Tom Craven

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.

The powder obtained from the seeds of the Moringa oleifera tree has been shown to be an effective primary coagulant for water treatment. When the seeds are dried, dehusked, crushed and added to water, the powder acts as a coagulant binding colloidal particles and bacteria to form agglomerated particles (flocs), which settle allowing the clarified supernatant to be poured off. Very little research has been undertaken on the parameters affecting the effectiveness of M. oleifera, especially in Malawi, for purification of drinking water and there is a great need for further testing in this area. Conclusive data needs to be compiled to demonstrate the effects of various water parameters have on the efficiency of the seeds. A parametric study was undertaken at Leeds Metropolitan University, UK, with the aim to establish the most appropriate dosing method; the optimum dosage for removal of turbidity; the influence of pH and temperature; together with the shelf life of the M. oleifera seeds. The study revealed that the most suitable dosing method was to mix the powder into a concentrated paste, hence forming a stock suspension. The optimum M. oleifera dose, for turbidity values between 40 and 200 NTU, ranged between 30 and 55 mg/l. With turbidity set at 130 NTU and a M. oleifera dose within the optimum range at 50 mg/l, pH levels were varied between 4 and 9. It was discovered that the coagulant performance was not too sensitive to pH fluctuations when conditions were within the optimum range. The most efficient coagulation, determined by the greatest reduction in turbidity, occurred at pH 6.5. Alkaline conditions were overall more favourable than acidic conditions; pH 9 had an efficiency of 65% of optimum, whilst at pH 5 the efficiency dropped to around 55%. The efficiency further dropped at pH 4, where the powder only produced results of around 10% of optimum conditions. A temperature range of 4–60 °C was studied in this research. Colder waters (<15 °C) were found to hinder the effectiveness of the coagulation process. The higher the temperature the more effective was the coagulation. It was also found that the age of the seeds, up to 18 months, did not have any noticeable effect on dose level and percentage reduction in turbidity, although at 18 months the seeds had a narrower dosing range to produce near-optimum reduction. Seeds aged 24 months showed a significant decline in coagulant efficiency.

A research project was commissioned to investigate the performance of Moringa oleifera compared with that of aluminium sulphate (Al2(SO4)3) and ferric sulphate (Fe2(SO4)3), termed alum and ferric respectively. A series of jar tests was undertaken using model water, different raw water sources and hybrid water containing a mixture of both of these types of water. The model water consisted of deionised water spiked with Escherichia coli (E. coli) at 104 per 100 ml and turbidity (146 NTU) artificially created by kaolin. Results showed that M. oleifera removed 84% turbidity and 88% E. coli, whereas alum removed greater than 99% turbidity and E. coli. Low turbidity river water (<5 NTU), with an E. coli count of 605 colony forming units (cfu)/100 ml was treated with M. oleifera and ferric. Results showed an 82% and 94% reduction in E. coli for M. oleifera and ferric respectively. Tests on turbid river water of 45 NTU, with an E. coli count of 2650 cfu/100 ml, showed a removal of turbidity of 76% and E. coli reduction of 93% with M. oleifera. The equivalent reductions for alum were 91% and 98% respectively. Highly coloured reservoir water was also spiked with E. coli (104 cfu/100 ml) and turbidity (160 NTU) artificially created by kaolin; termed hybrid water. Under these conditions M. oleifera removed 83% colour, 97% turbidity and reduced E. coli by 66%. Corresponding removal values for alum were 88% colour, 99% turbidity and 89% E. coli, and for ferric were 93% colour, 98% turbidity and 86% E. coli. Tests on model water, using a secondary treatment stage sand filter showed maximum turbidity removal of 97% and maximum E. coli reduction of 98% using M. oleifera, compared with 100% turbidity and 97% E. coli for alum. Although not as effective as alum or ferric, M. oleifera showed sufficient removal capability to encourage its use for treatment of turbid waters in developing countries.

About 80% of all illnesses and over one-third of deaths in developing countries are related to poor water quality and sanitation facilities. The majority of research work undertaken on water in developing countries has focussed on surface and borehole water with hardly any work being undertaken on shallow well water. A study was conducted between 2005 and 2007 to determine water quality from shallow wells in southern Malawi. Over 2,700 samples were analysed for microbiological, chemical and physical contamination, namely: total coliforms (TC), faecal coliforms (FC), turbidity, total dissolved solids, electrical conductivity, pH, hardness, ammonia, arsenic, nitrate, nitrite and sulphate. Sampling was undertaken during both the wet and dry season to find the change in water quality with season. The results indicated that shallow wells tested were heavily polluted with both TC and FC. The pollution levels were higher in the wet season than the dry season. About 94% of all the wells tested failed to meet the Ministry of Water Development (MoWD) TC guideline value of 50 cfu/100 ml for untreated drinking water in the wet season, while about 80% of the wells failed in the dry season. Approximately 83% of all the wells tested failed to meet the MoWD FC guideline value of 50 cfu/100 ml in the wet season, while about 50% of the wells failed in the dry season. The difference in season was significant for both total and faecal coliforms (p<0.05). The majority of the physico-chemical parameters were found to be within the recommended limits. Parameters that were found to be slightly out of the range were pH, turbidity total dissolved solids and electrical conductivity in a small number of wells. © 2010 by Nova Science Publishers, Inc. All rights reserved.