SA-fouled UF membranes were backwashed by water with different compositions.
The absence of divalent cations in backwash water significantly improved the HCE.
The HCE depended on released SA which was related to the amount of released Ca2+.
Multiple mechanisms governed the hydraulic cleaning of fouled UF membranes.
Monovalent salt backwashing was efficient for cleaning SA-fouled UF membranes.