Dewatering performance of aerobic granular sludge under centrifugal with different sludge conditioning agent.

The aerobic granular sludge(AGS) technology draw scientific researchers attention, and more and more scientific research focuses on it, due to its superior advantages, such as good settling performance, high biological phase, high toxicity resistance and multiple biological effects. With the rapid development of AGS technology, a considerable amount of residual AGS will be produced, and dehydration is the biggest bottleneck of sludge reduction. This study investigated the dewatering process and method of residual AGS cultured by continuous flow experiment. Experiments were conducted using centrifugal dewatering technology with a dosing scheme to analyze the granular sludge dewatering process, and investigate the release process of EPS component in AGS dewatering. Our results implied the specific resistance of AGS has a very low value ((1.82 ± 0.03) × 109 m/kg) and it was not obvious for the conditioning effect of chemical conditioner on AGS dewatering. However, the moisture content can be reduced to 63.5% after dewatering with the presence of inorganic substances. The addition of drinking water treatment plant sludge (Alum sludge) can improve the efficiency of the dewatering of AGS. A possible dewatering process of AGS dewatering was proposed which was divided into two stages: First, a considerable amount of free water in the sludge was quickly removed under the action of gravity without pressure filtration. Second, the bound water release required cooperation between applying centrifugal or pressing force to grind granular cells and separate protein-like substances with the inorganic matter inside the granular sludge. The possible mechanism of AGS dewatering and hypothesis dewatering process are useful to optimize the AGS dewatering process.

Combining Lattice Boltzmann method and genetic algorithm to optimize the layout of artificial floating islands in river network in China.

How to solve the pollution problem of water environment in river network is a hot issue in the world. Artificial floating island is an efficient way to deal with water pollution. Taking Jiashan, Zhejiang, China, as an example, Lattice Boltzmann method (LBM) is used to simulate the law of hydrodynamics and pollutant transport in river network. Lattice Boltzmann equations are established in both artificial floating island and non-artificial floating island sections, and the river network boundary is automatically identified. The simulation results have high accuracy and are more suitable for the establishment of complex boundaries. On this basis, combined with the genetic algorithm (GA) module, the location of the artificial floating island is optimized, and the retention ratio of the pollution in optimized layout of artificial floating island is between and 2.4 and 7.2%. The research results of this paper can provide theoretical reference for the selection and location of artificial floating island in practical engineering.

[Influence of Microplastics on the Development of Proteus Biofilm].

Currently, research on the effects of microplastics (MPs) in biofilms has mainly been focused on the mature biofilm communities, with a lack of sufficient details on the influence on different development stages of biofilms. Proteus and 1 µm polystyrene microplastics (PS-MPs), which are widely found in the environment, were selected as the research objects to explore the effects of microplastics on biofilms at different developmental stages. In our study, the effects of PS-MPs on biofilm biomass, extracellular polymer composition(EPS), and extracellular enzyme activity were investigated using an exposure test. Our results showed that the effect of PS-MPs on biofilms at different stages was similar, but the effect was significantly reduced with the development of biofilms. Biofilms at different development stages had different sensitivities to microplastics. In the reversible attachment stage, the no observed effect concentration (NOEC) of EPS composition, reactive oxygen species (ROS) production, and extracellular enzyme activity were significantly lower than those in other stages; however, the NOEC of total antioxidant capacity (T-AOC) and lactate dehydrogenase (LDH) activity were similar. This may be the result of ROS-mediated protein oxidation, which can be reduced but not completely eliminated by EPS in other stages of biofilm. This indicates that PS-MPs has a low toxic effect on biofilm.

Removal of nitrate from agricultural runoff in biochar electrode based biofilm reactor: Performance and enhancement mechanisms.

A biochar electrode based biofilm reactor was developed for advanced removal of nitrate from agricultural runoff. The corn-straw (Zea mays L.) biochar formed at 500 °C has an adsorption capacity of NO3--N up to 2.659 mg g-1. After 45-day start-up phase, the removal efficiency of nitrate reached 93.4% when impressed current was 20 mA, hydraulic retention time was 12 h and chemical oxygen demand/total nitrogen (C/N) ratio was 0.56 without additional carbon source. In comparison, neither electrochemical reduction alone nor microbial denitrification alone could obtain the ideal nitrate removal efficiency. The results implied that bio-electrochemical reduction was the main way of nitrate removal in the biofilm electrode reactor (BER). The denitrification efficiency of 88.9% could still be obtained when C/N = 0. It is because biochar can significantly promote the utilization efficiency of cathode electrons by microorganisms. Thus, biochar is a promising electrode material, which provides a new idea for the optimization of BER.

Deposition of polystyrene microplastics on bare or biofilm-coated silica analysed via QCM-D.

The mobility of microplastics (MPs) in aqueous media is closely related to their environmental risk. The naturally occurring silica substrate surface in the aquatic environment is easily colonized by microorganisms and forms a biofilm, which may affect the migration and distribution of MPs. Herein, a typical MP, polystyrene (PS), and Pseudomonas fluorescens (P. fluorescens) biofilms were selected to study the deposition and release of pristine or ultraviolet (UV)-aged PS MPs on silica and biofilms under different ionic strengths using a quartz crystal microbalance dissipation (QCM-D) system. Statistical analyses of the deposition experiments revealed a significant impact of P. fluorescens biofilms on deposition (p = 0.0042). The deposition rate of weathered MPs on the biofilms was 4.0 ± 0.1 to 16.3 ± 0.6 times that on silica. A release experiment revealed that the biofilm reduced the release fraction (fr) of weathered MPs by 34.5 ± 0.3 % compared to bare silica. In addition, the UV-ageing treatment reduced the deposition mass of MPs on the surface of silica by 27.6 ± 0.21 % compared to pristine microspheres. The analysis of the deposition mechanism revealed that the promotion and inhibition of biofilm or UV-ageing treatment on the deposition of microspheres could be attributed to the non-Derjaguin-Landau-Verwey-Overbeek (DLVO) force and the decreased electrostatic repulsion or the increased hydration repulsion, respectively.

Label-free ratiometric DNA detection using two kinds of interaction-responsive emission dyes.

A novel ratiometric method with label-free and dual-wavelength signal outputs was developed for DNA detection by employing two kinds of structure-specific dyes that characterising interaction-responsive emission property. The ratiometric platform for the fluorescent detection of DNA was based on target-induced structural transformation from stem-loop structure incorporating split G-quadruplex (SISG) to doubule-strand DNA (dsDNA). The SISG conformation will be disrupted upon binding to the target DNA of perfect complementary sequence, resulting in fluorescence decrease at 610nm as NMM releases from SISG and fluorescence increase at 450nm as DAPI inserts into the dsDNA. The method demonstrated its simplicity in that it saved the trouble of expensive and cumbersome functionalization process compared with reported ratiometric methods, and that the two dyes could be excited at the same excitation wavelength. More intriguingly, the combinatorial employment of the two kinds of structure-selective dyes demonstrated a result of "heterosis", in that this sensor simultaneously inherits the sensitivity of DAPI-based signal and the selectivity of G4-based signal. Besides that, this proposed biosensor has been successfully applied in serum sample for DNA detection, and provided a simple and sensitive method for potential DNA detection in bioanalysis, food analysis and disease diagnostic.