UF Session 2

Why there is no air scouring in PES IN-OUT modules

• poorer mechanical strength

• less elongation allowed compared to PVDF

Why backwash flux is higher for PES in-side out ?

• No choice, as air scouring is not allowed for PES

• It has better mech strength for higher flux

During BW step, so long BW pump is started, i can start the BW timer to clock the 35-40s.

• True

• False

Siphoning is allowed for UF train BW drain top. No vacuum breaker is required

• False

• True

How to determine if the coagulant mixing time is sufficient ?

• simple test with 0.45um filter paper and see if <1% of dosage passing through filter

• Measure total iron right after mixing point

• based on feeling...

FeCl3 is more widely used because

• Fe(OH)3 stable over wider pH range

• Less soluble compared to Al3+

• Both

when metal ion coagulant is added, water alkalinity will be reduced.

• True

• Fasle

Prehydrolyzed metal salts give better coagulation performance

• the salt is more stable , can control which polynuclear species to be operative

• flocs tends to be tough

• Less temperature dependent

• all above