Why are there no statues of Jimmy Carter in Imo State?
Part III: Water Treatment Technologies
So far, we have been able to see that water quality guidelines or requirements can be summed into three:
· Chemical
· Biological and
· Organoleptic Characteristics
We have also talked about the implication of education and affluence of a society on the water they consume means we are unlikely to see a hand pump in Maitama. This is a good illustration of the inverted “U” concept otherwise known as We have also talked about the implication of education and affluence of a society on the water they consume means we are unlikely to see a hand pump in Maitama. This is a good illustration of the inverted “U” concept otherwise known as Environmental Kuznets Curves a topic for another day.
So today, we shall proceed to talk about water treatment. The table below gives a good summary. If you have been following our series, you will recall that our discussion is limited to groundwater and rainwater.
Water treatment processes
Targets/Treatment Objectives:
This is the objective of the treatment-what we intend to remove. A point I would like to make here is that things like colour, odour and taste in water (organoleptic) are a result of something that the water contains. In other words, organoleptic characteristics are not a problem on their own but indicators. So if the water is coloured, for instance, it might be because it contains iron oxides. If it has taste, it might be because the mineral salt content could be high.
Processes Employed
If you observe the table carefully, you will find out we have four different processes. We shall now proceed to discuss them.
1. Particle Removal by Sedimentation:
Particle removal by sedimentation is usually the first step in water treatment. It is based on the simple fact that if you leave water undisturbed for a significant time, particles will settle out to the bottom. This physical process is the principle behind the self-cleansing mechanism of natural waters and is usually driven by gravity.
However, because this process usually takes a long time, certain chemicals known as polyelectrolytes are used to enhance sedimentation. This process is called coagulation-flocculation. A common polyelectrolyte you can find in our local market is an alum. The coagulation-flocculation process involves the adsorption of the coagulant on the surface of the particles. Now because these coagulants are charged, they impart some charges to the particles which enable them to form flocs (an agglomeration of these particles) which makes settling out easier.
2. Oxidation:
In chemistry, oxidation has several definitions. But only two would do for our discussion. Addition of oxygen to a substance or addition of an electronegative element such as chlorine. We can achieve oxidation in two ways. Firstly by aeration i.e. allowing our water to get adequate contact with atmospheric oxygen. This is process is usually very slow. It can be enhanced by using a stirrer which would usually add an extra cost to our process. A cheaper alternative might be to use an atomizer (akin to your shower mouthpiece) to aid air-water mixing by creating jet streams of water currents. If you live in Lekki you might want to experiment with this.
A more effective way of oxidation is by using chemical oxidants like ozone, chlorine, permanganate and hydrogen peroxide. Chemical oxidation is a triple-edged sword (if there is anything like that). This is because it is can target several treatment objectives. For example, recall we said the organoleptic are indicators of maybe minerals or organic matter which could be causing the taste, odour or colour. A strong chemical oxidant would oxidize the causative agents and leave us with clean water. Chemical oxidation is also very effective against the microbial community. For instance, chlorination an effective form of disinfection is in effect a method of oxidation. Hydrogen peroxide and ozone are other typical strong oxidizing agents that can inactivate microbes. Lastly, chemical oxidation is very effective against mineralized water. It can be used to oxidize both iron and manganese oxides which are the major causes of foul colour and odour of water on the Lagos Island and Niger Delta.
What comes to mind when we talk of chemical oxidants in our local market is the water guard. I hope you can see why their sellers and advertisers have a very unique and compelling value proposition? It is a triple-edged sword.
3. Disinfection:
Disinfection is solely targeted at inactivating microorganisms. Now because our main source of water is groundwater, the risk of microorganisms would be limited if you employ the services of a professional and follow standard procedures. Nevertheless, microorganisms are ubiquitous as my undergraduate lecturers would say. So given time, you would have growths in your tanks and pipes (recall the green stuff) which is why my friend from (series II) doesn’t drink tap water.
Three options for water disinfection exist for us in Nigeria. The first is using a strong oxidizing agent like chlorine or ozone. This is the brain behind the water guard whose active ingredient (AI) is hypochlorite which releases chlorine into the water. Another way to disinfect water is by using Ultraviolet (UV) radiation. Most sachet water companies employ this method. Lastly, we can boil the water. This is an old but effective method.
4. Filtration:
Does the name guinea worm ring a bell? Please google it. Well, the fact that an average Nigerian can relate better with ebola than a guinea worm shows the level of progress we have made. I am not sure the name Jimmy Carter would also ring a bell. But there was a time when guinea worm was a big problem in Nigeria. And Jimmy Carter, a former American president came to the rescue. Today not many know about it. I dare say not even all doctors today can diagnose it. I pray the same happens to Polio. So what exactly did he do? I cannot enumerate all. Why was it so effective? What means did we employ to deal with it? Boiling and filtration.
Filtration is a means of discriminating against constituents in water according to their size. This constituent might be particles, microbes or even mineral salts. A sand filter can target particles, carbon filters are effective against colour and odour causing substances as well as organics. Membranes a novel filter can eliminate substances based on their molecular weights and is effective for both microbes, particles and minerals. This means that filtration is as effective as chemical oxidation in water treatment. Unfortunately, filtration has died down in Nigeria. Why?
We can now summarize our lessons. Water treatment objectives in Nigeria can be achieved by:
Particle removal through sedimentation:
· Gravity
· Filtration
· Coagulation-Flocculation using polyelectrolytes
Disinfection:
· Filtration
· Boiling
· Chemical Oxidation
· UV radiation
Oxidation:
· Aeration
· Chemical Oxidation
Filtration:
· Sand filter
· Carbon filter
· Membranes
In this week’s article, I have discussed the various treatment options available in Nigeria. I have also shown that chemical oxidation and filtration are the most effective even though filtration has died a slow death in Nigeria. I have also shown why water guard vendors have an excellent value proposition. What beats my imagination is that in spite of the statue revolution in Imo State, none was erected in honour of former American President Jimmy Carter who helped to end the plague of guinea worm in developing countries like Nigeria. Please I hope you enjoyed reading through today and found this piece enlightening.
In our next piece, we shall critically review the effectiveness of these treatment options against various criteria like cost and operational constraints. Please do not forget to google guinea worm and see why boiling and filtration was so effective! And if you have the former Imo State Governor’s ears, I think Jimmy Carter deserves a statue.
Don’t you?
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