Multivariate statistical analysis for fluoride occurrence in groundwater in the Northern region of Ghana.

The presence of excess fluoride in groundwater in the Northern region of Ghana has resulted in the closure of many boreholes for drinking water supply to avoid the incidence of fluorosis and other related health effects. The fluoride concentration in 357 groundwater samples from the area ranged between 0.0 and 11.6mg/L, with a mean value of 1.13mg/L. Piper graphical classification, correlation coefficients, principal component analysis (PCA) and thermodynamic calculations were used as an approach to gain insight into the groundwater chemical composition and to help understand the dominant mechanisms influencing the occurrence of high fluoride waters. Spatial join procedure was used to examine the relationship between the underlying geology of the study area and fluoride distribution. Six groundwater types were identified for the area: Ca-Mg-HCO(3), Ca-Mg-SO(4), Na-Cl, Na-SO(4), Na-HCO(3) and mixed water type. PCA performed on the groundwater chemical data resulted in 4 principal components (PCs) explaining 72% of the data variance. The PCs represented the predominant processes controlling the groundwater chemistry in the study area which include; mineral dissolution reactions, ion exchange processes and evapotranspiration processes. PHREEQC calculations for saturation indices for the groundwater samples indicated they were largely saturated with respect to calcite and under-saturated with respect to fluorite, suggesting that dissolution of fluorite may be occurring in the areas where it is present. A review of the PCA results and an evaluation of the equilibrium state of the groundwater based on the saturation indices, suggest that some of the processes controlling the overall groundwater chemistry in the study area also influenced the fluoride enrichment. These predominant processes include the dissolution of the mineral fluorite, anion exchange processes (F(-)/OH(-)) involving clay minerals and evapotranspiration processes. Elevated fluoride levels in the study area were found to occur predominantly in the Saboba and Cheriponi districts and also in the Yendi, Nanumba North and South districts. These areas are underlain by the Middle Voltain formation (Obossom and Oti beds), comprising mainly of sandstone, limestone, conglomerate, shale, arkose and mudstone. Results of the hydrochemical analysis show that aside from the boreholes with elevated concentrations of fluoride (beyond 1.5mg/L), groundwater in the study area based on the parameters analyzed is generally chemically acceptable and suitable for domestic use.

Performance of Moringa oliefera as a biosorbent for chromium removal.

This study investigated adsorption of chromium on to a bio-adsorbent, Moringa oleifera seed. Different by-products of the seed processing were used as adsorbents. These include: the Whole Seed Powder (WSP), the Residue after Coagulant Extraction (RaCE) and an Activated Carbon (AC) prepared from the seed husk. Adsorption studies for the removal of Cr(III) and Cr(VI) were carried out in batch experiments and the effects of adsorbent dosage, contact time, pH and initial chromium concentration were analysed. Experimental results showed that maximum removal of Cr(III) and Cr(VI) was observed at pH 7 and pH 2, respectively. The percentage removals of Cr(III) by WSP, RaCE and AC were: 97, 94 and 99.9%, respectively. And the percentage removals of Cr(VI) by RaCE and AC were 47 and 83.2%, respectively. RaCE showed similar adsorption capacity to the WSP, which indicates that it is possible to extract a coagulant and use the waste product for adsorption. By using the RaCE, residual dissolved organic carbon in the treated water was significantly reduced compared to using the WSP. These results indicate that biomaterials can be considered as potential adsorbents for heavy metals removal from water or wastewater systems.

Comparison of single-step and two-step purified coagulants from Moringa oleifera seed for turbidity and DOC removal.

The coagulant proteins from Moringa oleifera purified with single-step and two-step ion-exchange processes were used for the coagulation of surface water from Meuse river in The Netherlands. The performances of the two purified coagulants and the crude extract were assessed in terms of turbidity and DOC removal. The results indicated that the optimum dosage of the single-step purified coagulant was more than two times higher compared to the two-step purified coagulant in terms of turbidity removal. And the residual DOC in the two-step purified coagulant was lower than in single-step purified coagulant or crude extract.

Single-step ion exchange purification of the coagulant protein from Moringa oleifera seed.

The coagulant protein from Moringa oleifera (MO) seed was purified using a single-step batch ion exchange (IEX) method. Adsorption and elution parameters were optimized. Impact of the purification on the reduction of organic and nutrient release to the water was studied. The matrix was equilibrated using ammonium acetate buffer, and the optimum ionic strength of NaCl for elution was 0.6 M. The time for adsorption equilibrium was between 90 and 120 min. Maximum adsorption capacity of the matrix, estimated with the Langmuir model, was 68 mg protein/g adsorbent. The purified protein does not release organic and nutrient loads to the water, which are the main concerns of the crude extract. This work suggests that a readily scalable single-step IEX purification method can be used to produce the coagulant protein and it can be carried out with locally available facilities. This will promote the use of MO in large water treatment plants and other industries.