This simulator shows an illustrative municipal wastewater train in 3D: a bar screen with a screenings conveyor, a primary hopper and scraper, an aerated racetrack channel with surface rotors, a secondary settling tank, and a return-sludge loop with a waste branch. Change influent flow and BOD, biological volume, aeration availability and return ratio to see how each stage shapes the effluent.
• A real-time 3D view with numbered, clickable parts: bar screen and screenings conveyor; primary hopper and scraper; aerated racetrack and surface rotors; secondary settling tank; return activated sludge and waste branch. Scene tools include home view, focus-selected-part, auto-rotate, expand and show/hide labels, and drag-to-orbit with pinch-to-zoom. • Experiment controls: influent flow (20–120 L/s); influent bod surrogate (100–400 mg/L); biological volume (500–2500 m³); aeration availability (0–1 fraction); return-sludge flow ratio (0–1 RAS / influent), plus a show flow/process markers toggle, pause/resume, single-step buttons (0.1 s and 1 s), a playback-speed selector and a restart trial action. • Live readouts: after primary stage; after biological stage; biological residence time; bOD surrogate removed; final solids carryover; return sludge flow. A model response curve is drawn beside the 3D view and updates as you change controls. • A Curves & measurements tab with two live charts, the model equations as written in the simulator and snapshot readouts; an Experiments tab with 2 guided presets (lose aeration; increase biological volume) plus a model-verification bench, timestamped event log and copyable trial report. • A Learn & assess tab with 3 lessons (solids and organics differ; biology needs suitable conditions; clarification retains suspended biomass), a 2-question knowledge check with reset, and a written model-scope statement.
Screens and primary settling remove coarse and settleable solids but do little for dissolved biodegradable material. In this model the primary stage takes out 30% of the influent BOD surrogate, and the remaining load is handled by the biological stage, whose removal rate depends on how much aeration is available and on the return-sludge ratio.
Biological residence time is volume divided by flow, so a larger biological volume or a lower flow lets the rate act for longer. Remove aeration entirely and the modeled biological rate falls to zero, leaving only the primary-stage removal in the effluent value.
The biological liquid carries suspended biomass, so a final settling tank must separate it before water leaves. The clarifier capture efficiency falls as overflow rate rises, and solids that are not captured appear as the final solids carryover value; the return-sludge pipe sends settled biomass back to the aeration channel while a waste branch takes the excess.
This is an illustrative steady-state train rather than a calibrated activated-sludge model. There is no biomass growth and decay, sludge-age control, nutrient balance or pathogen model, and the return-ratio factor and carryover curve are teaching assumptions, not equipment sizing rules.
A bar screen only captures coarse objects that are larger than its openings. Dissolved biodegradable material passes straight through, which is why a biological stage is needed to reduce the organic load.
The modeled biological rate goes to zero, so the biological-stage effluent equals the primary-stage concentration. The simulator demonstrates this with its lose-aeration experiment.
The biological liquid contains suspended biomass. Without a settling step that biomass would leave with the effluent, so the clarifier separates it and the return-sludge loop sends most of it back to the aeration channel.
No. It is an illustrative steady-state teaching train without biomass growth and decay, sludge age, nutrient removal or pathogens. Use it to understand relationships between flow, volume, aeration and clarification, not to size a plant.