Waid Omar

Bio: Waid Omar is an academic researcher from Al-Balqa` Applied University. The author has contributed to research in topics: Supersaturation & Seawater. The author has an hindex of 13, co-authored 36 publications receiving 452 citations. Previous affiliations of Waid Omar include King Faisal University & Yanbu Industrial College.

On the performance of electrocoagulation-assisted biological treatment processes: a review on the state of the art.

Abstract: The combined treatment systems have become a potential alternative to treat highly polluted industrial wastewater to achieve high-quality treated effluents. The current review focuses on the treatment systems compromising electrocoagulation (EC) as a pretreatment step followed by a biological treatment step. The reasons for applying EC as a pretreatment process were mainly to (1) detoxify the wastewater by removing inhibitors of the biotreatment step or (2) to remove the major part of the COD or (3) the dissolved materials that could cause fouling to membrane bioreactors or (4) to increase the activity of the microorganisms. This combination represents a new and promising application characterized by higher performance and removal efficiency. The main published findings related to this application are presented and analyzed. Besides, the statistical models used to optimize the process variables and the kinetics of microorganism growth rate are discussed herein. Most of the previous investigations were conducted in a laboratory-scale level with biologically treated water as a feed to the EC process. Only a few works applied a hybrid system consisting of the biological step and the EC step. In all studies, improved performance and higher removal efficiencies of the combined process were achieved particularly when applying aluminum electrodes, providing more than 95% removal efficiency. Many researchers have reported that they had faced a significant problem in the operation of the electrocoagulation process associated with the reduction of electrodes’ efficiency caused by deposits of the coagulation complex. This problem needs to be effectively resolved.

Solid Liquid Equilibrium, Metastable Zone, and Nucleation Parameters of the Oxalic Acid−Water System

Abstract: Measurements of the solubility and metastable zone for the oxalic acid−water system were obtained. The solubility was measured within the temperature range from 284.19 to 352.02 K. The mole fractio...

Application of Ultrasonics in the On-line Determination of Supersaturation

Abstract: An ultrasonic technique is used to develop a method based on the measurement of both ultrasonic velocity and temperature of the supersaturated media for the on-line determination of the supersaturation. It is demonstrated by the example of aqueous K 2 SO 4 solution in a seeded batch crystallizer. The feasibility of this technique was investigated using a commercial available sensor. The experimental measurements for the desupersaturation versus time trajectory proved that this technique can be successfully employed to measure supersaturation with sufficient accuracy and precision. Such sensor is preferred in the on-line application due to its fast response and the availability to be applied directly in the slurries without any need to the solid-liquid separation.

Rejection of salt mixtures from high saline by nanofiltration membranes

Abstract: Nanofiltration (NF) membranes have recently been employed as pretreatment unit operations in seawater desalination processes and as partial demineralization to seawater. The present paper investigates the performance of selected commercial NF membranes to reject salts of high concentrations at salinity levels representative of brackish and sea water. Two commercial nanofiltration membranes (NF90 and NF270) have been investigated in detail to study their performance in filtering aqueous solutions containing different salt mixtures in a cross-flow NF membrane process within the pressure range from 4 to 9 bar. Spiegler-Kedem model (SKM) was used to fit the experimental data of rejection with the permeate flux. The results showed that NF90 membrane was shown to have a distinct ability to reject both monovalent and divalent ions of all investigated mixtures with very reasonable values but with relatively low flux. This will make NF90 more suitable for the application in the pretreatment of desalination processes. On the other hand, NF270 can reject monovalent ions at relatively low values and divalent ions at reasonable values, but at very high permeate flux. The SKM model only fitted well the experimental data of divalent ions in salt mixture. Based on the evaluation of the overall performance of NF90 and NF270 membranes, their distinct ability to reject salts at high salinity from seawater is considered an advantage in the field of pretreatment of seawater feed to desalination units.

Influence of crystallization conditions on the mechanism and rate of crystal growth of potassium sulphate

Abstract: Growth rate of potassium sulfate crystals was studied in a fluidized bed crystallizer. Higher growth rates were observed at larger bed heights. Larger crystals grow faster than smaller size crystals due to the changed fluid dynamics. The growth rate was found to be very sensitive to the pH value of the solution. The growth rate increases with increasing the pH value and the increase of growth in the acidic medium is faster than in the basic medium. The presence of small amounts of Cr 3+ ions reduces the growth rate of potassium sulfate dramatically. The presence of Cr 3+ ions lowers the saturation temperature and increases the width of the metastable zone, i.e. shifts the metastability of the solution to be at lower level of supersaturation.