A fast microbial nitrogen-assimilation technology enhances nitrogen migration and single-cell-protein production in high-ammonia piggery wastewater.

Conventional methods, such as freshwater dilution and ammonia stripping, have been widely employed for microalgae-based piggery wastewater (PW) treatment, but they cause high freshwater consumption and intensive ammonia loss, respectively. This present work developed a novel fast microbial nitrogen-assimilation technology by integrating nitrogen starvation, zeolite-based adsorption, pH control, and co-culture of microalgae-yeast for the PW treatment. Among them, the nitrogen starvation accelerated the nitrogen removal and shortened the treatment period, but it could not improve the tolerance level of microalgal cells to ammonia toxicity based on oxidative stress. Therefore, zeolite was added to reduce the initial total ammonia-nitrogen concentration to around 300 mg/L by ammonia adsorption. Slowly releasing ammonia at the later phase maintained the total ammonia-nitrogen concentration in the PW. However, the pH increase could cause lots of ammonia loss air and pollution and inhibit the desorption of ammonia from zeolite and the growth and metabolism of microalgae during the microalgae cultivation. Thus, the highest biomass yield (3.25 g/L) and nitrogen recovery ratio (40.31%) were achieved when the pH of PW was controlled at 6.0. After combining the co-cultivation of microalgae-yeast, the carbon-nitrogen co-assimilation and the alleviation of pH fluctuation further enhanced the nutrient removal and nitrogen migration to high-protein biomass. Consequently, the fast microbial nitrogen-assimilation technology can help update the industrial system for high-ammonia wastewater treatment by improving the treatment and nitrogen recovery rates.

Simultaneous exposure to nanoplastics and cadmium mitigates microalgae cellular toxicity: Insights from molecular simulation and metabolomics.

In the severe pollution area of nanoplastics (NPs) and cadmium ions (Cd2+), the joint effects of their high environmental concentrations on primary producers may differ from those of low environmental doses. Thus, we investigated the physiological changes, cell morphology, molecular dynamic simulation, phenotypic interactions, and metabolomics responses of C. pyrenoidosa to high environmental concentrations of NPs and Cd2+ after 12-d acclimation. After 12-d cultivation, mono-NPs and mono-Cd2+ reduced cell density and triggered antioxidant enzymes, extracellular polymeric substances (EPS) production, and cell aggregation to defend their unfavorable effects. Based on the molecular dynamic simulation, the chlorine atoms of the NPs and Cd2+ had charge attraction with the nitrogen and phosphorus atoms in the choline and phosphate groups in the cell membrane, thereby NPs and Cd2+ could adsorb on the cells to destroy them. In the joint exposure, NPs dominated the variations of ultrastructure and metabolomics and alleviated the toxicity of NPs and Cd2+. Due to its high environmental concentration, more NPs could compete with the microalgae for Cd2+ and thicken cell walls, diminishing the Cd2+ content and antioxidant enzymes of microalgae. NPs addition also decreased the EPS content, while the bound EPS with -CN bond was kept to detoxicate Cd2+. Metabolomics results showed that the NPs downregulated nucleotide, arachidonic acid, and tryptophan metabolisms, while the Cd2+ showed an opposite trend. Compared with their respective exposures, metabolomics results found the changes in metabolic molecules, suggesting the NPs_Cd2+ toxicity was mitigated by balancing nucleotide, arachidonic acid, tryptophan, and arginine and proline metabolisms. Consequently, this study provided new insights that simultaneous exposure to high environmental concentrations of NPs and Cd2+ mitigated microalgae cellular toxicity, which may change their fates and biogeochemical cycles in aquatic systems.

UV-induced photodegradation of emerging para-phenylenediamine quinones in aqueous environment: Kinetics, products identification and toxicity assessments.

Substituted para-phenylenediamine quinones (PPD-quinones) are a class of emerging contaminants frequently detected in the aqueous environment. One of them, N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine quinone (6PPD-Q), was found to cause acute toxicities to aquatic species at extremely low environmental levels. The ubiquitousness and ecotoxicity of such pollutants underscore the importance of their transformation and elimination. In this work, we demonstrated effective removals of five PPD-quinones in aqueous environments under UV irradiation, with up to 94% of 6PPD-Q eliminated after a 40-min treatment. By applying high-resolution mass spectrometry (HRMS) non-targeted screening in combination with isotope labeling strategies, a total of 22 transformation products (TPs) were identified. Coupling with the time-based dynamic patterns, potential transformation mechanisms were identified as an •OH-induced photocatalysis reaction involving bond cleavage, hydroxylation, and oxidation. Computational toxicity assessment predicted lower aquatic toxicity of the TPs than their parent PPD-quinones. Our results in parallel evidenced an obvious reduction of PPD-quinones accompanied by the presence of their TPs in the effluent after UV disinfection in real municipal wastewater. This work builds a comprehensive understanding of the fate, transformation products, and related toxicological characteristics of emerging PPD-quinone contaminants in the aqueous environment.

Occurrence and Fate of Substituted p-Phenylenediamine-Derived Quinones in Hong Kong Wastewater Treatment Plants.

para-Phenylenediamine quinones (PPD-Qs) are a newly discovered class of transformation products derived from para-phenylenediamine (PPD) antioxidants. These compounds are prevalent in runoff, roadside soil, and particulate matter. One compound among these, N-1,3-dimethylbutyl-n'-phenyl-p-phenylenediamine quinone (6PPD-Q), was found to induce acute mortality of coho salmon, rainbow trout, and brook trout, with the median lethal concentrations even lower than its appearance in the surface and receiving water system. However, there was limited knowledge about the occurrence and fate of these emerging environmental contaminants in wastewater treatment plants (WWTPs), which is crucial for effective pollutant removal via municipal wastewater networks. In the current study, we performed a comprehensive investigation of a suite of PPD-Qs along with their parent compounds across the influent, effluent, and biosolids during each processing unit in four typical WWTPs in Hong Kong. The total concentrations of PPDs and PPD-Qs in the influent were determined to be 2.7-90 and 14-830 ng/L. In the effluent, their concentrations decreased to 0.59-40 and 2.8-140 ng/L, respectively. The median removal efficiency for PPD-Qs varied between 53.0 and 91.0% across the WWTPs, indicating that a considerable proportion of these contaminants may not be fully eliminated through the current processing technology. Mass flow analyses revealed that relatively higher levels of PPD-Qs were retained in the sewage sludge (20.0%) rather than in the wastewater (16.9%). In comparison to PPDs, PPD-Qs with higher half-lives exhibited higher release levels via effluent wastewater, which raises particular concerns about their environmental consequences to aquatic ecosystems.

Combined zeolite-based ammonia slow-release and algae-yeast consortia to treat piggery wastewater: Improved nitrogen and carbon migration.

Integration of zeolite-based ammonia adsorption and algae-yeast consortia was developed to remediate piggery wastewater (PW) containing high concentrations of total ammonia nitrogen (TAN) and total organic carbon (TOC). After optimizing the conditions of ammonia adsorption in the PW. Zeolite addition mitigated ammonia toxicity, allowing zeolites to gradually release ammonia while effectively attenuating algal oxidative stress caused by high TAN concentration. Coupling zeolite-based adsorption and yeast co-incubation further increased TOC degradation and available C/N ratio, thus improving biomass (4.51 g/L), oil yield (2.11 g/L), and nutrient removal (84.18%-99.14%). The integrated microalgae-based PW treatment exhibited higher carbon migration into biomass (46.14%) and reduced treatment costs than conventional approaches. Simultaneously, the lowest carbon migration to wastewater also meant the smallest carbon emission into water bodies. These findings demonstrate that this novel strategy can remove nutrients in raw PW effectively and produce high oil-rich biomass in a sustainable and environmentally-friendly manner.

In situ coagulation-electrochemical oxidation of leachate concentrate: A key role of cathodes.

To efficiently remove organic and inorganic pollutants from leachate concentrate, an in situ coagulation-electrochemical oxidation (CO-EO) system was proposed using Ti/Ti4O7 anode and Al cathode, coupling the "super-Faradaic" dissolution of Al. The system was evaluated in terms of the removal efficiencies of organics, nutrients, and metals, and the underlying cathodic mechanisms were investigated compared with the Ti/RuO2-IrO2 and graphite cathode systems. After a 3-h treatment, the Al-cathode system removed 89.0% of COD and 36.3% of total nitrogen (TN). The TN removal was primarily ascribed to the oxidation of both ammonia and organic-N to N2. In comparison, the Al-cathode system achieved 3-10-fold total phosphorus (TP) (62.6%) and metal removals (>80%) than Ti/RuO2-IrO2 and graphite systems. The increased removals of TP and metals were ascribed to the in situ coagulation of Al(OH)3, hydroxide precipitation, and electrodeposition. With the reduced scaling on the Al cathode surface, the formation of Al3+ and electrified Al(OH)3 lessened the requirement for cathode cleaning and increased the bulk conductivity, resulting in increased instantaneous current production (38.9%) and operating cost efficiencies (48.3 kWh kgCOD -1). The present study indicated that the in situ CO-EO process could be potentially used for treating persistent wastewater containing high levels of organic and inorganic ions.

Xanthine-derived reactive oxygen species exacerbates adipose tissue disorders in male db/db mice induced by real-ambient PM2.5 exposure.

Epidemiological and experimental data have associated exposure to fine particulate matter (PM2.5) with various metabolic dysfunctions and diseases, including overweight and type 2 diabetes. Adipose tissue is an energy pool for storing lipids, a necessary regulator of glucose homeostasis, and an active endocrine organ, playing an essential role in developing various related diseases such as diabetes and obesity. However, the molecular mechanisms underlying PM2.5-impaired functions in adipose tissue have rarely been explored. In this work, metabolomics based on liquid chromatography-mass spectrometry was performed to study the adverse impacts of PM2.5 exposure on brown adipose tissue (BAT) and white adipose tissue (WAT) in the diabetic mouse model. We found the effects of PM2.5 exposure by comparing the different metabolites in both adipose tissues of male db/db mice using real-ambient PM2.5 exposure. The results showed that PM2.5 exposure changed the purine metabolism in mice, especially the dramatic increase of xanthine content in both WAT and BAT. These changes led to significant oxidative stress. Then the results from real-time quantitative polymerase chain reaction showed that PM2.5 exposure could cause the production of inflammatory factors in both adipose tissues. Moreover, the increased reactive oxygen species (ROS) promoted triglyceride accumulation in WAT and inhibited its decomposition, causing increased WAT content in db/db mice. In addition, PM2.5 exposure significantly suppressed thermogenesis and affected energy metabolism in the BAT of male db/db mice, which may deteriorate insulin sensitivity and blood glucose regulation. This research demonstrated the impact of PM2.5 on the adipose tissue of male db/db mice, which may be necessary for public health.

A green approach to copper biodetoxification and sustainable agriculture application by vermicomposting in pig manure.

A green approach of copper (Cu) contaminated pig manure composting by earthworm Eisenia fetida was optimized. This work aims to assess the relationship between the bio-fertility properties and bioaccumulation of Cu during vermicomposting with five different doses of Cu. The optimal concentration of copper largely promoted the enrichment of nitrogen, phosphorus, and potassium, but the biological activities of earthworms could be inhibited once the Cu concentration exceed the threshold. When the Cu doses at 300 mg kg-1, the nutrient recovery rate (Irecovery) of available nitrogen, phosphorus and potassium reached their highest value, concomitant with largest C/N ratio reduced at 46.01 %. Moreover, nutrients recovery mechanism of total phosphorus increased up to 0.11 % h-1 and higher bioaccumulations in faces and intestine were detected by 1.79 and 0.99, respectively, during vermicomposting. The maximal enzyme activity rates (kmax) indicate that the enzyme activities, such as ROS and SOD, are sensitive bioindicators, which can be used to estimate the stress response of earthworms and Cu biotoxicity. The maximum specific growth rate (µmax) of the actinomycetes (TAct) increased gradually from 0.02 to 0.04 with the increase of Cu doses, but total fungi (TF) showed different response to µmax, which decreased firstly and then increased. It was demonstrated that Cu influenced the gut microbial community to vary the bio-fertility properties and bioaccumulation of Cu in the pig manure. All the findings refer that the vermicomposting could be the sustainable agricultural practices.

The synergistic effect between biofertility properties and biological activities in vermicomposting: A comparable study of pig manure.

Vermicomposting is a resource technology for managing animal excreta, whereas the internal relationships of the process are vital for its wide applications. The present study examined how macronutrient and micronutrient concentrations, microbial communities, and enzymatic activity of pig manure (PM) changed during the composting and vermicomposting processes and their internal interactions. The vermicomposting process increased macronutrients more significantly than composting (32.40% of total available nitrogen, 21.70% of total available phosphorous, and 12.70% of total available potassium). The vermicomposting reduced total organic carbon (7.91%), C/N ratio (61.35%), and humification index (56.47%) more than composting due to the quick decomposition of PM. After continual fertility optimization, the total microbial population, with the exception of total fungi, rose significantly to accelerate organics mineralization and improve macronutrients in vermicomposting compared to composting. Moreover, earthworm addition favored the stabilization of the PM containing higher concentrations of micronutrients after being catalyzed by the enhanced catalase activity and reduced sucrase activity after 90 days of vermicomposting. Principal component analysis and chord plots found that the generated vermicomposting products had higher fertility properties and biological activities induced by the synergistic effect of microorganisms and earthworms. These findings highlight vermicomposting is an eco-friendly management technology for processing PM and can be scaled up for agricultural applications.

Advanced treatment of dye wastewater using a novel integrative Fenton-like/MnO2-filled upward flow biological filter bed system equipped with modified ceramsite.

The deposal of residual hydrogen peroxide (H2O2) in Fenton-like system and the requirement of oxygen in bioreactor are essential parts for the treatment of integrative Fenton-like/bioreactor. A novel low-cost integrative Fenton-like and MnO2-filled upward flow biological filter bed (Fenton-like/MBFB) equipped with the modified ceramsite was constructed to evaluate the main properties and catalytic activity of modified ceramsite, and the optimal conditions of integrative system and compare integrative and traditional systems. In this study, the Fenton-like reactor with modified ceramsite had higher catalytic ability whose Acid Orange 7 (AO7) degradation efficiency reached to 79.3% due to large surface area and high porosity, compared with that with raw ceramsite (44.3%). Furthermore, total utilization efficiency of H2O2 in integrative system (from 32.41% to 53.51%) and removal efficiencies of COD and AO7 were remarkably improved, which would effectively decrease the waste of H2O2 and the setting of regulation pool and aeration tank. Thus, the integrative system can save 0.51 CNY/m3 in construction cost and 0.21 CNY/m3 in operating cost. The average COD removal efficiency, AO7 degradation efficiency and effluent DO concentration were achieved to 64.8%, 79.5% and 9.3 mg/L respectively in integrative system were achieved in integrative system during sixty successive runs. Also, the potential degradation pathway of contaminants was also proposed according to the OH-enhanced at Fenton-like reactor due to catalyst and adsorption of modified ceramsite and the removal of microorganisms and modified ceramsite for contaminants at MBFB. This study demonstrated the feasibility of integrative Fenton-like/MBFB filled with modified ceramsite for simultaneously decreasing operational cost and complexity and enhancing removal efficiency, thus provided a one-step alternative for refractory dye wastewater.

Simultaneous nitrogen and phosphorus removal by interactions between phosphate accumulating organisms (PAOs) and denitrifying phosphate accumulating organisms (DPAOs) in a sequencing batch reactor.

The identification of phosphate-accumulating organisms (PAOs), denitrifying phosphate-accumulating organisms (DPAOs) and their relationship is a key pathway for optimizing nitrate and phosphate removal efficiency in activated sludge. In this study, the acclimatization of microorganisms in sequencing batch reactor were performed with anaerobic/aerobic (A/O) and anaerobic/anoxic (A/A) cycles, the biomass changes of PAOs and DPAOs and the correlations were then discussed. The results indicated that after acclimatization, the nutrient removal efficiencies reached to 85.34% (COD), 93.64% (PO43--P) and 92.34% (NO3--N), respectively, with NO3--N:PO43-P of 1.5:1. The successful enrichment of PAOs and DPAOs (reached 97.9%) was verified by the change of relative metabolic activities, which was further proved by the change of bacterial diversity. The number of Candidatus Accumulibacter, Zoogloea, and Dechloromonas all increased at A/O and A/A stages while the number of Acinetobacter only increased at A/O stage. So Accumulibacter sp. was DPAO while Acinetobacter sp. was only PAO in this process, and genera Accumulibacter, Dechloromonas and Zoogloea greatly coordinated in denitrification and accumulating phosphorous though RDA and chord plot. This was worthy of attention and development to explore enhanced biological phosphorus removal (EBPR) in practical wastewater treatment via improving identification of bacterial species and symbiosis of bacteria community.

Co-cultivation of Rhodotorula glutinis and Chlorella pyrenoidosa to improve nutrient removal and protein content by their synergistic relationship.

With the continuous development of the livestock breeding industry, the amount of piggery wastewater discharged increases year by year, and the pressure of controlling environmental pollution continuously increases. A novel method using a co-culture of Chlorella pyrenoidosa and Rhodotorula glutinis in piggery wastewater was proposed in this study, which was aimed at treating piggery wastewater and producing useful products. The results showed that the optimal inoculum ratio of algae to yeast was 3 : 1 in the wastewater, which achieved the removal efficiencies of 58.53%, 36.07%, 33.20% and 56.25% for ammoniacal nitrogen (NH3-N), total nitrogen (TN), total protein (TP) and chemical oxygen demand (COD), respectively, after 6 d. The synergistic relationship of C. pyrenoidosa and R. glutinis was preliminarily validated using the oxygen/carbon dioxide exchange balance and scanning electron microscopy images. The co-cultivation system gained 59.8% (w/w) protein within 5 d which can be used as a feed additive, and produces aquatic animals with better growth and quality. Thus, the 1000 litre pilot scale bioreactor was used indoors and removed 82.65% of TN, 53.51% of TP, 93.48% of NH3-N and 85.44% of COD in 21 d which gave a better performance for TN (p < 0.05) than the bench scale results. This system improves the nutrition removal and protein production efficiencies, and is a promising method for piggery wastewater treatment and the pig breeding industry.

A novel one-step method for oil-rich biomass production and harvesting by co-cultivating microalgae with filamentous fungi in molasses wastewater.

Aiming at simplifying the harvesting procedure, reducing the production cost, and improving the quality of microalgae-based biodiesel, herein, a novel one-step method for oil-rich biomass production and harvesting was proposed by growing Chlorella sp. with Aspergillus sp. in molasses wastewater. Lipid content and fatty acid profile were measured to assess the suitability of microalgal-fungal biomass for biodiesel production. The results showed that the highest biomass yield (4.215 g/L) was obtained when the inoculation ratio of fungi and microalgae was 100. Activities of fungi positive impacted the decolorization of wastewater and the removal of suspended solids. Thus, co-cultivation system had better performance than mono-system of microalgae in the removal of nutrients in wastewater. Analysis of biomass compositions showed that compared with mono-system of microalgae, co-cultivation system produced biomass with higher lipid content (35.2%) and yield microbial cell oil with lower unsaturation degree, potentially increasing the quality of microbial-cell-lipid based biodiesel.