Enhanced photo-degradation of N-methyl-2-pyrrolidone (NMP): Influence of matrix components, kinetic study and artificial neural network modelling

New insights into algal-bacterial sludge granulation based on the tightly-bound extracellular polymeric substances regulation in response to N-Methylpyrrolidone

Algal-bacterial granular sludge (ABGS) system is promising in wastewater treatment for its potential in energy-neutrality and carbon-neutrality. However, traditional cultivation of ABGS poses significant challenges attributable to its long start-up period and high energy consumption. Extracellular polymeric substances (EPS), which could be stimulated as a self-defense strategy in cells under toxic contaminants stress, has been considered to contribute to the ABGS granulation process. In this study, photogranulation of ABGS by EPS regulation in response to varying loading rates of N-Methylpyrrolidone (NMP) was investigated for the first time. The results indicated the formation of ABGS with a maximum average diameter of ∼3.3 mm and an exceptionally low SVI5 value of 67 ± 2 mL g-1 under an NMP loading rate of 125 mg L-1 d-1, thereby demonstrating outstanding settleability. Besides, almost complete removal of 300 mg L-1 NMP could be achieved at hydraulic retention time of 48 h, accompanied by chemical oxygen demand (COD) and total nitrogen (TN) removal efficiencies higher than 90 % and 70 %, respectively. Moreover, possible degradation pathway and metabolism mechanism in the ABGS system for enhanced removal of NMP and nitrogen were proposed. In this ABGS system, the mycelium with network structure constituted by filamentous microorganisms was a prerequisite for photogranulation, instead of necessarily leading to granulation. Stress of 100-150 mg L-1 d-1 NMP loading rate stimulated tightly-bound EPS (TB-EPS) variation, resulting in rapid photogranulation. The crucial role of TB-EPS was revealed with the involved mechanisms being clarified. This study provides a novel insight into ABGS development based on the TB-EPS regulation by NMP, which is significant for achieving the manipulation of photogranules.

N-methyl pyrrolidone manufacturing wastewater as the electron donor for denitrification: From bench to pilot scale

Actual wastewater generated from N-methylpyrrolidone (NMP) manufacture was used as electron donor for tertiary denitrification. The organic components of NMP wastewater were mainly NMP and monomethylamine (CH3NH2), and their biodegradation released ammonium that was nitrified to nitrate that also had to be denitrified. Bench-scale experiments documented that alternating denitrification and nitrification realized effective total‑nitrogen removal. Ammonium released from NMP was nitrified in the aerobic reactor and then denitrified when actual NMP wastewater was used as the electron donor for endogenous and exogenous nitrate. Whereas TN and NMP removals occurred in the denitrification step, dissolved organic carbon (DOC) and CH3NH2 removals occurred in the denitrification and nitrification stages. The genera Thauera and Paracoccus were important for NMP biodegradation and denitrification in the denitrification reactor; in the nitrification stage, Amaricoccus and Sphingobium played key roles for biodegrading intermediates of NMP, while Nitrospira was responsible for NH4+ oxidation to NO3-. Pilot-scale demonstration was achieved in a two-stage vertical baffled bioreactor (VBBR) in which total‑nitrogen removal was realized sequential anoxic-oxic treatment without biomass recycle. Although the bench-scale reactors and the VBBR had different configurations, both effectively removed total nitrogen through the same mechanisms. Thus, an N-containing organic compound in an industrial wastewater could be used to drive total-N removal in a tertiary-treatment scenario.

Highly sensitive and repeatable recording photopolymer for holographic data storage containing N-methylpyrrolidone

The low photosensitivity of phenanthraquinone-doped poly(methyl methacrylate) (PQ/PMMA) severely limits its recording speed for holographic data storage. A high-performance holographic recording medium based on a unique combination of N-methylpyrrolidone (NMP) regulated PQ/PMMA has been developed. A NMP-PQ/PMMA photopolymer with high sensitivity, high diffraction efficiency and negligible volume shrinkage was successfully fabricated by tuning the composition of the PMMA matrix by varying the ratio of NMP to monomers. The photosensitivity is increased by 6.9 times (from 0.27 cm J-1 to 1.86 cm J-1), the diffraction efficiency is increased from 60% to > 80%, and volume shrinkage is decreased by a factor of 2 (from 0.4% to 0.2%). Further investigation revealed that the addition of NMP significantly reduced the molecular weight of PMMA and increased the amount of MMA residuals, while also improving the solubility of PQ molecules. More interestingly, for the first time, the NMP-PQ/PMMA material could record data information repeatedly at least 6 times. The present study elucidates that the introduction of NMP not only modulates the molecular weight of PMMA but also enables the residual monomer MMA to more easily combine with PQ to form a photoproduct for improved holographic performance.

Post-Global Pandemic Challenges and improvements in advanced detection and removal processes of toxic pollutants: Editorial

Every two years, the Pollutant Toxic Ions and Molecules Conference, PTIM, meets the environmentalist, biologist, chemists and health researchers in Costa de Caparica, Portugal, to showcase the latest technologies, methodologies and research advances in pollution detection, contamination control, remediation, and related health issues, as well as policy implications.