The removals of particles and total organic carbon (TOC) or natural organic matter (NOM) by clarification and
filtration processes depend highly on coagulation. Dissolved NOM is coveted into particles by
coagulation either by direct precipitation or by adsorption onto flocs. Favorable coagulation
chemistry of dose and pH affects this phase change of NOM, and affects subsequent particle
flocculation and separation of the flocs by clarification and by granular media filters.
The conventional view of coagulation is that coagulant dosing is controlled largely by the
raw water turbidity (Stumm and O'Melia, 1968) or by color for highly colored waters (Black et
al, 1963). One can say that these water cases represent certain water supply types; however, most
water supplies contain both turbidity and NOM. So the questions are, under what circumstances
does turbidity control, and under what circumstances does NOM control, coagulant dosing?
Edzwald (1993) showed that the raw water specific UV absorbance (SUVA) can be used to
answer these questions. This is explored in detail in this paper, but basically for waters with
intermediate to high SUVA the NOM controls, while turbidity controls for low SUVA waters.
The objective of this study was to present a framework and confirming data from full-scale
plants showing that water plants can set their alum dosage in response to the raw water UV (254
nm) level. Several full-scale plants of Aquarion have operated with this strategy for many years.
This paper presents data for a plate settling plant (Easton Water Treatment Plant (WTP)).
The oral presentation presents additional data for a dissolved air flotation plant and a
conventional settling plant. Includes 6 references, figures.
| Edition : | Vol. - No. |
| File Size : | 1
file
, 290 KB |
| Note : | This product is unavailable in Ukraine, Russia, Belarus |
| Number of Pages : | 6 |
| Published : | 11/01/2007 |
