This study tested a novel zirconium (Zr) based coagulant for
increased natural organic matter (NOM) removal that could be implemented at full-scale without the need for additional
processes. Zr has a preferred oxidation state of +4 and has a lower tendency to complete
hydrolysis than traditional coagulants, meaning that it provides more charge neutralizing
capacity, operates over a wider pH range than normally encountered with coagulation processes,
and is known to generate more robust flocs. The premise for using Zr as an alternative coagulant
is to understand that Zr can remove more NOM for the same dose and, therefore, reduce sludge
production during high NOM periods. This will provide the drinking water community with
important operational and mechanistic information on an alternative coagulant for improved
NOM removal.
The objective of this study involved an assessment into an alternative coagulant option using Zr
as the primary coagulant benchmarked against Fe coagulation for NOM removal and residual
turbidity.
Raw water was taken from Albert reservoir (Halifax, United Kingdom) and is considered typical of
a moorland water, being of high color and dissolved organic concentration and low alkalinity.
Coagulation and flocculation experiments were carried out using a Phipps & Bird PB-900 six-paddle
jar tester. After the addition of
coagulant, the sample was rapid mixed for one and a half minutes at 200 rpm. The jars were then
stirred for 15 minutes at 30 rpm before settling for an additional 15 minutes before sampling.
Samples were taken unfiltered for settled turbidity and zeta potential measurements. Further
samples were taken and filtered through glass fiber filter paper to remove any solids and each sample for dissolved organic carbon (DOC) using a Shimadzu TOC-5000A analyzer and ultraviolet light absorbance at 254 nm (UV<sub>254</sub>) using a Jenway 6505 UV/Vis spectrophotometer. The
removal of NOM using Zr as a coagulant was tested dependent on coagulant dose, coagulation
pH and zeta potential (measured with a Malvern Zetasizer 2000HSA). Results were
benchmarked against the performance of conventional Fe coagulants. Tests were also carried out
by blending Zr and Fe coagulants by mass from 0-100 % Zr and the same analysis as described
above was carried out. Includes 6 references, table, figures.
| Edition : | Vol. - No. |
| File Size : | 1
file
, 740 KB |
| Note : | This product is unavailable in Ukraine, Russia, Belarus |
| Number of Pages : | 7 |
| Published : | 11/01/2008 |
