Practical experience of backwashing with RO permeate for UF fouling control treating surface water at low temperatures

Abstract In an ultrafiltration (UF) pilot plant installation, the efficiency of backwashing with low conductivity water has been investigated. Fresh surface water was used as feed water and no inline coagulation or other pretreatment was used. Two types of backwash water were compared: UF permeate and reverse osmosis (RO) permeate. The pilot study was conducted at low temperatures (6.5–11 °C). Results show that backwash with RO permeate improved membrane fouling control efficiency. The optimization of the operational condition was 60-min filtration at a flux of 55 L m −2  h −1 and 30-s backwashing at a flux of 250 L m −2  h −1 , with a 93% recovery. Low temperatures (6.5–11 °C) accelerated the irreversible fouling, everyday-enhanced chemical backwash (ECB) (20-min soaking) was necessary and proved effective to keep a stable and extended operation. These findings indicate that it is possible to apply backwashing with RO permeate on the practical operation of UF plants for fouling control, treating surface water at low temperatures.