The presence of excess hardness causes white precipitates in boiled tap water raising
consumer's concerns on the quality of water they consumed. The Environmental
Protection Administration of Taiwan will lower the maximum hardness standard in
finished water from 500 to 150 mg/L as CaCO3 by the year 2003. By then, more than half
of the water treatment facilities in Taiwan will not be able to meet the new standard.
Because of this urgent need of water treatment plants to remove excess hardness, this paper presents a study on the feasibility of using a novel treatment process
combining membrane with outside-in flow configuration and fluidized-bed pellet
reactor for hard water softening.
Due to slow kinetics on CaCO3 precipitation without the presence of pellets, UF alone is
not an effective process for hardness removal with removal efficiency only 17%.
When three types of pellets, namely quartz sand, beach sand and heated-iron-oxide
particle (HIOP) were added separately, the removal efficiency of the combining
process is more than 60% at pH 9.0. Hardness removal efficiency increases with
increasing pH and surface area. However, no significant membrane fouling was
observed during these experiments. Considering the amount of pellets added for three
types of particles tested, HIOP pellet is the most economic one due to its small radius
(~5um). To provide 5 m2 of pellets' surface per liter of reactor, the volume of quartz
sand with radius of 0.6 mm will occupy around 50% of reactor volume while HIOPs
only occupy 0.42%. Raw water containing 5 to 20 mg/L as C of Aldrich humic acid
were treated by the combing process, where more than 60% of UV absorbance was
removed. Membrane fouling was not significant for the systems with humic acid
concentration less than 10 mg/L. Includes 9 references, tables, figures.
| Edition : | Vol. - No. |
| File Size : | 1
file
, 510 KB |
| Note : | This product is unavailable in Ukraine, Russia, Belarus |
| Number of Pages : | 13 |
| Published : | 06/16/2002 |
