Field notes on why we specify air pumps rather than blowers on small sewage treatment plants in the Philippines, where the dividing line sits, and why a quiet machine that stays switched on beats an efficient one that does not.
We now show an above-ground, no-excavation layout alongside the sunk concrete one on every job. Here is what the ground actually charges you, what it gives back, and what you can never do again once the cover slab is on.
Field notes on how we choose equipment for a sewage treatment plant when the criterion is after-sales support — including the one item we have not solved, and what specifying for serviceability changes in the design.
Reuse is not one requirement. Gardening, general washing, cooling tower makeup and toilet flushing each buy a different plant. Field notes on how we decide which one, and what it changes in the tanks and the running cost.
The layout decides what the civil works costs. Field notes on shared cross walls, one spine wall between sunk rows, rectangular clarifiers and why we leave the weir plate out of an underground tank.
Field notes from a poultry dressing plant: why an old lab result understated the load fifteen-fold, why the grease needed dissolved air flotation rather than an interceptor, and why we put a small DAF behind equalisation instead of sizing a big one for the wash-down peak.
Field notes on how we size and specify a sewage treatment plant: designing to the client's reuse rung, assuming the influent safely when nobody has a lab result, why the arithmetic worries us least, specifying for after-sales support, and the clarifier we standardised for underground tanks.
Nearly every first call asks how long a sewage treatment plant takes to build. Field notes from our Cebu jobs on what actually takes the time: civil works, the design basis nobody schedules, and the commissioning stage most contracts never write down.
An owner had three proposals with three different technologies on the cover. We quoted the same building all three ways ourselves. Field notes on what actually separated extended aeration, fixed film and a batch reactor on a Cebu site.
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 client put two quotations side by side and asked which one was cheaper. Neither of us could answer that from the cover page. Here is how we cost a sewage treatment plant per cubic metre treated, what sits inside that number, and where capital money buys running money back.
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.
