Valorization of treated swine wastewater and generated biomass by microalgae: Their effects and salt tolerance mechanisms on wheat seedling growth.

The extensive use of mineral fertilizers has a negative impact on the environment, whereas wastewater and microalgal biomass can provide crops with nutrients such as nitrogen, phosphorus, and potassium, and have the potential to be used as a source of fertilizers in circular agriculture. In this study, a step-by-step resource utilization study of algae-containing wastewater generated from microalgae treatment of swine wastewater was carried out. When wheat seedlings were cultivated in the effluent after microalgae separation, the root fresh weight, seedling fresh weight, and total seedling length were increased by 3.44%, 14.45%, and 13.64%, respectively, compared with that of the algae-containing wastewater, and there was no significant difference in seedling fresh weight, total seedling length, maximum quantum yields of PSII photochemistry (Fv/Fm), and performance index (PIABS) from that of the Hogland solution group, which has the potential to be an alternative liquid fertilizer. Under salt stress, microalgae extract increased the contents of GA3, IAA, ABA, and SA in wheat seedlings, antioxidant enzymes maintained high activity, and the PIABS value increased. Low-dose microalgae extract (1 mL/L) increased the root fresh weight, seedling fresh weight, longest seedling length, and total seedling length by 30.73%, 31.28%, 16.43%, and 28.85%, respectively. Algae extract can act as a plant biostimulant to regulate phytohormone levels to attenuate the damage of salt stress and promote growth.

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.

Integrated effects of operational temperature, HRT, and influent ammonium concentration on a CANON coupling with denitrification process treating for digested piggery wastewater: performance and microbial community.

In this study, an improved system called the completely autotrophic nitrogen removal over nitrite (CANON) process was presented and coupled with denitrification for the treatment of digested piggery wastewater (DPW). The effects of operating parameters, including hydraulic retention time (HRT) (1.6 d → 1.0 d), influent NH4+-N concentration (350 mg L-1 → 600 mg L-1), and temperature (41 â„ƒ → 17 â„ƒ), on the nitrogen removal performance and response characteristics of microbial population were investigated. Results showed that all considered parameters caused a remarkable effect on NH4+-N and total nitrogen removal efficiencies, and the chemical oxygen demand was more markedly affected by temperature. Candidatus_Kuenenia, Candidatus_Brocadia, Denitratisoma, norank_o_Xanthmonadales, norank_p_WWE3, and SM1A02 were the dominant genera influencing nitrogen removal in the improved CANON system for treating DPW. Redundancy discriminant analysis showed that the biological structure was positively correlated with the influent ammonium concentration, temperature, and HRT. The relative abundance of Candidatus_Kuenenia was perfectly correlated with HRT and temperature. However, environmental factors did not affect Candidatus_Brocadia and norank_p_WWE3. norank_c_Ardenticatenia, SM1A02, and norank_f_SJA-28 were all positively correlated with influent ammonium nitrogen concentration, but not correlated with HRT and temperature. The improved CANON process realized the nitrogen removal under high ammonium (NH4+-N) concentration and low C/N wastewater.

Long-term stability of reactor microbiome through bioaugmentation with Alcaligenes aquatilis AS1 promotes nitrogen removal of piggery wastewater.

Bioaugmentation is considered as an attractive method for nitrogen removal in water treatment, but its effectiveness in actual high-strength piggery wastewater has not been adequately verified and the mechanism of bioaugmentation in actual wastewater treatment system is not very clear especially from the perspectives of microbial communities and functional genes. This study investigated the mechanisms of a heterotrophic nitrifying-aerobic denitrifying strain Alcaligenes aquatilis AS1 in the bioaugmentation of continuous biological nitrogen removal of actual piggery wastewater at laboratory scale. The addition of strain AS1 significantly improved the nitrogen removal efficiency (more than 95% of NH4+-N and 75% of TN were removed) and raised the activated sludge resistance to shock loading. AS1 addition also significantly shifted the microbiota structure and interactions among microbial networks were enhanced to obtain the stable bacterial communities. Moreover, strain AS1 achieved effective proliferation and long-term colonization in activated sludge with a relative abundance of genus Alcaligenes more than 70% during the whole operation process and played a dominant role in biological nitrogen removal, while different genera were respectively enriched and involved in pollutants removal at different stages in the control group. In addition, the abundances of most functional genes involved in carbon (C) degradation, carbon fixation and nitrogen (N), phosphorus (P), sulfur (S) cycling in activated sludge were significantly increased in reactor AS1, indicating that strain AS1 not only relied on its unique C and N metabolic activities, but also recruited microorganisms with diverse functions to jointly remove pollutants in wastewater, which could be a common bioaugmentation mechanism in open reactors. This study proves the promising application prospect of strain AS1 in the treatment of high-strength piggery wastewater and shows great importance for guiding bioaugmentation application of functional strains in practical wastewater treatment systems.

Synergistic denitrification, partial nitrification - Anammox in a novel A2/O2 reactor for efficient nitrogen removal from low C/N wastewater.

A biofilm-based anaerobic-aerobic (A2O2) reactor was constructed to treat manure-free piggery wastewater. The reactor contained four compartments, among which the first two were anaerobic (A phase) and the last two were aerobic (O phase). Throughout around one-year operation, high-level nutrient removal was demonstrated. At an optimal reflux ratio of 100%, the average NH4+-N, TN, and COD removal efficiencies were high as 99.4%, 91.7%, and 79.4%, respectively, with the influent concentration of 220.6, 231.6 and 332 mg/L, respectively. The NH4+-N, TN, and COD concentrations in the final effluent were only 1.4, 18.5 and 65 mg/L, respectively. COD and nitrogen removal were mainly removed in the A phase and O phase, respectively. This result revolutionizes the previous perception that nitrogen is only removed in the A phase of conventional A-O configuration. Achievement of PN/A in the O phase was critical to the efficient nitrogen removal. Heterotrophic denitrification in the anaerobic compartments removed the nitrate produced by anammox, ensuring the high-level nitrogen removal. Anaerobic organic degradation was a major pathway for COD removal, as abundant methanogens detected in the A phase. This study provides a feasible technical scheme for the efficient nutrient removal from ammonium-rich wastewater.

Tracking antibiotic resistance gene transfer at all seasons from swine waste to receiving environments.

Antibiotic resistance genes (ARGs) in livestock farms have attracted a growing attention with potential effects on human health. As one of the most important organic fertilizer, swine waste provided an ideal environment for understanding the dissemination and accumulation of ARGs in agricultural ecosystems. Here we conducted a year-round follow-up trace from swine waste to receiving environments, with the purpose of revealing the contamination profiles and ecological risks of ARGs at different seasons. Results indicated that a variety of common ARGs and even high-risk ARGs (i.e., blaampC, blaOXA-1, blaTEM-1 and mcr-1) were prevalent from swine waste to farmland soil, with changing in various degrees from season to season. Regarding the occurrence pattern of ARGs, tetracycline resistance genes (tet-ARGs) were predominant genes at four seasons in all fresh pig feces, swine manure, manured soil and wastewater. The levels of most ARGs in solid waste were reduced at a different degree via natural composting, and the removal effect was best in summer, while ARGs decreased poorly after wastewater treatment, especially in winter (up to 10-1 copies/16S copies in the residual level), which increased the possibility of propagation to receiving environment. This concern was also validated by the investigation on farmland environment with long-term application of manure, where causing an increase in ARG abundances in soils (approximately 0.9-32.7 times). To our knowledge, this study is the first to demonstrate the distribution pattern of ARGs from swine waste to its receiving farmland environment at all seasons on this integrity chain.

Performances and mechanisms of sludge dewatering by a biopolymer from piggery wastewater and application of the dewatered sludge in remediation of Cr(VI)-contaminated soil.

In this study, a biopolymer was harvested from piggery wastewater to treat biological sludge. Effectiveness of the combination of polyaluminum chloride (PAC) and this biopolymer in sludge dewatering was investigated and the dewatering mechanism was discussed. Results showed that as high as 3.11 g of biopolymer can be harvested from 1 L of piggery wastewater by cultivating Bacillus megaterium. After treated by PAC with a dosage of 1.5 g/L at pH point of 7.5, specific resistance to filtration (SRF), moisture content (MC), settled volume after 30 min (SV30) and capillary suction time (CST) of the sludge were decreased to 3.4 × 1012 m/kg, 84.5%, 79.8% and 65 s, respectively, and dry solid (DS) was increased to 21.4%, indicated that sludge dewatering was obviously enhanced by PAC. After further treated by 2 g/L of the biopolymer, SRF, MC, SV30 and CST were further decreased to 2.1 × 1012 m/kg, 59.8%, 55.6% and 39 s, respectively, and DS was increased to 28.6%, indicated that sludge dewatering was further enhanced by the biopolymer. For the enhancing mechanism, on the one hand, the extracellular polymeric substances (EPS) was significantly disintegrated to release binding bound water, which was facilitating sludge dewatering; on the other hand, the synergistic effect of PAC coagulation and biopolymer flocculation, including charge neutralization and bridge-aggregation, were favorable to sludge dewatering. Additionally, we found that the dewatered sludge was helpful for remediation of chromium (Cr)(VI)-contaminated soil by raising soil pH and decreasing bioavailability of Cr(VI) in the soil, after remediated by 75 g/kg of the dewatered sludge for 60 days, the soil pH was increased from its initial value of 4.32-8.52, and the residue Cr(VI) in the soil extract was appeared as 2.2 mg/L.

Effective removal of nitrate by denitrification re-enforced with a two-stage anoxic/oxic (A/O) process from a digested piggery wastewater with a low C/N ratio.

The combined process of a long-term biogas digester and double anoxic/oxic tanks is very commonly used in piggery wastewater treatment in South China, but the effluent does not meet the discharge standard of total nitrogen (TN) and chemical oxygen demand (CODCr) due to a low C/N ratio and insufficient organic carbon in digested piggery wastewater. Thus, a typical two-stage anoxic/oxic (A1/O1/A2/O2) process, which is widely used to treat digested piggery wastewater in the engineering application, was selected for study on a laboratory scale. Finally, the average removal efficiency of ammonia nitrogen in the two-stage AO process was 98.7%; at the same time, the content of nitrate increased to 180-190 mg/L. To further eliminate nitrogen, an anaerobic tank (S1), which was equipped the sludge that was acclimated in our laboratory by a high nitrogen loading slurry, was employed to treat the effluent from the two-stage AO process and contributed more than 70% removal efficiency. Further analysis showed that ammonia-oxidizing bacteria (AOB) and nitrite oxidizing bacteria (NOB) in the O1 and O2 tanks together contributed to the conversion of ammonia nitrogen to nitrate, but the process of heterotrophic denitrification was inhibited in the A1 and A2 tanks because of insufficient carbon sources. In addition, most of the nitrate concentration was reduced under conditions with insufficient carbon sources, while Thauera-dominated the bacterial population in the sludge sample of the S1 tank.

Fuzzy multi-objective optimization case study based on an anaerobic co-digestion process of food waste leachate and piggery wastewater.

This paper presents the development and evaluation of fuzzy multi-objective optimization for decision-making that includes the process optimization of anaerobic digestion (AD) process. The operating cost criteria which is a fundamental research gap in previous AD analysis was integrated for the case study in this research. In this study, the mixing ratio of food waste leachate (FWL) and piggery wastewater (PWW), calcium carbonate (CaCO3) and sodium chloride (NaCl) concentrations were optimized to enhance methane production while minimizing operating cost. The results indicated a maximum of 63.3% satisfaction for both methane production and operating cost under the following optimal conditions: mixing ratio (FWL: PWW) - 1.4, CaCO3 - 2970.5 mg/L and NaCl - 2.7 g/L. In multi-objective optimization, the specific methane yield (SMY) was 239.0 mL CH4/g VSadded, while 41.2% volatile solids reduction (VSR) was obtained at an operating cost of 56.9 US$/ton. In comparison with the previous optimization study that utilized the response surface methodology, the SMY, VSR and operating cost of the AD process were 310 mL/g, 54% and 83.2 US$/ton, respectively. The results from multi-objective fuzzy optimization proves to show the potential application of this technique for practical decision-making in the process optimization of AD process.

Rapid aerobic granulation in an SBR treating piggery wastewater by seeding sludge from a municipal WWTP.

Aerobic sludge granulation was rapidly obtained in the erlenmeyer bottle and sequencing batch reactor (SBR) using piggery wastewater. Aerobic granulation occurred on day 3 and granules with mean diameter of 0.2mm and SVI30 of 20.3mL/g formed in SBR on day 18. High concentrations of Ca and Fe in the raw piggery wastewater and operating mode accelerated aerobic granulation, even though the seed sludge was from a municipal wastewater treatment plant (WWTP). Alpha diversity analysis revealed Operational Taxonomic Units, Shannon, ACE and Chao 1 indexes in aerobic granules were 2013, 5.51, 4665.5 and 3734.5, which were obviously lower compared to seed sludge. The percentages of major microbial communities, such as Proteobacteria, Bacteroidetes and Firmicutes were obviously higher in aerobic granules than seed sludge. Chloroflexi, Planctomycetes, Actinobacteria, TM7 and Acidobacteria showed much higher abundances in the inoculum. The main reasons might be the characteristics of raw piggery wastewater and granule structure.

Removal of tetracyclines from swine manure at full-scale activated sludge treatment plants.

The purpose of this study was to investigate the fate of three tetracyclines (TCs), namely oxytetracycline (OTC), chlortetracycline (CTC) and doxycycline (DC) at two different full-scale swine manure-activated sludge treatment plants. Throughout treatment, OTC, CTC and DC were removed by 71-76%, 75-80% and 95%, respectively. Removal of these TCs under physical treatment was deniable. On the contrary, the flocculation-coagulation and the secondary clarification resulted in a relevant reduction of the concentration of these TCs.

Mechanism of microplastics effects on the purification of heavy metals in piggery effluents by microalgae.

Microalgae is an effective bioremediation technique employed for treating piggery effluent. However, there is insufficient study on how the presence of microplastics (MPs) in wastewater affects the ability of microalgae to remove heavy metals from piggery effluent. This study aims to investigate the influence of two prevalent heavy metals found in piggery wastewater, Cu2+ (2 mg/L) and Zn2+ (2 mg/L), on their removal by microalgae (Desmodesmus sp. CHX1) in the presence of four types of MPs: polyethylene (PE), polyvinyl chloride (PVC), polypropylene (PP), and polyethylene terephthalate (PET). The results revealed that smaller particle size MPs promoted chlorophyll accumulation, while larger particles inhibits it. Additionally, higher concentrations of MPs promoted chlorophyll accumulation, while lower concentrations inhibited it. As for heavy metals, the presence of microplastics reduced the removal efficiency of Cu2+ and Zn2+ by Desmodesmus sp. CHX1. The highest inhibition of Cu2+ was 30%, 10%, 19%, and 16% of the control (CK), and the inhibition of Zn2+ was 7%, 4%, 4%, and 13%, respectively, under the treatments of PE, PVC, PP and PET MPs. Furthermore, Desmodesmus sp. CHX1 can secrete more extracellular polymeric substances (EPS) and form heterogeneous aggregates with MPs to counteract their pressure. These findings elucidate the impact of MPs on microalgae in bioremediation settings and offer useful insights into the complex relationships between microalgae, MPs, and heavy metals in the environment.

Microalgae: A Biological Tool for Removal and Recovery of Potentially Toxic Elements in Wastewater Treatment Photobioreactors.

Potentially toxic elements (PTE) pollution in water bodies is an emerging problem in recent decades due to uncontrolled discharges from human activities. Copper, zinc, arsenic, cadmium, lead, mercury, and uranium are considered potentially toxic and carcinogenic elements that threaten human health. Microalgae-based technologies for the wastewater treatment have gained importance in recent years due to their biomass high growth rates and effectiveness. Also, these microalgae-bacteria systems are cost-effective and environmentally friendly, utilize sunlight and CO2, and simultaneously address multiple environmental challenges, such as carbon mitigation, bioremediation, and generation of valuable biomass useful for biofuel production. Additionally, microalgae possess a diverse array of extracellular and intracellular mechanisms that enable them to remove and mitigate the toxicity of PTE present in wastewater. Therefore, photobioreactors are promising candidates for practical applications in bioremediation of wastewater containing toxic elements. Despite the increasing amount of research in this field in recent years, most studies are conducted in laboratory scale and there is a scarcity of large-scale studies under real and variable environmental conditions. Besides, the limited understanding of the multiple mechanisms controlling PTE biosorption in wastewater containing high organic matter loads and potentially toxic elements requires further studies. This chapter provides a schematic representation of the mechanisms and factors involved in the remediation of potentially toxic elements by microalgae, as well as the main results obtained in recent years.

Effects of microalgal (Tetradesmus obliquus MCX38) attachment on photobioreactor treatment efficiency of raw swine wastewater.

Attachment of microalgae on the inner surfaces of photobioreactors impacts the efficiency of swine wastewater treatment by reducing the light intensity, which has been overlooked in previous studies. This study investigated the relationship between microalgal attachment biomass and light intensity in photobioreactors, determined the optimal attachment time for effective pollutant removal, and clarified the mechanisms of microalgal attachment in swine wastewater. After 9 days of treatment, the attached biomass in the photobioreactor increased from 0 to 6.4 g/m2, decreasing the light intensity from 2,000 to 936 lux. At the 24 h optimal attachment time, the concentrations of chemical oxygen demand, ammonia nitrogen, and total phosphorus decreased from 2725.1, 396.4, and 87.2 mg/L to 361.2, 4.9, and 0.8 mg/L, respectively. Polysaccharides in the extracellular polymeric substances released by microalgae play a significant role in facilitating microalgae attachment. Optimizing the microalgal attachment time within photobioreactors effectively mitigates pollutant concentrations in swine wastewater.

Principles, challenges, and optimization of indigenous microalgae-bacteria consortium for sustainable swine wastewater treatment.

Indigenous microalgae-bacteria consortium (IMBC) offers significant advantages for swine wastewater (SW) treatment including enhanced adaptability and resource recovery. In this review, the approaches for enriching IMBC both in situ and ex situ were comprehensively described, followed by symbiotic mechanisms for IMBC which involve metabolic cross-feeding and signal transmission. Strategies for enhancing treatment efficiencies of SW-originated IMBC were then introduced, including improving SW quality, optimizing system operating conditions, and adjusting microbial activities. Recommendations for maximizing treatment efficiencies were particularly proposed using a decision tree approach. Moreover, removal/recovery mechanisms for typical pollutants in SW using IMBC were critically discussed. Ultimately, a technical route termed SW-IMBC-Crop-Pig was proposed, to achieve a closed-loop economy for pig farms by integrating SW treatment with crop cultivation. This review provides a deeper understanding of the mechanism and strategies for IMBC's resource recovery from SW.

Bioremediation of zinc and manganese in swine wastewater by living microalgae: Performance, mechanism, and algal biomass utilization.

The remediation effects of living Chlorella sp. HL on zinc and manganese in swine wastewater was investigated, and the responses of algal cells and the mechanism were explored. In the wastewater with Zn(II) concentration of 1.85 mg/L and Mn(II) of 1 or 6 mg/L, the highest removal of Zn(II) by Chlorella reached 86.72% and 97.16%, respectively, and the Mn(II) removal were 42.74% and 30.33%, respectively. The antioxidant system of cells was activated by a significant increase in superoxide dismutase and catalase enzyme activities and a significant decrease in malondialdehyde in the mixed system compared to the single system. The presence of Mn(II) could positively regulate the differentially expressed genes related to catalytic activity and metabolic processes between the single Zn system and the mixed systems, reducing the stress of Zn(II) on Chlorella and more favorable to chlorophyll synthesis. The heavy metal-containing microalgal biomass obtained has the potential as feed additives.

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.

Cultivation of Spirulina platensis for nutrient removal from piggery wastewater.

The discharge of livestock wastewater without appropriate treatment causes severe harm to the environment and human health. In the pursuit of finding solutions to this problem, the cultivation of microalgae as feedstock for biodiesel and animal feed additive using livestock wastewater coupled with the removal of nutrients from wastewater has become a hot research topic. In this study, the cultivation of Spirulina platensis using piggery wastewater for the production of biomass and the removal of nutrients were studied. The results of single factor experiments confirmed that Cu2+ seriously inhibit the growth of Spirulina platensis, while the influences of nitrogen, phosphorous, and zinc on the growth of Spirulina platensis can all be described as "low promotes high inhibits." Spirulina platensis grew well in the 4-fold dilution of piggery wastewater supplemented with moderate sodium bicarbonate, which indicated that it is the limiting nutrients for Spirulina platensis growth in piggery wastewater. The biomass concentration of Spirulina platensis reached 0.56 g/L after 8 days of culture at the optimal conditions proposed by the response surface method, which were as follows: 4-fold dilution of piggery wastewater, 7 g/L sodium bicarbonate, pH of 10.5, initial OD560 of 0.63, light intensity of 3030 lx, and light time/dark time of 16 h/8 h. Spirulina platensis cultured in the diluted piggery wastewater contained 43.89% protein, 9.4% crude lipid, 6.41 mg/g chlorophyll a, 4.18% total sugar, 27.7 mg/kg Cu, and 246.2 mg/kg Zn. The removal efficiency for TN, TP, COD, Zn, and Cu from the wastewater by Spirulina platensis was 76%, 72%, 93.1%, 93.5%, and 82.5%, respectively. These results demonstrated the feasibility of piggery wastewater treatment by the cultivation of Spirulina platensis.

Antibiotics resistance removal from piggery wastewater by an integrated anaerobic-aerobic biofilm reactor: Efficiency and mechanism.

Antibiotic resistance residual in piggery wastewater poses serious threat to environment and human health. Biological treatment process is commonly installed to remove nutrient from piggery wastewater and also effective in removing antibiotics to varying degrees. But the specific pathways and mechanisms involved in the removal of antibiotic resistance are not yet well-understood. An integrated anaerobic-aerobic biofilm reactor (IAOBR) has been demonstrated efficient in removing conventional nutrients. It is here shown that the IAOBR effectively removed 79.0% of Sulfonamides, 55.7% of Tetracyclines and 53.6% of Quinones. Antibiotic resistance bacteria (ARB) were simultaneously inactivated by ~0.5 logs. Antibiotic resistance genes (ARGs) and mobile genetic elements (MGEs) were decreased by 0.51 logs and 0.42 logs, respectively. The antibiotics were mainly removed through aerobic compartments of the IAOBR. The mass loss of antibiotics in the reactor was achieved by biodegradation and adsorption, accounting for 52.1% and 47.9%, respectively. An obvious accumulation of ARGs was observed in the activated sludge. The potential host of ARGs was analyzed via microbial community and network. Partial least squares-structural equation model and correlation analysis revealed that the enrichment of ARGs was positively affected by MGEs, followed by bacterial community and ARBs, but the effect of antibiotics on ARGs was negative. Outcomes of this study provide valuable insights into the mechanisms of antibiotic resistance removal in biological treatment processes.

CO2 capture and lipid production performance of microalgae in the S-shaped photobioreactor under different culture modes.

An S-shaped photobioreactor was designed by adding grooves and baffles in the traditional photobioreactor to improve the culture efficiency of microalgae. After that, the parameters of the characterization of the S-shaped photobioreactor, such as the mixing time, gas holdup, and gas-liquid mass transfer coefficient, were determined. The biomass, lipid production rate, and average CO2 capture rate of microalgae were then analyzed under different culture modes. Finally, the feasibility of using digested piggery wastewater combined with simulated flue gas was explored as a culture mode for the microalgae and the lipid properties of the microalgae were analyzed. The results revealed that, at a flow rate of 0.08 vvm, the mixing time was reduced by 8.5 s, the gas hold-up increased by 44.6% and the gas-liquid mass transfer ability was also improved. Improvements were also observed in the biomass values, lipid production rate, and average CO2 capture rate of the microalgae under different culture conditions, with respective values reaching 0.23 g·(L·d)-1, 70.28 mg·(L·d)-1, and 0.43 g·(L·d)-1 under the mixotrophic mode. Additionally, digested piggery wastewater combined with the simulated microalgae flue gas culture was determined to be feasible. The biomass, lipid production rate, and the average CO2 capture rate of microalgae, the values of which were 0.22 g·(L·d)-1, 52.55 mg·(L·d)-1, and 0.41 g·(L·d)-1, respectively. Lipid was observed to have the potential to produce high-quality biofuel.