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Thesis framework

1 CHAPTER ONE

1.3 Thesis framework

Chapter 1:

Outlines the objectives, experimental approach and organization of this thesis.

Chapter 2:

This chapter provides background information on heavy metal contamination in drinking water, sources of contamination and health effects resulting from these contaminants. Arsenic contamination of Waikato River and ground water is addressed. Arsenic chemistry and health effects of arsenic exposure on various organ on the human body are discussed. An overview of the treatment technologies (conventional and advanced) used for arsenic removal, as well as the advantages, disadvantages and removal efficiencies of each are covered in detail.

Chapter 3:

This chapter presents results of experiments that evaluate the chemical and physical properties of DMI-65 using X-ray fluorescence (XRF), X-ray diffraction (XRD), Fourier transform infrared (FTIR), Scanning electron microscope (SEM), Brunauer-Emmett-Teller (BET) and particle size distribution before and after activation. The effects of pH on As (III) and As (V) were investigated. Different kinetic models were applied to determine the kinetic data for As (III) and As (V) adsorption and to select the most suitable model. The models applied are the pseudo-first order, pseudo-second and Elovich kinetic models.

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An adsorption isotherm study was conducted to evaluate the interaction between As (III) and As (V) on DMI-65 at different pH values (5, 6, 7, and 8.5). The models used for determining DMI-65 adsorption capacity are Langmuir, Freundlich, Langmuir-Freundlich (L-F) and Dubinin-Radushkevich (D-R). Thermodynamics studies were conducted to determine adsorption capacity, Gibbs free energy, enthalpy, and entropy at different temperatures (283 K, 288 K, 293 K and 298 K) for both As (III) and As (V). Lastly, regeneration studies were carried out to determine the reusability of DMI-65 in removing As (III) and As (V).

Chapter 4:

This chapter presents results that investigate the performance of a fixed bed column in removing arsenic from contaminated raw water in terms of the breakthrough curve. In this study, the effect of flowrate (10 mL/min, 12.5 mL/min and 20 mL/min) and pH (5, 7 and 9) on the performance of DMI-65 was carried out. The following adsorption models were used in predicting the breakthrough curve of the effluent namely: Thomas model, Yoon-Nelson model, Adams-Bohart model and Clark model. Lastly, a nonlinear regression analysis was used in performing error analysis.

Chapter 5:

This chapter presents results of experiments that compare arsenic, UV254nm and turbidity removal from contaminated drinking water between dissolved air flotation (DAF) and sedimentation processes. Impact of pH and coagulant dose were equally investigated. Bench jar tests were conducted using polyDADMAC (2.0, 2.2, 2.4, 2.6 and 3 mg/L) and Chitosan from crab shell (0.2, 0.4, 0.6, 0.8 and 1.0 mg/L) and at various pH levels (4, 5, 6, 7, 8 and 9). Other operating conditions are rapid mixing (100 rpm, G value = 60 s-1), slow mixing (30 rpm, G value = 10 s-1), setting time and flotation time (10 min) and a saturated pressure of 4 bar.

Chapter 6:

This chapter presents the results of an investigation of the effect of competing anions on arsenic removal from a contaminated drinking water using a batch DAF process. PAC was used as a coagulant (concentration = 23.5 mg/L) at different pH levels (5, 6, 7, 8 and 9). The anions investigated are sulfate (SO42-), nitrate (NO3-), carbonate (CO32-) and phosphate (H2PO4-). The effect of three concentration levels

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(1, 5 and 10 mM) for each competing anion was studied with flotation time (10 min), saturated pressure (4 bar), rapid mixing (100 rpm) and slow mixing (30 rpm).

Chapter 7:

This chapter investigates the effect of coagulant (PAC) dose (2.35, 4.70, 9.40, 14.10 and 18.80 mg/L), pH (5, 6, 7, 8 and 9), flotation time (10, 20 and 30 min), phosphate concentration (0.5 mM, 2.5 mM and 10 mM) and saturated pressure (2, 3 and 4 bar) on separating arsenic from contaminated raw water. The efficiency of the treatment/separation process was evaluated by measuring arsenic, UV254nm and turbidity before and after treatment. Modification to the current Hamilton water treatment plant is also suggested including the cost analysis.

Chapter 8:

This chapter summarizes the results in this thesis and then concludes with overall recommendations for future work in separating arsenic from other contaminants in drinking water.

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