Investigating The Unique Properties of Ugandan Barkcloth as a Potential Filtration Material for Cleaning Contaminated Waters

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Main image: Final barkcloth. Source National Geograpic.

Written by Rosy Heywood, Research Associate, Centre for Print Research

On the Healthy Waters project one of our key focusses has been creating highly porous ceramic pots for direct filtration in low resource settings. I have recently been investigating a new material as either an alternative to ceramics or used in conjunction with it. The Ugandan barkcloth is made from bark of the native Mutuba tree (Ficus Natalensis). The bark regenerates itself for up to 100 years and the process of making it into useable cloth requires little resources and a moderate amount of labour compared to conventional cloth. No spinning of fibre, weaving of threads or dyeing of cloth is necessary. Although, sometimes the cloth is naturally dyed for aesthetic purposes. So, it is a very sustainable and renewable material.

Barkcloth making in Uganda is on the UNESCO Representative List of the Intangible Cultural Heritage of Humanity. The inner bark of the Mutuba tree (Ficus natalensis) is harvested in the wet season and beaten with wooden mallets until soft. The final cloth will be roughly 10 times its original size. Any tears are hand stitched and often fragments of cloth are stitched together to make larger pieces. The introduction of cotton has rendered barkcloth an endangered craft in Uganda. If using the cloth as a water filter proves successful, then it could give skilled jobs to local village people. The cloth is historically made by men but there is potential here to empower women by teaching them a new skill.

Simple cloth filters are used as a quick way to rid larger particles from contaminated waters. Studies have shown old worn sari cloth can reduce cholera incidence from water collected from ponds and rivers by half. (Huq et al, Colwell RR et al.)

The use of barkcloth from the Mutuba tree as a water filter has not yet been researched however there is some research of the properties of barkcloth for medical purposes and as a fashion textile. New research from science and textile researchers published in the Journal of Applied Microbiology examined the feasibility of using bark cloth as an antimicrobial fabric within wound care management. It found that Ugandan bark cloth could stop the growth of MRSA by more than 99 per cent. Researchers from Istituto Marangoni London and Manchester Metropolitan University have collaborated with artists, environmentalists, farmers and fashion design practitioners across the world to discover the potential applications of barkcloth including how it could be used as a responsible material in luxury fashion.

I have carried out an initial porosity test by folding the cloth twice and wrapping it over a bucket. Water was then poured through a perforated cup on top of the cloth. The cloth showed resistance to water initially and then slowly water was able to flow through. The filtered water had a slightly orange tinge and contained a small amount of bark fibres. I tried pre-soaking the barkcloth however the soaked water changed colour to an orange/red hue.

This proved more testing is required for better quality outputs. This line of experimental research is at a very early stage and further inquiry is required to find out if barkcloth is a suitable material for filtering water. Including a toxicity report of the barkcloth soaked water, flow rate analysis and testing it in conjunction with ceramic filter discs.

Biofiltration – a new future for fresh water

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Around the world, the pressure to secure future supplies of fresh water is mounting. Only 2.5% of the world’s water is fresh, and only 0.77% of that water is deemed accessible. As if that’s not enough, only 10% of that is reported to be suitable for human consumption. Water demand globally is projected to increase by 55% between 2000 and 2050, driven by growing population sizes and their demand for agricultural products, energy supply and drinking water.

UNICEF’s 2019 report estimates that 1 in 10 people still lack basic water services (a protected and accessibly drinking water source, use of an improved toilet or latrine, and handwashing facilities in the home). This includes the 144 million people who drink untreated surface water; the consumption of biologically contaminated water is estimated to cause almost half a million annual deaths.

Researchers at UWE Bristol’s Centre for Research in Biosciences have been developing methods of treating biologically contaminated water using biofiltration. In their recently published study ‘The control of waterborne pathogenic bacteria in freshwater using a biologically active filter’, researchers Joshua Steven, Robin Thorn, Gareth Robinson, Dann Turner, and Darren Reynolds, alongside Jack Lee of Origin Aqua Technologies, set out to investigate the control of three species of bacteria commonly associated with biologically contaminated water.

UWE academics identified an unmet need for low-energy, sustainable solutions for the provision of potable water in communities with limited infrastructure. This study aimed to see if biofiltration was a viable option for treating water, as it is cheaper and less energy-intensive than techniques like chlorination and ozonation. Biofiltration is a technique which involves using bacteria to break down and consume unwanted contaminants, utilising microbial biofilms in filter columns. Biofilms are self-supporting communities of microorganisms, established on granular filter media such as sand or ceramic – so, biofiltration essentially uses bacteria to control bacteria.

This study’s outcomes were promising: biofilter water systems showed a significant reduction in the presence of harmful pathogens. If scaled up, this pathogen-management technique has the potential to be used to treat stores of harvested rainwater, ground, and surface waters, preventing the regrowth of bacteria such as E. coli after water treatment. Other practical applications include using biofilters to reduce the biological burden of final sewage discharges, and potentially improving the water quality of inland bathing waters or drinking water supplies.

The full study can be found online in the journal npj Clean Water.

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