Omar Chaalal

Arsenic removal in drinking water: Impacts and novel removal technologies

Abstract Arsenic contamination of surface and subsurface waters has been reported in many parts of the world; the problem is particularly severe in Bangladesh. In view of epidemiological problems of arsenic ingestion, it is imperative to look for an effective technology for removal of arsenic in drinking water. Column studies were conducted at the University of Regina using manganese greensand to remove arsenic from drinking water. Iron addition was found to be necessary to achieve effluent arsenic level of 25 μg/L in manganese greensand filtration system. In view of the possible regulatory requirement to achieve arsenic levels of less than 5 to 10 μg/L, further studies were conducted using iron oxide-coated sand (IOCS). Batch studies with IOCS showed that effluent arsenic level could be achieved below 5 to 10 μg/L levels. High adsorption capacity (136 μg/g) of the IOCS showed that the media could be effectively used for achieving less than 5 μg/L of effluent arsenic level in the treatment systems, particularly in small water utilities. A preliminary study was conducted to remove arsenic from drinking water using rusticles containing bacteria, and bacterial growth in arsenic solution was also studied.

Use of thermophilic bacteria for bioremediation of petroleum contaminants

Several strains of thermophilic bacteria were isolated from the environment of the United Arab Emirates. These bacteria show extraordinary resistance to heat and have their maximum growth rate around 60 80 C. This article investigates the potential of using these facultative bacteria for both in situ and ex situ bioremediation of petroleum contaminants. In a series of batch experiments, bacterial growth was observed using a computer image analyzer following a recently developed technique. These experiments showed clearly that the growth rate is enhanced in the presence of crude oil. This is coupled with a rapid degradation of the crude oil. These bacteria were found to be ideal for breaking down long-chain organic molecules at a temperature of 40 C, which is the typical ambient temperature of the Persian Gulf region. The same strains of bacteria are also capable of surviving in the presence of the saline environment that can prevail in both sea water and reservoir connate water. This observation prompted ...

Uptake of Heavy Metals by Microorganisms: An Experimental Approach

Abstract Contamination in drinking water is the most common form of environmental problems encountered in water resources management. Some contaminants, present accidentally in drinking water, are very difficult to remove, such as heavy elements that are products of industrial waste. Lead is one of the most difficult-to-remove elements. This paper proposes a novel process for removal of lead compounds contaminants from water. The proposed method shows great efficiency. The technique uses thermophilic bacteria found in the United Arab Emirates near Al-Ain town located in Abu-Dhabi Emirates. These bacteria were isolated and used in a reactor coupled with a membrane system. The bacteria, the stirrer and the membrane housed in the reactor are arranged in a distinctive way to form the novel bio-stabilization process proposed in this research. This proposed technique could be used at low cost and with great confidence in the purification of drinking water. The system was found to be adequate for concentrations of lead in the range of 5–40 ppm. At the end of the operation the lead concentration reaches the level allowed by the World Health Organization regulations.

Project of Increasing Oil Recovery from UAE Reservoirs Using Bacteria Flooding

Due to the recent decline in oil prices, most of the enhanced oil recovery (EOR) processes, and especially the ones typically recommended for light crude such as micelles, polymer, or miscible gas injection processes have become economically unattractive. The oil industry currently is in dire need of a reasonable cost process that can both technically and economically be successful. For this reason, a tremendous amount of research effort was directed at UAE University to investigate the possibility of using bacteria, which is a minor cost material, to improve the oil recovery in UAE oil reservoirs. This project focused initially on the study of the interfacial tension (IFT) between crudes from four different UAE reservoirs (BH, UZ, St, and UAD) and a thermophilic bacteria solution. The bacteria were obtained from local water tanks. The system temperature was varied between 30°-100°C and salinity ranged from 0 to 100,000 ppm. Tertiary bacteria solution core flooding experiments were then performed using carbonate rocks at reservoir conditions without injection of nutrient with the bacteria during the core flooding experiments. A good amount of effort was directed, throughout the work, to characterize the bacteria used and identify the mechanism by which bacteria works to improve the oil recovery. Results of these laboratory studies show an abrupt reduction in IFT at high salinity and high temperature (i.e. reservoir condition) for all studied systems except for the St crude, which was sulfur rich. The IFT decreased from 40 dynes/cm to 0.07 dynes/cm for most of the studied systems. Also, tertiary bacteria flooding at reservoir conditions, on average, resulted in an incremental oil recovery of 15 to 20% of the pore volume.

Effect of Temperature on Biodegradation of Crude Oil

An active strain of anaerobic thermophilic bacteria was isolated from the environment of the United Arab Emirates. This project studied the effect of temperature, salinity and oil concentration on biodegradation of crude oil. Oil weight loss, microbial growth and the changes of the crude oil asphaltene concentration are used to evaluate the oil degradation by this strain. A series of batch experiments was performed to study the effects of bacteria on the degradation of crude oil. The effects of oil concentration, bacteria concentration, temperature and salinity on the biodegradation were investigated. The temperatures of the studied systems were varied between 35 and 75°C and the salt concentrations were varied between 0 and 10%. Oil concentrations were ranged from 5 to 50% by volume. Experimental work showed the bacteria employed in this project were capable of surviving the harsh environment and degrading the crude oil at various conditions. Increasing the temperature increases the rate of oil degradation by bacteria. Increasing the oil concentration in general decreases the rate of bacteria oil degradation. Salinity plays a major role on the acceleration of biodegradation process of crude oil. An optimum salinity should be determined for every studied system. The finding of this project could be used in either the treatment of oil spill or in-situ stimulation of heavy oil wells.

Cleanup of an Offshore Emulsion Spill, An Experimental Approach

An emulsion leak during offshore oil production operations is a real problem facing the oil industry. No work has been reported in the literature covering a technique for offshore emulsion spill cleanup. A vacuum collection system was used in this project to study the possibility of mechanical removal of emulsion spills. The system consists of a sea water unit, emulsion-collecting system, vacuum unit, and air distributors. A number of operating parameters were tested, such as air flow rate 0.0167 × 103–0.15 × 103 m3/sec), emulsion spill thickness (0.6–3.5 mm), the height of water column in the emulsion removal system (0.40–0.85 m), and the collection unit hole size and density. The system has been tested before for the oil spill and has been found to be a simple, fast cleaning process, efficient with minimum cost. The results of this study indicated that hole density in the collection unit has an effect on the emulsion cleanup process, and increasing the air flow rate increases the amount of emulsion removed from the system until a certain rate at which the opposed effect was observed, i.e., the studied system exhibited an optimum air flow rate for the collection of emulsion. In addition, the height of the water column has an effect on the cleaning process; an optimum water column height is needed to be determined for any designed emulsion removal system similar to the system used in this study.

An Experimental Study of Fluid Motion in a Bioreactor Agitated by Line-Source Bubble Plumes

The focus of this study is the movement of the fluid contained in a rectangular bioreactor agitated by line-source bubble plumes. The research included visualization of fluid motion by white polystyrene beads and supported by intensive video recording. Water velocity at the surface and at the bottom, as well as the velocity along the depth, have been measured in two aerated rectangular vessels (36 × 10−3 m 3 and 2 m 3 in volume) using tap water, as a function of the characteristic velocity (qg)0.33. It was confirmed that the best location of the perforated tube was in the middle of tank and the minimum air flow rate to maintain particle suspension was reached when the aerated surface was a rectangular surface in which the length is twice the width. In addition, the relationship between the fluid velocity, air flow rate, height of the liquid and flow patterns were discussed. Finally, a correlation for the velocity in the liquid was developed and found to be adequate in the scale-up of aerated tanks agitated by an air curtain.

A new technique of solar bioremediation

Abstract Disinfection with solar energy has been in practice for centuries. This article uses this old technology and builds on some of its unique features in order to develop an effective method of bioremediation. Recently, a strain of thermophilic bacteria was isolated from the environment of the United Arab Emirates. These bacteria show extraordinary resistance to heat and have their maximum growth rate around 80°C. They are found to be extremely efficient in remediating petroleum contaminants in the presence of high salinity water (simulated seawater). This article investigates the potential of using these facultative bacteria in a bioreactor in conjunction with solar irradiation. The bioreactor, recently developed at the UAE University, uses air flow through a transverse perforated pipe in order to create effective mixing, leading to optimum growth environment for bacteria. Solar energy is used in two ways. UV radiation from the sun destroys most pathogens and creates an environment that offers little competition for the thermophilic bacteria that cannot be destroyed with the UV. Also, the second advantage of the solar energy is the increase in temperature of the reactor water to a level that is more suitable for growth of the thermophilic bacteria. Heat also decreases the viscosity and interfacial tension of the petroleum contaminant, leading to the profuse emulsification. Emulsification makes more bacteria available to the petroleum contaminant and enhances bioremediation. Detailed pictorial visualization performed with a computer image analyzer showed the extinction of bacteria other than the useful thermophilic bacteria and helped measure their growth. Finally, mathematical models are developed for determining the degradation rate in the presence of solar exposure. Corrections are made to accommodate both the effects of temperature, salinity, and solar intensity. To the best of the knowledge of the authors, this coupling has not been done before. Predictive runs are conducted to observe the role of various governing parameters prevalent in environmental applications of solar disinfection systems.

A New Method to Investigate the Suspension of Solid Particles in Rectangular Tanks Agitated by a Source-Line Bubble Plumes

Abstract It is well known that when mechanically agitated vessels are used, the forces applied by the agitator moving in the fluid contained in the vessel maintain flow patterns in the fluid. In the tanks under study, the flow patterns are maintained by an air curtain rising within the vessel. The movement produced by this air curtain interchanges fluid between different parts of the vessel, maintains particle suspension and promotes gentle mixing that has applications in the field of biotechnology. The experimental work carried out in this article is focused on the study of mixing and the behavior of solid particles, using an air curtain as the means of mixing. The research included the fluid motion visualized by white polystyrene beads, video recording and a new method to investigate the suspension of solid particles. The new method introduced an index of deviation from acceptable suspension and was used as a tool to select the best design of tank-aerator combination suitable for suspension. Experimentally, the suspension was found to be a function of air flow rate and the type of aerator used. Two distinct factors were identified, namely, the aerator location and the shape of the aerated tank. It was confirmed that the best location was in the middle of the tank, and the minimum air flow rate to keep all the particles in suspension was reached when the aerated surface was a rectangular surface in which the length is twice the width. In addition, a relationship between fluid velocity, air flow rate, flow patterns and baffles disposition are discussed. Finally, a correlation for the velocity in the liquid was developed and found to be adequate in the scale-up of aerated tanks agitated by an air curtain.