Controller Concepts: Turbidity

Turbidity is a variable that could show promise in high-end controllers. Yes, beyond simply reading the Nephelometric Turbidity Units, (NTUs,) a sophisticated polymer system could actually control that value. Now we all know that flocking a high-rate-sand filter is a no no. This has always been true because manual flocculation is sure to “blind” the sand bed prematurely, requiring excessively frequent backwashing and premature loss of flow. Or, if fed too little, it will have no effect at all.

If we could manage micro-flocculation qualitatively, however – by measuring water turbidity with an accurate, expensive little turbidity meter fixed with a set-level relay – the controller would know when to shut off that tiny trickle of special polymer (or polyaluminum chloride) that’s being fed, and a chosen set-level of NTUs could be maintained. Now that’s filter automation! Look for it…