An owner had poured the outer walls of his plant room and asked whether his STP would fit. Whether it fits is not a property of the box — it is a property of the tenants he has not signed yet. Solving for treatment capacity at a fixed tank volume.
A client sent us two documents for the same building. The effluent table bound into his construction drawings came from a regulation superseded about ten years ago — stricter than the live rule in two rows, and silent on ammonia, nitrate and phosphate. Those three decide most of the plant.
A client's own specification declared 1,485 mg/L of suspended solids and also described the discharge as domestic sewage. The unlisted stream was a truck wash bay, the truck count could not be obtained, and the design had to be one that did not need it.
A retrofit where an unscreened building sewer decided the pump, the pump decided the hydraulics, and the hydraulics decided which chamber was doing equalisation — and what replaced it.
A clarifier return and sludge draw on one gravity line, so the plant has one pump in it — and the burst upflow rate I first calculated on the wrong basis, 2.0 metres per hour against an honest 1.26.
