Fouling and flux decline of reverse osmosis (RO), nanofiltration (NF), and ultrafiltration (UF) membranes associated with effluent organic matter (EfOM) during wastewater reclamation/reuse.

摘要

Bulk effluent organic matter (EfOM) consisted of refractory natural organic matter (NOM) and soluble microbial products (SMP). The NOM exhibited high aromaticity and low molecular weight (10,000 daltons), whereas the SMP possessed lower aromaticity with larger size compounds (>10,000 daltons). EfOM source waters possessed relatively low aromaticity compared to natural waters, due to a contribution of the SMP.; SNIP samples consisted mainly of high molecular weight (MW) fractions of polysaccharides and proteins, exhibiting a hydrophilic character. These compounds resembled aminosugars found in the bacterial cell wall and possibly generated from cell lysis during endogeneous phase. Solids retention time (SRT) affected the production of SMP. The SNIP production increased with an increased SRT. However, at long SRT (30 days), the level of SNIP was found to decrease, possibly due to biodegradation.; Colloidal fraction of EfOM isolates exhibited similar characteristics to those of SMP, i.e. high MW with low aromaticity. This fraction contained nitrogen-rich aminosugars, possibly originating from bacterial cell wall decomposition. Hydrophobic and transphilic fractions had the characteristics of humic-like materials, corresponding to refractory NOM contained in wastewater effluent.; Membrane filtration performance was dependent on membrane properties and feed water characteristics. Molecular weight cutoff (MWCO) and hydrophobicity of membrane material affected membrane fouling due to the mechanisms of size exclusion and hydrophobic interactions. The MWCO and surface charge of the membrane were influential in organic matter rejection with the effects of size exclusion and electrostatic repulsion.; Major characteristics of feed waters that affected fouling phenomena were the high MW fraction of EfOM and the aromaticity based on SUVA value. High MW compounds, characteristic of SNIP, exhibited a high potential for fouling and flux decline, whereas high SUVA compounds, corresponding to humic-like materials, showed low flux decline.; Cake/gel layer formation due to macromolecule/colloidal accumulation on the membrane surface was a major mechanism of membrane fouling associated with EfOM. Fouling potential was reduced when the amount of high MW compounds decreased.; Microfiltration and soil aquifer treatment (SAT) were both effective as pretreatment methods for reverse osmosis (RO), nanofiltration (NF), and ultrafiltration (UF) membranes. An integrated SAT-membrane system would be an effective multiple barrier system in wastewater reclamation for potable reuse.