MSQ model

MSQ (multi solute quality) allows the modelling of several interacting chemicals in the water system. This is an alternative to the previous approach to water quality in InfoWorks WS Pro that only allowed modelling of a single substance. The previous approach is now rebadged as “Basic water quality”. Basic water quality and MSQ can be simulated at the same time, but the “basic substance” will not interact with the substances in MSQ.

MSQ models reactions in terms of mass (rather than stoichiometry), typically mg/L for dissolved substances and mg/m² for adsorbed substances. Equations are defined in terms of conversion of mass from one substance to another, and reaction rates are proportionate to concentration.

Definition of the MSQ model

The core of a MSQ model is defined in the solute data object.

Details of MSQ within the network (control property pages)

Initial conditions for solutes can be overridden for pipes and nodes.

Constants can be reset for any pipe or for reservoirs.

Sources (solutes entering the system) can be specified for any nodes type.

These changes are made in the control object, on property pages.

Validation

The solute data object is checked for errors. Settings in the control are validated to make sure that property pages refer to solutes or constants that are known within the solute data object.

Simulation and results

MSQ runs in the usual water quality simulation. There are five types of result: three for links, and two for reservoirs/nodes. These general kinds of result are defined below but, for each, there will be multiple occurrences, one for each solute.

Link types

• Average surface concentration – concentration on the wall of the link, the average throughout the link (mass per area).
• Peak surface concentration – maximum concentration on the wall of the link. The link is divided into segments for computational purposes, so this peak is the maximum observed across all segments.
• Peak concentration – refers to the concentration of dissolved solute (that is, in the bulk of the pipe) and specifically to the maximum value observed across the segments.

Node types

• Dissolved concentration (mass per volume).
• Source concentration - incoming from a source profile (mass per volume).