Rashid I. Allayla

Modeling transport and biodegradation of BTX compounds in saturated sandy soil

Abstract Numerical models have been developed using finite difference and orthogonal collocation methods to simulate one dimensional transport with time-dependent pore water velocity. The modeling process includes sorption given by linear isotherm and biodegradation given by a variety of kinetics such as first-order, zero-order, Monod, non-growth associated Monod (Michaelis-Menten), Haldane and many other inhibitory and non-inhibitory kinetics. A number of initial and boundary conditions such as Dirichlets, Neumans, mixed, decaying, etc. have been modeled. The method of finite difference (for first order/zero order model only) and the method of orthogonal collocation (for all kinetics models) have been used to solve the governing transport equation. Numerical solutions have been verified with existing analytical solutions for special cases. Three models (first-order and/or zero-order, non growth associated Michaelis Menten, and Monod) have been inverted using a Gauss-Marquardt-Levenberg algorithm to assess the transport parameters. The models have been used to simulate one dimensional transport of BTX compounds in a pilot scale sand tank model. The data have been found to fit to all three kinetic models with acceptable coefficient of determination (R2) and parameter values. The high concentration data have been found to fit better to the Michaelis Menten and the Monod models than the first order/zero order model.

Tertiary treatment of sewage effluent via pilot scale slow sand filtration

Abstract In view of limited information available about the performance of actual size slow sand filtration as a tertiary process in sewage treatment a pilot scale study was conducted over a period of one year using the secondary treated effluent from North Aramco Wastewater Treatment Plant, Dhahran, at a flow rate of 0.16 m hr‐1 (2L min‐1) to determine the process efficiency. Two sizes of local sand, i.e., effective size (ES) = 0.31, uniformity coefficient (UC) = 2.00; and ES = 0.56, UC = 1.64, were evaluated in terms of removal of major pollution parameters such as organic matter, micro‐organisms and nutrients. Effective range of the filter depth was also investigated by conducting the experiments at three different depths of the sand bed, i.e., 135, 105, and 55 cm for each size of the sand. It was found that removals of BOD, COD, standard plate counts, nitrate, phosphate and sulphate vary from 79–92%, 40–60%, 88–93%, 17–30%, 8.3–84%, and 5–10%, respectively, at various sand depths for two different siz...

State‐of‐the‐art review of bioremediation studies

Abstract The state of the art bioremediation has been rapidly expanding during the last decade. Numerous articles are being published in a remarkable number of journals. Biodegradability of all possible organic pollutants is being tested in field and lab. New technologies are being discovered to biodegrade even the most recalcitrant organic chemicals. Many new books on bioremediation studies arc also being written and edited. Information is scattered in books, journals, conferences and many other sources. The objective of this paper is to summarize the available existing literature on bioremediation studies. Issues covered are bioremediation in context with other remediation technologies, biodegradability of different organic compounds under different condition as reported in lab and fields studies, factors affecting bioremediation, and review of existing literature on modeling and case studies.

Groundwater contamination studies - The state-of-the-art

Abstract With the increasing sense of awareness about our environment and the recognition of the need for its protection, the study of solute transport related to groundwater contamination has become the focus of numerous researchers. Different investigators approached the problem from many view points, and the resulting achievements are so extensive and scattered that it seems essential to inventory the completed works. This paper presents a systematic study of the available theoretical and experimental works. A complete picture of the present status of the problem is also provided. Issues that remain obscure or unaddressed by the current day investigators are pointed out to facilitate future research directions and/or alternatives to advance technology for a greater understanding and more comprehensive analyses of the solute transport phenomena related to groundwater contamination.

EFFECT OF GROUNDWATER VELOCITY ON PILOT SCALE BIOREMEDIATION OF GASOLINE CONTAMINATED SANDY AQUIFERS

The effect of groundwater velocity onbioremediation of gasoline contaminated sandy soil hasbeen investigated using a pilot scale sand tank model.The effect of hydrogen peroxide and contaminantconcentration are also included. A factorialexperiment has been conducted to study three factors,groundwater velocity, inlet BTX concentration andhydrogen peroxide dose. Observed concentration datacollected from the sand tank model have been used forestimating the transport parameters. Three differentbiodegrdation kinetics, namely first-order/zero-order,Monod and Michaelis Menten (a modification of Monodkinetics considering no microbial growth) kineticshave been used to model the biodegration. The datahave been found to fit all three models withacceptable coefficient of regression. Groundwatervelocity has been found to be the most significantfactor governing the biodegradation rate constants(determined from the first-order rate constant) of BTXcompounds. Hydrogen peroxide dose and BTX concentration have also been found to be significant factors.

Scenario planning for water resources: a Saudi Arabian case study

ABSTRACT Uncommonly rapid development of the oil-rich Eastern Province of Saudi Arabia has led to heavy stresses on the local groundwater resources and there has arisen concern for the adequacy of supply to sustain future growth. Whereas oil is the only significant export commodity, the demand for it has an important and immediate impact on water exploitation activities. In this article four development scenarios are considered, each resulting in a specific water abstraction pattern. The hydrologic consequences of each scenario are evaluated by means of a digital hydraulic groundwater model.

Numerical modeling of a multi-aquifer system in Eastern Saudi Arabia

Abstract A numerical quasi-three-dimensional groundwater flow model was constructed for a multiequifer system in eastern Saudi Arabia to determine the hydraulic properties of the system and to evaluate the consequences of various development alternatives. The aquifers modeled were the Alat, the Khobar and the Umm Er Radhuma of Paleocene-Eocene age, which are hydraulically connected with intervening aquitards. Steady-state and transient model calibrations demonstrated considerable spatial variations in transmissivities of the aquifers and vertical leakances of the aquitards. The reliabilities of these parameters were checked through sensitivity analysis. The model results have confirmed the hydraulic interaction between the aquifers via intervening aquitards. The calibrated model was subsequently utilized to predict responses of the aquifers over a planning horizon of 14 years (1987–2000) under three development alternatives. The model results indicated that the Khobar aquifer has a limited productivity in the Abqaiq region where dewatering is expected to occur if the existing trends in extraction rates are continued. The Umm Er Radhuma aquifer, however, has demonstrated relatively low declines in water levels, indicating very high potential for productivity. Freezing the current extraction rates throughout the planning period showed little change from the present conditions. Gradual introduction of conservation measures would be more effective in ensuring the long-term productivity of the aquifers.

Experimental study and numerical simulation of denitrification in saturated porous media

The effect of denitrification on the behavior of nitrate in saturated sandy soil was studied in the laboratory and the results were compared with the temporal and spatial concentration of nitrate in nonreactive (without denitrification) and reactive (with denitrification) cases. A laboratory model was fabricated to study steady one-dimensional flow and to transport nitrate with or without denitrification. Denitrification at various rates has been simulated with varied C∶N ratios and detention time. Retardation constant, dispersivity, and degradation constants have been computed using existing analytical models supporting adsorption and zero and/or first order production or decay. It was found that such analytical models can be used to fit the concentration of nitrate in saturated porous media for a C∶N ratio between 2 and 5.