Abstract:
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.
