A healthy sewage treatment plant smells like wet soil. When it smells like rotten eggs, ammonia, or spoiled food, it is telling you where to look, usually weeks before the lab report does. Field notes on reading an STP by smell, including the food processing plant that taught me the hard way.
Small STPs fail more often than large ones, and not because they are cheap. Field notes from Cebu on why 5 cubic meters a day is harder to operate than 500 — and how I design small sewage treatment plants differently now.
