AWWA JAW56401

Drinking water that contains algae canhave disagreeable tastes and odors.Because many algae contain significantquantities of taste- and odor-causingcompounds and toxins within theircells, it is preferable to remove algae intactrather than through cell lysis. In addition,to avoid frequent filter clogging and tominimize disinfection byproduct concentrations,it is preferable to remove the algaeprior to the filtration and disinfection stepsof the water treatment process.Intact algae cells can be removed bycoagulation, flocculation, and sedimentation.However, coagulation processes arefrequently disrupted by the presence ofalgae because raw water pH tends toincrease during algae blooms and becausealgae can excrete polysaccharides thatincrease coagulant demand. Therefore,utilities require strategies for the effectivecoagulation of algae.The authors discuss their findings ofoptimizing coagulant dosing by means ofcharge titrations. They maintain that onlinecoagulant dose control, via online streamingcurrent measurements, will allow utilitiesto maintain proper coagulant doseswhen raw water algae concentrationsand/or background water quality vary.In optimizing coagulation conditions,the following factors were evaluated:streaming current value, coagulationpH, and initial algae concentration.Experiments were performed with bothlaboratory-cultured Anabaena flos-aquaethat were spiked into a natural water anda natural algae bloom water that containedprimarily Anabaena spp. andSynedra spp. Includes 52 references, tables, figures.

Product Details

Edition:

Vol. 94 - No. 2

Published:

02/01/2002

Number of Pages:

11

File Size:

1 file , 480 KB