Wastewater includes not only the amount of water that was discharged after use back to the environment, but also runoff rainwater, which flows back to the environment through the sewage system or is captured and discharged directly to rivers, streams and soil.
Odpadna voda pa ni le ta voda, ampak tudi padavinska in meteorna voda, ki se zliva nazaj v okolje po kanalizacijskem omrežju ali pa se zajema in izpušča neposredno v reke, potoke in v zemljo.