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The impact of urbanization on the quality of drinking water sources is a challenge in many developing countries. In this research, the main source of drinking water was quantified, quality baseline defined, and a thematic decision support management tool developed to protect the quality using Aba, Nigeria. Data from primary and secondary sources were obtained from desktop search, empirical instruments, satellite data, hydrogeological investigations and water quality assessment. Geoscientific and statistical tools were used to analyse the landform, characterize the land use, and create management tools to protect the water source.
The results revealed that groundwater is the main source of water for both domestic and industrial uses. An average water consumption per capita rate of 35.9 l/day was estimated, which is low compared to the WHO recommendation. The landform and land-use analyses revealed that the area is low-lying, poorly drained, and the urban land-use is the fastest-growing class growing averagely at 0.6% /annum between 1986 to 2017. Some of the urban land-use practices that harm the quality of the groundwater were identified and mapped in a contamination hotspot map.
The results of the twenty-one quality indicators in the groundwater showed that the pH was acidic (3.7-5.6), total dissolved solids (TDS) ranged between 6.5 mg/l-364 mg/l. The mean concentrations of the remaining indicators were within the WHO limits for drinking water quality. But, the EC, TDS, chloride and nitrate revealed significant differences when tube-wells between densely and sparse built-up areas are compared. Again, four dominant water types were identified in groundwater. The Na-HCO3 water type was dominant mostly in the sparse built-up area and it is assumed as the background groundwater facies in the area. Whereas Mg, Ca-Cl, Na-Cl and Ca-HCO3 water types were predominant in the densely built-up area. The bacteriological assessments of drinking water from natural and alternative (i.e. beverages and packaged water) sources revealed the presence of E. Coli and Coliform bacteria in some samples of the natural water.
The groundwater quality distribution and vulnerability assessment maps were developed based on water quality index, and DRASTIC methodologies, respectively. The quality distribution map showed that > 98% of the area has a “suitable“ rating. While the vulnerability assessment map found that the groundwater has a “medium” baseline vulnerability covering about 80%. The differences in the results were due to some observed poor urban land-use practices in the area. Finally, a thematic decision support tool that delineates priority monitoring zones and suggests possible source protected areas tailored for the area was developed. This tool is cost-effective in protecting the groundwater quality and can be applied to other developing urban areas with similar physiological conditions.
Groundwater is the main source for potable water and domestic use in numerous countries around the world. However, water quality can be affected by pollution, which influences the natural environment and human health. One of the widespread pollutants in water is ammonia which is toxic to fish and causes eutrophication of lakes and wetlands. Constructed wetlands are promising in situ water treatment methods thanks to enhanced microbial growth within the plants’ rhizospheres, which creates an effective contaminant degradation zone. The ammonia in constructed wetlands can be removed either via total nitrification with further denitrification or partial nitrification coupled with anaerobic ammonium oxidation (anammox). However, so far, the role of anammox in constructed wetlands as well as its correlation with other nitrogen transformations remains unclear. The quantification of nitrogen turnover processes in constructed wetlands is difficult due to the complexity of the wetland systems.
Accordingly, the main aim of this research is to investigate pathways of ammonium removal in constructed wetlands treating contaminated groundwater. For this, several approaches were applied: a) physico-chemical parameters measurements; b) investigations of nitrogen stable isotope fractionation; c) stable isotope labelling approach; d) molecular biological methods. Also, seasonal and spatial variations in nitrogen transformations in several types of constructed wetlands (unplanted horizontal subsurface flow, planted horizontal subsurface flow, and floating plant root mat) were investigated.
The application of the stable isotope approach combined with common physico-chemical investigations enabled us to identify key factors influencing efficiency of nitrogen removal in constructed wetlands, which was the plant presence as substrate for attachment and growth of microorganisms. Ammonium removal efficiencies were not different between investigated seasons (spring, summer, and autumn), what could be explained by the fact that throughout all investigated seasons the air temperature remained high (above 10°C). While plant uptake accounted for significant part of ammonium removal during spring and summer in planted constructed wetlands, isotope fractionation patterns revealed that nitrification-denitrification were prevailing processes in planted constructed wetlands throughout the year, occurring in a linear way along the flow path, and not depending on depth in the root zone.
The research results also illustrated that in the planted horizontal subsurface flow constructed wetland, the functional genes of the nitrogen cycle were evenly distributed in a linear way along the flow path with prevalence at the superficial points. The same trend was observed for the nitrification and denitrification turnover rates using the isotope labeling techniques. Significant nitrate consumption under aerobic conditions diminishes nitrification rates and should therefore be taken into account when estimating nitrification turnover rates. This nitrate consumption was due to aerobic denitrification, the rate of which was comparable to that for anaerobic denitrification. Consequently, denitrification should not be considered as an exclusively anaerobic process. Phylogenetic analysis of hydrazine synthase (hzsA) gene clones indicated the presence of Brocadia and Kuenenia anammox species in the constructed wetland. Although anammox bacteria were detected by molecular methods, anammox activity could not be measured and hence this process appears to be of low importance in nitrogen transformations in these freshwater ecosystems.
In conclusion, this research demonstrated that combination of physico-chemical measurements with stable isotope and molecular biological approaches is an effective tool for investigation of nitrogen transforming processes in constructed wetlands. Such information is not only valuable for understanding of the processes ongoing inside these wastewater treatment facilities but also necessary for further technological improvement of constructed wetlands.
Groundwater samples were collected from 63 community wells and boreholes within south-western part of Ashanti Region of Ghana to examine their hydrogeochemical characteristics and elemental features to better understand the sources and mobilization processes responsible for arsenic (As) enrichment as well as the suitability of the groundwater for domestic and agricultural purposes. In addition, gold mine tailings dams were also investigated to ascertain the potential source of As and other trace metals (Fe, Cu, Mn, and Zn) contamination and their dissolution into the adjoining environmental media. Further, two point-of-use As removal technologies were evaluated for their effectiveness and appropriateness. A transparent small volume flow-through cell coupled with a calibrated hand held YSI® Multi-Parameter Water Quality Meter (Model YSI 6 l0-DM/600XL) was used simultaneously to measure indicator field parameters. Anions and cations were determined simultaneously in groundwater samples using Metrohm 761 Compact IC and Dionex 4500i IC system, respectively. Total As and trace metals analysis of the groundwater samples and gold mine tailings were performed on electrothermal and flame atomic absorption spectrometry. As speciation were performed using disposable cartridges. Spatial distribution maps were produced for hydrogen ion concentration (pH), total dissolved solids (TDS), total hardness (TH), electrical conductivity (EC), sodium adsorption ratio (SAR), residual sodium carbonate (RSC) and percentage sodium (% Na) using the geographic information system (GIS). Results for the analysis of groundwater samples from 63 boreholes and wells (depth 1.5-100 m) within the study area demonstrate that the groundwater composition varies from Ca–Mg–HCO3 to Na–K–HCO3 and anoxic in nature. As concentrations ranged from <0.1-72 µg/L and <0.1-83 µg/L during the dry and the wet seasons, respectively. High As concentrations were generally present in the shallow to medium depth (20-70 m) of the aquifer along with high Fe ranging from <0.01-12.3 mg/L and <0.01-16.3 mg/L during the dry and the wet seasons, respectively and relatively low Mn (1.8-498.0 µg/L during the dry season and 2.3-583.8 µg/L during the wet season). The data demonstrated that 59 % of the groundwater samples contained no detectable level of As, 17 and 22 % of the samples gave results with levels of As above the World Health Organization (WHO) guideline value for drinking water standard of 10.0 µg/L, while 24 and 19 % of the samples showed results below the WHO drinking water guideline value during the dry and the wet seasons, respectively. Dissolved inorganic As species predominate with arsenite (As-III) as the main form. It appears that high As concentrations in the study area result from the contribution of different mechanisms which can be grouped into two namely aquifers under oxidizing conditions (aided by sulphide alteration) and aquifers under reducing conditions resulting from the reduction dissolution of arseniferous iron oxyhydroxide that exist as a dispersed phase on the sedimentary grains of the aquifer. In addition, water residence time and different water use practices also influence As concentrations in the groundwater. The results of the gold mine tailings dam revealed elemental concentrations ranging up to 1752 mg/kg As, 75.16 wt.% Fe, 1848.12 mg/kg Mn, 92.17 mg/kg Cu and 177.56 mg/kg Zn. Sulphate was the dominant anion throughout the leachate, reaching a maximum dissolved concentration of 58.43 mg/L. The As concentration levels of the mine tailings were very much higher than the Netherlands soil protection guideline value of 55 mg/kg. A higher amount of the total As content in the mine tailings registered leaching levels in a range of 0.04–0.56 %. It was observed from the study that the groundwater was predominantly soft in nature and its pH in desirable range which is within safe limits for domestic use during the dry season while 82.8 % of the analyzed groundwater samples registered a non-desirable pH range (acidic) during the wet season. The results for the spatial distribution of pH, TDS, TH, EC, SAR, % Na and RSC of the groundwater samples analyzed generally appear to be within safe limits. The two point-of-use As removal technologies evaluated shown that the Three-earthen pot system is the most effective and appropriate technology. Moving forward, it is my anticipation that the findings of this study will serve as a master piece to advice policy makers, well and borehole owners about the dangers or potential risks associated with As and other trace metals in drinking water supplies sourced from groundwater and how these can be managed. In addition, this research has identified high-risk As-contaminated areas, potential health issues, methodology for assessing As in groundwater, and a broad outline of two point-of-use As treatment options which can target risk populations to protect public health and help shape the national, regional, municipal and districts water monitoring policies.
Groundwater is an important resource in Sub-Saharan Africa to supply water for domestic, industrial, mining and irrigation for agricultural purposes. In Ghana, groundwater supply program is mostly pragmatic to give people drinking water, however to ensure sustainability a long term groundwater management system is essential. One such approach is the use source protection (well protection) with the declaration and installation of protection zones. To achieve the goal of this research three hypothetical questions were asked which relates to the Availability and Vulnerability of groundwater, and the use of an analytical model to estimate source protection zones (SPZ). The regions of Adansi, Lawra, Sunyani and Sekyere West were chosen as study areas to test the hypothesis of this research with detailed investigation concentrating on Adansi area. The overall aim from the study areas was to estimate SPZ for Granite, Phyllite, Schist, Sandstone and weathered materials and give recommendations as to which activity should be permitted or otherwise within each of these zones. The available groundwater for a particular well or location was determined based on its hydraulic conductivity and specific capacity of a well. Regionalization of the available groundwater was achieved by comparing the results of the hydraulic conductivity and specific capacity with the regional structural map. To determine the vulnerability of the available groundwater, the radius of influence (ROI) for the different boreholes was determined using Sichard and Dupuits formula whilst for Source protection zones, Darcy and the volumetric equation was used. Results of hydraulic conductivity estimated from pumping test data for the five major rock types showed a trimodal distribution (E-5, E-6 and E-7 m/s). There was a general trend of decreasing hydraulic conductivity to decreasing transmissivity. Results of plots of specific capacity verses hydraulic conductivity shows that only rock types with hydraulic conductivity greater than E-5 m/s yields sustainable groundwater supply. Three aquifer types were encountered in the study areas which were pore aquifers in shallow or alluvial, regolith and fracture aquifers in bedrocks. High hydraulic conductivity from the different rock types corresponds to higher ROI. The results of hydraulic conductivity, specific capacity, ROI and SPZ are used as input parameters for the estimation of the suitability of a groundwater source. A ranking matrix was developed for easy interpretation of hydrogeological data by combining the results of the input parameters into a single score. Results from the ranking matrix were used to determine specific regulations for the various aquifers in the study areas. Within the fractured crystalline rocks with k ≥E-5m/s siting of wells should target fracture zones whilst pumping during abstraction phase can exceed 15m3/s/m. The intermediate source protection zone should be at least 150m. Conclusions from the study could be applied in other areas of Ghana and be implemented during the initial development, abstraction and groundwater policy phases of other groundwater projects.
Groundwater has been identified as the best source for rural water supply in most rural communities in the Northern region of Ghana because it eliminates the problems of water borne diseases which have affected communities in the region over the years. The guinea worm disease is presently not totally eradicated in the area and there are signals that its occurrence will be increasing in the near future if adequate measures are not implemented to curtail the problem. Adequate groundwater exploration and management appears to be the key to ensure that potable and safe water is available for the entire population of the region and that its availability on a sustainable basis is guaranteed. Groundwater facilities being provided in the area include; engineered hand dug wells, boreholes fitted with hand pumps and mechanised small towns’ piped schemes. Groundwater exploration programs implemented have however resulted in low success rates of borehole drilling because of the lack of a systematic and methodological approach. The available conventional geophysical techniques; one dimensional (1-D) electrical resistivity profiling and sounding as well as the electromagnetic (EM) methods have not been able to efficiently select suitable sites for successful borehole drilling because of their inability to successfully demarcate areas which are likely aquifer potential zones for successful groundwater abstraction. Current borehole drilling success rates especially in the Voltain rock formation are very low. The complex geological setting of groundwater systems in the area gives cause for the adoption and application of a systematic methodological approach in groundwater exploration utilising effective geophysical techniques. Available geophysical techniques which have been considered in this research work include; two dimensional (2-D) multi-electrode electrical resistivity survey, electro kinetic survey (EKS) and the radon survey.
Die durchgeführten Arbeiten standen in einem engen Zusammenhang mit Arbeiten der Firma HGN GmbH zur Erforschung von Grundlagen zur schonenden Grundwasserbewirtschaftung im Einzugsgebiet der Ise. Ziel des Forschungsvorhabens war die Entwicklung und Erprobung eines Modells zur Ermittlung des nachhaltig nutzbaren Grundwasserdargebots gemäß der EU-Wasserrahmenrichtlinie. Um zu einem auf ganz Niedersachsen übertragbaren Modell zu kommen, mussten mehrere einzelne Faktoren in eine Gesamtbetrachtung eingehen. In einem ersten Verfahrensschritt wurde das nutzbare Dargebot zum einen für einen Trockenzeitraum und zum anderen für eine normale Niederschlagsperiode berechnet. Es wurden je nach Berechnungsverfahren verschiedene Abschläge für geogene bzw. ökologische Faktoren in die Verfahren einbezogen. An dieses erste Berechnungsverfahren schließt sich in einem zweiten Verfahrensschritt ein Bewertungsschema zur Ermittlung der Sensitivität der Grundwasserkörper bzw. ihrer Vorfluter an. Die Auswahl der Eingangsparameter richtete sich dabei hauptsächlich nach den vorhandenen Daten zu Neubildung und Dynamik des Grundwassers sowie dem geologischen Aufbau. Um die Auswirkungen von Grundwasserentnahmen auf Gewässer und grundwasserabhängige Landökosysteme zu simulieren, wurden darüber hinaus Daten benötigt, die diesen Einfluss charakterisieren. Die Ermittlung der potentiellen Auswirkungen auf die grundwasserabhängigen Landökosysteme ist ein wichtiger Bestandteil dieser Arbeit und wird auf drei verschiedenen Wegen exemplarisch beschrieben. Zum einen als Basisabfluss-Analyse, als weiteres als Ermittlung der sensitiven Gewässerabschnitte und als letztes als Ermittlung des landschaftsnotwendigen Mindestwasserabflusses. Der erste Teil des Verfahrens zur Ermittlung des nutzbaren Grundwasserdargebots wurde größtenteils in Form von Berechnungen in Excel-Tabellen durchgeführt. Für den zweiten Teil des Verfahrens zur Ermittlung der sensitiven Gewässerabschnitte wurden die benötigten Daten größtenteils in ArcView eingelesen und zum Teil miteinander verschnitten.