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While soluble microbial products (SMP) and extracellular polymeric substances (EPS) in wastewater bioprocesses have been widely studied, a lack of standard quantification procedures make it difficult to compare results between studies. This study investigated the effect of temperature on SMP and EPS profiles for biological nutrient removal (BNR) sludges and aerobic membrane bioreactor sludge by adapting the commonly used heat extraction and centrifugation scheme, followed by colorimetric quantification of the carbohydrate and protein fractions using the phenol-sulfuric acid (PS) and the bicinchoninic acid (BCA) methods, respectively. To overcome known inconsistencies in colorimetry, total carbon (TC), total nitrogen (TN), and fluorometry analyses were performed in tandem. SMP samples marginally benefitted from heat extraction, owing to their mostly soluble nature, while EPS profiles were greatly influenced by temperature. 60 °C appears to be a suitable general-purpose extraction temperature near the lysis threshold for the sludges tested. The PS method's misestimation due to lack of specificity was observed and contrasted by TC analyses, while the TN analyses corroborated the BCA assays. Fluorometry proved to be a sensitive and rapid analytical method that provided semi-quantitative information on SMP and EPS constituents, particularly its proteinaceous components, with positive implications for robust wastewater process control.

 

This study examines membrane performance data of a pilot-scale gas-sparged anaerobic membrane bioreactor (AnMBR) over its 472 day operational period and characterizes the foulant cake constituents through a membrane autopsy. The average permeability of 336 ± 81 LMH per bar during the first 40 days of operation decreased by 92% by the study's conclusion. While maintenance cleaning was effective initially, its ability to restore permeability decreased with time. Wasting bioreactor solids appeared to be effective in restoring permeability where chemical cleans were unable to. The restoration mechanism appears to be a decrease in colloidal material, measured by semi-soluble chemical oxygen demand (ssCOD), rather than bioreactor total solids concentration. This is further supported through the use of fluorometry during AnMBR operation, which showed an increase in tyrosine-like compounds during heavy fouling conditions, suggesting that proteinaceous materials have a large influence on fouling. This was corroborated during membrane autopsy using Fourier transform infrared spectroscopy (FTIR). FTIR, scanning electron microscopy with energy dispersive X-ray spectroscopy, and transmission electron microscopy were used to characterize inorganic scalants and predominantly found phosphate salts and calcium sulfate. Fundamentally characterizing foulants and introducing novel and dynamic monitoring parameters during AnMBR operation such as ssCOD and fluorometry can enable more targeted fouling control.