Pretreatment options for municipal wastewater reuse using membrane technology

Increasing freshwater scarcity across the world means that wastewater reclamation is being considered as a key method in which to meet the growing demand. Evolution of water reuse schemes where high quality product is required such as for indirect potable reuse has led to the adoption in recent years of the integrated membrane scheme using a combination of microfiltration or ultrafiltration with reverse osmosis membrane. However, despite technological advancements, these membranes are still prone to fouling resulting in increased costs through cleaning or replacement. This thesis aims to look at pretreatment to reduce the fouling propensity of the microfiltration membranes via a 600m3 /d pilot plant which was commissioned to investigate indirect potable reuse. A range of pretreatments including pre-screening, pre-coagulation, powdered activated carbon and granular activated carbon were assessed based on fouling amelioration, water quality improvement and cost analysis. Results showed that ferric sulphate dosing was the most effective in terms of reducing the reversible fouling rate especially at high turbidity loads enabling higher flux to be realised leading to a small cost benefit. Activated carbon proved the most effective pretreatment in terms of organic removal and a significant reduction in the irreversible fouling rate. However, the cost involved in using this as a pretreatment is significant compared to possible cost savings through reduced requirement for chemical cleaning. This pretreatment is only viable if it obviates the need for a separate organic removal process.