An owner in Cebu asked why he could not just enlarge his septic tank instead of building an STP. We sampled the tank first. BOD was down, solids were down, and ammonia came out higher than it went in. Field notes on what a septic tank does, what it cannot do, and how we kept his tank and built the plant around it.
A plant that had passed the year before came back at BOD 82 against a Class C limit of 50, three weeks before its permit sampling. Field notes on why the TSS number answered most of it, the one extra laboratory number we ask for, and when this is a housekeeping fix and when it is a design problem.
A new sewage treatment plant failed its first compliance test on ammonia. Nothing was mechanically wrong. Field notes on what commissioning actually is, why BOD comes back before ammonia, and why the acceptance test date is a technical decision.
Open a struggling grease trap in Cebu and the layer on top is often grey, curdled and hard rather than soft and amber. That is not grease any more — it is calcium soap, made by our hard water. It explains why weekly bacteria dosing, skimmers and hot flushing do nothing, and why the fix starts at the tap.
A client read me his STP contract over the phone the week before he signed it: two pages, a list of tanks, and 90 per cent of the money paid before the plant ever saw sewage. These are the four plain-language questions I would ask before signing — none of them about equipment.
Your STP can pass BOD and TSS and still fail ammonia, because the bacteria that remove ammonia are slow, alkalinity-hungry, oxygen-hungry and easy to kill. Field notes on the four things that quietly wipe them out, the food processing plant where I created my own nitrification problem with one piping decision, and what I check before anyone orders more bacteria.
Bacteria dosing is a real tool for commissioning, restarts and shock recovery. It is not a fix for low DO, solids washout, short retention time or an ongoing toxic input. Field notes on when I recommend probiotics for a sewage treatment plant, when I refuse to, and the food processing plant that taught me the difference.
Field notes on what a sewage treatment plant operator actually does, why plants fail weeks after a good operator resigns, and how to tell an operator problem from a design problem.
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.
After years of designing and operating treatment plants around Cebu, I've learned that how dirty wastewater looks tells you almost nothing about how hard it will be to treat. Here's what actually makes a stream difficult, from someone who learned it the hard way.
Field notes on why the company that sizes your sewage treatment plant is usually the company that profits from the size, the arithmetic a bid comparison table hides, and what to ask for before you sign — written by someone who sits on both sides of the conflict.
