Preventing or mitigating the irreversible RO membrane fouling caused by dissolved organic matter and colloidal materials during surface water treatment

Reverse osmosis (RO) is increasingly being used for water treatment because of its small ecological footprint and improved membrane technology. However, a major challenge to the application of this technology in water treatment is the irreversible fouling observed in RO membranes. Fouling, mainly caused by dissolved organic matter (DOM) and colloidal materials (CM) in water, can increase the energy and maintenance costs and decrease the permeation flux and membrane life. Different pretreatments, such as coagulation, flocculation, sedimentation, and membrane-filtration, need to be applied upstream of the RO system to remove potential RO foulants. Membrane remediation by chemical cleaning also needs to be conducted to restore the membrane water flux. The purpose of the models constructed for the treatment trains in this pilot study is to investigate and identify system-specific performance parameters. The following paragraphs will discuss the findings from the investigations conducted during the Grand Forks Water Treatment Plant pilot study.;The pilot study on pretreatment indicated that DOM and turbidity could be effectively removed using ferric chloride (FeCl3) or polyaluminum chloride (PACl) as coagulants if the pH and chemical coagulant dose were optimized. Under the optimized pretreatment conditions, the irreversible fouling of RO membranes could be reduced or mitigated. This research showed that pretreatment, including coagulation, flocculation, sedimentation, and ultrafiltration, lead to the removal of 42.2% and 59.44% of DOM on using PACl and FeCl3 as coagulants, respectively, indicating improvement over the average baseline removal of 30% under non-optimized conditions. In addition, the removal of more than 90% turbidity (with PACl, at temperatures >20 °C; with FeCl3, at temperatures <4 °C) was achieved. PACl and FeCl3 exhibited very good removal efficiency for DOM and turbidity at doses of 40 and 50 mg/L, respectively, at pH 6.5.;In this study, a new testable neural platform prediction model was constructed for the removal of turbidity and total organic carbon (TOC) in the pilot pretreatment study at the Grand Forks Water Treatment Plant. (Abstract shortened by ProQuest.).