The role of extracellular organic matter on the cyanobacteria ultrafiltration process

The membrane fouling caused by extracellular organic matter (EOM) and algal cells and organic matter removal of two typical cyanobacteria (M.aeruginosa and Pseudoanabaena sp.)during ultrafiltration (UF) process were studied in this work.The results showed that EOM had a broad molecular weight (Mw) distribution and the irreversible membrane fouling was basically caused by EOM.Moreover,humic acid and microbial metabolites were major components of EOM of two typical cyanobacteria.Since EOM could fill the voids of cake layers formed by the algal cells,EOM and algal cells played synergistic roles in membrane fouling.Fourier transform infrared spectroscopy analysis indicated that the CH2and CH3chemical bonds may play an important role in membrane fouling caused by EOM.Interestingly,the cake layer formed by the algal cells could trap the organic matter produced by algae and alleviate some irreversible membrane fouling.The results also showed that although the cake layer formed by the algal cells cause severe permeate flux decline,it could play a double interception role with UF membrane and increase organic matter removal efficiency.Therefore,when using UF to treat algae-laden water,the balance of membrane fouling and organic matter removal should be considered to meet the needs of practical applications.

Effect of nitrogen/phosphorus concentration on algal organic matter generation of the diatom Nitzschia palea:Total indicators and spectroscopic characterization

Critical algal blooms in great lakes increase the level of algal organic matters（AOMs）,significantly altering the composition of natural organic matters（NOMs） in freshwater of lake.This study examined the AOM＇s characteristics of Nitzschia palea（N.palea）,one kind of the predominant diatom and an important biomarker of water quality in the great lakes of China,to investigate the effect of AOMs on the variation of NOMs in lakes and the process of algal energy.Excitation–emission matrix fluorescence（EEM） spectroscopy,synchronous fluorescence（SF） spectroscopy and deconvolution UV–vis（D-UV） spectroscopy were utilized to characterize AOMs to study the effects of nutrient loading on the composition change of AOMs.From results,it was revealed that the phosphorus is the limiting factor for N.palea＇s growth and the generation of both total organic carbon and amino acids but the nitrogen is more important for the generation of carbohydrates and proteins.EEM spectra revealed differences in the composition of extracellular organic matter and intracellular organic matter.Regardless of the nitrogen and phosphorus concentrations,aromatic proteins and soluble microbial products were the main components,but the nitrogen concentration had a significant impact on their composition.The SF spectra were used to study the AOMs for the first time and identified that the protein-like substances were the major component of AOMs,creating as a result of aromatic group condensation.The D-UV spectra showed carboxylic acid and esters were the main functional groups in the EOMs,with –OCH_3,–SO_2NH_2,–CN,–NH_2,–O– and –COCH_3functional groups substituting into benzene rings.