Notes
Working notes on process design. Written for engineers. No case studies with the numbers removed, and nothing that ends in a request to contact us.
Articles
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What COD fractionation is, and why a design without one is a design for somebody else's water
What the four fractions are, how they are measured, what respirometry adds, and what each fraction does to reactor volume and to oxygen demand — including two waters at the same COD that need different plants.
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Sizing a secondary clarifier on solids flux, not on overflow rate alone
Why a clarifier has to satisfy two criteria, why the overflow rate is referenced to the influent rather than to the mixed liquor, and what the answer does when the sludge volume index moves.
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Where the electricity in an activated sludge plant goes, and how to find out how much of it you do not need
Standard against actual oxygen transfer, what alpha does, why transfer efficiency per metre is not transfer efficiency, and how to get the process air demand from the load rather than from the blower nameplate.
One article is written but not published
Reading a Mexican discharge permit — NOM-001-SEMARNAT-2021, what it measures and how the limits are structured.
It is not published, and it will not be until the official text has been read against every date and every limit it quotes by someone competent to read it. A firm whose whole positioning is that you can check its numbers cannot be the firm that misquoted the discharge standard.