Ultrafiltration as a pretreatment for RO feedwater with enhanced UF backwash, which combines continuous
with pulse backwash, was investigated in a novel UF-RO process integration. Direct supply of RO
concentrate to the UF module served for UF backwash which was further enhanced with pulse backwash
generated using bladder-type hydraulic accumulators. Model analysis of the hydraulic accumulator operation,
which was validated via a series of field experiments, demonstrated a capability for accumulator
charging directly from the RO concentrate stream within a period of 30–40 s. Moreover, pulse backwash
over a short period (5 s) which was added to the continuous UF backwash (directly from the RO brine
stream), enabled peak UF backwash flux up to a factor of 4.2–4.6 higher than the normal filtration flux.
The above mode of UF operation with multiple consecutive backwash pulses was more effective than
with a single pulse, while inline coagulation further increased the UF performance. Relatively long-term
field operation (over eight days where) of the UF-RO system with self-adaptive triggering of UF backwash,
whereby the number of consecutive pulses increased when a higher membrane fouling resistance
was encountered, was highly effective in enabling stable UF operation over a wider range of water quality
conditions and without the need for chemical cleaning. These encouraging results suggest that direct UFRO
integration with enhanced pulse UF backwash is an effective approach for dead-end UF filtration
without sacrificing water productivity