http://en.wikipedia.org/wiki/Electrochlorination

Water purification - Wikipedia, the free encyclopedia

Thanks for your concern.

I am serving Karachi Water & Sewerage Board (KW&SB), Karachi, Pakistan as an Executive Engineer. Karachi is the largest city of Pakistan with an approximate population of about 20 million.

KW&SB is a provincial govt. controlled water and wastewater entity. we are managing about 180 MGD of potable water for domestic, industrial and commercial use.

Indeed, 16000 Kg of chlorine is a lot of disinfection demand. But it is for our Six Water purification plants inside and outside the city and other dosing points using Chlorine gas through 900/1200 kg cylinder.

Good advice. I would suggest George Clifford White's book on Chlorination. I know there is an updated version but not fully authored by White. I have not read or even acquired the book and am not likely to do so. I am very familiar with the older editions and go back to the first edition (I think there are 5 editions). The newer versions include alternative disinfection methods and there is an abundance of information on the manufacturing of chlorine (gas and liquid). A very good book and worth the money but I am not sure what edition to suggest but even a used version would be good.

EPA manuals are also good.

If you search long and hard enough on the WWW, you can download a free ebook of Clifford White's chlorination handbook.

I have a copy of it on my PC hard drive. I agree that it's the most invaluable text written on the subject. Even if you have to buy it, it is worth every Cent spent!

The EPA manual is invaluable as well!!!! I use both in my consulting engineering practice....

A very good place to start is the US Environmental Protection Agency (EPA) study, "Alternative Disinfectants and Oxidants Guidance Manual", EPA 815-R-99-014, available from the EPA website for download. The version I have was last updated April 1999- there may be newer versions or updated information on the EPA website that you might find helpful.

The problem of utilizing Ozone strictly for disinfection is it's relatively short longevity in the distribution system, and hence inability and ineffectiveness to provide long-term inactivation of microorganisms within the system. It is absolutely essential to provide the minimum prescribed disinfection residual throughout the water distribution system and storage facilities to insure the safety of the water supply, thus use of Ozone alone does not provide this. IMPO, using Ozone alone is a huge "crap shoot".

Yes, it is a very good method to initially reduce the overall production of Trihalomethanes (THMs), but it is not the end-all. Here in the US you will not find the Ozone as the sole disinfection agent in municipal water treatment, but rather it is used in conjunction with Chlorine, Chloramine or Chlorine Dioxide for disinfection of filtered water.

It is essential that the treatment plant unit processes are optimized to remove THM precursors (chiefly soluble and insoluble organics) as much as practical/possible prior to disinfection, especially if your water source is surface water (lake, reservoir, and/or river) and your raw water source chemistry is marginal or worse.

If you don't already have it at your water authority, download a free copy of EPANET from the US Environmental Protection Agency (USEPA) so that you can model your water distribution and storage tanks using different disinfection agents with differing concentrations. Make sure that you calibrate the model properly, otherwise you will end up with erroneous results!

ps: Another good textbook to have on hand is: "Integrated Design of Water Treatment Facilities" by Susumu Kawamura, John Wiley & Sons publishers. My © 1991 edition is still valid to this day! It has a very good section comparing the various disinfection agents that one utilize together with their respective pros & cons and cost effectiveness for various daily plant water production volumes. Very very invaluable!

pps: Another very good book, that describes disinfection alternatives in-depth, is from the UK: "Basic Water Treatment, 4th Edition", by Chris Binnie and Martin Kimber, RSC Publishing, © 2009.

I am a very strong advocate of ozone water treatment, having installed a number of systems for swimming pools as well as private potable water systems. The one issue with ozone for municipal distributed water supplies is that there is no effective residual, and water downstream can become contaminated. However, ozone used as a primary disinfectant reportedly can significantly reduce the amount of chlorine required to maintain water safe for drinking in a large distributed network.

Take a very good look at chlorine dioxide derived from activating sodium chlorite with an acid. Kills more pathogens with out the carcinogenic compounds created by chlorine reacting with organic material. 900 communities in North America use it for water purification. Sodium chlorite is derived from common salt through a process using electricity from what I have been told..

Hammy, I agree with you on the use of Chlorine Dioxide for an effective water disinfection agent, particularly if the raw water source is a surface water.

And yes, there are some very good "on-site" generator equipment available for producing Sodium Chlorite from common salt, but given the huge production volume that the OP provided us it may be impractical due to scale and economics.

I am not a water specialist but these folks have a huge project. I do not even know the cost variation but I have and do use chlorine dioxide in my health coach activities and make it my self with sodium chlorite and citric acid. We have bubbled it through water then the yellow water that is infused with chlorine dioxide is diluted and metered into drinking water at about 20 ppm. One farmer went from $20,000.00 euro in vet bills to zero in one year with his cattle herd. Even the people that use it find remarkable recovery from a huge range of ailments. I also worked with a farmer that infused H202 into his drinking water for a dairy herd and dropped his bacteria count into and well below accepted levels. No more milk problems. Maybe these folks from Pakistan should take a look at a UV system.. Health authorities in Canada seem to be in love with UV.

If you are interested in alternatives to chlorine disinfection, cavitation and electrolysis (for electroporation of microbes and in situ production of OH-, the most powerful oxidant of all) might work for you, even at the high flow rate you have. Although it is not yet in production, I believe this is the future. UV has shallow penetration (skin depth) and microbes can hide in the shade of suspended solids. Killing cryptosporidium and giardia requires something more powerful. Ultrasound for cavitation is not scalable to your needs. This patent application for a high volume continuous electromechanical disinfection apparatus has been allowed in the US so it will soon be a patent covering manufacture, use, and sale in the US. You would be welcome to use it in Pakistan, gratis. http://www.freepatentsonline.com/20090159461.pdf

Thank you for the information......it looks like an interesting technology.

Okay, it has a US Patent. And?

Was testing conducted by an independent testing laboratory? Has the AWWA, the USEPA and individual state water bureaus (usually under the auspices of state health depts.) evaluated this equipment and it's capabilities? And the results were for all of the above?

Sorry to sound skeptical, but patents can be issued for just about anything anyone can think of whether it is proven valid technology or not.....

I'll be believe it when the test results are published in acceptable trade journals and I have had the chance to view said documents under the peer review process.

No testing data are available yet. It is being actively worked on, though, and there is no reason to suppose that it can't work. Thanks for providing that checklist of testing agencies.

A patent protects the investment of time and money necessary to develop an idea into a product, and it assures that the idea is new and that nobody can show up later, after a big investment, and say: "Hey, that's mine!" If it were proven valid technology it would be more valuable than it is now, but clear title to a conjecture is worth something. If you wait until you have the proof and peer-reviewed publication, someone else might claim priority under the first to file rule.

The process seems akin to Gerald Pollard's (Prof at University of Washington) claims of the exclusion zone in water. I was unaware that hydroxyl radicals could be formed or would form in the process. These radicals will be extremely short lived (nano-second) but are useful in destroying many contaminants in water. And as pointed out when you use ozone or some alternative like radical generation you will lower the chlorine demand overall. In all these cases you will still require residual disinfection and that is usually found in the form of chlorine. As for this electromechanical development of hydroxyl radicals, I am not convinced yet. I would like to see at least a prototype in actual operation or at least read about it.

I have used UV/peroxide to develop radicals and clean sites with some form of industrial contamination. I have also used it on municipal water high in TOC and methane as a pretreatment to lower THM production in distribution water. We eventually resorted to simple peroxide injection into a well followed by filtration and Chloramination (addition of ammonia with the chlorine). These systems were relatively small but still carried a significant price tag. Siemans has equipment for on site generation of hypochlorite but each site would require justification.

The hydroxyl radicals form in electrolysis of water, which in this device happens very close to the microbe. So the short-lived radicals will have enough time to act. The pulsed electric fields from opposed rippled electrodes counter-rotating through an axial magnetic field cause currents in cell water, which, unlike pure water, is conductive. Cavitation, whether by shear or electrohydraulic means, occurs next to the microbes, which is where the structure of water is weakest. When the bubble expands, it sucks out gas from in and around the microbe, and when it collapses the microbe is crushed like a submarine by a depth charge.

Wilmont, yes I understand the need to obtain a patent approval to cover your bases.

That is, however, not my main concern and why I will remain skeptical of any technology that has not thoroughly tested independently, followed by a thorough water industry review process. In the end, if this process is to be implemented in the water works industry, it must be demonstrated that it works economically and effectively.

I, as a design engineer, cannot state nor justify to my municipal, commercial, and private client(s) that a water treatment unit process that is unproven technology will work for them regardless of the inventor's claims. As a Licensed/Registered design professional my primary duty, first and foremost, is to safeguard the public's health and ensure that the treated water that they consume is safe, free of pathogens, and completely potable.

I wish you luck in your endeavor to bring this technology to the industry....it'll be a long long road that you'll be traveling.