How much change in turbidity can it handle without needing to be re-zeroed?
In theory it can handle almost unlimited changes in turbidity without having to be re-zeroed, provided the nature of the turbidity particles is consistent. However in practice, raw water sources vary not only in the quantity of turbidity particles but also in both the nature of the suspended solids (eg different clays have different colloidal characteristics) as well as in pH and alkalinity. In addition, the sweep-floc effect (which is not related to charge) is more pronounced at higher dosages. We try to avoid giving a direct answer to the question of how much turbidity variation requires a re-zero because it is so plant specific that any answer could be dangerously misleading. The best thing a plant operator can do to answer this is to ask themselves ‘How much turbidity change signals that we are getting different water?’. Such as water which takes a different path into the river, or will have picked up different contaminants, rather than just more of the same dirt. Having said this,
