CHANGING GLASSES GIVES A FRESH PERSPECTIVE: FROM EMISSION TO IMISSION AS THE GUIDE

We are good at optimising the subsystems, without really understanding the interactions between these different subsystems. As a result, we take specific actions that may have a negative effect further down the line. It is also at the level of these subsystems that objectives are set out (and innovation is driven). For example, in the area of water, standards are imposed, and the discharged waste water from a sewage treatment plant must comply with these. When there is heavy rainfall (thereby diluting the waste water and lowering the performance of the water treatment) it will be decided to activate a number of overflows, so that the standards can be complied with. However, activating the overflows (whereby untreated water is discharged into a watercourse) can have a much larger negative impact than discharging less well-treated waste water.

Focusing on optimising the overall system could mean, for example, moving from an emission to an imission approach, starting from the concentrations in the environment (rather than at the point of discharge) in order to control different subsystems on this basis. In the example above, this would mean that, in the event of heavy rainfall, it would be more appropriate not to activate certain overflows, and to have the sewage treatment plant treat the waste water at a lower performance level (more flexible discharge standards). In the event of drought, the discharge standards could be tightened, as the performance of the installation would then be better. The point is to see what the ecology in the receiving water is equipped to do, and build and manage the infrastructure on this.

In a climate of more extreme weather conditions, it is becoming increasingly important to control the functioning of the subsystems, instead of the entire situation at ground level. To bring this about, another step still needs to be taken to integrate/link the various subsystems (as well as their models - which is not always obvious from a software point of view either). These include integrating sewage treatment models with watercourse models, drinking water models, models of other users: energy, transport, etc.

We are setting up a test in which we examine to what extent it is possible to control the situation on the ground with the models, processes and instruments that are currently devised and installed for this control on various subsystems, so that an approach towards systemic management becomes possible.