlorine, period. You can if you simply need to speed up the removal and waste energy at the same time.....but you appear to want to do the job cheaply, so energy wasting need not be made.....right?

The further beauty of chlorine being that it remains in water when under pressure and tends to disinfect the pipes in which it is carried (under pressure). Only finally leaving the water when no longer under pressure or when temperatures below approximately -45°C are not apparent, so low that only a few places in the world ever experience them. India probably not being one of them I would imagine!!!

There are several very useful and easy to understand studies that are available to anyone with an internet connection and a bit of spare time, about disinfection of water using various methods and chemicals, chlorine being simply one of them, but probably the most popular for both large and small users.....

Adding in rubbish about swimming pool water was completely irrelevant to the problem in hand as most people do not intentionally ingest such water. Though the levels of Chlorine are often higher than in drinking water, even to the extent of causing eye tissue irritation (personal experience), but not killing anyone when done correctly as far as I have been able to ascertain on the web.

I do expect someone, somewhere has sadly overdosed on chlorine (there are enough idiots around). But what were the levels incurred?????

It appears to me that you are simply making the subject of chlorine in drinking water far more complicated than either it is or than it needs to be....to my mind, if you find it too dangerous and/or too expensive for India, then you must look in another direction. Publicized infos are in abundance, you hardly need to be here looking for further "tips"....

In the UK, it has been used for more than 100 years, originally to stop certain epidemics, I am sure that many other countries have a similar history, its really nothing new.

It is also apparently well understood and detailed for those who need/want to know, even on the web. You appear to have either not read these documents or failed to fully understand them, sad.

Even my VERY limited and TINY personal experiences with regard to the disinfection of drinking water using chlorine, most of it many, many years ago proved to be far more accurate and to the point than most of your original comments on the subject....

Think about that!! Also, I do not even pretend to be a professional on the subject either.....far, far from it.....

If you had simply apologised for the errors and corrected them, we would not even be talking further....you didn't.

I know that everyone makes mistakes, its accepting/correcting them that gets difficult for some! Even for me, but it has to be done properly... (Been there, done that and NOT got the T-Shirt!!)

Another comment you made in the same post if I remember correctly that needs a bit more thought about on your behalf was:-

"It look that for drinking water UV is more safer than using Chlorine or Ozone."........

You should be more accurate in your comments. What I have read from yourself and others here has lead me to believe that this is simply not an accurate statement as the water system could remain full of dirt & germs even after the UV treatment...perhaps if one was fitted to each drinking water tap, you might be right, or in conjunction with chlorine for pipe and storage disinfection. Don't you agree?

There are several other inaccurate/misleading/wrong comments/statements you have made in this blog that we can leave for another day if you wish....

Have a nice day.

Note.

Taken from a Wiki page at (there is here further far more interesting infos than I have posted below by the way!):-

https://en.wikipedia.org/wiki/Water_chlorination#History

In a paper published in 1894, Moritz Traube proposed the addition of chloride of lime (calcium hypochlorite) to water to render it "germ-free." Two other investigators confirmed Traube's findings and published their papers in 1895.[13] Three years later, a full-scale test of Traube's laboratory work was conducted at Maidstone, England. In the midst of a typhoid fever epidemic, Dr. Sims Woodhead applied (on a one-time basis) about 4,200 ppm of chlorine in the form of chloride of lime to a drinking water reservoir and the distribution system.

Thanks for the correction.

It demonstrates that I should not trust my memory too much (too lazy to refer back!)

Interesting post.

You wrote:-

Disposal of used lamps may be a problem as they are tainted with mercury.

Could it be possible that a broken lamp might release Mercury in the water?

Andy Germany:
My comment is right about Chlorine as we are discussing here water for immediate use. If Chlorine is already present in water while Chlorinated water is pumped to you and you want to get rid of Chlorine then you have to heat the water. Why are you so insisting on this point?

Technically you can remove Chlorine under low pressure also but who is going to create vacuum. Whatever you do, Chlorine based Radicals can survive for months. They change their form according to pH and temperature of the water. Like dissolved Oxygen, there is dissolved Chlorine in water. Just Cl2 gas in water that part only can come out. Chemically associated Chlorine get trapped.

If we have a system of local processing and time delay storage and monitored delivery then we can have safe levels of Chlorine which we need not worry too much.
In India people call it fresh water when it arrives through pipe line and they fill these for immediate use in drinking vessels or drink immediately from tap.

They also store water in overhead tanks which is mainly used for cleaning and bathing and never for drinking.

There is no 24-hour water supply in India and water runs only for limited time not exceeding 1-hour daily. I am discussing problem of India and solution for India and not for USA or other countries where regulations are strictly implemented. In India they simply dump few bags of Calcium Hypo Chloride in water and such chemically mixed water is pumped to home directly. Water corrodes even stainless steel vessels and you can see a thick layer of Calcium hypo in it. If you drink it then you are drinking not just Chlorinated water but entire chemical also. People who do mixing of chemicals are not engineers but uneducated labors. They follow no norms. This problem is real and not some imaginary one.

GA.

Reading down from the top of this blog, you are to my mind, the first poster that appears to fully understand what he is talking about on the subject of drinking water disinfection and is able to write it down in a manner that even makes easy sense/reading to me personally.

Many thanks, we have now got common sense on our side!!

LOL LOL LOL !!!

I only read half way down, by then I had found many inconsistencies and inaccuracies and misunderstanding...the rest I simply ignored.

In the future, try not to kill or injure too many folks with your methods.

Remember the old adage:-

You can lead a horse to water, but he must be able to drink (disinfected water?) on his own!

You need to learn to drink.....

Yes, Mercury vapor lamp do have Mercury which is evaporated and then used for arc discharge to get UV naturally and visible light using phosphor coating on inner surface of the bulb.

www.state.nj.us/dep/dsr/research/mercury-bulbs.pdf

Kill? what do you mean?

This will be so inefficient that you will cook the produces before killing the bacterias.

I don't think that India has enough electricity to do what you are planning. What will happen to the water (or produce) treatment during the blackouts?

What you are talking about has been tried by manufacturers for many years but there isn't much commercial value yet. Especially in large installations where energy cost is of prime importance. Very few specialized applications can benefit from the theoretical techniques you are describing.

Generating nS pulses in the lab at low current and voltage is feasible but scaling it up to multi kW is extremely expensive. Believe me, I have such a system in my lab.

As I said before, good luck, you might succeed where many others failed.

The lamp is not in direct contact with the water. If a lamp break during usage, it will release its as in the quartz tube and vent to the atmosphere. Most of the lamp breakages happen during manipulation.

In reality, a single lamp doesn't hold much mercury. There isn't much problem if handled properly. The problem is the accumulation when thousands of lamps are changed every years and a small percentage breaks.

In the developed world, it is not such a large amount of mercury. The professional people handling the lamps are trained and the disposal is per local regulation.

It is another beast when we are talking about the developed world.

marcot:

I know that high voltage pulse technology is only at the research level being far expensive, far unsafe to use and it almost requires a local power reactor. Perhaps loss of energy in water or fluid going to be much larger and it may also generate a lot of radicals (wanted or unwanted both). water and food drinks are almost at same price level so economically this technology does not look viable.

I am also not sure if plasma in controlled atmosphere can do some good to the food but UV has shown some promises which can be generated in plasma of Halogen gases or just air. My experiments with air arc plasma shows that electrodes corroded quickly and this perhaps may be happening due to impact of accelerated electrons and ions. I have used Gold plated electrodes and they lasted only few million pulses at best. For Excimer LASER we use Fluorine 157nm emission wavelength UV.

If the locale in India will support it, why not use direct incident solar UV light? One could easily find a source of UV pass band light filter, so as not to entice algae to grow in the water. I would filter the water first. Then I would use a plate system to produce a thin film of water being exposed to the radiation. If normal incident solar light is not strong enough in UV, try experimenting with parabolic mirror system with dichroic mirror light filtration to (1) raise the level of UV A and B while (2) limiting the exposure to light that promotes algal growth that also heats the water.

I have not a clue what you would do to have drinking water at night, unless stored.

I suppose that chlorine is far better, provided that a constant dosing that will not overtreat or undertreat is available that does not require expensive equipment. Even if the chlorine is over done, by sitting the container out in bright sunlight, the water would become dechlorinated by the next day. I am making no claim as to whether this would efficacious to the health of those who consumed such water.

A final option is ozonation, but that is generally somewhat expensive to implement on a large scale compared to chlorine, although it might just be possible on a small scale with a hand cranked generator of suitable voltage. Ozone formed in "air" would then have to entrained through a venturi system into the water (again after filtration).

James Stewart:

There isn't enough UV from solar radiation and only in zones where there are Ozone holes of larger size appearing, the UV may be on higher side. Background UV from Fluorescent Lamp is much higher than open sun UV. You can use Infrared and visible solar spectrum for heating or solar energy but UV isn't enough to be used for killing Pathogen. UV simply gets absorbed in air and this layer of air is too wide / thick to let lot UV reach earth in high intensity due to its ionization capability and is mostly trapped in the Ionosphere.

For other information, it is better to know mainly from standard references related to water treatment plants operated using Chlorine, Ozone, UV etc. It is a professional area and we are talking about professional technology at the start up stage to analyze all options with some details that otherwise may get over sighted. Here in this discussions there are many good comments and partial observations that have given some good clues of what to be done in the planning of an over all system. Still I need to talk to the professional teams to get data that is relevant to the level permitted for the food and drink (water) at supply level. We can't ignore standards and scientific data else will be questioned by anyone and everyone and it will not serve the purpose we intend to do.

Our aim here is to reduce chances of problems specifically at homes for just in case water delivered can't be trusted and what kind of second level purification system is to be used in such cases to avoid problems. We all have specified limits for Chlorine at 0.5ppm to 1.5ppm concentration level that should be there in the municipal or commercial water delivery system and water must have been treated for sediments and minerals at the distribution point itself. However, this is not happening.

Our concern is that water may not have these standards when it reaches at our homes, then what is that we are supposed to do? These are extra devices we are talking about so they are not complete solution or replacement for water purification plants. Some time they may look unwanted if supply water is good and sometime they may look doing only partial job as these are not designed to clean anything and everything to follow standards. These are precautionary measure to remain healthy as long as one can do so when problem is known to occur randomly or frequently or consistently.

At least in Texas (or anywhere else one can get a sunburn from over-exposure to the sunlight), there is enough UV to totally remove chlorine from water, and in fact this is the procedure to produce "zero" water for low-level chlorine tests. Even light coming through a glass window is sufficient for this purpose.

You should consider a biological solution to the pathogen problem. The higher power that designed earth did so in a way that simple mankind could survive. Perhaps intentionally growing algae in the water is a good thing, as long as the water can be reasonably clarified downstream (prehaps by the use of colloidal clay to peptize algal cells (and pathogens) and precipitate them. Before you simply "blow off" my argument, try an experiment and actually run ATP tests on the water incoming, and after this treatment.

Another trick might just be to use media filtration first, followed by microfiltration or ultrafiltration - but these require head pressure, either natural or electric powered.

Final note: use ORP instrument, as polluted water will show a much lower reading.

I disagree.

If sun UV exposure alone was enough to kill the Pathogen then they will have no chance to be in the nature. Pathogen are surviving organisms and that is one reason why we need to do something extra to kill then until they build resistance to the means of killing we use now. They must be learning to survive against Chlorine, Ozone and also UV. They survived for millions of years and will be here for millions of years in future as well.

If you collect radiation in larger flux somehow then perhaps you may be able to get some results. Direct sunlight is of no use.

Perhaps you might have seen something like this one

http://www.rsc.org/publishing/chemtech/volume/2009/03/solar_power_kills_bacteria.asp

So if you spend a day in sunlight, do you think you become a germ free man? Our outer skin layer is dead layer and its peeling out from exposure or you getting sun burn or getting skin cancer from sun exposure need not be mixed up into water purification.

In principle Photons can only be attenuated in numbers but can never be reduced to zero so you can say that some UV will reach water if you place water filled bottles in sun light. May be some Pathogen may get killed but by then many will also multiply so what is the end result? Bring me scientific data in numbers to prove the point.

Some people may count on solar heat rather than UV as in India naturally the environmental temperature in open sun can be as high as 48oC in summer. That sure may do some damage to the bacteria that can survive only less than 40oC. This point is positive one. If heat exposure is for several hours then some Bacteria may be drastically reduced in number. Cell multiplication process may also slow down in similar way as it happens at low temperature in freezer. With slightly focused light you can have a solar cooker so temperature of the water exposed to focused sun light may be as high as near boiling point. This is as good as boiling water.

If there is some good scientific quantitative study that exists somewhere with positive results then let us have a look at it.

Obviously you hopefully read the part where in the article you cited, the author mentions that it is the total dose of solar radiation, not the intensity that results in complete disinfection. I submit to you that if a simple filtration system (even operated by gravity head pressure) is combined with a solar irradiation system where the water is maintained in a thin film, then the low flow rate through a reasonably large area (a few m²) where the light largely makes two trips through (reflective back layer) will do a pretty good job.

If you wish to have a point of use system where there is supply pressure, then install a large carbon block filter from Amway (these use a solid block of activated carbon and produce amazing results), and they have the option of including a downstream UV source (for assurance purposes), where the user had household electric supply available.

I have another idea to share in another reply to your OP.

With 48C in direct sunlight, how hot behind glass - as in solar hot water?

A sufficient length of piping would get the water hot enough to kill the pathogens, then chill for drinking.

Shyam: I recently saw a speech (online) from a University of Washington (I believe, or it may have been Washington State University). This astute gentleman was discussing the observations relative to long-range order of dipoles in water of the order of several hundred thousand to several million molecules deep. Many have observed the so-called "exclusion zone" in water containing colloids. I consider suspended bacteria and protozoa to be suspended living matter. These would also be excluded from the exclusion zone, which has been measured to be from 200 to 500 micrometers depth (at all surfaces including the air interface). It has further been demonstrated that the exclusion zone is maintained under flow conditions not greatly turbulent. By novel techniques the speaker also demonstrated variation of pH from the exclusion zone to the bulk water zone (having the lower pH value).

Imagine a simple concentric tube arrangement with the smaller tube fixed with its outer diameter approximately 300 micrometers from the inner wall of the outer tube. It is completely unimportant the nature of the materials at this point. Demonstrations have been made (by others) that suspended particles can be removed to a very high degree of efficiency by this method where the flow from the outer tube is captured, and the flow from the inner tube is discarded or recycled. To gain the utmost assurance, one could easily have several of these devices in series to remove all planktonic organisms, potentially even viruses.

When this technique is combined with UV or other radiation, before during or after separation I could foresee an exquisitly reliably safe source of drinking water.

And drink only from a silver chalice.

I have achieved over 80C with a home made panel - in Scotland with ambient around 20C, so I believe that using electricity to boil the water is unnecessary. The chalice is just to be sure.

good man.

James Stewart:
Colloidal particles do show order when they are subjected to vibrations. They almost look like a solid structure having neat and clean geometric patterns. You can't kill Amoeba by cutting it in two is well known. Most of the miniature organisms have lots of functions chemistry that let them live in complex surroundings and perhaps they may also be adopting to situations (all may not be alike if you pick from different sources).

Most of the Plankton is know to be at surface or just below it. Actually this name itself applies for such organisms plant and animal both that live on surface or just below the surface of water. Perhaps it is having greater relationship to solar radiation as water both. They are part of the food chain for other living organisms. Bacteria grow in lower pH and it is their natural process like making curd from milk. Normally Bacteria multiply at rapid rate within temperature range and if temperature does not suit them then they may be able to change form and hibernate and comeback at right temperature suitable for re-transforming.

When you start UV exposure and living organism start failing in its normal activities, then its own survival system must be pushing it either into greater resistant state or hibernation state if it has any such well developed mechanisms else will end up into fragmented soup of bio-protein molecules which is again a food for surviving organisms. Just the way we treat cancer by irradiation in multiple steps with waiting time for recovery the same is also valid for these living organisms. They all have time dependent phases and some phases are so vital that single UV hit can destroy them during sensitive period. If you keep exposure On for long then more such living cells may die. Some cell can repair and some may never be hit so there is a chance of greater hit with greater flux. Both high flux rate and low flux rate integrated over time may have effect on cells. I am only afraid the such a small flux from solar UV has little cross section to find and hit living cells. If these living cells are intently looking to locate near surface or surfaces then their chances of being hit are much higher. UV will generate secondary electrons under Photoelectric effect or Compton effect. These electrons if they are part of the genetic chain and if such chain breaks due to the kinetic energy then cell will get killed. The mean free path that is expected for electrons is about 5mm from the surface so effect on deeper layers going to be minimal.

I have seen those SODIS pictures and in some experiments thin bags were used and in some bottles of water and some had dark top surface. I think only part of this project may be scientific and most of it looks unjustified. I am not sure about their statistical data which shows about 50% people being benefited. If people are ware that they are sick due to poor quality water then obviously they will look improving the situation and that can show some results. Awareness can make a difference. If you know that the water is poisonous then you are simply not going to drink it and will look for an alternative source of water.

Many people do not consider cold and cough serious problems. Some even don't care about Malaria and live along with mosquitoes. Whether pathogen will kill man or man will digest Pathogen remains to be seen in such typical situation.

It is very hot in summer here and water in water storage tanks get so hot that you can't use of bathing and have to cool it for a while. We have to cool rooms using AC or water evaporating type coolers. Moisture content is very low. Now that it started raining here relative humidity is 70%RH in my room and temperature must be near 25oC now. This place is 212m above sea level.

I must use the heat freely available from solar radiation so I will like to place a solar water heating system on top of the house roof. Geezer installed in the bath room is not used in summer as water is naturally hot from overhead tanks. We get some sediments in the tank and these must be part of the pipe line and settled suspended matter from incoming water. A layer that settles down in the pit need to be cleaned regularly.

Good points.

Not sure if this was mentioned in this thread yet...but it has always been my understanding that UV doesn't actually kill bacteria, rather it renders it incapable of reproducing. Please, someone with more experience than me please chime in.

If this is the case, UV by itself would be insufficient. You would need to use chlorine, bromine or ozone. Of the three, I suspect ozone would be the most desirable as it has a very short half life (somewhere around 30 minutes I think) - although it wouldn't provide long term disinfection. Ozone would also be easy to generate, and although not completely benign, much safer than dealing with chlorine or bromine gas.

I also wonder if Iodine would be an option?

I don't believe you quite understood what I was saying. The long range order is for water molecules near surfaces, and this long range order excluded particles including organisms. This can be used to produce a biofilter that is entirely reliable based just on flow between concentric tubes of appropriate geometry.

MrGeneRall:

Appearance wise fluorine exists as a pale yellow gas that is poisonous in nature, while chlorine is similarly poisonous but exists as a pale green colored gas. Iodine is commonly found as a black shiny piece of solid, and upon heating it forms a violet vapor. Lastly, bromine brownish liquid is extremely volatile in nature and is also considered toxic. Read more at Buzzle: http://www.buzzle.com/articles/halogens-properties-of-halogens.html

Here is more about Halogen gases

http://www.rsc.org/chemsoc/visualelements/pages/data/intro_groupvii_data.html

Iodine directly enters Thyroid and Fluorine form HF with water very quickly which can dissolve almost anything. Chlorine looks much safer. Bromine and Iodine are often used as Tincture of iodine or Tincture of Bromine as Antiseptic and both are applied externally on wounds. I am not sure if you can drink them.

Are you guys still at this thread? OMG......an apparent act of futility.

I has to concur with Leveles' last post, #49. Get the raw water clean as possible and then chlorinate the crap out of the water. Even a simple slow sand water filter is highly effective because it relies on both physical and biological for TS and pathogen removals. Coupled with a activated carbon layer buried between the sand and gravel layers you can attack the DSS together with taste and odor problems too. And it's nearly idiot proof to operate....just have to make sure to keep the raw water application rate within the acceptable limit ranges......benchtop testing of the filter is imperative!

Why the fixation on gaseous chlorine, which is dangerous, difficult to handle, requires specialized expensive equipment, and totally inappropriate for small water systems.

Use LIQUID sodium hypochlorite.....all you need is the appropriate sized metering pump, pulsing meter, simple injector and a barrel. Relatively inexpensive and nearly Village Idiot proof. Heck, you can even you chlorine bleach (non-scented of course), which is really inexpensive and easy to obtain almost anywhere! Like who cars about the chlorine taste as long as it saves lives and prevents water borne illnesses??????

The key to successful disinfection is to provide adequate raw water filtration prior to disinfection, be it Log3, log 4 or log 5 removals of pathogens like Giardia and/or Cryptosporidium and protozoa, etc etc......

I highly recommend the last link below regarding Dr. David Hendrick's AWWA manual on slow Sand Water Filtration. It may be a little old, but it covers the basics very well and is extremely comprehensive.

http://www.cdc.gov/safewater/sand-filtration.html

http://www.who.int/water_sanitation_health/publications/ssf9241540370.pdf

http://www.slowsandfilter.org/http://books.google.com/books?id=WO6A_4JAdVsC&pg=PT176&lpg=PT176&dq=AWWA+slow+sand+water+filtration&source=bl&ots=9uPkSdUAS-&sig=Ok7gp80ey6q0B1ttAwUdomI5L0w&hl=en&sa=X&ei=P_LKUeOHLMeX0QGqrYC4AQ&ved=0CGgQ6AEwCQhttp://onlinelibrary.wiley.com/doi/10.1002/ep.670120417/abstractI highly recommend

http://onlinelibrary.wiley.com/doi/10.1002/ep.670120417/abstract

No idea.

One reason that gas is favoured is the shelf life of liquid Hypo. I suspect that in the India context, the reactive benefit would be of questionable (and significantly variable) capability, while gas is significantly more stable.

We use Hypo in the main dosing plants because turnover means that it is always fresh, but use gas at remote locations to "top up" the residual. (Some of our reservoirs are 130km by pipe away from the treatment plant and will pass through four other reservoirs before reaching that point.)

For Shyam's home treatment system, it would seem better to use "unscented household bleach" (around 4% solution) at a rate of 0.5ml per L of water processed and then have it stand for at least 4 hours. (WHO suggested practice 500ml per thousand Liters as disinfection for rainwater stored in tanks.)

I don't necessarily agree with Shyam's approach on this item as it would still rely on an unreliable electricity supply, UV lamps that have deterioration of output through their life along with other issues. One would hope that his research concludes (As those Mythbusters might say.) "Plausible", but who would do it that way knowing the alternatives??

Water in this zone is heavily loaded with Calcium and perhaps Sodium Hypo can be tried. W will have a problem of silting of the tank and frequent cleaning may be necessary. Right now we do this once a year but may be necessary one a month after mixing Hypo. We have 1000L tanks so as suggested, 500ml or perhaps 500g Hypo to be mixed which will be 30 times in a month silted in a tank's bottom.

Good Idea.

Liked your post, you demonstrate good common sense (which has often been missing in this blog since it started!!)

I also use the UV reactor for water treatment and it is working very well.I bought this from waterwastewaterasia.It is very good in quality and also working very efficiently.

I would refer you to the works of Professor Gerald Pollack of Washington State University. He has found that the exclusion zone for particles suspended in water can be to almost 0.5mm, in the following conditions:

(1) water must be in contact with a hydrophilic surface (Nafion membrane works well),

(2) there must be a minimum residence time for the EZ to form, thus there is a limit to flow rate.

(3) exposure to sunlight provides the energy necessary to form the EZ.

No imagine a nested capillary system: One tube is approximately 0.3 mm smaller outside diameter than the inside diameter of the Nafion tube. the smaller tube extends a usable distance away from the opening in the outlet of the Nafion tube. Pure water comes out of the Nafion tube, whilst the polluted (collodial suspension of particles, bacteria, solutes, etc.) water exits the central capillary.

Now imagine this in the form of a stack of Nafion disks slowing rotating in a cylinder, similar to a boundary layer (Tesla turbine) pump, and with ports for the EZ (boundary layer) water and the polluted water. By increasing the number of discs in the stack(s), and modules of stacks, one can increase throughput of such a system arbitrarily.

Now go out and get the patent for this before I do.

I have used UV as a supplement to an ultrafiltration system for brining operations (Cheese). This company Xenon Corporation has a pulsed UV,

http://www.xenoncorp.com

where it can deliver more energy to the process, plus it has a lot of data to back it up......

Exactly, about 15 years ago, they were using high pressure pasteurization to pasteurize orange juice (Flow International) and initial test showed it did a great job, and looked promising.

But it didn't take long for the pathogens to 'repopulate'