Fluoride contamination in groundwater sources in Southwestern Nigeria: Assessment using multivariate statistical approach and human health risk

The present study investigated the ionic and fluoride concentrations in tap water and its associated health risk to local dwellers of Ogun State (Abeokuta south), Nigeria. 63 samples were collected from twenty-one different locations. Results obtained revealed the mean concentration of fluoride (F–) as 1.23 mg/L. Other water quality parameters such as total dissolved solids (TDS), electrical conductivity (EC), F–, Fe2+, and SO42– surpassed the WHO guidance for drinking water. Strong positive correlation was observed between F– and TDS; F– and pH; TDS and EC; TDS and Mg2+; TDS and SO42–; TDS and HCO3–; EC and HCO3–; EC and SO42–; Na+ and Cl–; SO42– and Cl–. In addition, Empirical Bayesian Kriging (EBK) model was employed to spatially distribute the concentration of the analyzed elements within the study region. The chronic daily dose (CDD) and hazard quotient (HQ) were also used to evaluate the health risk associated with F–, considering dermal and ingestion as pathways. The results revealed that the associated HQ for infants between the age range of 6–12months within about 91% of the study region surpassed the accepted HQ limit. However, the HQ for age categories 11–16years; >65years; 18–21years; 21years; 16–18years within 95.2%, 90.5%, 80.95% and 100% of the study location were less than 1. Conclusively, the HQ values obtained in this study should serve as a baseline information for water management authorities, policymakers and the society at large towards addressing these pollution issues

An Optimization Approach for Assessing the Reliability of Rainwater Harvesting

This study was aimed at developing an optimization approach to rainwater harvesting (RWH) considering three (3) water consumption scenarios (WCS). These scenarios which include basic water need (BWN), pour flush (PF) and full plumbing connection (FPC) corresponding to 50 litres per capita per day (lpcd), 75(lpcd) and 150(lpcd) respectively were simulated for different categories of buildings. Reliability of supply was determined by first obtaining composite surplus/deficit of rainwater followed by optimizing the redistribution of surplus rainwater harvested to deficient buildings. Results showed that when total annual rainfall intercepted by roof exceeded total demand, 100% reliability of water supply was guaranteed. Reliability was found to be a linear function of storage. When reliability of supply is possible, the optimized storage bears an inverse exponential relationship to the roof plan area per capita. The relationship between surplus/deficit and roof plan area per capita follows a onephase decay pattern. An optimal redistribution of surplus water from self-sufficient buildings to deficient ones gave an improvement in supply reliability from 64 to 87% for basic water need, 47 to 58% for pour flush and 28 to 29% for full plumbing connection

Assessment of geospatial and hydrochemical interactions of groundwater quality, southwestern Nigeria

Groundwater pollution resulting from anthropogenic activities and poor effluent management is on the rise in Nigeria. Hence, groundwater used for domestic purposes is questionable and therefore calls for scientific scrutiny. Investigation of hydrochemical interactions and quality of groundwater resource is essential in order to monitor and identify sources of water pollutants. As a result, groundwater samples were collected from 21 locations in Abeokuta South, Nigeria and analyzed for physicochemical parameters using standard methods. Results obtained were subjected to hydrochemical and geospatial analyses. Water quality parameters investigated exhibited wide variations from location to location. Fe2+, Mg2+, SO4 2−, Cl−, total hardness (TH), Mn, Na+, NO3 −, SiO2, and alkalinity exhibited the highest levels of variation with coefficients of variation of 131.3, 92.8, 83.9, 76.7, 65.9, 64.3, 57.6, 57.2, 57.0, and 52.5, respectively. The average pH value was 6.76 with 71% of the water samples being slightly acidic. Na2+, Mg2+, Fe2+, and EC contents exhibited the most violation of drinking water standards with percent violations of 100, 52.4, 47.6, and 47.6%, respectively. Parameters, such as Mn, Ca2+, NO3 −, and CO3 2−, were within the WHO guideline values for drinking water in all the samples. The highest level of significant correlation was found to exist between Na+ and Cl− (r = 0.84, α = 0.01). Six principal components, which explained 83.5% of the variation in water quality, were extracted with the first (34.1%) and second components (15.7%) representing the influence of mineral dissolution and anthropogenic practices, respectively, on the hydrochemistry of the area. Four hydrochemical clusters were identified with distinctly partitioned water quality. Further analysis revealed that 38, 29, 24, and 9% of the samples were the Na-K-HCO3, Na-K-Cl- SO4, Ca-Mg-HCO3, and Ca-Mg-Cl-SO4 types, respectively. Anthropogenic activities are increasing threat to groundwater quality in the study location and therefore call for urgent attention. There is also a need for routine monitoring of groundwater in Abeokuta

Probabilistic risk assessment and spatial distribution of potentially toxic elements in groundwater sources in Southwestern Nigeria

The study investigated the concentration of potentially toxic heavy metals (PTHM) in groundwater sources (hand-dug wells and boreholes), spatial distribution, source apportionment, and health risk impact on local inhabitants in Ogun state. One hundred and eight water samples from 36 locations were analysed for Cr, Ni, Pb, Fe, Mn, Mg, Ca and Al. Mean values of 0.013, 0.003, 0.010, 0.088, 0.004 and 3.906 mg/L were obtained for Pb, Cr, Ni, Fe, Mn, and Al respectively at Iju district. Meanwhile, the average values of Pb, Ni, Fe, Mn, and Al concentrations at Atan district were 0.008, 0.0023, 0.011, 0.003, and 1.319 mg/L respectively. Results also revealed that the 44.4% and 11.13% of the borehole and well-water samples surpassed the World Health Organization limits for Pb at Atan. In Iju, the concentration of Pb and Al were relatively high, exceeding the stipulated standard in 100% of the samples. The Multivariate statistical analysis employed produced principal factors that accounted for 78.674% and 86.753% of the variance at Atan and Iju region respectively. Based on this, PTHM were traced to geogenic sources (weathering, dissolution, leaching) and anthropogenic emissions from industrial activities. In addition, the hazard quotient values obtained from the health risk assessment identified potential non-carcinogenic risk due to Pb via ingestion route. Ni was found to have high carcinogenic risk on adult and children, having exceeded the threshold limit. The outcome of the carcinogenic risk assessment revealed that 88.67% (for adults) and 1.12% (for children) of the cancer risk values surpassed the specified limits at Iju, whereas the cancer risk values were considerably lesser at Atan. In conclusion, the report of this study should serve as a beacon that will spark up strategic planning, comprehensive water resource management, and extensive treatment schemes in order to address the health complications linked with environmental pollution

Efficacy of disinfectants and brand reputation on bathing water quality improvement

This study evaluated the antibacterial efficacy of some disinfectants widely used in Nigeria in the elimination of common bacteria found in bathing water. Four (4) skin disinfectants Ivy, Dettol, Izal, and Septol, were added to sterile distilled water containing Escherichia coli (E. coli), Klebsiella spp. and Bacillus spp. which were isolated from a swimming pool. From a total of 288 samples, results revealed that all the antiseptic performed below par in destroying bacillus except for Ivy (41.67 %) and Dettol (12.50 %), which showed tenuous performance in this regard. Septol showed no significant difference in destroying bacteria with a higher number of CFU/100 mL eliminated irrespective of the contact time (p = 0.258). In contrast, Ivy showed high significant difference with bacteria destruction as contact time progressed (p = 0.011). The logistic regression model developed revealed that an increase in dosage promoted the removal of organisms while longer waiting times were only significant for Septol (p = 0.045) and Ivy (p = 0.002). Nagelkerke R2 model fitted properly for Izal and Septol with values of 0.97 and 0.786. The findings of this study showed stark variance among the treatment capacities of these antiseptics. They provided sufficient knowledge in the selection of the available skin disinfectants in the market that are most likely to destroy bacteria in bathing water. Therefore, the inability of these products to correlate with their intended purpose leaves room for re-assessment by their producers and by relevant monitoring agencies in the country to meet the demands of a rapidly growing number of end-users in dire need for improved bathing water quality

Estimation of longitudinal dispersion co-efficient: A review

Accurate determination of longitudinal dispersion coefficient in rivers or streams is necessary for pollution control and management. This can be achieved through tracer studies and has proven to be a reliable method for measuring pollution spread. However, tracer studies practise which is expensive, time gulping and requiring large labour input have been substituted with empirical approaches thereby reducing the applicability of the dispersion coefficient models generated. This study reviews the various models derived as well as methods associated in the collection of tracer concentration data (measurement) existing in the literature. A sustainable approach to this study was identified and research needs were also listed