The Treatment of Aquaculture Wastewater with Biological Aerated Filters: From the Treatment Process to the Microbial Mechanism.

Algal cell proliferation has posed significant problems for traditional water treatment facilities; these problems are attributed to surface hydrophilicity and electrostatic repulsion. Biological aerated filters (BAFs) have been extensively used in wastewater treatment to remove pollutants such as algal cells by utilizing the adsorption and separation capabilities of the filter media. In this study, a BAF was supplemented with biological filter medium (Marchantia polymorpha) to assess its effectiveness of pretreating aquaculture wastewater. In terms of process performance, steady and consistent treatment was achieved by the BAF with M. polymorpha (BAF2) under an algal cell density as high as 1.65 × 108 cell/L, with average removal rates for NH4+-N and algae cells of 74.4% and 81.9%, respectively. The photosynthetic activity parameters (rETRmax, α, Fv/Fm, and Ik) of the influent and effluent were quantitatively assessed, and M. polymorpha was found to remove algae by disrupting the photosynthetic system of the algal cells. Furthermore, the addition of the M. polymorpha filter medium enhanced the community structure of the functional microbes in the BAF system. The highest microbial community richness and diversity were observed in the BAF2. Meanwhile, M. polymorpha promoted an increase in the abundance of denitrifying bacteria, including Bdellovibrio and Pseudomonas. Overall, this work offers a unique perspective on the aquaculture wastewater pretreatment process and BAF design.

Efficient Microcystis aeruginosa coagulation and removal by palladium clusters doped g-C3N4 with no light irradiation.

Efficient treatment of cyanobacterial blooms in eutrophication waters by safe and reliable nanomaterials is a big challenge for reducing environmental health risks. Herein, a novel strategy combining palladium clusters (Pdn) with g-C3N4 nanocomposite was presented to achieve high-efficient removal of Microcystis aeruginosa cells through coagulation and breakage. Interestingly, 95.17% of algal cells (initial concentration of 5.6 × 106 cells mL-1) were promptly removed in the Pd/g-C3N4 (5%) system within only 10 min and without visible light irradiation and persulfate activation. Both the release of potassium ion and microcystin during the removal process and the transmission electron microscope observations of Microcystis aeruginosa cells proved that the integrity of the algal cell membrane was destroyed. The removal of Microcystin-LR (MC-LR) were further confirmed in the next process. Pd metal interaction and breakage against algal cells may cause disruption of algal cells. This study describes a novel technology for the superfast removal of harmful algae and may provide a new insight into the control of cyanobacterial blooms in practical applications.

Heterogeneously activation of H2O2 and persulfate with goethite for bisphenol A degradation: A mechanistic study.

Advanced oxidation processes (AOPs) based on the activation of hydrogen peroxide (H2O2) and persulfate (PS) by minerals have received increasing interest for environmental remediation. Herein, H2O2 and PS activation systems employing goethite as a catalyst were discovered for the rapid degradation of BPA with the generation of reactive oxidation species (ROS) and for the reduction of total organic carbon (TOC) in aqueous solutions. The morphology of goethite were characterized by XRD, SEM, BET, TEM, etc. As a result, the oxidant efficiency of the goethite/H2O2 system (75.9%) was higher than that of the goethite/PS system (61.4%) after 240 min due to the restricted radical scavenging. According to the results of electron paramagnetic resonance (EPR) and radical quenching experiments, the main active ROS during the BPA degradation process were OH and SO4-. The two reaction systems were all pH-dependent that BPA can be effectively degraded in the goethite/PS system under acidic, neutral and weakly alkaline conditions, while the most inefficient degradation under alkaline conditions in the goethite/H2O2 system. Moreover, goethite showed good structural stability in the two systems. Several reaction products were detected using LC-MS, and the mechanisms for three systems were proposed. Density functional theory (DFT) was employed to study the conceivable degradation pathways of BPA in the two processes. This work reveals novel mechanistic insights regarding H2O2 and PS activation over goethite and implies the great potential application of the PS/mineral process in water and wastewater treatment.

Enhanced photocatalytic reduction for the dechlorination of 2-chlorodibenzo-p-dioxin by high-performance g-C3N4/NiO heterojunction composites under ultraviolet-visible light illumination.

Polychlorinated dibenzo-p-dioxins (PCDDs), characterized by their high persistency and bioaccumulation, are widely detected in the environment. In this study, high-performance g-C3N4/NiO heterojunctions were fabricated to degrade 2-chlorodibenzo-p-dioxin (2-CDD) under ultraviolet-visible (UV-vis) light illumination. Experiments revealed that the pure g-C3N4 and range of g-C3N4/NiO heterojunctions were synthesized by the mixing and heating method, and then were characterized by XRD, TEM, XPS and PL etc. The composites exhibited enhanced dechlorination activities under anoxic conditions. After comparison, the g-C3N4/NiO (4:6) showed optimal dechlorination performance such that 70.4% of 2-CDD was removed within 8 h and 52.3% of 2-CDD was transformed to dibenzo-p-dioxin (DD), about fourfold higher than the pristine g-C3N4. The transformation of 2-CDD was accompanied by the resale of Cl ion, and the additional oxygen was proven to be able to consume electrons and hydrogen ions, thus greatly inhibiting the degradation of PCDD in systems. The g-C3N4/NiO (4:6) can be reused at least seven times, and the mechanism was proposed in detail to promote photoinduced electrohole separation and provide active sites. This study extends the use range of g-C3N4/NiO heterojunctions and develops a new technology to degrade PCDDs with striking activity and stability.

Luminescent vesicular nanointerface: a highly selective and sensitive "turn-on" sensor for guanosine triphosphate.

A novel amphiphilic Tb(3+) complex (TbL(3+)(I)) consisting of a +3 charged head and a hydrophobic alkyl chain has been developed. It spontaneously self-assembles in water and forms stable vesicles at neutral pH. TbL(3+)(I) has no aromatic groups (functioning as an antenna), and its intrinsic luminescence is thus minimized. These features lead to the self-assembling TbL(3+)(I) receptor molecules demonstrating an increased luminescence intensity upon binding of nucleotides. Upon addition of guanosine triphosphate (GTP), the luminescence from Tb(3+) was notably promoted (127-fold), as the light energy absorbed by the guanine group of GTP was efficiently transferred to the Tb(3+) center. In the case of guanosine diphosphate (GDP) and guanosine monophosphate (GMP), respectively, 78-fold and 43-fold increases in luminescence intensity were observed. This enhancement was less significant than that observed for GTP, due to fewer negative charges on GDP and GMP. No other nucleotides or the tested nonphosphorylated nucleosides affected the luminescence intensity to any notable extent. In marked contrast, all tested nucleotides, including guanine nucleotides, barely promoted the luminescence of molecularly dispersed receptors, TbL(3+)(II), indicating that the confinement and organization of molecules in a nanointerface play vital roles in improving the performance of a sensing system. This Tb(3+) complex nanointerface is successfully used for monitoring the GTP-to-GDP conversion.