Challenges and Solutions for Global Water Scarcity.

Climate change, global population growth, and rising standards of living have put immense strain on natural resources, resulting in the unsecured availability of water as an existential resource. Access to high-quality drinking water is crucial for daily life, food production, industry, and nature. However, the demand for freshwater resources exceeds the available supply, making it essential to utilize all alternative water resources such as the desalination of brackish water, seawater, and wastewater.

Competitive study of homogeneous and heterogeneous Fenton-like flow-through propoxur oxidation in ROC solution.

Reverse osmosis is used as a tertiary treatment for wastewater reclamation. However, sustainable management of the concentrate (ROC) is challenging, due to the need for treatment and/or disposal. The objective of this research was to investigate the efficiency of homogeneous and heterogeneous Fenton-like oxidation processes in removing propoxur (PR), a micro-pollutant compound, from synthetic ROC solution in a submerged ceramic membrane reactor operated in a continuous mode.

Comparing the effects of Cu-Ti/RuO-IrO electrode configuration on the electro-reduction of nitrate.

Nitrate pollution is a global problem as it affects both the environment and human health. The objective of this research was to study the effect of electrode configuration on the electro-reduction of nitrate. Coaxial cylindrical (inner rod and outer tube copper cathodes) and vertical plate parallel copper cathodes paired with Ti/RuO-IrO (rod, tube, and plate) configurations were studied under various current densities and initial nitrate concentrations.

A hybrid iron oxyhydroxide agglomerates-ultrafiltration process for efficient removal of chromate.

Hexavalent chromium (Cr(VI)) is often detected in groundwater, surface water and soils. The objective of the research was to study a hybrid process of adsorption onto iron oxyhydroxide agglomerates (IOAs) and ultrafiltration (UF) for removal of Cr(VI) from aqueous solution. Initially, the adsorption of the chromium onto IOAs was characterized by SEM and Raman analyses.

Electrochemical removal of nitrate from a Donnan dialysis waste stream.

The objective of this work was to investigate electrochemical removal of nitrate from a high salinity waste stream generated by Donnan dialysis. Donnan dialysis for nitrate removal is a promising technique. It produces a distinctive composition of a high salinity waste stream of NaCl or NaSO that requires a viable disposal method.

Removal of silica from brackish water by integrated adsorption/ultrafiltration process.

A lab-scale unit of the hybrid continuous stirred tank reactor (CSTR) adsorption/ultrafiltration (UF) system was used to evaluate the removal efficiency of silica from brackish water. The semi-batch adsorption process was carried out using iron oxy/hydroxide agglomerates (IOAs) as adsorbent and hollow fiber ultrafiltration membrane as a barrier to the adsorbent passage to the product water. The effect of residence time, concentration of silica, and adsorbent dosage on the silica removal and UF membrane blockage was examined.

Modeling Remineralization of Desalinated Water by Micronized Calcite Dissolution.

A widely used process for remineralization of desalinated water consists of dissolution of calcite particles by flow of acidified desalinated water through a bed packed with millimeter-size calcite particles. An alternative process consists of calcite dissolution by slurry flow of micron-size calcite particles with acidified desalinated water. The objective of this investigation is to provide theoretical models enabling design of remineralization by calcite slurry dissolution with carbonic and sulfuric acids.

Rotating cylinder technique for assessing the effectiveness of anti-scalants.

A novel technique for evaluating the relative inhibition effectiveness of different anti-scalants is presented. The technique is based on the ability of anti-scalants to modify the scale deposition mechanism from mass transfer control to surface control. A rotating cylinder system which is known to provide well controlled mass transfer conditions is used to determine the scaling rate of a supersaturated solution dosed with various feed concentrations of an anti-scalant.

Adsorption-desorption mechanism of phosphate by immobilized nano-sized magnetite layer: interface and bulk interactions.

Phosphate adsorption mechanism by a homogenous porous layer of nano-sized magnetite particles immobilized onto granular activated carbon (nFe-GAC) was studied for both interface and bulk structures. X-ray Photoelectron Spectroscopy (XPS) analysis revealed phosphate bonding to the nFe-GAC predominantly through bidentate surface complexes. It was established that phosphate was adsorbed to the magnetite surface mainly via ligand exchange mechanism.

Synthesis, performance, and modeling of immobilized nano-sized magnetite layer for phosphate removal.

A homogeneous layer of nano-sized magnetite particles (<4 nm) was synthesized by impregnation of modified granular activated carbon (GAC) with ferric chloride, for effective removal of phosphate. A proposed mechanism for the modification and formation of magnetite onto the GAC is specified. BET results showed a significant increase in the surface area of the matrix following iron loading, implying that a porous nanomagnetite layer was formed.

Comparative disinfection efficiency of pulsed and continuous-wave UV irradiation technologies.

Pulsed UV (PUV) is a novel UV irradiation system that is a non-mercury lamp-based alternative to currently used continuous-wave systems for water disinfection. PUV polychromatic irradiation disinfection efficiency was compared to that from continuous-wave monochromatic low-pressure (LP) and polychromatic medium-pressure (MP) UV systems, using two types of actinometry (ferrioxalate and iodide-iodate) and an absolute spectral emission method for fluence measurement. All three methods were in good agreement.

Inactivation of E. coli, B. subtilis spores, and MS2, T4, and T7 phage using UV/H2O2 advanced oxidation.

The goal of this study was to evaluate the potential of an advanced oxidation process (AOP) for microbiocidal and virucidal inactivation. The viruses chosen for this study were bacteriophage MS2, T4, and T7. In addition, Bacillus subtilis spores and Escherichia coli were studied.

Photodegradation of metolachlor applying UV and UV/H2O2.

Metolachlor is one of the most widely used herbicides in the world for controlling weeds. It has been detected in both ground and surface waters in the United States, and there are rising concerns in regard to its health risks and in developing effective treatment processes for its removal from water. Degradation of metolachlor via ultraviolet (UV) photolysis and an UV/hydrogen peroxide advanced oxidation process (AOP) was studied.

Photolysis, oxidation and subsequent toxicity of a mixture of polycyclic aromatic hydrocarbons in natural waters.

Photodegradation of a mixture of three polycyclic aromatic hydrocarbons fluorene (FLU), dibenzofuran (DBF), and dibenzothiophene (DBT) using UV and UV/HO processes was studied. Treating a mixture of the PAHs stimulated a more realistic contamination composition present in polluted water. Effects of pH, PAH concentration, and water matrix composition on removal rates and efficiencies of these compounds are discussed.

Aqueous photodegradation and toxicity of the polycyclic aromatic hydrocarbons fluorene, dibenzofuran, and dibenzothiophene.

Decay kinetics resulting from the application of UV and UV/H(2)O(2) to the polycyclic aromatic hydrocarbons (PAHs) fluorene, dibenzofuran and dibenzothiophene was studied. Batch experiments were conducted with both low-pressure monochromatic (253.7nm) and medium pressure polychromatic (200-300nm) UV sources alone or in the presence of up to 25mg/L hydrogen peroxide, in a quasi-collimated beam apparatus.

Relative rate constants of contaminant candidate list pesticides with hydroxyl radicals.

The objective of this study was to establish the relative rate constants for the reactions of selected pesticides (linuron, diuron, prometon, terbacil, diazinon, dyfonate, terbufos, and disulfoton) listed on the U.S. EPA Contaminant Candidate Listwith UV and hydroxyl radicals (*OH).

Degradation and by-product formation of diazinon in water during UV and UV/H(2)O(2) treatment.

Kinetics and degradation products resulting from the application of UV and UV/H(2)O(2) to the US EPA Contaminant Candidate List pesticide diazinon were studied. Batch experiments were conducted with both monochromatic (low pressure [LP] UV 253.7 nm) and polychromatic (medium pressure [MP] UV 200-300 nm) UV sources alone or in the presence of up to 50 mg l(-1) H(2)O(2), in a quasi-collimated beam apparatus.

Degradation of the pharmaceutical metronidazole via UV, Fenton and photo-Fenton processes.

Degradation rates and removal efficiencies of Metronidazole using UV, UV/H2O2, H2O2/Fe2+, and UV/H2O2/Fe2+ were studied in de-ionized water. The four different oxidation processes were compared for the removal kinetics of the antimicrobial pharmaceutical Metronidazole. It was found that the degradation of Metronidazole by UV and UV/H2O2 exhibited pseudo-first order reaction kinetics.

Trihalomethanes aqueous solutions sono-oxidation.

Ultrasonic (US) irradiation, hydrogen peroxide (H(2)O(2)), Fenton's oxidation and the combination of the processes were investigated for destruction and removal of the following trihalomethanes (THMs) compounds from aqueous solutions: CHCl(3), CHBrCl(2), CHBr(2)Cl, CHBr(3), and CHI(3). H(2)O(2) had no significant effect on the THMs sonodegradation. The coupled US and Fenton processes did not affect the CHCl(3), CHBrCl(2), and CHBr(2)Cl sonolysis efficiency.

Effect of various reaction parameters on THMs aqueous sonolysis.

Ultrasonic irradiation was investigated for destruction of the following THMs: CHCl(3), CHBrCl(2), CHBr(2)Cl, CHBr(3), and CHI(3). The effect of pH, temperature, and the organics initial concentration on the THMs sonodegradation at acoustic frequency of 20 kHz was studied. An increase of the solution temperature resulted in a faster sonodegradation rates.

Sonochemical removal of trihalomethanes from aqueous solutions.

In this research, ultrasound irradiation was employed to degrade the trihalomethanes, THMs: CHCl3, CHBrCl2, CHBr2Cl, CHBr3, and CHI3. The kinetics reaction rates and removal efficiencies of the THMs compounds, as a sole component in the aqueous solutions, were studied. Batch experiments were conducted at an ultrasonic frequency of 20 kHz and acoustic intensity of 3.

Mechanisms and inorganic byproducts of trihalomethane compounds sonodegradation.

Organic pollutants can be sonodegraded by two pathways: pyrolysis, oxidation by free radicals, or the combination of both. The sonolytic degradation mechanisms and byproducts formation of aqueous trihalomethanes (THMs) were investigated at acoustic frequency of 20 kHz. The main sonodegradation mechanism of the chloroform, dichlorobromomethane, dibromochloromethane, and bromoform was found to be pyrolysis.