Reducing the effect of cyanobacteria in the microfiltration of secondary effluent

摘要

Cyanobacterial blooms in the lagoons of sewage treatment plants can severely impact thenperformance of membrane plants treating the effluent. This paper investigates the impact ofnMicrocystis aeruginosa in a secondary effluent on the microfiltration filterability and cleaning ofnthe membrane. Alum coagulation and dissolved air flotation (DAF) were investigated to removenthe algae and so enhance the volume of effluent processed, and their influence on reversible andnirreversible fouling. Degree of fouling due to the algal components was found to be in decreasingnorder of algal cells, algal organic matter and extracellular organic matter. Alum coagulation withn5mgL21 as Al3+ led to a substantial increase in permeate volume, an increase in dissolvednorganic carbon removal, and a foulant layer which protected the membrane from internal foulingnbut which was hydraulically removable resulting in full flux recovery. Pre-treatment by DAF orn1.5mm filtration following alum coagulation enhanced the flux rate and permeate volume butnexposed the membrane to internal irreversible fouling.