Muftah H. El-Naas

Biodegradation of phenol by Pseudomonas putida immobilized in polyvinyl alcohol (PVA) gel

Batch experiments were carried out to evaluate the biodegradation of phenol by Pseudomonas putida immobilized in polyvinyl alcohol (PVA) gel pellets in a bubble column bioreactor at different conditions. The bacteria were activated and gradually acclimatized to high concentrations of phenol of up to 300 mg/l. The experimental results indicated that the biodegradation capabilities of P. putida are highly affected by temperature, pH, initial phenol concentration and the abundance of the biomass. The biodegradation rate is optimized at 30 degrees C, a pH of 7 and phenol concentration of 75 mg/l. Higher phenol concentrations inhibited the biomass and reduced the biodegradation rate. At high phenol concentration, the PVA particle size was found to have negligible effect on the biodegradation rate. However, for low concentrations, the biodegradation rate increased slightly with decreasing particle size. Other contaminants such heavy metals and sulfates showed no effect on the biodegradation process. Modeling of the biodegradation of phenol indicated that the Haldane inhibitory model gave better fit of the experimental data than the Monod model, which ignores the inhibitory effects of phenol.

Assessment of electrocoagulation for the treatment of petroleum refinery wastewater.

Batch electrocoagulation experiments were carried out to evaluate the removal of sulfate and COD from petroleum refinery wastewater using three types of electrodes: aluminum, stainless steel, and iron. The effects of current density, electrode arrangement, electrolysis time, initial pH, and temperature were investigated for two wastewater samples with different concentrations of COD and sulfate. The experimental results indicated that the utilization of aluminum, as anode and cathode, was by far the most efficient arrangement in the reduction of both the contaminants. The treatment process was found to be largely affected by the current density and the initial composition of the wastewater. Although electrocoagulation was found to be most effective at 25 degrees C and a pH of 8, the influence of these two parameters on the removal rate was not significant. The results demonstrated the technical feasibility of electrocoagulation as a possible and reliable technique for the pretreatment of heavily contaminated petroleum refinery wastewater.

Reduction of COD in refinery wastewater through adsorption on date-pit activated carbon.

Experiments were carried out to evaluate the batch adsorption of COD from petroleum refinery wastewater on a locally prepared date-pit activated carbon (DP-AC), and its adsorption effectiveness was compared to that of commercially available BDH activated carbon (BDH-AC). Adsorption equilibrium and kinetic data were determined for both adsorbents and fitted to several adsorption isotherm and kinetics models, respectively. The Langmuir monolayer isotherm fitted well the equilibrium data of COD on both adsorbents; whereas, the kinetics data were best fitted by the pseudo-second order model. Modeling of the controlling mechanisms indicated that both intrinsic kinetics and mass transfer contributed to controlling the adsorption process. Mass transfer seemed to be the dominant mechanism at low COD content, while intrinsic kinetics dominates at high concentrations. In general, the adsorption effectiveness of locally prepared DP-AC was proven to be comparable to that of BDH-AC. Therefore, DP-AC can be utilized as an effective and less expensive adsorbent for the reduction of COD in refinery wastewater.

Aerobic Biodegradation of Phenols: A Comprehensive Review

Phenol and its derivatives are hazardous pollutants that are highly toxic even at low concentrations. The management of wastewater containing high concentrations of phenols represents major economical and environmental challenges to most industries. Biotechnology has been very effective in dealing with major environmental challenges through utilizing different types of bacteria and biocatalysts to develop innovative processes for the biodegradation, biotreatment, and biosorption of various contaminants and wide range of hazardous materials. Biological treatment has proved to be the most promising and most economical approach for the removal of many organic water pollutants such as phenol. Numerous studies have been published in the literature dealing with the biodegradation of phenols utilizing different types of biomasses and different types of reactors. The authors offer a comprehensive review of the present research on the biodegradation of phenols and presents trends for future research and development, with emphasis on an integrated approach that may be adopted to get synergistically enhanced removal rates and to treat the contaminated effluents in an ecologically favorable process.

Removal of aluminum from aqueous solutions by adsorption on date-pit and BDH activated carbons.

The use of a locally prepared date-pit activated carbon and the commercially available BDH activated carbon for the removal of trivalent aluminum from aqueous solutions was examined at various conditions. In the acidic range of aluminum solubility (up to pH value of 4), both adsorbents exhibited maximum (almost equivalent) capacities for adsorbing aluminum at the pH value of 4. Date-pit activated carbon was more capable of adsorbing traces or low concentrations of aluminum ions in the solution. At low initial concentrations of aluminum and low pH, the uptake of aluminum using date-pit activated carbon was 0.305 mg/g, while that using BDH activated carbon was only 0.021 mg/g. However, the BDH activated carbon was more effective in adsorbing aluminum with high concentrations and low pH. Furthermore, date-pit activated carbon exhibited higher initial adsorption rates as compared to BDH, which showed higher rates at longer periods of time.

A comprehensive review of electrocoagulation for water treatment: Potentials and challenges

Electrocoagulation is an effective electrochemical approach for the treatment of different types of contaminated water and has received considerable attention in recent years due its high efficiency in dealing with numerous stubborn pollutants. It has been successful in dealing with organic and inorganic contaminants with negligible or almost no generation of by-product wastes. During the past decade, vast amount of research has been devoted to utilizing electrocoagulation for the treatment of several types of wastewater, ranging from polluted groundwater to highly contaminated refinery wastewater. This paper offers a comprehensive review of recent literature that has been dedicated to utilizing electrocoagulation for water treatment, focusing on current successes on specific applications in water and wastewater treatment, as well as potentials for future applications. The paper examines such aspects as theory, potential applications, current challenges, recent developments as well as economical concerns associated with the technology. Most of the recent EC research has been focusing on pollutant-specific evaluation without paying attention to cell design, process modeling or industrial applications. This review attempts to highlight the main achievements in the area and outlines the major shortcomings with recommendations for promising research options that can enhance the technology and broaden its range of applications.

Reject Brine Management

Desalination has been growing rapidly as an industry and as a field of research that combines engineering and science to develop innovative and economical means for water desalting. Many countries in the world, especially in the Middle East, depend heavily on seawater desalination as a major source of drinking water and have invested considerable efforts and financial resources in desalination research and training. Desalination plants have seen considerable expansion during the past decade as the need for potable water increases with population growth. It is estimated that the world production of desalination water exceeds 30 million cubic meters per day and the desalination market worldwide is expected to reach

A Novel Plasma Technique to Stimulate Tight Carbonate Rocks

30 billion by 2015. One of the major economical and environmental challenges to the desalination industry, especially in those countries that depend on desalination for potable water, is the handling of reject brine, which is the highly concentrated waste by-product of the desalination process. It is estimated that for every 1 m3 of desalinated water, an equivalent amount is generated as reject brine. The common practice in dealing with these huge amounts of brine is to discharge it back into the sea, where it could result, in the long run, in detrimental effects on the aquatic life as well as the quality of the seawater available for desalination in the area. Although technological advances have resulted in the development of new and highly efficient desalination processes, little improvements have been reported in the management and handling of the major by-product waste of most desalination plants, namely reject brine. The disposal or management of desalination brine (concentrate) represents major environmental challenges to most plants, and it is becoming more costly. In spite of the scale of this economical and environmental problem, the options for brine management for inland plants have been rather limited. These options include: discharge to surface water or wastewater treatment plants; deep well injection; land disposal; evaporation ponds; and mechanical/thermal evaporation. Reject brine contains variable concentrations of different chemicals such as anti-scale additives and inorganic salts that could have negative impacts on soil and groundwater. This chapter highlights the main concerns as well as the environmental and economical challenges associated with the generation of large amounts of reject brine as a by-product of the desalination process. The chapter also outlines and compares the most common options for the treatment or disposal of reject brine. The chapter focuses on a novel approach to the management of reject brine that involves chemical reactions with carbon dioxide in the

PHENOL BIODEGRADATION BY RALSTONIA PICKETTII EXTRACTED FROM PETROLEUM REFINERY OIL SLUDGE

Tight formations are normally fractured using different fluids under high pressure to improve well permeability and consequently improve productivity. In this paper, a new sophisticated technique is proposed to treat tight formations, especially those containing large deposits of heavy oil. The technique consists of exposing the wellbore to an argon plasma jet to insure instantaneous and efficient heat transfer to the surrounding wellbore rocks. The high temperature associated with the plasma jet changes the basic properties of the rock, resulting in a significant increase in its porosity and permeability. In this study the effect of high temperature on the carbonate rock porosity and permeability is investigated. Limestone rocks were subjected to high temperatures ranging from 800 to 1200°C. At temperatures beyond 600°C, the carbonate rock decomposes to form calcium oxide and carbon dioxide. Thermogravimetric analysis (TGA) of carbonate samples indicated that the rate of decomposition at atmospheric pressure depended mainly on reaction temperature. At low temperatures, the rate of reaction was so slow that only 5% of the carbonate converted to calcium oxide in a period of 1 h, while at 1000°C complete conversion was achieved in 5 min. The changes of the pore structure under different temperatures were also observed using scanning electron microscope (SEM). Porosity and permeability analysis of heated carbonate samples indicated that the porosity and permeability increased by 100% and 4500%, respectively, at 1000°C.

Microbial Degradation of Chlorophenols

Phenol-degrading bacterial strains have been extracted from oil-sludge samples collected from a local refinery. A selective medium was used to isolate the active strain capable of utilizing phenol as a sole carbon source, which was identified as Ralstonia pickettii. The growth kinetics of mixed and isolated R. pickettii suspensions were investigated using different initial concentrations of phenol in the range of 25 to 200 g m−3 at 35°C and pH of 8.5. The results were compared to those of a commercially available mixed bacterial suspension, which was either acclimatized to 100 g m−3 phenol concentration, extracted from PVA particles that were subjected to real petroleum refinery wastewater containing phenol, or an isolated active strain grown on a selective medium that was identified as Pseudomonas putida. The effect of substrate inhibition was observed using all bacterial suspensions, and the growth results were used to determine the parameters of a suitable kinetic model. It was found that the phenol biodegradation ability of the indigenous bacteria, R. pickettii, isolated from refinery sludge was comparable to that of the commercially available bacteria.