AWWA MTC64566

This slide presentation outlines the successful operation of four membrane treatment plants on the island of Maui in the state of Hawaii. Maui water ischaracterized as: "flashy" due to open feedsources, streams and irrigation ditches;typically high iron; and,"difficult" to treat water. The four membrane facilities include: Lahaina 3 x 90 CMF;Olinda 2 x 90 CMF;Kamole 8 x 90 CMF; and,Iao 3 x 90 CMF. Lahaina operational challenges include:algae growth in Pre Sedimentation,short filter runs andfrequent CIP's; and,high color episodes in raw water, 25 true color units. Lahaina treatment solutions:algae- Stop return of decanted backwash water toheadworks;Install a roof over basin to prevent algal growth,initiate cleaning with H₂O₂;High Color- Addition of Aluminum Chlorhydrate to raw water.Dosage 2-3 ppm. Olinda operational challenges include:color removal- True color of raw water 180 - 200 color units;coagulant selection limited- Very low raw water alkalinity water, typically < 10- Ferric Chloride depresses pH- Alum creates too large a floc and blinds membrane- Cationic polymer not compatible with membranes- Aluminum Chlorhydrate produces a small floc thatremoves well from membrane; and,fouling. Olinda treatment solutions included:color removal - true color of raw water 180 - 200 color units, andAluminum Chlorhydrate addition 18 - 21 ppm;sludge production- Sedimentation;Membrane Fouling- Process Audit, membrane autopsy result iron fouling, initiate cleaning regime with sodium metabisulfite. Kamole operational challenges include:no Pre-sedimentation- solids accumulation in modules;large turbidity swings- Average turbidity 2 - 5 ntu, andrain event spikes 100 - 600 ntu; algae in raw water; and,fouling. Kamole treatment solutions included:no Pre-sedimentation- Regular process audits to insure backwasheffectiveness;High Turbidity- Aluminum Chlorhydrate dosage up to 15 ppm;Algae- Installed a modern traveling screen, andinitiated cleanings with H₂O₂; and,fouling- Initiate cleaning regime with sodium metabisulfite. Iao operational challenges included:plant was originally intended to betemporary;no pretreatment; and,no raw water feed water system. Iao treatment solutions:no Pre-sedimentation/pre-treatment- Installed modern self-cleaning strainer;No Raw water feed system- Regular process audits required to insurebackwash efficiency.

Product Details

Edition:

Vol. - No.

Published:

03/01/2007

Number of Pages:

32

File Size:

1 file , 2.6 MB