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 third world countries and 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.

How to measure water security?

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Photo: Figure 1. Haitians queue for water in Carrefour-Feuilles Slum. The experiential scale-based metrics attempt to capture other sides of water (in)security, such as the burden associated with queuing for water. Photo by United Nations Photo

This blog is a summary of a published open access article: Octavianti and Staddon (2021). A review of 80 assessment tools measuring water security. WIREs Water. https://doi.org/10.1002/wat2.1516


Adapted by Dr Thanti Octavianti

There are many definitions of water security. It could simply refer to water for domestic use, such as for drinking and cooking, or it could mean water in every aspect of life, including water for the environment, water for economic development and water associated with hazards, such as floods and droughts.

These diverse conceptions also lead to different methods to measure water security. Chad Staddon and I systematically reviewed 107 publications proposing methods and tools to measure water security, and we found:

  1. There are two dominant research clusters in the field:
    • metrics that are based on the physical availability of water with measurement ranging from municipal to global scale and usually expressed in a volumetric unit. We group them as “resource-based metrics”.
    • metrics that are based on people’s experiences with water, usually measured at individual or household level and asking, for example, if one has worried about water or if one has had to change their plans because of their water situations. We group them as “experiential scale-based metrics”.

The former cluster is bigger compared with the latter, which is emerging.

  1. Both clusters are quite distinct in their characteristics. For example, resource-based metrics were mostly formulated by natural scientists and engineers. Domains of measurement vary from metrics solely focusing on freshwater resources to some with a very broad focus (to include water-related disasters, biodiversity, among others).

On the contrary, most experiential scale-based metrics have strong social science elements in them. Water supply and hygiene and their relations to well-being are the main domains being measured.

By understanding the landscape, we argue that the more local the level of measurement and the more specific water domains included, the more meaningful and actionable recommendations would be.

Finally, measuring water security is a resource-intensive process. Selecting which approach to use will be based on the purpose of the investigation and scholarly interests, and we hope this paper would be able to help researchers and practitioners make some informed choices when developing or using a water security metric.

Short bio:

Dr Thanti Octavianti is a Lecturer in Applied Geography, Department of Geography and Environmental Management, UWE Bristol. She is a social scientist with research interest in water security measurement and urban flood resilience.

Centro de Competencias del Agua Workshop

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Over the last decade UWE Bristol, through the International Water Security Network, has partnered with Centro de Competencias del Agua in research focussing on the role of “nature-based solutions” (also called “green infrastructure”) in helping highland Peruvian communities adapt to climate change (see link to earlier collaborative activities here).  In recent years Peru has enacted laws for supporting “payment for ecosystems services” (PES) and sustainable development of indigenous communities.   From 4.00 to 6.00 pm (Peru time) on Wednesday June 15, 2022 the CCA team is hosting an on-line workshop to discuss the latest results from research focussing on indigenous knowledge and nature-based solutions for sustainable development.   There will be a particular focus on challenges facing Apurímac, Ayacucho and Huancavelica, three of the poorest districts with the highest indigenous populations in the Peruvian highlands and the role of indigenous knowledge and practice in aiding adaptation. The workshop will discuss research into indigenous processes of capturing and storing rainwater for its infiltration and refill of aquifers or other bodies of water, such as springs and slopes, referred to as “Sowing and harvesting water.” 

The event will be broadcasted via the Facebook page of the Andes Water Program at https://www.facebook.com/CentroDeCompetenciasDelAgua

¡Te esperamos!

Biological filtration using different porosities of ceramic media

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By Sadie Hadrill (MRes Student)

Freshwater is essential for life on Earth, and the role of freshwater is fundamental to society and for maintaining healthy ecosystems. Biological filtration is a sustainable biotechnology used to remediate biological and chemical contaminants within water. This is performed by establishing polymicrobial biofilms (diverse microbial communities) on a granular substrate, that can be housed within a column, here referred to as a biofilter. Biofilters develop efficient sorptive (attachment) capacity within diverse microbial communities of biofilms.

Filtration media has come in many forms prior to recent experimentation including sand, charcoal and granular activated carbon. Different filter media properties, including permeability, surface area and porosity, can determine the performance of the biofilter. As such, practical knowledge is needed regarding the impact of the type of filter media used. In this example we used ceramic media, more specifically terracotta clay, varying in porosity as described in the previous blog post. The team at UWE’s Centre for Print Research (CFPR) created ceramic media of low, medium and high porosities to determine the impact of porosity on the biofilter systems.

Biofilter maturation

The three variations of ceramic media were equally distributed into three individual filter columns (9 filters in total) and connected to 25 L tanks containing tap water. To aid the beginning stages of biofilm maturation, the water tanks were inoculated with pond water to introduce environmental organisms.

Figure 1. Laboratory scale biofilters containing three different types of clay media, varying in porosity: A) Low porosity, B) Medium porosity and C) High porosity.

Over four weeks of biofilm maturation, the biofilters were monitored weekly for nutrient concentrations (such as phosphates and nitrates) and bacteria. Samples were extracted from both the filter media and the circulation water for analysis.

Figure 2. Laboratory scale biofilter columns containing ceramic media (A), connected to a four-channel peristaltic pump (B) and circulation tanks (25 L) containing mains tap water (C).

An investigation of porosity of media and pathogen removal

Once the biofilters had undergone maturation, the experiment investigated the removal of Escherichia coli (E. coli)and Enterococci, both are bacterial indicators of faecal contamination. Over a 24-hour period pond water was circulated through the biofilters containing the different porosity ceramic media. Samples of the circulated pond water were collected every three hours and analysed for the presence of the E. coli and Enterococci.

Preliminary results indicated a decline in both E. coli and Enterococci recovered from samples taken over a 24-hour period. However, initial findings suggest that the ceramic media porosity has little impact on E. coli and Enterococci removal as there was little difference between the bacteria counts for the three different porosities of ceramic media.

Further experimental work is ongoing to explore pathogen removal in more detail and to determine if the size of the ceramic media (e.g. smaller ceramic beads) impacts the performance of the biofilter.

Testing Ceramic Methods for Producing Beads for Biofilm Water Treatment

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By Rosy Heywood, Research Associate at Centre for Print Research.

Main image: Fig 1: Boxes of organic foam impregnated ceramic beads and plain ceramic beads adjacent to a pot of traditional beads

In a previous blog post, by my colleague Sonny Lightfoot, we introduced the research being conducted into creating ceramic beads as a medium to grow biofilm within a water filter. We have now created 3 types of ceramic beads which have been tested for water filtration; organic foam impregnating method, clay and sawdust burn off method and plain ceramic. For each method we used the same terracotta clay, made the beads into 20mm pieces, and fired the beads at the same max kiln temperature of 1100˚.

Organic foam impregnating method

For this set of beads we laser cut compressed cellulose sponge into 20mm circles, expanded them in water and dipped them into clay slip. The beads were then left to dry and fired. During the firing process the sponge burns off leaving the porous structure behind. This method has been used to test beads with high porosity and high surface area creating lots of sites for the biofilm to grow onto.

Figure 2: Dipping laser cut sponges into terracotta clay slip

Sawdust and clay method

For this set of beads we mixed fine sawdust with clay at a 5:3 ratio. We are currently experimenting with the best ratio and method of mixing but to produce these beads we mixed by hand initially then used an electric mixer to fully combine the two components. We then extruded the clay using a hydraulic extruder into lengths and cut using a 3D printed jig into 20mm pieces. The beads were then left to dry and fired. During the firing process the sawdust burns off leaving a porous structure behind. This method has been used to test beads with high porosity.

Figure 3: Freshly extruded and cut sawdust and clay beads before firing

To produce the plain ceramic pieces we used the same method as above but without adding the sawdust. This method will test the effectiveness of the natural porosity of ceramic.

After firing we then tumbled the beads in a ball mill to smooth the edges. The beads were then dried in an oven and tested for effectiveness by MSc student Sadie Hadrill and PhD candidate Josh Steven in the science labs on Frenchay campus. Stayed tuned for another blog post coming soon where Sadie and Josh detail their process and results from the testing.  

Developing the methods and experimental work

Since creating these beads, the team and I in the CFPR labs have been experimenting with ways of combining sawdust with clay in large batches and the ratio of sawdust to clay. We have also been furthering our design research by modelling a coil pot from sawdust clay to test it’s suitability for pot making and experimenting with high surface area to low volume shapes using the organic foam impregnating method. These shapes could be tessellated or interlocked to create a unique structure for a vessel to naturally purify water using the biofilm method. The idea is to create a uniquely beautiful and practical container to filtrate water with the design inspired by natural biomorphic structures that can tesselate into user determined patterns and shapes. This experimental research is at its early stages and will slowly develop over the course of the project alongside our bead and porosity testing.

Figure 8: Organic foam impregnated ceramic tessellating shapes experiment

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