Fluoride Removal from Groundwater by Adsorption Technology: The Occurrence, Adsorbent Synthesis, Regeneration and Disposal

ISBN-13: 9780815392071 / Angielski / Miękka / 2017 / 276 str.

Abdulai Salifu (UNESCO-IHE Institute for

Opis

In the Eastern corridor of Northern region of Ghana, presence of high fluoride concentration in the groundwater has made many drilled boreholes unusable for drinking. Little is, however, known about the factors contributing to the occurrence of high fluoride in this part of Ghana and it's spatial distribution. Treatment of the fluoride-contaminated groundwater by adsorption is also hampered by the lack of suitable adsorbents that are locally available. Based on principal component analysis, and saturation indices calculations, this thesis highlights that, the predominant mechanisms controlling the fluoride enrichment probably include calcite precipitation and Na/Ca exchange processes, both of which deplete Ca from the groundwater, and promote the dissolution of fluorite. The mechanisms also include F-/OH- anion exchange processes, as well as evapotranspiration processes which concentrate the fluoride ions, hence increasing its concentration in the groundwater. Spatial mapping showed that the high fluoride groundwaters occur predominantly in the Saboba, Cheriponi and Yendi districts. The thesis further highlights that, modifying the surface of indigenous materials by an aluminium coating process, is a very promising approach to develop a suitable fluoride adsorbent. Aluminum oxide coated media reduced fluoride in water from 5. 0 +/- 0.2 mg/L to â ¤ 1.5 mg/L (which is the WHO health based guideline for fluoride), in both batch and continuous flow column experiments in the laboratory. Kinetic and isotherm studies, thermodynamic calculations, as well as analytical results from Fourier Transform Infrared Spectroscopy and Raman spectroscopy, suggest the mechanism of fluoride adsorption onto aluminium oxide coated media involved both physisorption and chemisorption processes. Field testing in a fluoritic community in Northern Ghana showed that the adsorbent is also capable of treating fluoride-contaminated groundwater in field conditions, suggesting it is a promising defluoridation adsorbent. The adsorbent also showed good regenerability potential that would allow re-use, which could make it practically and economically viable. Additional research is, however, required to further increase the fluoride adsorption capacity of developed adsorbent.

O autorze

Abdulai Salifu is a Civil and Environmental Engineer, and obtained his BSc. degree (Civil Engineering) from the Kwame Nkrumah University of Science and Technology (KNUST), Kumasi, Ghana. He obtained his Post-Graduate diploma degree (passed with distinction) in Community Water Supply and Sanitation, from Loughborough University of Technology (LUT), England (U.K) and his MSc. degree in Environmental Engineering from the University of Newcastle upon Tyne, England (U.K). He worked for several years in the water sector in Ghana as a Water and Sanitation Engineer, where he worked in multi-disciplinary team professionals comprising of; Hydrogeologist, Sociologists, Health and Hygiene Education Specialist, IT Specialist and Planners, involved mostly in the provision of water supply and sanitation facilities as well as health/hygiene education to rural communities and small urban towns. He was involved in the planning and implementation of several water and sanitation projects in the Northern region of Ghana, financed by several External Support Agencies (ESAs), including the World Bank, European Union (EU), Agence Francais de Developpment (AFD), UNICEF, Japanese International Corporation Agency (JICA) and the Canadian Development Agency (CIDA).