Effects of effluent organic matters on endocrine disrupting chemical removal by ultrafiltration and ozonation in synthetic secondary effluent.

Endocrine disrupting chemicals (EDCs) in the secondary effluent discharged from wastewater treatment plants are of great concern when water reuse is intended. Ozonation and ultrafiltration (UF) are powerful technologies reported to eliminate EDCs. Due to the importance of effluent organic matters (EfOMs) in secondary effluent, the effects of three kinds of EfOM on the treatment of five EDCs using ozonation and UF were investigated. The three kinds of EfOM studied were humic acid sodium salt (NaAH), bovine serum albumin (BSA) and sodium alginate (NaAg); and the five EDCs were estrone, 17ß-estradiol, estriol, 17α-ethynyl estradiol and bisphenol A. The results showed that EfOM accelerated the decay rate of ozone and inhibited the degradation efficiency of EDCs by ozonation in the order NaAH>BSA>NaAg. The ultraviolet absorbance at 280nm (UVA280) has potential for use as a surrogate indicator to assess EDC removal via ozonation without conducting difficult EDC analyses. When the decline in UVA280 exceeded 18%, the five EDCs had been completely removed. The UF behavior of NaAH, BSA and NaAg was found to follow the cake filtration law. The fouling potential of EfOM followed the order NaAg>NaAH>BSA; while EfOM on the membrane surface enhanced EDC removal in the order NaAH>BSA>NaAg. The mean retention rate of the membrane was increased by 24%, 10% and 8%, respectively. The properties of EDCs and EfOM cakes both influenced the EDC removal rates due to adsorption, size exclusion and charge attraction.

A small molecule norspermidine in combination with silver ion enhances dispersal and disinfection of multi-species wastewater biofilms.

Detrimental biofilms have become a great concern in many areas due to their strong resistance and insensitivity to traditional antimicrobial agents. Norspermidine is a potent small molecule for biofilm dispersal. In this study, silver ion, a conventional inorganic biocide, was combined with norspermidine and used for control and removal of multi-species biofilms formed by a mixed culture from wastewater treatment systems. Results showed that silver ion (0.01-1 mg/L) treatment alone failed to remove the existing wastewater biofilms. Norspermidine at the concentrations of 500-1000 µM was capable to disrupt and disperse the existing biofilms with a biofilm reduction of 21-34 % after 24-h exposure. The combined treatment with norspermidine (500 µM) and silver ion (0.01 mg/L) increased biofilm reduction to 48 % (24-h exposure). The combined treatment also enhanced biofilm disinfection ratio (82 %, 2-h exposure) by 2.0- and 2.6-folds compared to norspermidine (27 %) or silver ion (23 %) treatment alone, respectively. Confocal laser scanning microscopic (CLSM) observations found that norspermidine could disrupt biofilm matrix and promote biofilm dispersal via breaking down exopolysaccharides. The combined treatment increased the reduction in biofilm cell density and viability, possibly due to the damage of biofilm matrix, enhanced silver ion diffusion in biofilms, and increased biofilm sensitivity. These findings indicate that the combination of a small molecule norspermidine with a traditional biocide silver ion presents a novel strategy to remove and kill biofilms, which have a potential application in addressing wastewater biofilm-related issues.

A small-molecule norspermidine and norspermidine-hosting polyelectrolyte coatings inhibit biofilm formation by multi-species wastewater culture.

Norspermidine is a potent and non-bactericidal small-molecule inhibitor of biofilm growth. In this study, impacts of norspermidine on biofilm control and existing biofilm dispersal by a mixed culture from wastewater treatment systems were investigated. A surface-mediated releasing approach for prevention of bacterial biofilm formation was established via encapsulating norspermidine into polyelectrolyte multilayer coatings. Results showed that the presence of norspermidine (500-1000 µM) in medium remarkably prevented biofilm formation. Norspermidine was also effective in disassembling pre-formed biofilms. Norspermidine-containing multilayer coatings were successfully fabricated on glass slides via layer-by-layer deposition in polyethylenimine (PEI) and poly(acrylic acid) (PAA) solution. This coating exhibited a high anti-biofilm property against a mixed culture and three pure strains (Bacillus subtilis, Pseudomonas aeruginosa, and Escherichia coli). The loading amount and space distribution of norspermidine in the multilayer coating were key factors influencing its anti-biofilm efficacy. The polymer coating with norspermidine loaded in each bilayer (each-layer-type) exhibited better anti-biofilm efficacy than the bottom-type and the top-type coating, which showed a stable biofilm inhibition rate of about 60 % even after 5-day leaching in aqueous solution. Norspermidine could retard bacterial adhesion and destruct biofilm matrix by reducing exopolysaccharides and extracellular DNA (eDNA) associated with bacteria instead of growth inhibition. Norspermidine and the norspermidine-hosting coatings in this study offer a great potential for the control of biofilms in the settings of water purification and wastewater treatment systems, which shows the advantage of broad spectrum and less risk of evolved bacterial resistance compared to conventional microbicidal agents (e.g., antibiotics).

Effects of D-amino acids and norspermidine on the disassembly of large, old-aged microbial aggregates.

The increasing threat of microbial aggregates in many fields highlights the need to develop methods to promote their disassembly. This study investigated the coupled effects of d-tyrosine (d-Tyr) and norspermidine on the disassembly of a type of old-aged (more than 6 months), large (about 900 µm) microbial aggregate formed by mixed culture. Results showed that d-Tyr and norspermidine acting together effectively triggered the disassembly of microbial aggregates, with disassembly ratio enhanced by 30-164% compared to the control at the concentration of 50-500 µM of d-Tyr and norspermidine. d-Tyr and norspermidine reduced the content of extracellular protein and polysaccharide in microbial aggregates and altered the matrix structure of extracellular polymeric substances as confirmed by a confocal laser scanning microscope. The microbial aggregates lost stability after treatment with d-Tyr and norspermidine as could be seen from the increase in surface negative charge and decrease in cell hydrophobicity. Fourier transform infrared spectroscopy analysis revealed that norspermidine could directly interact with polysaccharide and caused the disappearance of an IR band at 1152 cm(-1) that may be correlated with the functional group C-O-C. Overall, the combined application of d-amino acids and norspermidine offers an effective approach to disassemble large and resistant microbial aggregates.

Responses of anaerobic granule and flocculent sludge to ceria nanoparticles and toxic mechanisms.

Effects of CeO2-NPs on anaerobic fermentation were investigated from the processes of acidification and methanation with anaerobic granule sludge and anaerobic flocculent sludge as the targets. Results showed that acidification process was more sensitive to CeO2-NPs than methanation process. Both types of sludge produced less short-chain fatty acid compared to the control, with a reduction of 15-19% for the flocculent sludge at the dosage of 5, 50 and 150 mg CeO2-NPs/g-VSS, and a reduction of 35% for the granular sludge at 150 mg CeO2-NPs/g-VSS. CeO2-NPs caused no inhibition to methanation process. Most of CeO2-NPs distributed on the surface of sludge as revealed by fluorescence labeled CeO2-NPs. The toxicity of CeO2-NPs to anaerobic sludge did not result from reactive oxygen species. Physical penetration and membrane reduction may be important toxic mechanisms.

Degradation behavior of 17alpha-ethinylestradiol by ozonation in the synthetic secondary effluent.

Endocrine disrupting chemicals (EDCs) in the secondary effluent discharged from wastewater treatment plants (WWTPs) are of great concern in the process of water reuse. Ozonation has been reported as a powerful oxidation technology to eliminate micropollutants in water treatment. Due to the complexity of the wastewater matrix, orthogonal experiments and single factor experiments were conducted to study the influence of operational parameters on the degradation of 17a-ethinylestradiol (EE2) in the synthetic secondary effluent. The results of the orthogonal experiments indicated that the initial ozone and natural organic matter (NOM) concentration significantly affected EE2 degradation efficiency, which was further validated by the single factor confirmation experiments. EE2 was shown to be effectively degraded by ozonation in the conditions of low pH (6), NOM (10 mg/L), carbonate (50 mg/L), but high suspended solid (20 mg/L) and initial ozone concentration (9 mg/L). The study firstly revealed that the lower pH resulted in higher degradation of EE2 in the synthetic secondary effluent, which differed from EDCs ozonation behavior in pure water. EE2 degradation by ozone molecule instead of hydroxyl radical was proposed to play a key role in the degradation of EDCs by ozonation in the secondary effluent. The ratio between 03 and TOC was identified as an appropriate index to assess the degradation of EE2 by ozonation in the synthetic secondary effluent.