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Abstract Ferric chloride (FC) is widely used in sewage treatment and sludge conditioning, which could be inevitably accumulated in waste-activated sludge (WAS). However, its effect on short-chain fatty acids (SCFAs) production from WAS anaerobic fermentation has yet to be thoroughly investigated. This study aims to reveal how different dosages of FC affect the production of SCFAs and elucidate the corresponding mechanism. Experimental results showed that 16 mg Fe/g total suspended solids (TSS) of FC was favorable for SCFAs production, with the maximum production was 3.3 times of the control. Mechanistic study revealed that FC induced dissimilatory iron reduction (DIR) and enhanced hydrolase activities, contributing to the disintegration of WAS flocs and the hydrolysis of complex organics. Moreover, FC stimulated the productivity of HAc by promoting the release of carbon-rich substrates and accepting the intermediate electrons generated in acetogenesis process. Further study indicated FC inhibited the methanogenesis and changed the acid-fermentation type by affecting pH and ORP, which was conducive to SCFAs accumulation. Microbial community analysis confirmed that FC enriched the bacterial microorganisms related to hydrolysis and acidogenesis, and increased the abundance of Fe(III)-reducing genera. However, excessive FC (>16 mg Fe/g TSS) inhibited SCFAs production, due to the strong aggregation increased mass transfer resistance and the “over-acidification” damaged the microbial community.

Abstract Thermal desalination technologies play a dominant role in seawater desalination, especially in GCC countries. However, the energy-intensive nature of these technologies limits their applications to relatively affluent regions. Therefore, it is of great significance to introduce new heat sources, e.g. renewable energy and industry waste heat, for thermal desalination. The spray-assisted low-temperature desalination (SLTD) is a novel technology that utilizes low-grade heat sources effectively. This paper specially adopts the SLTD technology to sensible heat sources. The performance of a conventional steam-driven SLTD system employing sensible heat sources is firstly investigated. Analytical results reveal that the conventional configuration is unable to make full use of the sensible heat sources. In order to improve energy utilization, the configuration is modified to enable internal heat recovery. The proposed configuration is able to boost the freshwater production by as much as 79%, while the desalination cost is reduced by 11%.

T oilfield is the fractured-vuggy carbonate reservoir at a temperature of around 130 °C, with salinity of up to 22 × 104 mg/L. In order to solve the problem of the high water cut in the late development stage of T oilfield, we selected XN-T from 27 kinds of swelling retarding particles by testing their swelling capacity, and coated a thin film to improve its retarding swelling capacity. The mechanisms of strong water absorption and water-holding abilities of particles were analyzed by infrared spectrometry and SEM. In the core flow experiment, the plugging rate was found to be 98.42%. Finally, the injection parameters of the coated particles were optimized to maximize the water plugging and profile control ability, resulting in an optimal particle size of 0.4–0.6 mm and a mass fraction of 10%.

Extreme events normally have negative effects on crop growth. Many studies have reported findings on drought and flood events, while only sparse studies have focused on new types of extreme events, such as drought-flood abrupt alternation (DFAA). We attempted to gain an insight on the effects of DFAA over two-year field experiment on biomass, grain yield and quality, then simulated the yield loss to DFAA in history and future in summer maize planting area in the Northern Anhui Plain. Results show that DFAA significantly reduced root biomass and shoot biomass by 77.1% and 60.1% compared with that in the control systems. The negative effect lasted until mature stage. The grain yield loss was 14.1%–38.4% in different DFAA treatments. The numerical simulation reveals that the average annual yield loss due to DFAA has been increasing in the Northern Anhui Plain, with 21.19%–30.98% during 1964–2017, 14.10%–33.40% during 2020–2050. The spatial distribution of yield loss changed as well. This study increases our knowledge of the effects of DFAA on crop production and highlights the need to consider the targeted countermeasures.

Abstract Previous studies on N 2 -ECBM (N 2 -enhanced coalbed methane) have focused on experimental investigation or numerical simulation of coalbed methane recovery processes using pure N 2 or binary gas (CO 2 /N 2 ) injection. Experimental studies on the changes in pore structure and permeability during N 2 injection have been limited. In this study, N 2 injection experiments, mercury intrusion porosimetry and permeability measurements were conducted to investigate the changes in pore structure and permeability caused by N 2 injection of semi-anthracite coal from the Lu'an mining area in the Qinshui basin, Shanxi Province, China. The results show that the total pore volume markedly increases during N 2 injection, with increases in transition pores, mesopores and macropores of 8.0%, 50.0% and 138.3%, respectively. Nitrogen injection improves the pore size distribution: the incremental pore volume variances of transition pores, mesopores and macropores after treatment are 2.1%, 47.8% and 141.0%, respectively. Porosity and permeability markedly rise during N 2 injection, by 22.6% and 29.9%, respectively. These results demonstrate that N 2 injection mainly affects macropores, followed by mesopores and transition pores, and reformation of the micropores is limited. Nitrogen injection alters the pore structure of coal, which leads to an increase in the pore volume and improvement of the pore size distribution and connectivity: these changes facilitate the diffusion and transfusion of coalbed methane. The permeability of the coal sample was improved as a result of N 2 injection, indicating that N 2 injection could be used to enhance the permeability of CBM reservoirs. These findings will lead to a better understanding of the interactions between pores and N 2 during N 2 injection and hence can be applied to improve CBM recovery for non-productive or low-productivity CBM wells.

Arbuscular mycorrhizal fungi (AMF) can form symbiotic relationships with most terrestrial plants and regulate the uptake and distribution of antimony (Sb) in rice. The effect of AMF on the uptake and transport of Sb in rice was observed using pot experiments in the greenhouse. The results showed that AMF inoculation increased the contact area between roots and metals by forming mycelium, and changed the pH and Eh of the root soil, leading to more Sb entering various parts of the rice, especially at an Sb concentration of 1,200 mg/kg. The increase in metal toxicity further led to a decrease in the rice chlorophyll content, which directly resulted in a 22.7% decrease in aboveground biomass, 21.7% in underground biomass, and 11.3% in grain biomass. In addition, the antioxidant enzyme results showed that inoculation of AMF decreased 22.3% in superoxide dismutase, 9.9% in catalase, and 20.7% in peroxidase compared to the non-inoculation groups, further verifying the negative synergistic effect of AMF inoculation on the uptake of Sb in rice. The present study demonstrated the effect of AMF on the uptake and transport of Sb in the soil–rice system, facilitating future research on the related mechanism in the soil–rice system under Sb stress.

China is confronted with an unprecedented water crisis regarding its quantity and quality. In this study, we quantified the dynamics of China?s embodied water use and chemical oxygen demand (COD) discharge from 2010 to 2015. The analysis was conducted with the latest available water use data across sectors in primary, secondary and tertiary industries and input?output models. The results showed that (1) China?s water crisis was alleviated under urbanisation. Urban consumption occupied the largest percentages (over 30%) of embodied water use and COD discharge, but embodied water intensities in urban consumption were far lower than those in rural consumption. (2) The ?new normal? phase witnessed the optimisation of China?s water use structures. Embodied water use in light-manufacturing and tertiary sectors increased while those in heavy-manufacturing sectors (except chemicals and transport equipment) dropped. (3) Transformation of China?s international market brought positive effects on its domestic water use. China?s water use (116?80 billion tonnes (Bts))(9) and COD discharge (3.95?2.22 million tonnes (Mts)) embodied in export tremendously decreased while its total export values (11?25 trillion CNY) soared. Furthermore, embodied water use and COD discharge in relatively low-end sectors, such as textile, started to transfer from international to domestic markets when a part of China?s production activities had been relocated to other developing countries.

In this study, the electrochemical softening method was used to treat the simulated drainage of the converter station, and the treatment effect under different water inlet conditions was investigated. The results show that the hardness removal rate is from 10% to 80% when the residence time is from 0.5h to 4h, and the longer the residence time is, the higher the removal rate is. The maximum scale removal capacity reached 2.67g/h/m2 when residence time was 1h. Through the formula fitting of several groups of tests, it is concluded that the removal effect can be expressed by the formula C0/C=0.9627e(17.73at/V) under different water intake (residence time).