Polluted Water

Polluted Water is a liquid element that appears throughout the colony as a common by-product of sanitation, generators, and several natural sources. It is one of the earliest renewable liquids players typically accumulate, and it sits between useful resource and hazard: it can be cleaned back into Water, used directly by several plants and machines, or left to off-gas Polluted Oxygen if not managed carefully.

Its most distinctive behavior is that it emits Polluted Oxygen. In tile form, Polluted Water attempts to release gas only upward, even in a vacuum, and it stops doing so once the pressure above it reaches 1.8 kg. Emission is probabilistic: five times per second, each tile has a 1% chance to convert 0.1% of the surface cell’s mass, up to 1 kg per check. A full 1000 kg surface tile therefore averages about 30 kg of Polluted Oxygen per cycle, but the output is not perfectly steady. The emission calculation only uses the first 1000 kg of a tile, so extra mass does not increase off-gassing. For maximum Polluted Oxygen production, it is better to spread Polluted Water across multiple tiles rather than stacking it into a few heavy ones. Bottled Polluted Water behaves differently and releases Polluted Oxygen at a fixed rate of 1/25000 of its mass per second, or 40 g/s. Polluted Water stored in Liquid Reservoirs does not emit any Polluted Oxygen at all, making reservoirs useful for safe storage.

Polluted Water can be produced by many common systems. Duplicant stress vomiting and delayed toilet use create it, while Lavatories, Showers, Wash Basins, and Sinks also convert clean Water into Polluted Water. Lavatories are water positive, producing 11.7 kg of Polluted Water while consuming 5 kg of Water; the other sanitation buildings are water neutral. It also comes from Polluted Water Vents and Cool Slush Geysers, from Carbon Skimmers, and as a by-product of Algae Distillers, Algae Terrariums, Natural Gas Generators, and Petroleum Generators.

It has several important uses:

• Water Sieve converts 5 kg/s Polluted Water plus 1 kg/s Sand or Regolith into 5 kg/s Water and 200 g/s Polluted Dirt.
• Boiling Polluted Water produces Steam and a small amount of Dirt equal to 1% of the mass, with a minimum of 1 g of Dirt.
• Pincha Pepper, Thimble Reed, Bog Bucket, and Arbor Tree all use Polluted Water as domestic irrigation.
• Fertilizer Synthesizer consumes Polluted Water along with Dirt and Phosphorite to produce Fertilizer and Natural Gas.
• Gulp Fish can convert Polluted Water into clean Water.

Polluted Water is also a useful coolant because of its high specific heat capacity and wider liquid temperature range than Water, Brine, or Salt Water. It is especially valuable early in the game when cold or hot liquid handling is still limited. At the same time, germs are not removed by filtration, so contaminated Polluted Water must be treated separately if it is intended for safe reuse. Most naturally occurring and produced Polluted Water is germ-free, so keeping clean and infected supplies apart is usually enough.