Orange Water Contamination

What is 'orange water'?

It is water that contains oxidized iron, causing significant discoloration and a blood-like taste. It is perfectly sanitary; however, it is not pleasant to drink (unless you're a vampire), and it is not suitable for washing clothes.

Where has EWB-MSU had problems with orange water contamination?

EWB-MSU has had problems with orange water contamination at the following schools:

Elwangale Primary School*
Munyanza Primary School*
Shirali Primary School

*It is up for debate whether the orange water problem at these schools is due to a high iron content or some other mysterious malady. According to Mohammed Ali at Haikail, Munyanza's water has been tested and actually has a very low iron content and Elwangale's pump has been broken so we couldn't test the water, however they described it as "having a bad smell."

EWB-MSU has helped drill 8 boreholes; why do only three have orange water contamination?

The reason only three of our wells have been contaminated with orange water is related to the fact that different pumps (which include the drawtubes) and casings were used at those particular sites. First, let's differentiate between a draw tube and a casing. A draw tube is part of the pump and is what the water actually travels up. The casing is what holds back the soil and allows the water to flow into the base of the draw tube. There is enough space between the casing and the draw tube for water to sit stagnant.

Generally our chapter uses Afridev handpumps which are approved for depths between 10 and 45 meters. Afridev handpumps have either PVC or HDPE (a.k.a. plastic) draw tubes. At Shirali, Munyanza, Ikomero, and Elwangale water was present only at depths much greater than those of some of the other schools we have worked with, and thus, a type of pump that was approved to draw from depths greater than 45 meters was needed. The pump chosen to fulfill this requirement was the India Mark II Extra Deep Well Handpump which is approved for depths between 40 and 90 meters. So what's the problem? The India Mark II Extra Deep Well Handpump uses a galvanized iron draw tube (as opposed to the plastic variety utilized by the Afridev). Additionally, at Munyanza and Elwangale a steel (iron alloy) casing was used; whereas at every other site (including Shirali and Ikomero) PVC or HDPE casings were implemented. For more information and details concerning the various varieties of handpumps available, click here.

Primary schools known to have India Mark II Extra Deep Well Handpumps inlcude:

Ikomero
Shirali
Munyanza

Primary schools known to have steel casings include:

Elwangale
Munyanza

Why doesn't Ikomero have orange water issues?

All the other wells with India Mark II Extra Deep Well Handpumps have orange water contamination, what's different about Ikomero?

Well, Mike Lavell did some water quality testing testing in the summer of 2010; more specifically, he did some water quality tests at Ikomero. He found the pH of the water to be greater than 8.5 and the hardness of the water to be between 136.8 mg/L and 153.9 mg/L of CaCO3. Reading "What causes orange water?" may help you understand what this means if you don't already. From these results, one can see that the quality of the water at Ikomero is both drastically different from that of the water found elsewhere in Khwisero and particularly non-corrosive.

Additionally, Ikomero is arguably the nicest public primary school in Khwisero. It has a lot more funding than many of the other schools and thus the ability to better maintain its pump.

What causes orange water?

Oh man! There's a lot involved, so let's keep it basic and take it slow.

Corrosive Water Conditions in Khwisero

There are three major qualities that contribute to corrosive water: hardness, alkalinity, and pH. The hardness of a substance is a measure of the amount of calcium and magnesium that is dissolved in it, the more calcium or magnesium, the harder the water, the less corrosive it is. 'Soft' water is very corrosive. The addition of calcium and magnesium to a substance increases its alkalinity, which brings us to our next major quality…Alkalinity is the ability of a substance to neutralize any acid or base that it may come in contact with. In other words, alkalinity is a measurement of the substance's buffering capacity or its resistance to a change in pH. Think of the pH of a solution as a see-saw (one end indicates a basic solution and the other end indicates an acidic solution), the alkalinity of that same solution is how stiff the pivot point of the see-saw is. So if the pivot point is very stiff, the solution has a very high alkalinity and it is very difficult to change from a basic solution to an acidic one or vice versa. It is sometimes (and often) due to the amount of naturally occurring carbonate or bicarbonate compounds which have been dissolved by the water. Finally, pH is a measure of how acidic or basic a substance is; a high pH (up to 14) indicates basic properties; a low pH (down to 0) indicates acidic properties; a pH of 7 indicates that the substance is neutral. Corrosion is minimal when water is neutral with a hardness greater than 50 mg/L of CaCO3 and a high alkalinity.

Now, how does water in Khwisero compare in terms of hardness, alkalinity, and pH? Well, Mike Lavell's research showed the following:

pH: Nearly all water tested from rivers, boreholes, and springs (both improved and unimproved) had a pH of less than 6.5. Rainwater was found to be slightly acidic as well (although it fell on a sheet metal roof prior to testing). Additionally, water which was initially neutral was found to have a pH less than 6.5 after sitting in a clay storage pot overnight. This indicates that something about the soil of the area (out of which the clay pot was made) causes the water to become acidic.

Hardness: The average hardness of waters tested varied between 32.2 and 51.1 mg/L of CaCO3. Several places had extremely soft water with a hardness as low as 17.1 mg/L CaCO3. In other words the water in Khwisero ranges between somewhat "neutral" (although technically there is no "neutral" water with respect to hardness) and very soft.

Alkalinity: While dependent on a number of factors, one of the primary influences on alkalinity is the soil/clay/rock that the water travels through on its way to the underground aquifers that our boreholes tap into. As can be seen by visiting this site which summarizes the most commonly found soils in Kenya, most of Kenyan soil is described as acidic and not noted for any significant presence of carbonate or bicarbonate.

In summary, the pH and hardness of waters tested in Khwisero indicate that the conditions necessary for a neutral, non-corrosive environment are not present in most of the areas in which we have drilled or will likely drill wells.

Galvanized Iron in Acidic Water

One definition of corrosion describes it as: the disintegration of an engineered material into its constituent atoms due to chemical reactions with its surroundings. Essentially, when you put a piece of galvanized iron in acidic (and consequently corrosive) water, the acidity of the water starts to break down or 'eat away' the metal. The zinc coating on the iron (deposited in the galvanizing process), while meant to slow down or prevent corrosion, has little to no chance of doing so in a corrosive environment. Thus, as the galvanized iron draw tubes (and casings) of our boreholes sit in these acidic waters, they begin to break down into their "constituent atoms" (i.e. iron and a little zinc). However, because the water is so far underground, the situation is very anaerobic (lacking oxygen); this means that as the iron breaks down, the majority of of it exists in its soluble ferrous form (its dissolved form) until the water becomes over-saturated. This iron-rich water (at least before becoming over-saturated) appears clear while in an anaerobic environment; however, as soon as the water is pumped to the surface where it can interact with oxygen, it begins to oxidize (rust) and turn orange-ish red, converting to an insoluble ferric form. This is why when the Kenyans boil the water it becomes much more red, because heat is a great catalyst in the oxidation process.

Boreholes

While one might initially think that water barely comes into contact with the draw tube or casing of a borehole until someone begins pumping water out of it, the situation in actuality is more akin the the one represented in the picture below.

borehole%20testing_original.jpg

As can be seen, the water in the space between the draw tube and the casing sits at a higher elevation than the water of the aquifer itself (this because the water found in a confined aquifer is under pressure exceeding that of atmospheric pressure). In fact, the water in the draw tube actually sits at an even slightly higher level than the water in the casing (for the same reason water sits higher in your straw than the rest of your drink…aka capillary action). Depending upon the pressure of the aquifer, the water in the casing and draw tube may sit as far as 60 meters above the actual depth at which water is discovered. This gives the acidic water lots of time to break down the draw tube or casing and over-saturate the water with iron. Thus, the problem of orange water is somewhat self-perpetuating; if the pump were used very frequently, the orange color and blood-like taste of the water would be diminished to perhaps insignificant or even unnoticeable levels. However, as soon as the well is perceived to be 'dirty,' people stop using it, and the problem worsens.

What options exist for prevention and remediation?

This problem began with the very first project EWB-MSU ever implemented. This project was built in the spring of 2006 at Shirali Primary School. Seven years later, we still haven't managed to fix it and have even implemented a number of wells that have the same problem. This is a BIG deal, and it is unacceptable to continue making the same mistake due to a lack of knowledge transfer and forethought. What are some of our options for prevention and remediation?

Prevention

Option #1 (Pump Type): First of all, it should be noted again that even though water may be discovered at 80 meters, the pressure of the aquifer may allow for the water to be drawn from something like 30 meters. In such instances, obviously, an Afridev handpump can and should be used.

Option #2 (Pump Type): There exists an Afridev handpump model, the Afridev Deep Well Pump with Bottom Support, which is approved for use between 40 and 80 meters. Mohammad Ali, the director of Haikal Investments in Kakamega, says that the parts are available and that he does not think it is a bad option but suspects it may need frequent repairs although he is still unsure of this fact seeing as he hasn't implemented one yet. Because all Afridev pumps are VLOM (Village Level Operation and Maintainence) approved, parts are affordable and repair is fairly simple. India Mark pumps are not VLOM approved, meaning parts are more expensive and villages must generally hire a specialsit to conduct repairs. For more information and details concerning the various varieties of handpumps available, click here.

Option #3 (Pump Type): India Mark II's can now be fitted with completely plastic parts (i.e. everything underneath the ground will be plastic or brass). Again, however, India Marks are difficult and more expensive to repair than Afridevs.

Option #4 (Casing Type): No matter the depth (relatively speaking), there are plastic casings strong enough to handle the soil pressure, and once in place they are reliable and sturdy. However, there are two instances in which things can get a bit tricky: 1) When placing in intially, it is very easy to fracture. 2) When doing any kind of maintanance where something may need to be fished out of the borehole, again, it can fracture very easily. If the casing is fractured, we can do something called telescoping, which entails placing a second smaller diameter casing and gravel pack inside the broken casing. This is assuming the diameter of the first casing is large enough. If the second smaller casing is broken at some point in the future, as I understand it, there is not much that can be done…aka we're kind of screwed.

Option #5 (Casing Type): Although stainless steel is extremely expensive it is very sturdy (not easy to break in implementation or maintainance). It it won't corrode.

Remediation

Option #1: Replace the metal underground parts of Shirali's pump with PVC parts.

Option #2: Replace the existing pump at Shirali with an Afridev Deep Well Pump with Bottom Support.

Option #3 (not my favorite): Drill a new well, especially at Elwangale or Munyanza (<—if their orange water is indeed related to a high iron content) where a steel casing was used and replacing the pump would not solve the problem entirely.

Option #4: At places like Elwangale, we could implement a mandatory (if you will), point of use filter that the the water would go through before being able to be collected by the water pumper. This design would need to allow the iron in the water sufficient time to oxidize (convert to its insoluble ferric form), as iron in its soluble ferrous form cannot be filtered out with a sand filter. In order to aid the iron in a rapid oxidation process, it might be useful to have it slow drip over charcoal and through limestone gravel prior to entering the actual sand filter. This is certainly a more complicated solution, seeing as the school would need to be trained in sand filter maintenance, and there would be a potentially significant wait period between pumping the water and being able to use the water. However, apparently iron oxidizing and filtering systems can be bought as pump head attachments according to Haikal.

Option #5: Show the schools struggling with this issue that if the pump is utilized very frequently, the orange water contamination will be minimal. In this way, they could perhaps have someone pump it extensively each morning and at regular intervals throughout the day.