Abstract
Performance of ultrafiltration membranes were investigated with submerged membrane in terms of removal of soluble microbial products (SMP) (as proteins and carbohydrates) and fouling mechanisms. Cellulose (UC) and polyethersulphone (UP) membranes with different molecular weight cut off (MWCO) (5, 10, 30 kDa for UC and 5, 10, 20 kDa for UP) were tested in the bioreactor. The quality of permeate was compared in terms of SMP and COD. There was no significant difference in the total SMP removal effectives for both the UC and UP membranes with different MWCO characteristics. However, UP membranes were relatively more effective in removing soluble carbohydrates, while UC membranes were more effective in removing soluble proteins. The submerged membrane bioreactor achieved organic removal efficiencies ranging from 98.1±0.2% to 99.2±0.3% based on the soluble COD levels. Analysis of the membrane performance data by resistances-in-series model indicated that cake fouling was the dominant membrane fouling mechanisms. Increasing the MWCO was resulted in higher membrane flux but lower SMP removal. Morphological examination of the membranes by SEM and AFM showed significant accumulation of organisms on the membrane surface.
Highlights
Submerged membrane bioreactors (SMBRs) for wastewater treatment and water reuse applications have received significant interest in recent years as they offer operational and design benefits by eliminating the need for a secondary settling tank, require smaller reactor volume, and decrease sludge volume and quantity
Effectiveness of UF membranes with different molecular weight cut off (MWCO) were evaluated for soluble microbial products (SMP) removal as total (SMPt), carbohydrate (SMPc), and protein (SMPp)
There was no significant difference in the removal effectives of SMPt for both the UC and UP membranes with different MWCO characteristics
Summary
Submerged membrane bioreactors (SMBRs) for wastewater treatment and water reuse applications have received significant interest in recent years as they offer operational and design benefits by eliminating the need for a secondary settling tank, require smaller reactor volume, and decrease sludge volume and quantity. Performance characteristics of submerged membrane bioreactors with micro and macro systems have been studied to evaluate the effect of operational parameters on sludge filterability and process performance [1, 2]. Physiological properties of sludge from SMBRs have been studied in terms of extracellular polymeric substances [3,4,5], carbohydrates and proteins [6], and soluble microbial products [7, 8]. Extracellular polymeric substances (EPS) or soluble microbial products (SMP) are large molecular weight compounds that are released by bacteria. They consist of proteins, polysaccharides, lipopolysaccharides, lipoproteins or complex mixtures of these biopolymers with a variety of functional sites
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