Optimal sizing of roof gutters and hopper for rainwater harvesting.

Bernoulli's equation was applied to a section of hopper collector to determine the appropriate dimensions of the hopper for rainwater harvesting. Also, the hopper surface area (SFA) for a given volume was minimized by differentiating it in relation to the slant angle (SA). Combining the rational formula-Manning's equation and the best hydraulic section criteria-expressions were obtained for the optimum sizes of rectangular and circular gutters. Minimum hopper SFA for a given volume was found to occur at an optimum hopper SA of 35.282°. With the optimum conditions, design charts were produced for the hopper, circular, and rectangular roof gutters. The ratio of hopper larger radius to the smaller radius designated as (α) gave hopper dimensions with excessively wide upper radius for values of 0.1 ≤ α ≤ 0.2. Alpha (α) values of 0.8 and 0.9 gave values of R and Z which are almost too close to be distinguished. The valid range of α for hopper design was found to be 0.292 ≤ α ≤ 0.8. The study revealed that roof plan area has more effect on hopper dimensions than gutter slope. In addition, the case of excessive long gutters can be addressed by placing the hopper at the lateral epicenter of the eaves. In this regard, regions with abundant rainfall can solve water scarcity issues if proper design parameters of RWH components are considered in order to avoid waste of water through the overflow of water collection systems.

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+, SO42-, 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 CO32-, 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.

Health risk assessment of heavy metal variability in sachet water sold in Ado-Odo Ota, South-Western Nigeria.

The sales of sachet water (SW), also known as "pure water" (PW), in Nigeria is a lucrative business. It serves many people, especially low-income earners, by providing a more affordable access to safe drinking water when compared with table water. However, some of the producers of SW do not effectively treat raw water before packaging them for sale. This study investigates the presence and concentrations of heavy metals, such as chromium (Cr), iron (Fe), manganese (Mn), copper (Cu), aluminum (Al), and zinc (Zn) in some samples of SW sold within Ota, Ogun State, Nigeria. Samples of SW from nine different producers were purchased for four consecutive weeks and analyzed to determine the concentrations of these heavy metals in them. Furthermore, health risk indicators, such as chronic daily intake (CDI) and health risk indices (HRI) for children and adults, were calculated separately. The metal concentrations were compared with allowable limits set by the World Health Organization (WHO), Nigerian Industrial Standard (NIS), and the United States Environmental Protection Agency (US EPA). High concentrations of Cr, Fe, and Al were found in all the nine samples and exceeded the maximum allowable limits (MAL) of all the standards considered. However, the concentrations of Zn, Mn, and Cu were within permissible limits. The HRIs of heavy metals were in the order of Cu > Fe > Zn > Mn > Al > Cr, but since the standard limits set for some metals were exceeded, proper and effective treatment is required to safeguard the health of consumers.

An integrated assessment of land use impact, riparian vegetation and lithologic variation on streambank stability in a peri-urban watershed (Nigeria).

Bank erosion is an important source of sediment and phosphorus to inland fluvial systems and is generally responsible for more than half of the total watershed sediment export. Numerous studies have quantified bank erosion and the spatio-temporal variation of sediment flux in different watersheds. However, there is sparse research to date on the linkages between bank erosion/accretion and sediment export under different land uses, especially in rapidly evolving peri-urban watersheds. This research, therefore, integrated remote sensing techniques and repeated field survey of erosion pin plots to quantify bank erosion and sediment flux in the 80 km2 Nkisi River watershed (NRW), southeast Nigeria, over a three-year period. The impact of land use change on streambank erosion was evaluated by utilising remotely sensed Landsat datasets of 2003, 2010, 2016 and 2019. Geotechnical tests were used to characterise the lithologic properties of the banks, while the Bank Stability and Toe Erosion Model (BSTEM) was used to determine the stability of the banks under various hydrological conditions and mechanical properties of the riparian vegetation. Mean bank recession rates increased from 10.7 cm during the 2017-2018 monitoring period to 17.5 cm for the 2019-2020 monitoring period. The percentage of total watershed export ascribed to bank erosion in the three stream reaches varied from 6.6 to 44.9%. The high rates of bank erosion and accretion within the NRW were attributed to rapid changes in land use, which evolved from grassland and woodland to cropland, built-up and bare land. The BSTEM accurately predicted the high erosion rates of the streambanks and showed that riparian vegetation has a mechanical effect on bank stability. However, the mechanical effect diminishes as the depth to water table rises during high streamflow events.

Equilibrium and thermodynamic investigation of biosorption of nickel from water by activated carbon made from palm kernel chaff.

Novel biosorbents were derived from a waste product of palm kernel oil extraction known as palm kernel chaff (PKC). One portion of the PKC was carbonized in a furnace and then activated chemically, while the other half was activated without carbonization. Both were designated as CPKC and UPKC, respectively. The two biosorbents so produced were then used to conduct batch equilibrium and kinetic sorption studies at 30 °C, 35 °C and 40 °C and pH 3.0 and 9.0 for an agitation period of 5, 10, 20, 40, 60, 90, and 120 min. The Koble-Corrigan, Dubinin-Radushkevich, and the Freundlich isotherms fitted the experimental data very well with R2 values of 0.97 to 1.0, 0.95 to 1.0, and 0.96 to 1.0, respectively. The linear type II Langmuir isotherm performed much better (0.96 ≤ R2 ≤ 1.0) than the nonlinear isotherm. The maximum sorption capacity was obtained as 120.6 mg/g using CPKC at pH 9.0 and 35 °C. The Langmuir separation coefficient values (0.022 ≤ RL ≤ 0.926) show that the sorption of nickel to PKC is favorable. The most favorable sorption condition was found for CPKC at pH 9 and temperature of 40 °C. The values of sorption energy (8.21 ≤ E ≤ 14.27) and the isosteric heat of sorption (-133.09 ≤ ∆Hx ≤ -17.92) indicate that the mode of sorption is mostly ion exchange. Thermodynamic parameters also show that the process is exothermic and entropy-driven. The pseudo-second-order kinetic model shows the best correlation compared to the other kinetic models. The coefficient of correlation for the pseudo-second-order model was mostly within the range of 0.999-1.000 for 90% of all kinetic studies carried out.

HERisk: An improved spatio-temporal human health risks assessment software.

Risk assessment is considered an essential tool to assist in the management and mitigation of polluted areas, especially those associated with economic activities that significantly degrade the environment, such as mining. However, most of the methodologies of risk assessment adopt the deterministic approach of using a fixed value for ascertaining the hazards derived from exposure to chemical pollutants. However, this is not the case of the Human, Ecological and Radiological Risk (HERisk) code, which allows space-time assessments of ecological, radiological, and human health risks. Indeed, this work aims to describe this new software (enhanced version of HHRISK), which not only improves the performance of the code but also increases its applicability and versatility. To showcase its usefulness in evaluating ecological pollution and human health risk were studied the contents of potentially toxic elements (Co, Cu, Fe, Mn, Ni, Pb, and Zn) in soils and surface waters from the nickel mining area in the municipality of Itagibá (Bahia, Brazil). The obtained results showed that metals are non-homogeneous distributed, suggesting the presence of local enrichment sources, mainly related to human activities. The statistical analyses carried out revealed that mining and agricultural activities are possibly responsible for the contents of these pollutants in both soils and surface waters. The calculated ecological indices of pollution confirmed anthropogenic pollution around the mining area, especially in the locations closest to sterile waste piles. The results of the human health risk assessment revealed that the ingestion of meat and contaminated water are the main routes for entering the potentially toxic elements to the human body and that Co is the chemical specie that poses the highest risk in the entire region. The hazard index (HI) values indicated that the whole area around the mine should be considered as a high risk for human health.

Estimation of some trace metal pollutants in River Atuwara southwestern Nigeria and spatio-temporal human health risks assessment.

Over twenty thousand persons rely on water from Atuwara River for drinking and other domestic purposes, hence the need to ascertain the human health risk inherent in such practice. Seventy-two water samples were collected from River Atuwara during the dry and wet seasons of 2018, and the concentration of heavy metals (Pb, As, Ni, Cr, Zn, Cu, and Cd) were measured using ICP-OES. A newly developed human health risk assessment method, HHRISK code was used to estimate the health risks associated with consumption of water from Atuwara River. Results obtained revealed that the concentration of heavy metals in the river was as follows: Cd < Ni < Pb < Cr < Cu < As < Zn in the wet season and Cd < Pb < Ni < Cu < Cr < As < Zn during the dry season. Principal component analysis suggested that industrial effluents, agricultural activities and base-rock interaction are responsible for pollution of Atuwara River. The cumulative hazard index (HIcum) obtained was 678.0 ±â€¯36.8 (for adult) and 1392.0 ±â€¯132 (for child) for non-carcinogenic risks. A cumulative carcinogenic risk (CRcum) of 1.01E-1±5.26E-3 and 4.96E-2±5.05E-3 was obtained for adult and children respectively, suggesting that up to 1 in 10 adults and 1 in 20 children may suffer from cancer over their lifetime as a result of consumption and exposure to water from River Atuwara. These results highlight the fact that unavailability of safe drinking water in many parts of the world remains a real and persistent risk which must be tackled.

An integrated assessment of land-use change impact, seasonal variation of pollution indices and human health risk of selected toxic elements in sediments of River Atuwara, Nigeria.

River sediments contain environmental fingerprints that provide useful ecological information. However, the geochemistry of River Atuwara sediments has received less attention over the years. One hundred and twenty-six sediments from 21 locations were collected over a two-season period from River Atuwara, and a detailed investigation of the land use and land cover (LULC) change between 1990 and 2019, analysis of selected toxic and potentially toxic metal(oid)s (TPTM) (Cu, As, Cd, Pb, Ni, Cr, Zn, Fe, Co and Al) using ICP-OES, pollution index assessment, potential source identification (using center log-transformation approach), potential ecological, and human health risk assessment were conducted. The results of the LULC change revealed that the built-up area increased by 95.58 km2, at an average rate of 3.186 km2/year over the past 30 years. The mean concentration of metal(oid)s increased in the order of Cd < As < Cr < Pb < Co < Ni < Cu < Zn < Fe < Al, and Cd < As < Cr < Co < Pb < Ni < Cu < Zn < Fe < Al during the dry and wet seasons, respectively. Meanwhile, the statistical analysis of the data spectrum inferred possible contamination from lithological and anthropogenic sources. According to the pollution load index, 90.48% of the sediment samples are polluted by the metal(oid)s. Potential ecological risk assessment identified Ni, As, and Cd as problematic to the ecological community of River Atuwara. Regarding the metal-specific hazard quotient via ingestion route, the risks are in order of Co â‰« As â‰« Pb > Cr > Cd > Al > Ni > Cu > Zn > Fe for both seasons and the carcinogenic risk for children via ingestion route presented a value higher than the safe limits for As, Cd, Cr, and Ni during both seasons. This outcome highlights the need for prompt action towards the restoration of environmental quality for communities surrounding River Atuwara.

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.