Domain: Engineering — Civil & Environmental Engineering
Target concept: Fluoride Wastewater Treatment

Video generation prompt: Two flue gas desulfurization wastewater conical flasks are placed side by side, with lime milk added to the left one and no addition to the right one. After stirring, they are allowed to settle.

Evaluation guide:
(i) Target concept: Selective fluoride precipitation via calcium hydroxide addition in desulfurization wastewater.
Minimum mechanism: Ca²⁺ from lime milk must react with dissolved F⁻ to form solid CaF₂; this requires supersaturation and nucleation, hence precipitate appears only after stirring and settles over time; no reaction occurs without lime milk.
(ii)Storyline: Frame 0–2: Two identical conical flasks stationary, side-by-side, empty or containing identical wastewater. Frame 3–4: White lime milk dispensed into left flask only (no contact with right). Frame 5–6: Identical stirring motion applied simultaneously to both flasks (vortex formation visible). Frame 7–10: Both flasks completely still; left develops visible granular sediment at base while supernatant clarifies; right remains homogeneous and transparent; all observed from fixed frontal lab-bench perspective with full flask visibility.

Manual:
Experimental Procedure
1. Place two identical conical flasks side-by-side on a lab bench.
2. Add lime milk (white opaque suspension) to left flask only.
3. Stir both flasks identically for equal duration.
4. Cease stirring and allow both flasks to stand undisturbed.
Observation of Experimental Phenomena
After settling: left flask shows white precipitate at bottom with clearer supernatant; right flask remains uniformly clear with no sediment.
Summary of Experimental Principles
Lime milk (Ca(OH)₂) reacts with fluoride ions (F⁻) in wastewater to form insoluble CaF₂ precipitate — removal requires alkaline coagulation. No lime = no precipitation.

Prompt Grounding rubric:
level_1: Fewer than two flasks appear, or only one visible conical flask, or the two flasks are stacked/overlapping instead of positioned beside each other on the bench, or lime milk (a white, milky suspension) is never added to either flask, or no stirring motion of any kind is depicted, or the flasks are never shown sitting undisturbed after stirring.
level_2: Two conical flasks holding wastewater sit beside each other, but the video is missing at least one of: (a) lime milk added only to the left flask, (b) a visible stirring action applied to the contents, (c) a subsequent still/settling period before the video ends.
level_3: Two conical flasks of flue gas desulfurization wastewater are shown side by side; a white, milky lime milk suspension is poured or dispensed into the left flask only while the right flask receives nothing; both flasks are then stirred; stirring stops and both flasks are left undisturbed for a visible settling period; these stages (starting pair, lime milk addition, stirring, settling) occur in this order.
level_4: The left-flask-only lime milk delivery, synchronized stirring, and settling stages from the level-3 depiction are all present, and additionally: both flasks sit at matching height, scale, and camera distance so their contents can be directly compared; lime milk enters only the left flask with no droplets or splashes reaching the right flask; the stirring motion (e.g., swirling or rod-stirring) is applied to both flasks in the same manner and for a comparable length of time; once stirring ends, neither flask is picked up, tilted, or relocated during the settling period.
level_5: Beyond the level-4 setup, nothing (steam, hands, labels, glare) ever blocks the view of either flask's contents, both flasks stay in frame together at consistent scale from the lime-milk addition through the end of settling, and a viewer can look at the two flasks side by side at any single moment and tell their state apart without needing to see earlier frames.

Scientific and Causal Correctness rubric:
level_1: No scientifically meaningful difference emerges between the flasks: e.g., both look identical before and after, or a solid forms in the right (no-lime-milk) flask, or the left flask's contents stay visually unchanged after lime milk is stirred in.
level_2: Lime milk is stirred into the left flask, but the video does not show the expected outcome: e.g., after settling, both flasks look equally clear or equally cloudy, or a solid layer appears in the right flask, or the left flask never develops any turbidity or sediment.
level_3: After stirring and settling, the left flask shows a layer of white solid at the bottom with a supernatant above it (either turbid or cleared), while the right flask stays visually uniform with no solid layer forming; the difference between the two flasks tracks with lime milk having been added only to the left one.
level_4: Beyond the level-3 outcome, the timing is right: the white solid in the left flask becomes visible only once stirring is underway or just after (not the instant lime milk touches the wastewater), and continues to accumulate at the bottom through the settling period rather than appearing all at once; the right flask never develops any solid at any point in the video; the left flask's liquid above the settled solid looks less cloudy by the end of settling than it did right after stirring.
level_5: Beyond the level-4 outcome, the physical picture is fully coherent: the solid collecting in the left flask looks granular and uneven rather than a smooth gel or floating film, and stays confined to the bottom rather than drifting back into suspension; the clarified liquid above it is noticeably more see-through than the freshly stirred cloudy mixture; the right flask shows no particles settling or clumping at any frame, staying visually consistent with untreated wastewater throughout.

Spatiotemporal Consistency rubric:
level_1: A flask's position or appearance breaks the physical setup partway through: e.g., one of the two flasks vanishes from the frame or is replaced by a different container, the flasks swap left/right positions, the stirring motion suddenly runs backward, a flask's shape or size changes between shots, or the lighting or shadows on the flasks shift abruptly between shots with no change in light source to explain it.
level_2: The scene holds together overall but one clear break remains: e.g., a flask's position or tilt changes noticeably between the stirring shot and the settling shot with no visible cause, there is a hard cut where the transition from adding lime milk to stirring skips or repeats, or one flask is hidden from view for a large portion of the video while the other stays visible.
level_3: Both flasks stay in the same left/right spots and the same orientation from the opening shot through the final settling shot; the sequence of pouring lime milk into the left flask, then stirring both, then letting them stand plays out in that order without jump cuts, frozen frames, or reversed motion.
level_4: Beyond the level-3 continuity, the motion itself reads as physically smooth: the stirring looks like one continuous motion of matching speed and style in both flasks, the pouring of lime milk finishes before stirring starts, and once settling begins neither flask shifts position, tips, or shakes for the remainder of the video.
level_5: Beyond the level-4 continuity, the two flasks stay sharply in focus and keep a constant size and shape in every frame (neither flask appears to stretch, bend, or blur while the camera holds its shot), so a viewer can directly compare the settled solid in the left flask against the unchanged right flask without any visible warping or geometric drift across the video.