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( a ) Cumulative probability diagram of total dissolved solids (TDS). Box plots of TDS for the three groups are also shown on the cumulative probability curve. ( b ) Average composition (meq/l) of the three groundwater groups
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Groundwater resources in some parts of the lower section of the Shire River valley, Malawi, are not potable for rural domestic water supply due to high salinity. Knowledge of spatial variation of water quality is essential in locating and sustaining usable water supplies. In this study, a comprehensive assessment of the quality of groundwater from...
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... particular, a cumulative probability distribution of TDS was exam- ined in order to group the samples on the basis of salin- ity. Figure 5a shows that two threshold values can be dis- cerned for the data. An upper threshold of 6838 mg/l and lower threshold of 780 mg/l for TDS (Fig. 5a) were then used to group the data into three major populations. ...
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... (cf. Park et al. 2005;Panno et al. 2006; Mondal and Sigh 2011). In particular, a cumulative probability distribution of TDS was exam- ined in order to group the samples on the basis of salin- ity. Figure 5a shows that two threshold values can be dis- cerned for the data. An upper threshold of 6838 mg/l and lower threshold of 780 mg/l for TDS (Fig. 5a) were then used to group the data into three major populations. The lower threshold value is also the median TDS of the dataset, whereas the upper threshold is similar to the value calculated by using the common method for cal- culating thresholds as mean plus two standard deviations (μ + 2σ ; Reimann et al. 2005;Koh et al. 2009). Group ...
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... value is also the median TDS of the dataset, whereas the upper threshold is similar to the value calculated by using the common method for cal- culating thresholds as mean plus two standard deviations (μ + 2σ ; Reimann et al. 2005;Koh et al. 2009). Group I samples, representing 51% of all samples, are charac- terised by relatively low salinity (Figs. 5a and 5b) (Fig. 2b). These are mainly distributed in the bedrock outcropping areas on the east bank and parts of the west bank of Shire River (Fig. 3b). Group (Fig. ...
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... as mean plus two standard deviations (μ + 2σ ; Reimann et al. 2005;Koh et al. 2009). Group I samples, representing 51% of all samples, are charac- terised by relatively low salinity (Figs. 5a and 5b) (Fig. 2b). These are mainly distributed in the bedrock outcropping areas on the east bank and parts of the west bank of Shire River (Fig. 3b). Group (Fig. ...
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... + , although weath- ering of amphiboles (e.g. sediment derived from the semi- pelitic gneiss) and pyroxene (e.g. in sediment derived from the charnokites and basalts; Fig. 1) may also contribute to the Ca 2+ concentration, whilst Mg 2+ may be derived from the mafic minerals. The samples in Group I constitute the background population in the CPD (Fig. 5a), with relatively low mineralisation. The dissolution of feldspars and fer- romagnesians usually leads to low mineralisation (Drever 1997; Appelo and Postma 2005;Dongarrà et al. 2009) which is attributable to the "good" water quality associated with Group I samples, as evidenced by computed values of WQI, SAR and RSC (cf. Figs. 3 and ...
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... further increase in sodium ion concentrations in Group II samples is at- tributable to mixing with high TDS groundwater from the areas of high salinity (Group III samples), which are in prox- imity of Group II samples. The samples in Group II consti- tute an overlap of the background (Group I) and anoma- lous (Group III) populations in the CPD (Fig. 5a). The high salinity and alkali hazard (Fig. 6b) relatively high salinity renders the groundwater resources a "poor" quality classification (Fig. 7). Samples in Group III have anomalously high levels of major ions (salinity) and overall show similar composition (Na-Cl type), with the exception of sample 209 (Na-SO 4 type) (Fig. 11). The ...
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... (Fig. 7). Samples in Group III have anomalously high levels of major ions (salinity) and overall show similar composition (Na-Cl type), with the exception of sample 209 (Na-SO 4 type) (Fig. 11). The samples are characterised by high pCO 2 values (log P CO 2 (atm) range of −1.81 to −0.91) and high sulphate (in addition to high chloride) content (Fig. 5b). The majority of the samples in Group III exhibit molar Na + /Cl − ratios close to unity as expected for the dissolution of halite (Fig. 10a), suggesting an original saline groundwater result- ing from dissolution of halite, with rock-water interactions modifying the Na + content. The influence of evaporation, as a general driver to ...
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... samples in Group III constitute an anomalous (Group III) population in the CPD (Fig. 5a) and they act as point sources of contamination of high salinity on a back- ground population of fresh groundwater. The limited spatial extent of the saline zones explains the high variation in salin- ity and major ions. Because of the high salinity and major ion content of these samples, their computed WQI values are classified in the ...
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As a result of increasing population, industrialisation and water demand in agricultural sectors, groundwater table is lowering in most part of district of Purba Midnapur, West Bengal. It is a serious threat as regards to groundwater quantity and quality due to seawater intrusion. In this study, coastal aquifers of Purba Midnapur district are selec...
Citations
... The need for clean and safe drinking water resources keeps rising due to rapid population growth, urbanization and industrialization [2]. Water of good quality and accepted standards is required for domestic usage, agricultural irrigation, recreation and industrial manufacturing applications, among others [3]- [5]. Most people residing in remote areas in Sub-Saharan African countries depend on borehole water resource for domestic use as it is considered the safest and the cleanest. ...
... These results are similar to those reported by other Malawian researchers and elsewhere who have worked on assessment of borehole water quality in different parts of Malawi. Most of these studies have reported and indicated that water from the underground sources contained high levels of Fluoride and is not safe for human consumption by residents in those areas where the study was undertaken [2,5,6,10,19,20]. ...
Aims: The objective of this study was to determine the levels of fluoride in borehole water samples. Study Design: The total of eight samples were collected from five villages in Chiradzulu and transported in cooler ice-bath to the laboratory for the analysis. Place and Duration of Study: The study was conducted in the Department of Chemistry and Chemical Engineering Laboratories, at University of Malawi in the month of June. Methodology: The ion selective electrode technique was used to assess fluoride levels. Physicochemical water parameters were measured with multi-meters. Results: The results obtained ranged from 2.26 to 3.08 mg/L, 136 to 561 mg/L, 261-1212 μs/cm and 6.27 to 6.97, for Fluorides, TDS, conductivity and pH, respectively. Levels of fluorides exceeded permissible limits for borehole water established by WHO and were below the standards for MBS Conclusion: The results attained in the scope of the study support coloration of teeth observed amongst individuals in study communities, helping to understand that groundwater is not suitable for consumption. Therefore, the study provides recommendation for urgent implementation of defluoridation measures to provide clean and safe water for the existing community members.
... as the location to develop and field test the 20-L SODIS bucket system. Located in the Shire Valley, groundwater is highly saline in areas, making it unsuitable for domestic consumption (Monjerezi and Ngongondo, 2012). As a result, although groundwater boreholes are installed in several communities, many households still prefer to use unprotected surface water sources for drinking water. ...
Two billion people worldwide consume unsafe drinking water. The problem is particularly pronounced in Sub-Saharan Africa, where more than a quarter of the population relies on unimproved surface water sources. Based on the principles of solar water disinfection (SODIS), a new household water treatment technology, the SODIS bucket, was developed to improve the microbial quality of water from these sources based on controlled tests in a laboratory setting. This study set out to evaluate the efficacy of the technology in a field setting, in rural communities in the Chikwawa District in southern Malawi.
SODIS experiments were carried out in two different vessels (1-L PET bottles and 20-L polypropylene SODIS buckets), over three months using unprotected water sources normally used by community members. Vessels were exposed to direct sunlight for 8 h per day in a village setting and were sampled at regular intervals to determine total coliforms, E. coli, turbidity, UV transmittance and UV dose.
In these experiments, the SODIS bucket reached inactivation targets for E. coli (<1 CFU/100 mL) in two of seven experiments and for total coliforms in one of seven for total coliforms (<50 CFU/100 mL), despite having greater UV doses than were seen in the evaluation carried out under controlled conditions during the bucket's development. PET bottles reached inactivation targets for both E. coli and total coliforms in five of seven experiments. There was no single factor that could be identified as preventing adequate inactivation, but the role of organic matter, inconsistent nature of the water source, and vessel size, when coupled with organic matter, were identified as contributing factors. This study highlights the need for further prototyping to provide a suitable pre-treatment step for unprotected water sources, and the importance of field testing with real-life parameters to ensure new technologies are context appropriate.
... Evaluation of water quality for drinking purposes WQI is a comprehensive algorithm with a high coupling that is broadly used in the appraisal of drinking water quality (Monjerezi and Ngongondo 2012;Singaraja et al. 2015). According to Eqs. 11, 12, and 13, the WQI is calculated. ...
To explore the hydrochemical characteristics and water quality difference of groundwater between desert and oasis, 90 groundwater samples were collected in the Liyuan River Basin. Multiple means such as Piper diagram, correlation analysis, ions ratio were used to analyze the origin of hydrochemical composition and evaluate groundwater quality. The results showed that the main hydrochemical types of the oasis and desert groundwater are Ca·Mg-HCO3 and Na·SO4 respectively. The groundwater NO3− content was lower than the WHO limit; groundwater was less affected by human activity. Oasis groundwater chemical composition mainly comes from the dissolution of minerals, and the chemical composition of desert groundwater is strongly influenced by evaporation and cation exchange. The water quality index (WQI) results show that the oasis’s water quality is good, and the water quality of the desert is inferior to the oasis. Because of the high salinity of desert groundwater, desert groundwater is less suitable for irrigation than oasis groundwater. The lack of vegetation may lead to groundwater degradation, so it is necessary to protect vegetation health in dry areas to prevent desertification.
... However, the computed WQI values are classified into five classes as water unsuitable for drinking (WQI > 300), very poor water (200 < WQI < 300), poor water (100 < WQI < 200), good water (50 < WQI < 100) and excellent water (WQI < 50). A study by (Monjerezi and Ngongondo 2012), conducted research and random selection of the shallow wells and boreholes as the mainly used water resources in developing countries particularly in Chikwawa district in Malawi, and parameters such as pH, TDS, EC, temperature chloride, nitrates, sodium and others were analyzed. The indicators of the groundwater quality were calculated to determine the suitability of the groundwater resources for domestic purposes. ...
... and Ca 2+ and absorption of Na + and K + during cationic exchange results in such enhancement (Yidana 2010;Monjerezi and Ngongondo 2012). The bivariate plot of Ca 2+ + Mg 2+ vs. HCO 3 − + SO 4 2− can shed light upon the active geochemical processes in the study area. ...
The present study area falls beside the coastal zone of Tamil Nadu, and Puducherry is characterized by varied geological formations that mostly contain groundwater resources that are primarily utilized for domestic, agricultural, industrial, and other utilities. The study aims to differentiate various hydrogeochemical processes responsible for disparities in water chemistry. Groundwater samples were collected from 66 sites during the two major seasons: pre-monsoon and post-monsoon. The analytical data were separated into terrain vice and utilized for preparing graphical plots as well as mathematical calculations to obtain the existing relationship among chemical constituents and water quality. The Ca-HCO3, Na-Cl, Ca-Na-HCO3, mixed Ca-Mg-Cl, Ca-Cl, and Na-HCO3 are the main hydrochemical facies observed from the groundwater samples. The ionic relationship among the samples indicates the control of direct and reverse ion exchange in the concentration of Ca²⁺, Mg²⁺, Na⁺, and K⁺ in groundwater. Moreover, silicate weathering contributes more in comparison with carbonate and evaporite dissolution. Gibbs plots reveal that water-rock interaction and evaporation processes are the main mechanisms controlling the water chemistry. The saturation index of different mineral phases indicates groundwater to be oversaturated with silicate mineral phases irrespective of the terrain. Statistical methods like correlation and principal component analysis were also performed to differentiate the specific association and possible source of the dissolved constituent in the groundwater. The study concludes the influence of multiple processes such as silicate weathering, direct and reverse ion exchange, secondary dissolution, saline water intrusion, and anthropogenic sources as the main reasons responsible for variation in groundwater chemistry.
... Groundwater is the most important freshwater source specially for arid and semi-arid regions due to lack of surface water sources and low precipitation rates in those regions. Around 25% to 40% of the drinking water in the world is extracted from groundwater [2]. ...
... In addition, lack of management of the groundwater use that can lead issues such as sea water intrusion [8], human health and plant growth problems [9]. It also effects the economic development and social prosperity [2]. In many cases, groundwater contamination is irreversible and stopping the source of pollutants will not restore its quality [10]. ...
The rapid growth in the world population resulted in an increase of the freshwater needs in many sectors. Groundwater is the most important freshwater source specially for arid and semi-arid regions due to lack of surface water sources and low precipitation rates in those regions. In this study, monthly groundwater quality data were collected from eleven well fields in Sharjah over the period of 2004-2017. Water quality parameters including bicarbonate, calcium, chloride, fluoride, magnesium, sodium and sulphate were selected for the analysis. In the study, water quality index (WQI) process is used to develop groundwater quality index (GWQI) for Sharjah using above mentioned water quality parameters. Mann-Kendall and Spearman’s Rho tests were adopted as non-parametric trend tests for temporal (trend) analysis of GWQI, whereas inverse distance weighting interpolation was used in GWQI spatial trend analysis. Temporal trend analysis results showed significant trends in 8 out of 11 well fields. Spatial analysis showed the highest values for salinity ions in the well fields closest to the northern region, whereas the lowest values were detected in the southern region.
... Our comprehensive mapping of rural water supplies in Malawi indicate international aid programmes have drilled nearly 60,000 boreholes and wells, most without prior hydrogeological knowledge or assessment of potential geo-hazards, with 24.5% resulting in poor performance and another 14.1% resulting in failure and abandonment [2][3][4]. The proportion suffering from poor water quality is unknown, however issues with iron, salinity, fluoride, and others are widespread [3,[5][6][7][8]. Considering the reliance on groundwater in Malawi, significant focus is needed to mitigate risks of geogenic fluoride and to sustainably assess and manage existing supplies. ...
Fluoride concentrations in Malawi's groundwater are primarily controlled by geogenic sources that are highly variable and may cause a heterogeneous fluoride occurrence and local-to-regional variations in fluorosis health risks posed. Our aim was to address the challenge of developing a national solution to predicting groundwater vulnerability to geogenic fluoride risk in the country of Malawi where incidences of fluorosis are reported and typical developing world problems of limited data and resources abound. Previously there have only been sporadic, local-scale studies linking fluoride occurrence with health risks in Malawi with no attempts to tackle the issue nationally. We hence develop a screening method for predicting groundwater vulnerability to geogenic fluoride in the form of detailed risk maps developed from statistical relationships shown between groundwater fluoride occurrence and known geogenic fluoride sources. The approach provides for dynamic update and informed acquisition of new data and hence ongoing improving capacity to manage fluoride risks in Malawi. Our screening method provides a technical basis for redefining national fluoride policy to ensure commensurate management of health risks posed. Specifically, the approach provides a pathway for stepped progression from the current 6 mg/L Malawian standard for fluoride in drinking water to adoption of the World Health Organisation 1.5 mg/L guideline standard.
... The salinity of the sampled waters showed a great variation depending on the different sampling points. The high salinity values recorded in wells P3 and P5 are linked to an interaction resulting from the contact between the waters and the rock which contains them [23]. However, the high value recorded in mayo-Barka would be linked to the nature of the soil and the abundance of anthropogenic activities around the site. ...
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Despite the increasing volume of evidence demonstrating the efficacy of solar water disinfection (SODIS) as a household water treatment technology, there still appear to be significant barriers to uptake in developing countries. The potential of SODIS is often treated with scepticism in terms of effective treatment, volume, and safety, and is dismissed in preference for more accepted technologies such as ceramic filters and dose chlorination. As part of WATERSPOUTT (EU H2020 688928), our study used a transdisciplinary methodology to co‐create an innovative SODIS system in rural Malawi. The formative work focussed on the design of (1) an appropriate and acceptable system, and (2) a context specific intervention delivery programme using a behaviour centred design. Initial research identified specific water needs and challenges, which were discussed along with a co‐creation process with potential end‐users, through a series of shared dialogue workshops. Specifications from end‐users outlined a desire for higher volume systems (20 litres), which were ‘familiar’ and could be manufactured locally. Development of the ‘SODIS bucket’ was then undertaken by design experts and local manufacturers, with input from end users, and subject to controlled testing to ensure efficacy and safety. Concurrent data was collated using questionnaires (n=777 households), water point mapping (n=121), water quality testing (n=46) and behaviour change modelling (n=100 households). These identified specific contextual issues (hydrogeology, water access, gender roles, social capital, and socio‐economic status), and behavioural determinants (normative, ability and self‐regulation factors) which informed the development and delivery mechanism for the implementation toolkit. This article is protected by copyright. All rights reserved.
... The alluvial aquifer was also enriched in Ca and SO 4 during the downstream flow of groundwater through dissolution of carbonate and barite (BaSO 4 ) minerals, gypsiferous materials and gypsum and are the major sources of sulphate (Montoroia et al., 2002;Jamshidzadeh and Mirbagheri, 2011;Monjerezi and Ngongondo, 2012;Azaza and Gueddari, 2012;Liu et al., 2015;Walter et al., 2017). Corniello and Ducci (2014) attempted the hydrogeochemical characterization of the main aquifer of the "Litorale Domizio-Agro Aversano NIPS" (Campania-Southern Italy) and reported sulphate concentration of 978.7 ppm. ...
Most abundant form of sulphur in the geosphere has been sulphate. Sulphate, with sulphur in the plus six oxidation state is very stable. Sources of sulphate in groundwater include mineral dissolution, atmospheric deposition and other anthropogenic sources (mining, fertilizer, etc.). Gypsum is an important contributor to the high levels of sulphate in many aquifer of the world. Sulphate is not as much as toxic, but it can cause catharsis, dehydration and diarrhoea, and when ingested in higher amount through dietary absorption, the levels of methaemoglobin and sulphaemoglobin are changed in human and animal body. The role of sulphate in aqueous phase and sedimentary phase has been discussed. There is only limited work on sulphate pollution remediation in groundwater at national and international level; therefore, in the light of rising attention in sulphate as a contaminant, different sources of sulphate, its distribution and available different remediation techniques for groundwater system reported so far have been discussed in the present paper. Abiologic processes’ thermochemical sulphate reduction (TSR) also plays significant role in reduction of sulphate.
