| immaculate(adjective, feature, characteristic, detail, purification) |
| natural complex(expression, biology, environment, science, ecology) |
| percolate(verb, process, purification, decontamination) |
| pure(adjective, feature, characteristic, detail, purification) |
| purify(verb, process, purification, decontamination) |
| situation(noun, nature, ecology, world, ecosystem) |
| spotless(adjective, feature, characteristic, detail, purification) |
| sterile(adjective, feature, characteristic, detail, purification) |
| subsoil water(expression, type, water, ecosystem) |
| surface water(expression, type, water, ecosystem) |
| tidy(adjective, feature, characteristic, detail) |
| unsullied(adjective, feature, characteristic, detail, purification) |
| waste-water(noun, type, water, ecosystem) |
| water table(expression, type, water, ecosystem) |
| atmosphere(noun, nature, ecology, world, ecosystem) |
| bionomics(noun, nature, ecology, world, ecosystem) |
| channel(noun, type, water, ecosystem) |
| cloaca(noun, type, water, ecosystem) |
| depurate(verb, process, purification, decontamination) |
| distill(verb, process, purification, decontamination) |