Effect of influent nutrient ratios and hydraulic retention time (HRT) on simultaneous phosphorus and nitrogen removal in a two-sludge sequencing batch reactor process

A laboratory-scale anaerobic–anoxic/nitrification sequencing batch reactor (A2N- SBR) fed with domestic wastewater was operated to examine the effect of varying ratios of influent COD/P, COD/TN and TN/P on the nutrient removal. With the increased COD/P, the phosphorus removals exhibited an upward trend. The influent TN/P ratios had a positive linear correlation with the phosphorus removal efficiencies, mainly because nitrates act as electron acceptors for the phosphorus uptake in the A2N-SBR. Moreover, it was found that lower COD/TN ratio, e.g. 3.5, did not significantly weaken the phosphorus removal, though the nitrogen removal first decreased greatly. The optimal phosphorus and nitrogen removals of 94% and 91%, respectively were achieved with influent COD/P and COD/ TN ratios of 19.9 and 9.9, respectively. Additionally, a real-time control strategy for A2N-SBR can be undertaken based on some characteristic points of pH, redox potential (ORP) and dissolved oxygen (DO) profiles in order to obtain the optimum hydraulic retention time (HRT) and improve the operating reliabili

Enantiocomplementary synthesis of chiral alcohols combining photocatalysis and whole-cell biocatalysis in a one-pot cascade process

As a powerful tool in synthetic organic chemistry, photocatalysis has the features of green, better atom economy, and mild conditions [1-2]. Recently, some cascade reaction protocols have been properly designed by combining photocatalysis and biocatalysis[3-4]. For example, Zhao and Hartwig reported an asymmetric reaction which coupled photocatalysts for E/Z isomerization of alkenes with ene-reductases for the reduction of carbon–carbon double bonds, to generate valuable enantioenriched products [5], which achieved the dual-advantages of both photocatalysis and biocatalysis. We envisioned a photochemo-enzymatic one-pot whole-cell process to convert a series of carboxylic acids into corresponding chiral alcohols with good yields (up to 93%) and excellent stereoselectivity (up to 99% ee). The photocatalysis step was conducted in aqueous phase by using O2 as oxidant and the following whole cell bioreduction without the addition of the expensive cofactor NADPH was a much milder and more efficient approach to obtain chiral alcohols. All these advantages indicate that the photochemo-enzymatic one-pot transformation may have great potential in green synthetic chemistry. Please click Additional Files below to see the full abstract

Inactivation and adaptation of ammonia-oxidizing bacteria and nitrite-oxidizing bacteria when exposed to free nitrous acid

Inactivation and adaptation of ammonia-oxidizing bacteria (AOB) and nitrite-oxidizing bacteria (NOB) to free nitrous acid (FNA) was investigated. Batch test results showed that AOB and NOB were inactivated when treated with FNA. After an 85-day operating period, AOB in a continuous pre-denitrification reactor did not adapt to the FNA that was applied to treat some of the return activated sludge. In contrast, NOB did adapt to FNA. NOB activity in the seed sludge was only 11% of the original activity after FNA batch treatment, at 0.75 mg HNO2-N/L. NOB activity in the pre-denitrification reactor was not affected after being exposed to this FNA level. Nitrosomonas was the dominant AOB before and after long-term FNA treatment. However, dominant NOB changed from Nitrospira to Candidatus Nitrotoga, a novel NOB genus, after long-term FNA treatment. This adaptation of NOB to FNA may be due to the shift in NOB population makeup

Filamentous and non-filamentous bulking of activated sludge encountered under nutrients limitation or deficiency conditions

Although the limitation or deficiency of nutrients, such as nitrogen (N) and phosphorus (P), has been one of the frequently reported factors causing filamentous or non-filamentous bulking of activated sludge, the mechanisms are still unclear. In this work, the long-term effects of N and P limitation or deficiency on sludge settleability and bioflocculation characteristics were investigated in six sequencing batch reactors (SBRs) fed with wastewater with different nutrient availability. The sludge volume index (SVI), microbial community structures, intracellular poly-β-hydroxyalkanoates (PHAs) and extracellular polymeric substances (EPS) were characterised over time. Bulking was not observed in SBRs with N limitation or deficiency, in which SVI remained below 150. mL/g. In contrast, bulking was encountered in those reactors with P deficiency. The occurrence of non-filamentous bulking was associated with a higher carbohydrates fraction and a lower proteins fraction in EPS. In the case of filamentous bulking, SVI correlated negatively with the amount of PHAs. Our experimental data support the hypothesis that the occurrence and/or the type of bulking in activated sludge could be affected by the combination of kinetic selection, microbial storage, as well as the EPS composition

The effect of poly-β-hydroxyalkanoates degradation rate on nitrous oxide production in a denitrifying phosphorus removal system

Poly-beta-hydroxyalkanoates (PHAs) and free nitrous acid (FNA) have been revealed as significant factors causing nitrous oxide (N2O) production in denitrifying phosphorus removal systems. In this study, the effect of PHA degradation rate on N2O production was studied at low FNA levels. N2O production always maintained at approximately 40% of the amount of nitrite reduced independent of the PHA degradation rate. The electrons distributed to nitrite reduction were 1.6 times that to N2O reduction. This indicated that electron competition between these two steps was not affected by the PHA degradation rate. Continuous feed of nitrate was proposed, and demonstrated to reduce N2O accumulation by 75%. While being kept low, a possible compounding effect of a low-level FNA could not be ruled out. The sludge used likely contained both polyphosphate- and glycogen-accumulating organisms, and the results could not be simply attributed to either group of organisms. (C) 2014 Elsevier Ltd. All rights reserved

Bidirectional associations between hearing difficulty and cognitive function in Chinese adults: a longitudinal study

BackgroundMiddle-aged and older adults frequently experience hearing loss and a decline in cognitive function. Although an association between hearing difficulty and cognitive function has been demonstrated, its temporal sequence remains unclear. Therefore, we investigated whether there are bidirectional relationships between hearing difficulty and cognitive function and explored the mediating role of depressive symptoms in this relationship.MethodWe used the cross-lagged panel model and the random-intercept cross-lagged panel model to look for any possible two-way link between self-reported hearing difficulty and cognitive function. To investigate depressive symptoms’ role in this association, a mediation analysis was conducted. The sample was made up of 4,363 adults aged 45 and above from the China Health and Retirement Longitudinal Study (CHARLS; 2011–2018; 44.83% were women; mean age was 56.16 years). One question was used to determine whether someone had a hearing impairment. The tests of cognitive function included episodic memory and intelligence. The Center for Epidemiologic Studies Depression Scale, which consists of 10 items, was used to measure depressive symptoms.ResultsA bidirectional association between hearing and cognition was observed, with cognition predominating (Wald χ2 (1) = 7.241, p < 0.01). At the between-person level, after controlling for potential confounders, worse hearing in 2011 predicted worse cognitive function in 2013 (β = −0.039, p < 0.01) and vice versa (β = −0.041, p < 0.01) at the between-person level. Additionally, there was no corresponding cross-lagged effect of cognitive function on hearing difficulty; rather, the more hearing difficulty, the greater the cognitive decline at the within-person level. According to the cross-lagged mediation model, depressive symptoms partially mediates the impact of cognitive function on subsequent hearing difficulty (indirect effect: −0.003, bootstrap 95% confidence interval: −0.005, −0.001, p < 0.05), but not the other way around.ConclusionThese results showed that within-person relationships between hearing impairment and cognitive function were unidirectional, while between-person relationships were reciprocal. Setting mental health first may be able to break the vicious cycle that relates hearing loss to cognitive decline. Comprehensive long-term care requires services that address depressive symptoms and cognitive decline to be integrated with the hearing management

Concrete sewer pipe corrosion induced by sulphuric acid environment

Corrosion of concrete sewer pipes induced by sulphuric acid attack is a recognised problem worldwide, which is not only an attribute of countries with hot climate conditions as thought before. The significance of this problem is by far only realised when the pipe collapses causing surface flooding and other severe consequences. To change the existing post-reactive attitude of managing companies, easy to use and robust models are required to be developed which currently lack reliable data to be correctly calibrated. This paper focuses on laboratory experiments of establishing concrete pipe corrosion rate by submerging samples in to 0.5 pH sulphuric acid solution for 56 days under 10ºC, 20ºC and 30ºC temperature regimes. The result showed that at very early stage of the corrosion process the samples gained overall mass, at 30ºC the corrosion progressed quicker than for other temperature regimes, however with time the corrosion level for 10ºC and 20ºC regimes tended towards those at 30ºC. Overall, at these conditions the corrosion rates of 10 mm/year, 13,5 mm/year and 17 mm/year were observed

Structural variation and introgression from wild populations in East Asian cattle genomes confer adaptation to local environment

BACKGROUND: Structural variations (SVs) in individual genomes are major determinants of complex traits, including adaptability to environmental variables. The Mongolian and Hainan cattle breeds in East Asia are of taurine and indicine origins that have evolved to adapt to cold and hot environments, respectively. However, few studies have investigated SVs in East Asian cattle genomes and their roles in environmental adaptation, and little is known about adaptively introgressed SVs in East Asian cattle. RESULTS: In this study, we examine the roles of SVs in the climate adaptation of these two cattle lineages by generating highly contiguous chromosome-scale genome assemblies. Comparison of the two assemblies along with 18 Mongolian and Hainan cattle genomes obtained by long-read sequencing data provides a catalog of 123,898 nonredundant SVs. Several SVs detected from long reads are in exons of genes associated with epidermal differentiation, skin barrier, and bovine tuberculosis resistance. Functional investigations show that a 108-bp exonic insertion in SPN may affect the uptake of Mycobacterium tuberculosis by macrophages, which might contribute to the low susceptibility of Hainan cattle to bovine tuberculosis. Genotyping of 373 whole genomes from 39 breeds identifies 2610 SVs that are differentiated along a "north-south" gradient in China and overlap with 862 related genes that are enriched in pathways related to environmental adaptation. We identify 1457 Chinese indicine-stratified SVs that possibly originate from banteng and are frequent in Chinese indicine cattle. CONCLUSIONS: Our findings highlight the unique contribution of SVs in East Asian cattle to environmental adaptation and disease resistance