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Sewage and its potential as a drinking water source

  • Sewage and its potential as drinking water source

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Resources are all around us.But rarely do we think of water as a resource especially when considering wastewater. Yet for over 50 years, Veolia, a utility company has been converting wastewater into drinking water in Windhoek, Namibia. A tall order it would seem. However, come to think of it, water constitutes over 90% of wastewater. If that’s the case, why can’t we go the extra mile to reclaim it?

Wastewater treatmentplants

The main wastewater treatment plant in Nairobi receives over 160 cubic metres of wastewater on a daily basis. That’s 160,000 litres of wastewater daily. This converts to over 58 million litres of wastewater annually! Of course this water is loaded with all sorts of pollutants, from microorganisms to fecal matter, from dissolved compounds to suspended matter, from metals to detergents. There’s no shortage of contaminants when considering wastewater. But what do we do with it after treatment?

It’s discharged into the surrounding rivers and streams. These same rivers and streams feed into our water reservoirs and through the same cycle of water treatment again after sometime. If that’s the case, wouldn’t it make some sense to reclaim this same water by treating it? Wouldn’t it make more sense to rechannel this recovered water for industrial amd domestic use? What should happen in order to make such an ambitious move work?

Harmful microorganisms

Being the most feared water pollutants, efficiently removing microorganisms from our water is central if we are considering reuse. Though chlorination seems to work for drinking water treatment, wastewater is a whole different ballgame. By that, I mean that several disinfection stages must be considered for complete removal of harmful bacteria and viruses. More R and D must be geared towards testing some methods in this regard:

Disinfection of wastewater is key. But so is decontamination from risky substances suspended and dissolved in it.

Dissolved and suspended matter

One way of reducing suspended matter from wastewater is through the wastewater treatment process itself. Depending on the efficiency of the process, effluent from wastewater treatment plants can be further purified from suspended and dissolved matter. Though microorganisms might be risky, some might be useful in degrading some suspended matter further. This is one strategy employed in wastewater treatment. However, more techniques could be applied to completely degrade other dissolved and suspended substances. The use of metal oxides such as titania, zinc oxide and magnesium oxide is gaining prominence due to their strong catalytic activity against some dissolved pollutants.

The use of adsorption is also important in this regard. Adsorption is the ability of a material to accumulate pollutants on its surface thereby acting as a ‘filter’. Useful adsorbents in water treatment include zeolites, silica, activated carbon, rice husk ash etc. In other words, there are a whole range of ways prospective innovators could use to recover water from wastewater effluent.

Conclusion

To guarantee clean drinking water for all (a constitutional right), innovators need to roll up their sleeves and get to work. Already the existing water resources are overstretched. So why not consider non-conventional resources such as wastewater effluent?

Other nations (like Namibia) have done it successfully.

So can we.

Originally posted in John Mmbaga's blog

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