Tank design

By Agua Para La Salud (APLS) Posted on Wed 25 Jul 2012, over 12 years ago

Would you post on this site pictures of your previous project?
Did you consider construction of ferro- cement tanks which have longer durability?

Tank design

By Bank-On-Rain Posted on Thu 26 Jul 2012, over 12 years ago

In the reply above I reference the final report for another school project on our PWX page of a similar system using the 5000 liter tanks, including photos.

We did consider ferro-cement, but I have seen these develop leaks, perhaps a result of poor construction? In any case, we are satisfied with the durability of the plastic tanks, but I'd prefer tankage that was not based on petroleum (plastic) or require high energy to produce, like cement. I am very interested in trying ISSB for tank constuction, but think we must learn a little more about how well tanks built with these blocks hold up over time.

Mike

Safe drinking water

By Aqua Clara International Posted on Thu 26 Jul 2012, over 12 years ago

Several times you mentioned that the Rain Water Harvesting tanks will provide 'safe drinking water' for the beneficiaries. What mechanisms are in place to ensure the water will be safe for drinking?

Safe drinking water

By Bank-On-Rain Posted on Thu 26 Jul 2012, over 12 years ago

If properly collected from a relatively clean tile or metal roof, rain water is about as good as it gets. Proper collection includes leaf/debris excluders, first flush diverters and well maintained screens on the vents and inputs.

Over time some organic material will find its way into the tank, but a biofilm establishes along the interior surfaces and floor of the tank that actually traps and consumes potential pathogens. It is important to position outlets 10 cm - 20 cm above the bottom so the tank does not completely go dry, destroying the biofilm. For the same reason we do not suggest "cleaning" the tank unless absolutely necessary due to accidental filling with dirty water (don't want surface water added during dry seasons or even well water that can often be contaminated and compromise the next batch of rainwater). The biofilm that naturally forms on the tank interior surfaces functions in a similar way to the biofilm on the sand grains in a bio-sand filter -- the active ingredient that makes them effective.

Mike

Safe drinking water

By Agua Para La Salud (APLS) Posted on Thu 26 Jul 2012, over 12 years ago

The concept of leaving the bioilogical growth on the inside of the tanks for trapping pathogens is, it appears, an extension of the "schmutzdecker"(?) process in slow sand filter , but in a new application. Do you have water tests of this process to back up the claim that the water is safe for drinking?

The proposal indicates that the tanks have a sun light blocking coating , and rain water is free of nutrients which leads to the question-- where does the biological layer ( algae?) get its energy and nutrient?

Safe drinking water

By Aqua Clara International Posted on Thu 26 Jul 2012, over 12 years ago

Thank you for the response and explanation Mike. Despite the potential work of the biofilm, it appears that there are still quite a few variables you mentioned which could potentially contaminate the Rain Water Harvesting units, thus not guaranteeing clean drinking water all of the time.

Maybe this is already included in the Health and Hygiene training component....however, have you considered adding Safe Water Storage Units to the proposal. The school staff could clean these daily and then add the appropriate amount of aquagard or other inexpensive purifier prior to distributing the water to the students? This simple addition will eliminate potential ills if and when a tank does become contaminated.

Safe drinking water

By Bank-On-Rain Posted on Thu 26 Jul 2012, over 12 years ago

Lynn and Paul,

Even using a first flush diverter, some organic matter will enter the storage tanks (pollen, bird droppings, etc.), but in small quantities. I will find the reference, a study testing stored water found improvement over time -- and I will look this up and post.

Safe Storage Units are a possibility, as are additional filtration, but one of the objectives is to provide a simple, sustainable system that improves the quality of available water supplied. A simple RWH system alone eliminates transmission of pathogenes of human origin and reduces other contamination by 90%. A problem in adding complexity is that the added steps become more likely to be missed from time to time. Perhaps the biggest potenial for negating the investment in safe water at a school is illness picked up by a student at home. If kids continue to miss classes due to illness from contaminated water at home, these lost days reflect on the school statistics -- a major metric of how the school system is performing. The sanitation training in the school will hopefully translate into improved practices in the home, but if it is too complicated, compliance will be poor.

The Community-Led Total Sanitation Training (CLTS) by our partner organization in Sierra Leone, Safer Future Youth Development Programs, provides trianing in basic sanitation, how illness can be transmitted and simple methods to improve health at home and in school. This includes solar disinfection by leaving water bottles in direct sunlight (UV) for 4 hours, improtance of hand washing and latrine contruction. I have visited 6 villages where the CLTS program had been implemented and was impressed that 100% of the households had constructed proper latrines and solar disinfection was being practiced, even in villages with operating wells.

The school systems are intended to improve the water quality for the kids, but also to provide a demonstration of simple ways that safe drinking water may be available in the community. Home-sized RWH systems using locally available recycled containers can be affordable, reduce the need to carry water (at least during the wet season) and benefit health.

Mike

Safe drinking water

By Aqua Clara International Posted on Fri 27 Jul 2012, over 12 years ago

Thanks for the response Mike. It is true that there is no way to guarantee compliance with any system or program 100% of the time.
I look forward to learning more from the 'Study testing stored water'

Safe drinking water

By Bank-On-Rain Posted on Fri 27 Jul 2012, over 12 years ago

Paul,

The referenced paper can be found at:
www.ctahr.hawaii.edu/hawaiirain/Library/papers/Rana_Md.Sohel.pdf

Mike

Safe drinking water

By Bank-On-Rain Posted on Fri 27 Jul 2012, over 12 years ago

Paul,

Actually that is not the reference I was looking for, but is one of several that suggest water quality improvement with storage time. I have others in my files with similar statements, but have not yet found the time-series study.

Mike

Safe drinking water

By Bank-On-Rain Posted on Fri 27 Jul 2012, over 12 years ago

Here are a few more
www.ctahr.hawaii.edu/hawaiirain/Library/papers/Rana_Md.Sohel.pdf

and

From: “Rain Water Quality Guidelines: Guidelines and practical tools on rainwater quality”
Rainwater Harvesting Implementation Network, Amsterdam, The Netherlands
Version 1, 15-07-2008,

2.2.2.4 Storage
The storage can be described as the structure or medium in which the rainwater is stored. In
RAINs current programme three different types of RWH systems can be defined: above ground
tanks, below ground tanks and sand dams. Contamination can be prevented by:
•Using non-toxic construction materials;
•Using adequate covering to prevent influence from direct sunlight, human, animal and
organic matter from entering the storage system and mosquito breeding.
Contamination might have occurred in the previous levels. Treatment of the water can be
applied when found necessary (see table 1 and annexes 3 a, b and c). Residence in the storage
system itself provides opportunities for water purifying processes such as sedimentation,
bacterial die-off and filtration (for sand dams), increasing the water quality over time.
Cleaning of the storage system should only be done if the previous water was found to be
contaminated (see annex 6).

Sampling tanks each year for 3 years
http://www.sciencedirect.com/science/article/pii/S0043135407000759

Quality improvement with storage
http://search.informit.com.au/documentSummary;dn=358922220770593;res=IELENG

University of Warwick, RWH water quality improves with storage
http://www.ctahr.hawaii.edu/hawaiirain/Library/papers/Pathak_Namrata.pdf

Untreated RWH water stored in tanks generally meets or exceeds WHO standards
http://www.ctahr.hawaii.edu/hawaiirain/Library/papers/Pathak_Namrata.pdf

Rainwater often safer than water supplied through mains with chlorine treatment
http://rainharvesting.com.au/rainwater-knowledge-centre/rainwater-quality-and-safety

Safe drinking water

By Aqua Clara International Posted on Mon 30 Jul 2012, over 12 years ago

Thank you for the articles Mike. It is interesting to learn that the biofilm that grows inside the tanks helps reduce the amount of contamination in the water.
However, almost all of the articles conclude that additional purification may also be needed due to the number of variables at each water collection site which cannot be controlled.

At the end of the day, RWH units are a great source of water and I trust that these units, combined with your H&H training will provide clean water for the students and staff at the school.

Safe drinking water

By Bank-On-Rain Posted on Tue 31 Jul 2012, over 12 years ago

Paul,

We consider RWH as a major step in sanitation and hygiene. Obviously there will be ongoing improvements as there have been in the last 2 centuries in the First World. Unfiltered RWH water would not be cerified for potable use by most western health departments, but if properly maintained, RWH can provide clean, safe water.

The second step may well be a filter system at the school, but for now the availability of water from a clean source is a big step, but does not exclude the possiblity of problems that could potentially compromise it. The same could be said regarding wells or even municipal systems. This project is intended as a demonstration to show students and staff that there may be an affordable alternative to carrying water significant distances on a daily basis. RWH may not be a universal solution, but in Sierra Leone with 3 meters of precipitation over part of the year, it certainly should be an option.

Combined with innovations to reduce the cost of tankage (like ISSB construction), RWHcould become an affordable local solution to the water problem in many areas.

I can see that there could be valuable collabortation with Aqua Clara International to combine RWH with bio-sand filters.

Thanks for your input,
Mike

Safe drinking water

By Aqua Clara International Posted on Tue 31 Jul 2012, over 12 years ago

Thank you Mike. Yes, we are already combining these two in our programs in Kenya which is why your project is so interesting to me. We are also hoping to have our BSF builders also start selling RWH tanks to local families in their respective communities.....thus this info is extremely useful for me.

I've also seen the ISSB tanks built in Tanzania but hope to learn more via these exchanges as well.

Best of luck with your project
Paul

Safe drinking water

By Bank-On-Rain Posted on Tue 31 Jul 2012, over 12 years ago

Paul,

As an example for use in a simple and inexpensive household system, we used recycled plastic containers as part of the system at Barina School. We contacted the hospital ship (Mercy Ship) that was stationed in Freetown about food-grade drums used to transport medical alcohol, etc.. They were willing to provide these 200 liter used containers at no cost to non-profits for use in household RWH systems. Similar containers can be found in food processing plants, UN food relief projects and elsewhere and may be available for the cost of hauling them away. These drums were also available in local markets, where we purchased them for about US$20 each.

Just a thought.

Safe drinking water

By Aqua Clara International Posted on Tue 31 Jul 2012, over 12 years ago

We will definitely look into these options as well. The more our CDE's can offer people, the better for everyone involved.

Thanks for the ideas
Paul

ISSB Machine

By Aqua Clara International Posted on Tue 31 Jul 2012, over 12 years ago

Makiga Engineering in Nairobi makes the machines to produce the ISSB blocks.
Not sure who makes them in West Africa

Here is the website. FYI

http://makiga.com/#

Cheers
Paul

Safe drinking water

By Agua Para La Salud (APLS) Posted on Fri 27 Jul 2012, over 12 years ago

Thanks Mike. I just wanted to hear it from you.
We have the same problem with rain systems in Guatemala. The most difficult part of a project is the human factor that can negate infrastructure intentions. It is better to have a 90% improvement in water supply then to take water from seriously contaminated sources and using it for drinking. It has taken the US 170 years since the civil war to try to turn around bad hygiene habits it is unrealistic to think that it can be done in a decade in other parts of the world where conditions are worse than US conditions 170 years ago. Many of these human solutions will take multiple generations to see results if constant effort is applied.

Where we have installed rain systems and other storage at schools the teachers and Peace Corps volunteers are repórting better school attendance and the parents are also commenting on fewer illness with children.