RESUMO
This study researched microbial community succession in response to sludge composting efficiency and heavy metal detoxification during municipal sludge co-composting with spent mushroom and spent bleaching. The change law of key physicochemical properties, the heavy metals contents and forms during composting were analyzed, and the passivation of heavy metals after composting was explored. High-throughput sequencing was used to analyze the microbial community structure of treat 2 during composting, and the correlation analysis of microbial community structure with heavy metal contents and forms were carried out. The results showed that the sludge of each treatment reached composting maturity after 26 days of composting. Organic matter content, electrical conductivity, pH and seed germination index of treat 2 were all in line with the standard limit of agricultural sludge. Because of the presence of compost bacteria addition, the passivating heavy metals performance of treat 2 satisfied the standard limit of agricultural sludge after composting, which was superior to that of treat 1 and treat 3. The diversity of microbial communities in treat 2 decreased during composting. Extensive bacteria such as Bacillus, Geobacter, Lactobacillus, and Pseudomonas, which possessed the abilities of heavy metal passivation and organic oxidizing, were dominant in treat 2 during the heating stage. However, as composting proceeded, Tuberibacillus with ability of organic oxidizing gradually became the most dominant species at the thermophilic and cooling stages. Changes in microbial function varied from changes of microbial community in treat 2, subsequently affected the performances of heavy metal passivation and organic oxidizing during composting.
RESUMO
A detailed study has been carried out on monohydroxycucurbit[7]uril-based stir-bar sorptive extraction (SBSE). A polydimethylsiloxane coating was produced by a sol-gel technique and doped with monohydroxycucurbit[7]uril ((HO)1Q [7]) as a selective sorbent phase. (HO)1Q [7] was chemically bound to the sol-gel silica substrate through hydrolysis and polycondensation. The coating possesses a porous surface, shows strong solvent resistance and good thermal stability, and has a long lifespan. Four groups of compounds, with polarities ranging from apolar polycyclic aromatic hydrocarbons to polar ketones, aromatic amines and phenols, were selected as test analytes. They were extracted with the coated stir bar, then desorbed with methanol and quantified by high-performance liquid chromatography with ultraviolet detection. The limits of detection range between 1.3 and 15 µg L-1, the linear ranges extend from 5 to 10,000 µg L-1, and the relative recoveries from spiked samples range between 76.4 and 97.9%. The intraday relative standard deviations range from 2.3 to 8.6% (for n = 3, at 500 µg L-1). Compared with a commercial PDMS-coated stir bar and a polyether sulfone-coated stir bar, the new stir bar shows wider applicability and better extraction efficiency for each group of compounds. In addition, the stir bar can simultaneously extract mixtures of chemicals of different polarities. This endows it with the potential for recovering a broad group of polar organic compounds. Graphical abstractA stir bar for sorptive extraction based on monohydroxycucurbit[7]uril has been prepared by a sol-gel technique. The stir bar coupled with HPLC with UV detection allows for the determination of a variety of polar compounds and multicomponent mixtures, respectively.
