Effect of alum addition on the performance of submerged membranes for wastewater treatment.
The effect of aluminum sulfate (alum) addition on membrane performance was investigated, with a particular focus on membrane fouling. During initial operation, alum was added and the performance monitored. After terminating alum addition, the transmembrane pressure (TMP), which is indicative of membrane resistance to flow or fouling, increased. Accompanying the increase in TMP was an increase in the organic nonsettleable fraction (colloidal + dissolved) content of the mixed liquor and deterioration of permeate quality and floc strength. Permeate polysaccharide concentrations increased significantly, suggesting a preferential binding of solution polysaccharides by alum. Upon reinitiating alum addition, the TMP only partially recovered, indicating some irreversible fouling, while mixed liquor nonsettleable organic material, permeate quality, and floc strength returned to initial levels. These results suggest that direct alum addition to membrane bioreactors can improve membrane performance by reducing the organic fouling material and improving floc structure and strength. It appears that bulk liquid polysaccharides may contribute to irreversible membrane fouling, and this fraction can be efficiently controlled through the alum addition.
Holbrook
R David
RD
Department of Civil and Environmental Engineering, Virginia Polytechnic Institute and State University, Blacksburg, VA 24061, USA.
Higgins
Matthew J
MJ
Murthy
Sudhir N
SN
Fonseca
Anabela D
AD
Fleischer
Edwin J
EJ
Daigger
Glen T
GT
Grizzard
Thomas J
TJ
Love
Nancy G
NG
Novak
John T
JT
D000534:Alum Compounds / Q000737:chemistry*; D008567:Membranes, Artificial; D011134:Polysaccharides / Q000737:chemistry; D011312:Pressure; D014865:Waste Disposal, Fluid / Q000295:instrumentation / Q000379:methods*; D018508:Water Purification / Q000295:instrumentation / Q000379:methods*
D000534:Alum Compounds; D008567:Membranes, Artificial; D011134:Polysaccharides; C041524:aluminum sulfate