Appropriate rooftop water tank cleaning and disinfection

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I'm working on an urban project in Tripoli, where water quality is a major concern. Almost all residents are living in 3-8 storey buildings with piped water that is stored in rooftop water tanks. These tanks are never/rarely cleaned, so residents are complaining of sand, algae, etc. It's unclear if water contamination is due to the tanks or the pipes (it may be both). 

We're setting up WASH Committees in buildings to maintain shared facilities, and want to come up with a relatively short tank-cleaning procedure that we can train them to perform. The cleaning and disinfection procedures that I've found so far entail lengthy soaking time (anywhere from 6-24 hours), which may deter them from cleaning the tanks regularly. Has anyone found a shorter procedure that is effective and easy/safe enough to teach residents to do themselves?

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31 Answers

  1. شركة ركن نجد لتنظيف الخزانات بجدة والتي تسعي لأن تكون افضل شركة تنظيف خزانات لكافة احياء مدينة جدة حيث نقدم خدمات تنظيف الخزانات للفلل و العمائر السكنية والشركات مع تقديم خدمات التعقيم والتطهير لأرضيات وجوانب الخزانات كما تقدم في شركة ركن نجد أفضل خدمات  شركة تنظيف خزانات بجدة

  7. Dear Stephanie:

    Dear Stephani: We have a very simple solution, just add a very small quantity of oyr 100% organic sokution to your tanks once a month. We would add at approx. 8ppm. Our product is safe for human consumption and may be ingested in it's fully concentrated form without harm. See our web site - www.soleco-technology.com or email me directky at--- pettman@soleco-technology.com --- Regards, Hugh Pettman


  8. The old adage prevention better than cure aptly applies to the problem. Algae is an impurity whic forms after the water enters your storage tank. This is mainly because the water under storage is exposed to sunlight which the prime promoter of algae. If it is ensured that sunlight does not reach the water and limit the storage quantity to 3 days usage will help. As to othe impurities which fouls up. The pumped water should undergo thorough testing for dissolved and suspended solids. Depending upon the test results remediation methods, many available in the industry is to take place. This way the duration between two successive cleaning will be very long.

  10. Thanks everyone for the responses!

    To give some more details about the situation: we are targeting roughly 30 000 households in 2 communities. Many of these tanks are open top and uncovered. About 50% of them are made of plastic, the other 50% are made of cement (and most of the cement tanks are uncovered because of where they're placed). The majority of households in one community are receiving less than 3 hours of piped water a day, so they are primarily relying on stored water. Some households have a separate tap for drinking water, so they may be drawing from that tap during the times water service is available and storing it separately. Our survey on drinking water sources gave us conflicted data - almost all HH claim to be using piped water, but validation sessions suggest that a number of them may be buying bottled water.

    There are no detailed studies on the piped system as this is an old and extremely volatile area where the municipality is afraid to enter. Household connections are all unpaid for and privately made - there is no documentation on these.

    Roughly 13% of HH we surveyed stated that they treat their water. Most use boiling. Chlorine tablets and filters are too expensive here, and they are not widely available.

    This project is primarily hygiene promotion, so there is no technology component. We are setting up building-level WASH Committees to inform residents about tank disinfection, among other things.

    We ended up supplying WASH Committees with large bottles of Javel (3.5% active chlorine) because that is the most widely available household chlorine in the market. The procedure we taught them was to use detergent to clean the outside and inside of the tank. They were taught to mix a disinfecting solution by diluting the chlorine to 100 mg/L. The solution was applied to the inside surface of the tank, which was to be kept wet with the solution for 1 hour (they would have to wipe the inner walls of the tank with the solution several times over the course of the hour to make sure of this). This minimized the amount of water needed to clean the tanks and the higher chlorine concentration shortened the amount of time.

    Afterwards, they were to flush it out 2 times or until they could no longer smell the chlorine from their taps.

    We taught them this two weeks ago, and we have so far heard that one committee has done some tank cleaning but we have not gotten a detailed report about how they did it. More monitoring will be happening over the next few weeks to see how much this procedure was taken up.

    Tanks range from 40 L to 1000+ L in capacity. Chlorine testing strips are very expensive here. There are no community tanks - most surveyed households have individual tanks and a few have none at all.

    We're finalizing the baseline assessment report, and I can post a link up with the details of the situation when its completed. This will hopefully pave the way for an actual water treatment project.


  11. Stephanie,

    It has been a month since your initial post. I must say that you have gotten a lot of recommendations. Have you done any cleaning protocols yet? If so, just curious what you settled on?

  12. Dear Stephanai Tam

    Procedure of the Roof water tank

    1. Inform all residence persons using water before cleaning the tank(about one day so that they adjust accordingly)
    2. Open man hole cover
    3. Disconnect all In/out line isolation valves.Drain total water.
    4. Tank cleaning manually for any dirt/sand/algae etc.
    5. Apply some Bleaching Powder wait 10 min and washed out all effluent.
    6. Rinse with fresh water and drain out.
    7. Then tank to be taken in line again. Closed man hole cover properly and locked.
    8. Informed to all residence persons they drain water for five min with opening tap
    9. This exercise takes about one hour .

    Good luck!

    Prem Baboo

  13. Hi Stephanie our company invented a portable system which cam go directly in the tank or plumbed in line to the tank. What our machine does is super oxygenates water to 30 -50 parts per million killing any algae growth naturally without adding chemecals. www.gaiawater.com

    Let me know if this is something you would like to use. Les

  14. I think I did answer a similar question or maybe a similar discussion thread! Sand and debri has to be physically removed, manually. Vedic Sciences (from ancient times in India) do not follow the same concept and approaches. Guruvani white developed by Swami Valmiki Sreenivasa Ayyangarya in milligram size quntities is kept in continuous contact inside the tank by dangling it in a porous packaging of thin cloth with an outer layer of plastic mesh and weighted down with a small stone, to make it sink deep into the tank. Cotton thread hangs it with sufficient leangth to make contact at as low water level as possible.Guruvani White is actually an internal medicine and is brittle and hence all this packaging to make it last as lomg as possible .Its action can be called as that of a Bio catalyst, although its principles baed on vedic sciences differ. It is available in small quantities at present .Its testing and validation needs to follow protocol established by the scientist himself, as there may not be  available, enogh expertise to evaluate it! However reduction in TDS BOD, COD can be measured, but water chemical test results may be erratic, and hence the neeed to establish proper protocols with the inventor.What is relevant is that it has been tried out successfully in large scale commercial applications with consistent results, provided prescribed application procedures are strictly adhered to.the water becomes safe enough for drinking, cooking,bathing and toliet flush. Some uploaded files may please be refrred to.

  15. Where does the sand come from?? Are these open top tanks? Algae is understandable with no on-going disinfection. How often are the tanks filled? Is the water supply only turned on periodically? In many countries, the distribution system has so many breaks that the utility cannot leave the water on for very long or they will lose too much water to leakage. And when the water is turned off, the water then leaks back into the piping and the water that enters the piping when the pressure is turned off is typically contaminated. When the water is turned back on, contaminated water is delivered to the tanks. When the water from the roof top tank enters their house, do they drink it without further treatment? Do they only drink bottled water? Do they filter the water and then drink it? Do they boil the water and drink it? What is the normal use for this water? I can understand individual tanks vs a community tank. With a community tank, if no one has a finanacial motive to keep the water treated and safe, it will not be done. Is there a community building association? Is there a person in the building that can be trained to take care of the water tanks - and paid from a community fund (tenants of the building)? With individual tanks, the people living in the apartment, etc. will be much more inclined to take care of the tanks. What is the typical size of the tanks? For initial cleaning, there is probably no shortcut to manual cleaning. As I have stated before, if the tank is big enough to get in to for cleaning, make sure the tank is adequately ventilated. Many people have died inside unventilated tanks! Maintaining disinfection in the tank is the best solution in the long term, but this will require continual treatment and monitoring. If my guess about breaks in the main water lines is true, the on-going disinfection is important. Chlorine (bleach) is cheap. Are these tanks easy to get to on the roof? Chlorine test strips (even from a pool suppl;y store) are a relatively easy way to check for chlorine residual at the sink in the house. Have you written a report describing the details of your problem and the issues you are facing? That would help in determining the appropriate solution. Are the people in the apartments being educated on the importance of disinfection? As an example, I was surveying small communities in the north of Brazil. They have many rain water collelction tanks. The government provides them bottles of bleach to disinfect the tanks. Many of the people use the bleach to clean their clothes rather than treat the water!! The solution isn't always simple.

  16. We have a simple photocatalytic treatment system which can be automated or set-up to be run manually . There is no lenthy soak time, as we design systems to cope with 1-20cu.m/hr.

  17. It is at least strange to go on keeping water tanks on the roof and expect the residents to mind about water's safety. Did you consider of stopping the use of those roof tanks? From what I get, there are pipes to the roof. So it would be safer to connect all the residencies to a main pipe that brings now the water to the building and worry about cleaning and disinfecting the water in its beginning, whatever that is (e.g. sourse, treatment plant of any type etc)

  19. Stephanie,

    We can provide a method where the disinfection of not only the tanks but also the pipes is carried out on a constant basis. Besides this our process disinfects the water and maintains potability.

    The first time clean up takes time but once this is done and the water is regularly dosed with our Purojal DW disinfect there is no need to clean the tanks or pipes regularly as the tanks and pipes remain sanitized 24x7x365 days a year.

    If you are interested in getting more information please send me an email at advenvtech@gmail.com.

    Best Rgds.

    Chetan Shukla

    Director

    Clean Env. Tech. Pvt. Ltd.

  20. If you are getting inside the tank to clean it, especially if you are using chemicals, be sure the tank is adequately ventilated with fresh air.

  21. Hi Stephanie

    It would be helpful to know a little more as suggested in some of the other replies. What is the type of water? Are the tanks covered? Have you done any bacteriological tests?

    The presence of sand and algae suggests only a problem of material accumulation. Is there any slime growth on the walls of the tanks?

    Sediment can be removed by draining down the tank and simply scooping it up before rinsing and refilling the tank. You will need to make sure you don't disturb the sediment during this process. It is worth taking sensible precautions to avoid introducing contamination and use clean equipment, wear gloves etc. The tank could be filled and dosed with a little extra disinfectant to provide a residual to deal with any residual contamination but so the water was still fit for purpose (for example with water purification tablets). If there was any likelihood of faecal contamination (presence of animals or their droppings for example) then a more thorough disinfection would be necessary.

    Also, consider what can be done to prevent sediment accumulation. Open tanks will permit algal growth and be exposed to wind blown sand. Keeping them covered, therefore, would be good. What about the water supply; there may also be a source of sediment from carry over from water treatment.

    If there is any slime growth, the tank should be drained and the walls and base simply scrubbed clean, rinsed and flushed with clean water before being refilled with water for use. It may be possible to have some control over growth by maintaining a disinfectant residual in the water supply, if one does not exist.


  22. Hi

    you have not said anything about source of water -bore well, treated municipal, drawn from lake/pond/river/stream? Some very good solutions have already been offered. As for algae, if the storage is totally prevented from sunlight, algae growth will be minimal. 

  23. Hi

    you have not said anything about source of water -bore well, treated municipal, drawn from lake/pond/river/stream? Some very good solutions have already been offered. As for algae, if the storage is totally prevented from sunlight, algae growth will be minimal.

  24. normally algae growth is hig when your tank is exposed to sunlight, you may protect the tank but if not lets try the regular cleaning and sanitizing process;

    1. Prepare a tank, with open top. a hose and a motor pump

    2. Calculate the volume of your tank, then make a 1% volume concentration of phosphoric acid

    3. Use your tank, fill with water then add the amount of acid to make 1%

    4. Pump it up, then by gravity it should go back down to the tank- make it re-circulating for 30 minues only

    5. You should see the scales being drained and dissolved by the phosporic acid

    6. After a month, repeat the process but use a sodium hypochlorite- make 1% concentration

    7. Repeat then the cycle monthly, acid first then next month hypochlorites.

    8. No need to rinse too long and too much of the water. The phosporic acid is a food grade, the hypochlorite will simply evolve.

    Please message me if in case for follow up. eg_ricarte@yahoo.com

  25. Dear Ms. Tam,

    i would recommend a manual processing first to remove all the visuable dirt and as a second step a surface-desinfektion with hydrogen peroxide solution. This requires several technical equipment of the tanks like a drain, two chambers for non-interrupted water-supply and several more. In many cases, cleanings are not done because those responsible have no idea how to handle the process without getting stress. So my recommendation is -> first chance the technical equipment into something workable and then second do the cleaning and desinfection without getting in trouble with the residents.

  26. Dear Ms. Tam,

    What is the material of construction of the tank and pipe line. You will have to clean the tanks first manually , then rinse it with KMnO4 with a wet cloth . Wash it with water . Install a on line screen filter . You can repeat chemical cleaning once in six month.

    Regards .

    Rakesh sharma.

  27. I have attached a file on Guruvani white meant for such public water supply tanks and reservoirs.It will not remove dirt, sedimentation which can be desilted normally. The water will however be fit for drinking purposes,despite such debri remaining in water, including organic bio solids if any as also dissolved solids, nitrates,chemicals, POP heavy metals etc. Sorry for this second post as there was a problem earlier!

  28. We have Vedic Sciences based solutions for tanks and reservoirs of public water supplies to be sanitized and also the water rendered fit for humans, animals and plants use.but not by killing pathogens, algae etc with toxins.I have already uploaded a file which can be accessd at my profile page and I have attached it once again to this reply. We have not yet started helping international clients on large scales but many international visitors have apprecieated these techniques when they visited India and observed Swami Valmiki in action.

  30. The issue is that disinfection is a product of disinfectant concentration x time. So you can decrease the time by increasing the concentration. Unfortunately that adds risk that you send water with an excessive disinfectant concentration to the end user's tap.

    Your procedure would need to ensure adequate rinsing & no risk that sections of pipe between tank and valve are filled with excessively high disinfectant concentrations, which are then inadequately rinsed out.