Impact of sewage sludge treatment processes on the removal of the endocrine disrupters nonylphenol ethoxylates

Several treatment processes of mixed sludge naturally contaminated with nonylphenol ethoxylates (NPE) were compared in order to evaluate their efficiency for the removal of these endocrine disrupters. Anaerobic and aerobic treatments were carried out in continuous stirred tank reactors, operated separately or combined together, at mesophilic and thermophilic temperatures and with or without ozone post-treatment. Anaerobic mesophilic removal of NPE consisted of complete removal of nonylphenol diethoxylate, incomplete removal of nonylphenol monoethoxylate and non stoechiometric production of nonylphenol, with consequently a NPE removal of 25%. At thermophilic temperature, anaerobic digestion led to an increase of the total solids removal efficiency, while improving NPE degradation (30%). Under thermophilic aerobic condition, the three compounds were removed simultaneously with a NPE removal efficiency higher than under anaerobic condition (39%). This removal is always well correlated to the total solids removal meaning that bioavailability remains the main limiting factor. Combination of either thermophilic aerobic-mesophilic anaerobic or mesophilic anaerobic-ozonation treatments enhanced the NPE removal by comparison to single systems (45% and 48%, respectively). These results confirm the high potential of existing and up-grading sewage sludge treatments to degrade such refractory and aged compounds.     

Re-evaluation of the conformational structure of sulfadiazine species using NMR and ab initio DFT studies and its implication on sorption and degradation

In the environment, the sorption and the degradation of organic pollutants are of increasing interest. The investigation of the chemical structures provides a basis for the development of a suitable binding model approach and for the mechanistic understanding of the chemical fate processes. The aim of this study was the identification of different species of the antibiotic compound sulfadiazine (SDZ) using (1)H and (13)C NMR experiments and ab initio density functional theory (DFT) calculations. In the neutral, aprotic solvent dimethylsulfoxide-d(6) (DMSO-d(6)), a new sulfadiazine structure containing an O-H-N hydrogen bond was identified. In the protic solvent water-d(2) and in dependence on pH and the position of the amidogen hydrogen atom nine possible SDZ conformations were analyzed and five structures were identified. Good conformity between theory and calculation of (1)H NMR was observed. Unfortunately, (13)C NMR is not sensitive enough for comparison and differentiation. In order to verify the identified structures, additional NBO/NLMO (natural localized molecular orbital) analyses were conducted (calculation of net atomic charges, bond polarity, atomic valence, and electron delocalization). Finally, conformation optimizations were performed in order to investigate the stability of the SDZ species. We showed that SDZ contains no S=O double bond, but that it has two S-O single bonds. Surprisingly, negative charges were observed at the pyrimidine nitrogen atom. With these results, the known structure of SDZ was revised. Studies of the geometrical structure and the torsion angles showed that SDZ is very flexible and can be easily fitted to the sorbent. These observations would explain the strong sorbance and hence the rapid formation of non-extractable residues in the environment because SDZ acts as a strong ligand. These results show that that the sulfonamide hydrogen is important for the biological activity but the pyrimidine nitrogen and the sulfonamide oxygen is responsible for the sorbance in environment.     

Hydrochemical characteristics and quality assessment of shallow groundwater in Yangtze River Delta of eastern China

Environmental Science and Pollution Research - Water resource is in high demand within the Yangtze River Delta, given its developed economy. Long-term exploitation of this resource has posed risks...