Settled water turbidity and clarifier sludge strength move from their normal values to their peak values as the solids load rises. Sludge gets thicker during events, so the peak %DS is higher.

Filter run time drives how often filters wash. Enter the run times you see (normal, and what runs drop to in an event), or let the tool predict them from the solids the media can hold per run. Each wash takes a filter out of service for drain-down, wash and refill, then the filter runs to waste.

The washwater tanks set the shortest filter run the plant can handle: each wash fills a tank, which then settles, decants and desludges before it can take another wash. If runs get shorter than that, output has to come down.

Clarifier sludge and settled washwater sludge collect in the sludge balance tank. The thickener draws from it, limited by its hydraulic loading rate (default 1.5 m³/m²/h) and solids loading rate (default 4 kg/m²/h, the TT016 design rate). Thickened sludge goes to storage, and dewatering draws it down when it runs.

Dewatering runs on its normal schedule until thickened storage passes the extended-schedule trigger, then runs longer hours (and weekends, if allowed). The assist machine starts at its own trigger. When thickened storage is full the thickener stops drawing, the balance tank fills, and plant output has to come down.

Supernatant, centrate and filter-to-waste go to a discharge where one is consented, and are returned to the plant inlet otherwise.

Enter normal raw water quality and the chemical doses you use in normal conditions, then describe the event. A preset fills in a typical event shape for the source type; adjust it to your own records.

Event models one rain event (and, in Premium, a second one): a rise to the peak, a period at the peak, then a receding limb that gets back to within 10% of normal after the recession time. A second event adds to whatever is left of the first. Coagulant, PAC and lime doses follow the event from the normal dose to the peak dose.

Sustained holds poor quality for a set number of days after a normal day, to find the capacity the plant can keep up, for example a storage dam after a cyclone. Record (Premium) runs your own turbidity record through the plant.

The chart shows treated water capacity each hour, in two ways. Reacting runs at design capacity until a stage cannot keep up, then makes as much as that stage allows. Planned assumes the event is forecast: dewatering runs extended hours with the assist machine from the start to empty the sludge storage, and through the event the plant holds the highest steady output that never overfills it.

The band under the chart shows which stage limits output each hour. Colour bands are prompts to look, not instructions to act. Storage levels, the incoming load and the peak use of each stage are below, then a day-by-day table.

Treated storage is drawn on against demand (reduced in wet weather). If it reaches its minimum level, supply falls short.

Residuals storage is often sized to work an event off over several days. A second event inside that window finds the storage already full, and capacity takes a much bigger hit. This tab repeats the run with the second event (the Event 2 settings on Source & event) starting from half a day to 14 days after the first.

For each gap it shows the water lost against design and the extra lost compared with the two events well apart. The exposure window is the shortest gap at which the pair costs no more than the two apart. With your events per month, it gives the chance of a second event inside that window. Rain events cluster, so treat the chance as a lower bound.

This tab assumes the plant reacts to the second event as limits are reached.

Export PDF prints a report of the inputs, key results, findings and the day-by-day table. Export CSV gives the inputs, the daily table and the hourly results for a spreadsheet.

Save JSON downloads the whole design so it can be loaded again here or shared. Loading a file replaces the current inputs.