Short communication Stability and phase separation behaviour of systems of particles in a medium with added polymer

The stability of barium carbonate (BaCO3) suspensions in the presence of the dispersants, xanthan gum, sodium carboxymethylcellulose and carrageenan, has been studied using a phase separation technique. These materials have been found to stabilise the BaCO3 suspensions by increasing the viscosity of the medium. Of the three polymer dispersants, xanthan gum is the most effective in stabilising and destabilising the suspensions. The experimental results are compared to the phase separation and stability of non-aqueous latex suspensions in the presence of non-adsorbing (free) polymers. The systems consist of poly (hydroxystearic) acid (PHS) coated poly(methylmethacrylate) (PMMA) particles in dodecane and well-characterized cis-poly(isoprene) (PIP) and poly(isobutylene) as the non-adsorbing added polymers. Water SA Vol 32(1)pp:111-11

Development of sustainable drinking water quality solutions for rural communities in the developing world

In developed countries potable water is usually taken for granted, where advanced infrastructure and a strong economy has allowed waterborne diseases (such as cholera and dysentery) to be virtually eradicated. In contrast, developing countries have poor infrastructure, lack development, stability and vibrancy. Consuming untreated, and potentially contaminated, groundwater extracted from shallow wells is the only option. The primary aim of this study was to undertake an extensive field water quality-sampling programme in rural villages throughout Malawi. About 95 % of all the wells tested failed to meet safe drinking water values for untreated water in the wet season, while about 80 % of the wells failed in the dry season. The main forms of contamination emanate from bacteriological and physical constituents. As noted in the United Nations post-2015 water agenda, water quality is just as important as water quantity—the two are inextricably linked. Hence, there is currently a great need to develop more appropriate, cost-effective options to treat water; particularly to reduce the 3.5 million deaths related to inadequate water supply and sanitation each year. Subsequently the aim was directed towards investigating a sustainable, yet appropriate, way to treat shallow well water to significantly improve quality. The most suitable method to remove coliforms and turbidity from water is via the process of coagulation, using aluminium sulphate (alum) or ferric sulphate (ferric). The limited availability and relative expense of these chemicals has led to other more appropriate indigenous coagulants being sought for developing countries. Natural plant extracts have been available for water purification for many centuries. However, the science and engineering application of the use of plant extracts have not really been developed. To start to address this, Leeds Beckett University and the University of Malawi—The Polytechnic have shown that a locally available plant extract, Moringa oleifera, which grows wild throughout rural villages in developing countries, can be used to improve water quality in the order of 80–94 %. The flocculent capacity of M. oleifera is closely comparable to that of a well-established chemical coagulant, alum