Sewer basins, overflows and flood retention run on fixed rules

Sewer storage basins are used by fixed rules

What happens. Storage basins and tanks in the sewer network fill and empty by level switches and local rules. Each basin acts on its own, without knowing how full the others are or what rain is coming.

What it costs. Some basins overflow while others still have room. The overflow goes to the river, and the wastewater plant at the end gets the water as a peak, not spread over the hours.

Why the usual fix fails. Building more storage is expensive and takes years. Tuning the level switches helps for the rain that the tuning was made for.

How a fixed-price remote diagnosis checks it. From level, flow and rain records and the network plans I look at how the basins could be used together. The fixed-price remote diagnosis tells you whether predictive control of the whole network, using a rain forecast, can use the storage that exists better, and what data and model it needs.

Background: Economic predictive control

New rules call for overflow plans and network analysis

What happens. The revised European urban wastewater directive asks larger cities to draw up integrated plans for wastewater and storm water, backed by a hydrodynamic analysis of the sewer network. It sets an indicative limit for overflows (VKU).

What it costs. Overflow volumes have to fall, and most cities cannot afford to rebuild the network to achieve it. The analysis creates a workload for engineers who are already scarce.

Why the usual fix fails. A hydrodynamic model that stays on the shelf after the plan is delivered helps only on paper. New tanks and larger pipes are the usual answer and take decades.

How a fixed-price remote diagnosis checks it. From the network model, level and flow records and the rain series I check how much of the overflow could be avoided by controlling tanks and weirs in real time instead of building. The fixed-price remote diagnosis tells you whether such control is worth planning into the integrated plan, and what the model and the sensors must deliver.

Background: Optimal paths, schedules and setpoint plans

Flood retention is operated on uncertain forecasts

What happens. Reservoirs and controlled polders (flood retention areas) are opened and held by thresholds and operating rules. The forecast that triggers the decision is uncertain.

What it costs. Retention is used too early and the space is missing for the peak, or too late and the peak goes downstream. Both are visible in damage and in public trust.

Why the usual fix fails. A threshold based on one gauge does not see how the flood wave from several tributaries combines. More safety margin in the operating rule costs retention volume exactly when it is needed.

How a fixed-price remote diagnosis checks it. From gauge and reservoir records, forecast archives and the operating rules I check how the decisions would have gone under forecast-based operation. The fixed-price remote diagnosis tells you whether predictive operation that includes the forecast uncertainty improves the use of retention, and what it would take.

Background: Economic predictive control