F acilities like deep wells where oxygen content is low, the iron and manganese-bearing water is colourless. This is because the iron and manganese are dissolved. When the water is exposed to air, the iron and manganese are oxidized and change from colourless, dissolved forms to coloured, solid forms. Oxidation of dissolved iron particles in water changes the iron to white, then to yellow and finally to red-brown solid particles that settle out of the water. Iron that does not form particles large enough to settle remains suspended [colloidal iron] and leaves the water with a red tint (1). Manganese is usually dissolved in water, although some shallow wells contain colloidal manganese [black tint]. These sediments are responsible for the staining properties of water with high concentrations of iron and manganese (2). These precipitates or sediments may be severe enough to plug water pipes (1). Additionally, iron and manganese can affect the flavour and colour of food and water. According to Skimpton D (1) manganese is objectionable in water even when present in smaller concentrations than iron. There is therefore need to treat water for iron and manganese. Iron and manganese is naturally present in many aquifers throughout the world. While iron can start causing aesthetically undesirable taste and odour problems at concentrations above 0.3 ppm, concentrations of up to 3.0 ppm are often acceptable to local people; higher levels could cause people to revert to traditional unprotected sources (2) which are most times contaminated. Furthermore, according to (3,4), a big problem that frequently results from iron or manganese in water is iron or manganese bacteria. These bacteria occur in soil, shallow aquifers and some surface waters. The bacteria feed on iron and manganese in water and form red-brown [iron] or black-brown [manganese] slime in toilet tanks and can clog water systems. Technically the main problems associated with iron in water can be summed up as follows (3-6) (i) It can cause an unpleasant taste in the water; (ii) when iron precipitates out of solution it can clog up valves, small bores, pipes and other water accessories; (iii) the "brown water" is ineffective for washing; (iii) the iron can give rise to "iron bacteria [organisms that prey on iron compounds, for example frenothrix, gallionella and leptothrix]".There are a number of Iron and Manganese removal methods. However, these methods are dependent on the form and concentration of the iron and manganese in the water. WHO (7) mentions that, the approach to dealing with naturally occurring chemicals will vary according to the nature and source of the chemical. Key water treatment methods for iron and manganese are briefly explained below:(i) Water Softener Iron and Manganese Removal: this method is suited for removing low concentrations of iron and manganese. It relies on the process of cat-ion exchange to remove minerals that cause hard water such as calcium, magnesium and other constituents such as iron and manganese (8); (ii) Manganese Greensa...

A gravity-driven wood filtration system, incorporating granular activated carbon (GAC) as an appropriate point of-use technology for the rural poor, has been designed, tested and optimized. Four systems were assessed in respect of metal, bacteria and particle removal when exposed to polluted river water with and without GAC. These were evaluated using fresh, wet preserved and dry preserved Southern African indigenous wood species. Initially, all filter systems with the following indigenous wood species Combretum erythrophyllum in System 1, Tarchonanthus camphoratus in System 2, Leonotis leonurus in System 3 and Salix mucronata in System 4 did not incorporate GAC. The systems recorded 83.3, 85.4, 94.3 and 57.3% Escherichia coli removals, respectively, for fresh filters. Incorporation of GAC in Systems 1 and 4 showed high potential for significant E. coli removals (>99.9%) . Particulate removals were: 97% TSS (total suspended solids) and 96% turbidity removals by System 1; and 100% TSS and 100% turbidity removals by System 4. Metal removals by the combined systems were noteworthy and in the following order: Fe > Pb > Ni > Al > Zn > Cu > As > Cr > Cd > Mn (with average removals for the first five >90% and the last five >50%). Each combined system consistently met turbidity guidelines (≤5 NTU) and produced water with pleasant aesthetic aspects.

The study investigated two engineered fabrics and five cloth fabrics for low cost drinking water treatment. An optimized fabric filtration method has been developed and tested. Numerical models for predicting particulate removal efficiency have been developed for each fabric as support tools for selecting optimal process configuration. Both engineered fabrics showed better performance and achieved the most effective particulate removal for the highest number of layers used. Sequential filtration was done on eight layers for representative fabrics of each type and recorded higher contaminant removal than one filtration run. Geotextile 1 was better than geotextile 2 in particulate removal and recorded Escherichia coli removals of up to 1.4 log removal value (LRV) for eight-layer normal filtration and 3.0 LRV for four-pot sequential filtration. Brushed cotton was best among the cloth fabrics in particulate removal but performed below expectation in bacterial removal. It recorded E. coli removals of only 0.04 LRV and 0.2 LRV for eight-layer normal filtration and four-pot sequential filtration, respectively. Effluent turbidity decreased exponentially with number of fabric layers, in line with porous media filtration theory. The optimized filtration method produced very clear drinking water of relatively safe quality using geotextile 1. Appropriate disinfection is still recommended to ensure continued water safety.

Three novel and two commercially available low-cost point-of-use (PoU) water treatment technologies were comparatively evaluated using a specialized comparison framework targeted at them. The comparison results and specialized framework have been discussed. The PoU systems were evaluated principally in terms of performance, flow rate and cost per volume of water treated (quantitatively), ease of use, potential acceptability and material availability (qualitatively) with main focus on rural and suburban settings. The three novel systems assessed were developed in an ongoing research project aimed at developing a multibarrier low-cost PoU water treatment system. The comparative evaluation and analysis revealed that the commercially available systems may often produce water free of pathogens (with an apparent 100% removal for Escherichia coli and fecal coliforms) but may not be affordable for application to the poorest groups in much of the developing world. The novel systems, which were principally constructed from local materials, were more affordable, can supply relatively safe water and can be constructed by users with minimal training. Overall, bacterial removal effectiveness, ease of use, flow rate, material availability, cost and acceptability aspects of water were identified as key to potential adoption and sustainability of the evaluated low-cost PoU systems.

Two low-cost sand filtration systems incorporating granular activated carbon (GAC) and non-woven geotextile respectively were assessed for Point-of-Use water treatment. Laboratory scale models were evaluated in respect of selected heavy metals, bacterial and particulate removal when exposed to surface water for five months. System 1 (ISSF-1) incorporated GAC and system 2 (ISSF-2) incorporated non-woven geotextile. Filter-mats were placed on the filter surfaces of both systems. Flow rates ranged between 8 and 15 L/h for longer water contact with the GAC and bio-layer. On average, E.coli removals were 96% and 94%, while fecal coliform removals were 96% and 95%, by ISSF-1 and ISSF-2 respectively. Average TSS removals were 98% and 92%, while turbidity removals were 97% and 91%, by ISSF-1 and ISSF-2 respectively. Average metal removals were: Arsenic (21%), Cadmium (82%), Lead (36%), Iron (65%) and Manganese (94%) by ISSF-1, Arsenic (17%), Cadmium (<LoD), Lead (<LoD), Iron (92%) and Manganese (98%) by ISSF-2. Both models consistently met turbidity guideline (5 NTU) and can remove significant amounts of particles. Both systems can treat the poor-quality water used to provide relatively safe water and could be improved further for heavy metal removal. However, to guarantee continued safe-water supply, supplementary treatment by chlorination is recommended.