Anton Purnama

Boundary retention effects upon contaminant dispersion in parallel flows

Mass transfer between a flowing region and an adjacent stationary medium can greatly alter the overall contaminant dispersion. Here, an extension is given of Taylors (1953) method to encompass this class of complications. The only mathematical assumption made is that the mass flux transfer at the boundary depends linearly upon the concentration at earlier times. Expressions are derived for the longitudinal shear dispersion coefficient. Detailed results are presented for the effects both of reactions and of retention at the bed upon contaminant dispersion in turbulent open-channel flow.

Two outfalls in an estuary : Optimal wasteload allocation

When two outfalls are discharging wastewater into a narrow (rapidly mixed) estuary within a tidal excursion of each other, the pollutant concentrations experienced at the two outfall sites are strongly inter-dependent. It is shown how a given total tidally integrated effluent load can be allocated optimally between the two outfalls so that the peak concentration (in time and position) of the principal contaminant species is minimized. Graphical results show the dependence of the wasteload allocation and of the peak concentration upon the pollutant decay rate, the separation between the outfalls and the fresh water flow along the estuary. Optimization with respect to any one of a mixture of pollutants is close to optimal for a wide range of other pollutants.

The dispersion of chemically active solutes in parallel flow

The irreversible loss of chemically active solutes by reactions at the boundary and the reversible adsorption on the flow boundary have been observed experimentally. Removal of solutes at the boundary alone reduces the rate of longitudinal shear dispersion; in contrast, the retention of solutes in the region close to the flow boundary alone increases the rate of longitudinal shear dispersion. Here an extension is given of the method of moments for chemically active solute dispersion to encompass this class of complications. Expressions are derived for the longitudinal shear dispersion coefficient and skewness. The results are applied to the practical example of a chemical flow reactor to quantify the effect of flow boundary retention when there exists reaction at the pipe wall. 17 refs.

Recent Progress in Desalination, Environmental and Marine Outfall Systems

The huge quantities of water produced along with oil make production of water one of the main challenges in the oil and gas industry. In the past, water produced in oil production was considered a tiresome by-product which represented a significant liability and cost to oil and gas production. Recently this attitude has changed and this water is now seenmore as a resource than a by-product. By 2025, 2.8 billion people (from 48 countries) will be living in water-scarce and water-stressed countries. The Sultanate of Oman is considered a semi-arid country where the average annual rainfall is about 100 mm. Petroleum Development Oman (PDO) produces around 700,000 m/day of water associated with hydrocarbon production. Currently under half of this amount is injected back into reservoirs as water for reservoir management. The production of excessive quantities of water is the reason behind abandoning oil and gas wells, leaving huge quantities of hydrocarbons behind. Upgrading of low quality water (i.e. oil production water) for greening the desert or growing biofuels is becoming a strategic enabler for the sustainable development of remote oil fields. Although opportunities exist for the beneficial use of oil production water, there may be situations where treatment may not be economically feasible. In addition to volume, water quality is the other key determinant of suitablemanagement options. Due to the poor quality of oil production water which contains a complex M. Al-Haddabi (*) School of Chemical and Petroleum Engineering, Curtin University, GPO Box U1987, Perth, WA 6845, Australia College of Agricultural and Marine Sciences, Sultan Qaboos University, Muscat, Oman e-mail: mans99@squ.edu.om H. Vuthaluru • H. Znad School of Chemical and Petroleum Engineering, Curtin University, GPO Box U1987, Perth, WA 6845, Australia e-mail: H.Vuthaluru@exchange.curtin.edu.au; H.Znad@curtin.edu.au M. Ahmed College of Agricultural and Marine Sciences, Sultan Qaboos University, Muscat, Oman e-mail: ahmedm@squ.edu.om

An Overview: Desalination, Environmental and Marine Outfall Systems

Desalination is the method of removing salts from brackish or sea water in order to produce fresh water. Desalting is a natural and continual process which is an essential part of the water cycle. After rainfall, rain water carries dissolved minerals and other materials along the way to the sea, which makes the water increasingly salty. Through the sun’s energy, the evaporation of water leaves the salts behind and the resulting water vapor forms clouds that produce rain thus continuing the water cycle.

Modeling Dispersion of Brine Discharges from Multiple Desalination Outfalls

Discharging brine effluents through long sea outfalls are an economic disposal strategy for coastal seawater desalination plants. The interactions of two or more brine discharge plumes are expected as many desalination outfalls often tend to be closely clustered together along open coastlines. A far field mathematical model using a two-dimensional advection diffusion equation in a highly simplified flat seabed is presented to study the dispersion and merging of brine discharge plumes in shallow coastal waters. The analytical solutions are illustrated graphically by plotting contours of concentration to replicate the overlapping plumes following discharges from multiple desalination outfalls. To assess the potential environmental impacts, the radius and the concentration at the end of the allocated mixing zone around the outfall are formulated. The compounded concentration at the edge of the regulatory mixing zone is then used as a measure for assessing the effectiveness of multiport diffusers over the single (port) outfall discharge. It is found that the modern engineering practice which installs a multiport diffuser at the end of the outfall pipe does minimize the impacts.

Simulation of Sediment Discharges during an Outfall Dredging Operation

CORMIX-GTS simulations are carried out to study suspended muddy sediment plumes following the discharge of the spoils taken from the seabed during a marine outfall pipeline dredging operation. Single port discharges are considered at three different locations at 400 m, 800 m, and 1200 m from the shoreline with water depths ranging from 3.5 m to 10.5 m. For discharges in the shallow near-shore region at 400 m offshore, most of the dredge materials are deposited at the seabed and the simulated suspended sediment plumes are found to be carrying a concentration of less than 1 kg/m3 of mainly fine silt and clay. For discharges in the deeper far-shore region at 1200 m offshore, the sediment plumes are more elongated and carrying a concentration of more than 3 kg/m3. Iterative simulations are also conducted to analyse the inherent uncertainty in the input data by varying the ambient velocity and the port’s horizontal angle of discharge.

Environmental Quality Standards for Brine Discharge from Desalination Plants

When many desalination plants are operated closely together along coastal areas, the continuous brine discharges through marine outfall systems from these cluster plants can have a significant impact on the coastal marine environment. The potential impact can be minimized and regulated by treatment and recycling technologies, by limiting the concentration values of brine at the discharge point and also by imposing concentration values within a prescribed circular mixing zone in the coastal waters via the outfall design.

Numerical analysis and optimization : NAO-III, Muscat, Oman, January 2014

A Conic Representation of the Convex Hull of Disjunctive Sets and Conic Cuts for Integer Second Order Cone Optimization.- Runge-Kutta methods for ordinary differential equations.- A Positive Barzilai-Borwein-Like Stepsize and An Extension for Symmetric Linear Systems.- Necessary Optimality Conditions for the Control of Partial Integro-Differential Equations.- The AMPL Modeling Language-an Aid to Formulating and Solving Optimization Problems.- An Interior-Point L1-Penalty Method for Nonlinear Optimization.- An L1-Penalty Scheme for the Optimal Control of Elliptic Variational Inequalities.- Dynamics Characterization Based Geo-Statistical Prior Sampling.- Solving Multiscale Linear Programs Using the Simplex Method in Quadruple Precision.- Real and Integer Extended Rank Reduction Formulas and Matrix Decompositions: A Review.- Distributed Block Coordinate Descent for Minimizing Partially Separable Functions.- Models for Optimization of Power Systems.- On Chubanovs Method for Solving a Homogeneous Inequality System.