Lecture

Water Quality Modeling

Graph Chat

Chat with Graph Search

Ask any question about EPFL courses, lectures, exercises, research, news, etc. or try the example questions below.

DISCLAIMER: The Graph Chatbot is not programmed to provide explicit or categorical answers to your questions. Rather, it transforms your questions into API requests that are distributed across the various IT services officially administered by EPFL. Its purpose is solely to collect and recommend relevant references to content that you can explore to help you answer your questions.

In course

ENG-400: Water quality modeling

This course builds on environmental chemistry and microbiology taken in previous courses. The emphasis is on quantification using the public domain package, PHREEQC, which is an excellent computation tool. Numerous applications are investigated during the ...

Description

This lecture introduces Water Quality Modeling, covering topics such as the installation of PHREEQC software, alternative installation methods, and limitations of the software. It also explains the structure of a PHREEQC simulation, database reading, and the description of solutions. The lecture provides examples of chemical concentrations, mass to moles conversion, and balanced solutions. It concludes with a discussion on equilibrium constants and the importance of charge balance in solutions.

Instructor

David Andrew Barry

Research InterestsSubsurface hydrology, constructed wetlands, ecological engineering, in particular contaminant transport and remediation of soil and groundwater; more generally, models of hydrological and vadose zone processes; application of mathematical methods to hydrological processes; coastal zone sediment transport, aquifer-coastal ocean interactions; hydrodynamics and modelling of lakes.

Official source

Related concepts (32)

Chemical equilibrium

In a chemical reaction, chemical equilibrium is the state in which both the reactants and products are present in concentrations which have no further tendency to change with time, so that there is no observable change in the properties of the system. This state results when the forward reaction proceeds at the same rate as the reverse reaction. The reaction rates of the forward and backward reactions are generally not zero, but they are equal. Thus, there are no net changes in the concentrations of the reactants and products.

Molar concentration

Molar concentration (also called molarity, amount concentration or substance concentration) is a measure of the concentration of a chemical species, in particular of a solute in a solution, in terms of amount of substance per unit volume of solution. In chemistry, the most commonly used unit for molarity is the number of moles per liter, having the unit symbol mol/L or mol/dm3 in SI unit. A solution with a concentration of 1 mol/L is said to be 1 molar, commonly designated as 1 M.

Equilibrium constant

The equilibrium constant of a chemical reaction is the value of its reaction quotient at chemical equilibrium, a state approached by a dynamic chemical system after sufficient time has elapsed at which its composition has no measurable tendency towards further change. For a given set of reaction conditions, the equilibrium constant is independent of the initial analytical concentrations of the reactant and product species in the mixture.

Determination of equilibrium constants

Equilibrium constants are determined in order to quantify chemical equilibria. When an equilibrium constant K is expressed as a concentration quotient, it is implied that the activity quotient is constant. For this assumption to be valid, equilibrium constants must be determined in a medium of relatively high ionic strength. Where this is not possible, consideration should be given to possible activity variation. The equilibrium expression above is a function of the concentrations [A], [B] etc.

Dynamic equilibrium

In chemistry, a dynamic equilibrium exists once a reversible reaction occurs. Substances transition between the reactants and products at equal rates, meaning there is no net change. Reactants and products are formed at such a rate that the concentration of neither changes. It is a particular example of a system in a steady state. In physics, concerning thermodynamics, a closed system is in thermodynamic equilibrium when reactions occur at such rates that the composition of the mixture does not change with time.

Related lectures (64)

Water Quality Modelling: Density Calculation and Saturation Index

Explains the role of density in solution calculations and the concept of saturation index.

Water Quality Modelling: Equilibrium Phases

Explores equilibrium phases in water quality modelling, illustrating with examples of mineral precipitation and pH adjustment.

Water Quality Modelling: EC, Alkalinity, Hardness, Carbonate Chemistry

Explores EC, alkalinity, hardness, and carbonate chemistry in water quality modelling, emphasizing measurement methods and ion relationships.

Water Quality Modeling: Kinetics in PHREEQC

Explores water quality modeling, focusing on reaction kinetics, equilibrium constants, and temperature effects, with practical examples of calcite precipitation and iron oxidation.

Chemical Equilibria and Reactivity