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Rice husks: Agro-waste useful in water treatment

  • Rice husks: Agro-waste useful in water treatment

Rice production releases tonnes of waste material called rice husks.

Though different innovations on their usage have been tried, one promising application is in water filtration.

But rice husks cannot be used as they are. They must first be amended to a form fit for water filter use.

Rice husk ash

Rice husks or hulls are the outer covering of the rice seeds which are discarded after threshing.

Since the husks are rich in silica, they could find use in various applications such as construction, industrial silica production and even in silicon production for energy applications.

The silica concentration in the husks could be increased by ashing the material at high temperatures.

Besides eliminating a high carbon content, ashing creates charged centres on it’s structure capable of removing specific water pollutants.


Though not all metals are harmful, toxic heavy metals are in a class of their own since a number of them are categorized as carcinogens.

Though municipal treated water has no heavy metal concentration, water abstracted from urban streams or from the ground is bound to have a significant metallic concentration.

Rice husk ash is known to discriminately target heavy metals in water through a process known as surface adsorption.

It could prove a useful filter especially in remote or inner city neighborhoods with little or no access to municipal treated water.


Rice husk ash is useful in the removal of dye pollutants.

This is very useful in neighborhoods that rely on streams polluted by nearby textile or plastic industries.

Rice husk water treatment therefore could go a long way in preventing exposure to carcinogenic dyes such as those containing benzidine.


The increase in urban farming practices only means that water pollution by pesticides is a reality we must grapple with.

Rice husk ash possesses many charged reaction centres on it’s surface capable of degrading several types of pesticides if perchance they are dissolved in drinking water.

Cheap rice husk ash water filters are therefore an area of innovation available to communities with this need.

In conclusion

Due to the increase in water scarcity, innovators in the area of water treatment will enjoy an open space for experimenting and prototyping.

This is bound to open up markets for water filters and water supply to communities in dire need of this commodity.

Originally posted on John Mmbaga's Blog

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