AWWA WQTC69370

This study tested a novel zirconium (Zr) based coagulant forincreased natural organic matter (NOM) removal that could be implemented at full-scale without the need for additionalprocesses. Zr has a preferred oxidation state of +4 and has a lower tendency to completehydrolysis than traditional coagulants, meaning that it provides more charge neutralizingcapacity, 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 coagulantis to understand that Zr can remove more NOM for the same dose and, therefore, reduce sludgeproduction during high NOM periods. This will provide the drinking water community withimportant operational and mechanistic information on an alternative coagulant for improvedNOM removal.The objective of this study involved an assessment into an alternative coagulant option using Zras the primary coagulant benchmarked against Fe coagulation for NOM removal and residualturbidity.Raw water was taken from Albert reservoir (Halifax, United Kingdom) and is considered typical ofa 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-paddlejar tester. After the addition ofcoagulant, the sample was rapid mixed for one and a half minutes at 200 rpm. The jars were thenstirred 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. Furthersamples 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 (UV₂₅₄) using a Jenway 6505 UV/Vis spectrophotometer. Theremoval of NOM using Zr as a coagulant was tested dependent on coagulant dose, coagulationpH and zeta potential (measured with a Malvern Zetasizer 2000HSA). Results werebenchmarked against the performance of conventional Fe coagulants. Tests were also carried outby blending Zr and Fe coagulants by mass from 0-100 % Zr and the same analysis as describedabove was carried out. Includes 6 references, table, figures.

Product Details

Edition:

Vol. - No.

Published:

11/01/2008

Number of Pages:

7

File Size:

1 file , 740 KB