Molecular-scale characterization of groundwater treatment sludge from around the world: Implications for potential arsenic recovery

Iron (Fe)-based treatment methods are widely applied to remove carcinogenic arsenic (As) from drinking water, but generate toxic As-laden Fe (oxyhydr)oxide waste that has traditionally been ignored for resource recovery by the water sector. However, the European Commission recently classified As as a Critical Raw Material (CRM), thus...

Fluoride removal by Ca-Al-CO₃ layered double hydroxides at environmentally-relevant concentrations

In this study, F⁻ removal by Ca–Al–CO₃ layered double hydroxides (LDHs) was investigated at environmentally-relevant concentration ranges (2–12 mg/L) to below the WHO guideline, with an emphasis on the effect of LDHs’ modification, as well as the effects of initial F⁻ concentration, adsorbent dose, pH,...

As(III) removal in rapid filters: Effect of pH, Fe(II)/Fe(III), filtration velocity and media size

In the top layer of aerated rapid sand filtration systems, uncharged As(III) is biologically converted to charged As(V). Subsequently, the main removal mechanism for As(V) is adsorption onto oxidised, flocculated Fe(III) (hydrous ferric hydroxides; HFO). The aim of this research was to understand the interactions between As and Fe in...

Biological As(III) oxidation in rapid sand filters

The objective of this study was to investigate whether arsenic-oxidising bacteria (AsOB) will grow and survive in rapid sand filters. Additionally, the interdependence of other groundwater constituents (Fe(II), Mn(II), NH₄) with biological As(III) oxidation was investigated. For this purpose As(III) oxidation was monitored in pilot...

As(III) oxidation by MnO₂ during groundwater treatment

The top layer of natural rapid sand filtration was found to effectively oxidise arsenite (As(III)) in groundwater treatment. However, the oxidation pathway has not yet been identified. The aim of this study was to investigate whether naturally formed manganese oxide (MnO₂), present on filter grains, could abiotically be responsible...

Manganese removal from groundwater: Role of biological and physico-chemical autocatalytic processes

In The Netherlands, Belgium and other European countries, manganese is removed from groundwater by aeration followed by rapid (sand) filtration. Although manganese removal from groundwater has been studied extensively, the mechanisms that control the ripening of filter media are not yet fully understood. <br/><br/>This thesis highlights the role...

Reduction of ripening time of full-scale manganese removal filters with manganese oxide-coated media

Effective manganese removal by conventional aeration-filtration with virgin filter media requires a long ripening time. The aim of this study was to assess the potential of manganese oxide-coated media to shorten the ripening time of filters with virgin media, under practical conditions. A full scale filter filled with virgin sand and a full...

Het onderzoek naar de gekombineerde behandeling van met hexacyanoferraat verontreinigd grondwater en stedelijk afvalwater