Microplastics have aroused increasing concern as they pose threats to aquatic species as well as human beings. They do not only contribute to accumulation of plastics in the environment, but due to absorption they can also contribute to spreading of micropollutants in the environment. Studies indicated that wastewater treatment plants (WWTPs) play an important role in releasing microplastics to the environment. Therefore, effective detection of the microplastics and understanding their occurrence and fate in WWTPs are of great importance towards microplastics

Anaerobic digestion of waste activated sludge (WAS) is currently enjoying renewed interest due to the potential for methane production. However, methane production is often limited by the slow hydrolysis rate and/or poor methane potential of WAS. This study presents a novel pretreatment strategy based on free nitrous acid (FNA or HNO2) to enhance methane production from WAS. Pretreatment of WAS for 24 h at FNA concentrations up to 2.13 mg N/L substantially enhanced WAS solubilization, with the highest solubilization (0.16 mg chemical oxygen demand (COD)/mg volatile solids (VS), at 2.13 mg HNO2-N/L) being six times that without FNA pretreatment (0.025 mg COD/mg VS, at 0 mg HNO2-N/L). Biochemical methane potential tests demonstrated methane production increased with increased FNA concentration used in the pretreatment step. Model-based analysis indicated FNA pretreatment improved both hydrolysis rate and methane potential, with the highest improvement being approximately 50% (from 0.16 to 0.25 d(-1)) and 27% (from 201 to 255 L CH4/kg VS added), respectively, achieved at 1.78-2.13 mg HNO2-N/L. Further analysis indicated that increased hydrolysis rate and methane potential were related to an increase in rapidly biodegradable substrates, which increased with increased FNA dose, while the slowly biodegradable substrates remained relatively static.

Background Bread wheat is one of the most important and broadly studied crops. However, due to the complexity of its genome and incomplete genome collection of wild populations, the bread wheat genome landscape and domestication history remain elusive. Results By investigating the whole-genome resequencing data of 93 accessions from worldwide populations of bread wheat and its diploid and tetraploid progenitors, together with 90 published exome-capture data, we find that the B subgenome has more variations than A and D subgenomes, including SNPs and deletions. Population genetics analyses support a monophyletic origin of domesticated wheat from wild emmer in northern Levant, with substantial introgressed genomic fragments from southern Levant. Southern Levant contributes more than 676 Mb in AB subgenomes and enriched in the pericentromeric regions. The AB subgenome introgression happens at the early stage of wheat speciation and partially contributes to their greater genetic diversity. Furthermore, we detect massive alien introgressions that originated from distant species through natural and artificial hybridizations, resulting in the reintroduction of ~ 709 Mb and ~ 1577 Mb sequences into bread wheat landraces and varieties, respectively. A large fraction of these intra- and inter-introgression fragments are associated with quantitative trait loci of important traits, and selection events are also identified. Conclusion We reveal the significance of multiple introgressions from distant wild populations and alien species in shaping the genetic components of bread wheat, and provide important resources and new perspectives for future wheat breeding. Electronic supplementary material The online version of this article (10.1186/s13059-019-1744-x) contains supplementary material, which is available to authorized users.

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Biological nitrogen removal through the nitrite pathway (NH → NO → N) is favorable for wastewater treatment plants without sufficient carbon sources. This study demonstrates an innovative approach for attaining the nitrite pathway based on sludge treatment using free ammonia (FA, i.e., NH). This approach is based on our innovative discovery in this study that FA at 210 mg NH-N/L is far less biocidal to ammonium-oxidizing bacteria (AOB) than to nitrite-oxidizing bacteria (NOB). A total of 22% of the activated sludge from the sequencing batch reactor (SBR) receiving synthetic domestic wastewater was treated in an FA treatment unit at 210 mg NH-N/L for 1 day. The FA-treated sludge was afterward recirculated back to the SBR. A nitrite accumulation ratio of above 90% was quickly achieved (in 40 days) and maintained stably in the SBR, indicating the establishment of the nitrite pathway. The NOB population and activity after implementing FA treatment was less than 5% of those without FA treatment, suggesting the washout of NOB. In contrast, the AOB population and activity in the SBR were not affected. The nitrogen-removal performance was significantly improved after incorporating the FA approach. The FA approach is a closed-loop approach and is economically and environmentally attractive.