AWWA ACE56155

The presence of excess hardness causes white precipitates in boiled tap water raisingconsumer's concerns on the quality of water they consumed. The EnvironmentalProtection Administration of Taiwan will lower the maximum hardness standard infinished water from 500 to 150 mg/L as CaCO3 by the year 2003. By then, more than halfof 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 processcombining membrane with outside-in flow configuration and fluidized-bed pelletreactor for hard water softening.Due to slow kinetics on CaCO3 precipitation without the presence of pellets, UF alone isnot an effective process for hardness removal with removal efficiency only 17%.When three types of pellets, namely quartz sand, beach sand and heated-iron-oxideparticle (HIOP) were added separately, the removal efficiency of the combiningprocess is more than 60% at pH 9.0. Hardness removal efficiency increases withincreasing pH and surface area. However, no significant membrane fouling wasobserved during these experiments. Considering the amount of pellets added for threetypes 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 quartzsand with radius of 0.6 mm will occupy around 50% of reactor volume while HIOPsonly occupy 0.42%. Raw water containing 5 to 20 mg/L as C of Aldrich humic acidwere treated by the combing process, where more than 60% of UV absorbance wasremoved. Membrane fouling was not significant for the systems with humic acidconcentration less than 10 mg/L. Includes 9 references, tables, figures.

Product Details

Edition:

Vol. - No.

Published:

06/16/2002

Number of Pages:

13

File Size:

1 file , 510 KB