Free water surface constructed wetlands: review of pollutant removal performance and modeling approaches.

Free water surface constructed wetlands (FWSCWs) for the treatment of various wastewater types have evolved significantly over the last few decades. With an increasing need and interest in FWSCWs applications worldwide due to their cost-effectiveness and other benefits, this paper reviews recent literature on FWSCWs' ability to remove different types of pollutants such as nutrients (i.e., TN, TP, NH4-N), heavy metals (i.e., Fe, Zn, and Ni), antibiotics (i.e., oxytetracycline, ciprofloxacin, doxycycline, sulfamethazine, and ofloxacin), and pesticides (i.e., Atrazine, S-Metolachlor, imidacloprid, lambda-cyhalothrin, diuron 3,4-dichloroanilin, Simazine, and Atrazine) that may co-exist in wetland inflow, and discusses approaches for simulating hydraulic and pollutant removal processes. A bibliometric analysis of recent literature reveals that China has the highest number of publications, followed by the USA. The collected data show that FWSCWs can remove an average of 61.6%, 67.8%, 54.7%, and 72.85% of inflowing nutrients, heavy metals, antibiotics, and pesticides, respectively. Optimizing each pollutant removal process requires specific design parameters. Removing heavy metal requires the lowest hydraulic retention time (HRT) (average of 4.78 days), removing pesticides requires the lowest water depth (average of 0.34 m), and nutrient removal requires the largest system size. Vegetation, especially Typha spp. and Phragmites spp., play an important role in FWSCWs' system performance, making significant contributions to the removal process. Various modeling approaches (i.e., black-box and process-based) were comprehensively reviewed, revealing the need for including the internal process mechanisms related to the biological processes along with plants spp., that supported by a further research with field study validations. This work presents a state-of-the-art, systematic, and comparative discussion on the efficiency of FWSCWs in removing different pollutants, main design factors, the vegetation, and well-described models for performance prediction.

Potential of hospital wastewater treatment using locally isolated Chlorella sp. LH2 from cocoon wastewater.

Chlorella sp. is able to grow and transform inorganic and organic contaminants in wastewater to create biomass. In the present study, Chlorella sp. LH2 isolated from cocoon wastewater was able to thrive in hospital wastewater, then remove nutrients and eliminate E. coli ATCC 8739. The results indicated that optimal cultivation conditions of Chlorella sp. LH2 in hospital wastewater were pH of 8, light:dark cycle of 16:8 at 30oC. The inhibitory effect of chlorination on algae growth was accompanied with the chlorine concentration. BOD5:COD ratio of 0.77 indicated biodegradability of hospital wastewater. The untreated and treated wastewatee samples were collected to investigated the nutrient removal efficiency after 10 days. Untreated and treated results were192 ± 8.62 mg/l 23.91 ± 2.19 mg/l for BOD5; 245 ± 9.15 mg/l and 47.31 ± 5.71 mg/l for COD. The treated value met the required standards for hospital wastewater treatment. The removal efficiency total nitrogen and total phosphorus were 68.64% and 64.44% after 10 days, respectively. Elimination of E. coli ATCC 8739 after 7 days by Chlorella sp. LH2 was 88.92%. The results of this study suggest the nutrients and pathogens removal potential of Chlorella sp. LH2 in hospital wastewater for further practical applications.

Sustainable treatment of aquaculture water employing fungi-microalgae consortium: Nutrients removal enhancement, bacterial communities optimization, emerging contaminants elimination, and mechanism analysis.

Fungi-microalgae consortium (FMC) has emerged as a promising system for advanced wastewater treatment due to its high biomass yield and environmental sustainability. This study aimed to investigate the nutrients removal, bacterial community shift, emerging contaminants elimination, and treatment mechanism of a FMC composed of Cordyceps militaris and Navicula seminulum for aquaculture pond water treatment. The fungi and microalgae were cultured and employed either alone or in combination to evaluate the treatment performance. The results demonstrated that the FMC could improve water quality more significantly by reducing nutrient pollutants and optimizing the bacterial community structures. Furthermore, it exhibited stronger positive correlation between the enrichment of functional bacteria for water quality improvement and pollutants removal performance than the single-species treatments. Moreover, the FMC outperformed other groups in eliminating emerging contaminants such as heavy metals, antibiotics, and pathogenic Vibrios. Superiorly, the FMC also showed excellent symbiotic interactions and cooperative mechanisms for pollutants removal. The results collectively corroborated the feasibility and sustainability of using C. militaris and N. seminulum for treating aquaculture water, and the FMC would produce more mutualistic benefits and synergistic effects than single-species treatments.

A review of emerging membrane-based microalgal-bacterial processes for wastewater treatment: Process configurations, biological and membrane performance, and perspectives.

Microalgal-bacterial (MB) consortia create an excellent eco-system for simultaneous COD/BOD and nutrients (N and P) removals in a single step with significant reduction in or complete elimination of aeration and carbonation in the biological wastewater treatment processes. The integration of membrane separation technology with the MB processes has created a new paradigm for research and development. This paper focuses on a comprehensive and critical literature review of recent advances in these emerging processes. Novel membrane process configurations and process conditions affecting the biological performance of these novel systems have been systematically reviewed and discussed. Membrane fouling issues and control of MB biofilm formation and thickness associated with these emerging suspended growth or immobilized biofilm processes are addressed and discussed. The research gaps, challenges, outlooks of these emerging processes are identified and discussed in-depth. The findings from the literature suggest that the membrane-based MB processes are advanced biotechnologies with a significant reduction in energy consumption and process simplification and high process efficiency that are not achievable with current technologies in wastewater treatment. There are endless opportunities for research and development of these novel and emerging membrane-based MB processes.

Native microalgal-bacterial consortia from the Ecuadorian Amazon region: an alternative to domestic wastewater treatment.

In low-middle income countries (LMIC), wastewater treatment using native microalgal-bacterial consortia has emerged as a cost-effective and technologically-accessible remediation strategy. This study evaluated the effectiveness of six microalgal-bacterial consortia (MBC) from the Ecuadorian Amazon in removing organic matter and nutrients from non-sterilized domestic wastewater (NSWW) and sterilized domestic wastewater (SWW) samples. Microalgal-bacterial consortia growth, in NSWW was, on average, six times higher than in SWW. Removal rates (RR) for NH4 +- N and PO4 3--P were also higher in NSWW, averaging 8.04 ± 1.07 and 6.27 ± 0.66 mg L-1 d-1, respectively. However, the RR for NO3 - -N did not significantly differ between SWW and NSWW, and the RR for soluble COD slightly decreased under non-sterilized conditions (NSWW). Our results also show that NSWW and SWW samples were statistically different with respect to their nutrient concentration (NH4 +-N and PO4 3--P), organic matter content (total and soluble COD and BOD5), and physical-chemical parameters (pH, T, and EC). The enhanced growth performance of MBC in NSWW can be plausibly attributed to differences in nutrient and organic matter composition between NSWW and SWW. Additionally, a potential synergy between the autochthonous consortia present in NSWW and the native microalgal-bacterial consortia may contribute to this efficiency, contrasting with SWW where no active autochthonous consortia were observed. Finally, we also show that MBC from different localities exhibit clear differences in their ability to remove organic matter and nutrients from NSWW and SWW. Future research should focus on elucidating the taxonomic and functional profiles of microbial communities within the consortia, paving the way for a more comprehensive understanding of their potential applications in sustainable wastewater management.

WITHDRAWN: Effects of hydraulic retention time and cultivation on nutrients removal and biomass production in wastewater by membrane photobioreactor: Modeling and optimization by machine learning and response surface methodology.

This article has been withdrawn at the request of the Editor-in-Chief.

Hydraulic retention time governed the micro/nanostructures of titanium-incorporated diatoms and their photocatalytic activity.

Titanium-incorporated diatoms are promising biomaterials to photodegrade micropollutants such as pharmaceuticals and personal care products (PPCPs). Hydraulic retention time (HRT) is a key parameter for diatom cultivation and the incorporation of titanium into diatom frustules. This study assessed how HRT governs the micro/nanostructures, titania (TiO2) content and distribution, and the photocatalytic activity of titanium-incorporated diatom frustules. We cultivated a diatom strain Stephanodiscus hantzschii using a feed solution containing titanium(IV) in membrane bioreactors (MBRs) at a solids retention time (SRT) of 10 d and staged HRTs from 24 to 12 and to 6 h. The decrease in HRT reduced the porosity of diatom frustules but increased their silicon and titania contents. When the HRT decreased from 24 to 12 and to 6 h, the specific surface areas of the diatom decreased from 37.65 ± 3.19 to 31.53 ± 3.71 and to 18.43 ± 2.69 m2·g-1 frustules, while the titanium (Ti) contents increased from 53 ± 14 to 71 ± 9 and to 85 ± 13 mg Ti·g-1 frustules. The increase in the influent flow rates of the MBRs with decreasing HRTs likely enhanced nutrient diffusion inside the diatom valve pores, facilitating the uptake and incorporation of silicon and titanium. The titanium-incorporated frustules were effective in removing two representative PPCPs, bisphenol A (BPA) and N,N-diethyl-meta-toluamide (DEET), from water. As photocatalytic activity depends on the amount of titanium, decreasing the HRT substantially increased the photocatalytic activity of the titanium-incorporated frustules. In batch tests under ultraviolet light, frustules from the diatom cultivated at HRTs of 24, 12, and 6 h had the pseudo-first-order removal (mainly through photodegradation) rate constants of BPA of 0.376, 0.456, and 0.683 h-1, respectively. Under the same experimental condition, the pseudo-first-order removal rate constants of DEET by the frustules cultivated at HRTs of 24, 12, and 6 h increased from 0.270 to 0.330 and to 0.480 h-1.

Nitrogen and phosphorus removal performance of sequential batch operation for algal cultivation through suspended-solid phase photobioreactor.

Nitrogen (N) and phosphorus (P) absorbed by algae in the suspended-solid phase photobioreactor (ssPBR) have emerged as an efficient pathway to purify the effluent of wastewater treatment plants (WWTPs). However, the key operational parameters of the ssPBR need to be optimized. In this study, the stability of the system after sequential batch operations and the efficiency under various influent P concentrations were evaluated. The results demonstrated that the ssPBR maintained a high N/P removal efficiency of 96 % and 98 %, respectively, after 5 cycles. When N was kept at 15 mg/L and P ranged from 1.5 to 3.0 mg/L, the system yielded plenty of algae products and guaranteed the effluent quality that met the discharge standards. Notably, the carriers were a key contributor to the high metabolism of algae and high performance. This work provided theoretical ideas and technical guidance for effluent quality improvement in WWTPs.

Unveiling the power of COD/N on constructed wetlands in a short-term experiment: Exploring microbiota co-occurrence patterns and assembly dynamics.

Constructed wetlands (CWs) are a cost-effective and environmentally friendly wastewater treatment technology. The influent chemical oxygen demand (COD)/nitrogen (N) ratio (CNR) plays a crucial role in microbial activity and purification performance. However, the effects of CNR changes on microbial diversity, interactions, and assembly processes in CWs are not well understood. In this study, we conducted comprehensive mechanistic experiments to investigate the response of CWs to changes in influent CNR, focusing on the effluent, rhizosphere, and substrate microbiota. Our goal is to provide new insights into CW management by integrating microbial ecology and environmental engineering perspectives. We constructed two groups of horizontal subsurface flow constructed wetlands (HFCWs) and set up three influent CNRs to analyse the microbial responses and nutrient removal. The results indicated that increasing influent CNR led to a decrease in microbial α-diversity and niche width. Genera involved in nitrogen removal and denitrification, such as Rhodobacter, Desulfovibrio, and Zoogloea, were enriched under medium/high CNR conditions, resulting in higher nitrate (NO3--N) removal (up to 99 %) than that under lower CNR conditions (<60 %). Environmental factors, including water temperature (WT), pH, and phosphorus (P), along with CNR-induced COD and NO3--N play important roles in microbial succession in HFCWs. The genus Nitrospira, which is involved in nitrification, exhibited a significant negative correlation (p < 0.05) with WT, COD, and P. Co-occurrence network analysis revealed that increasing influent CNR reduced the complexity of the network structure and increased microbial competition. Analysis using null models demonstrated that the microbial community assembly in HFCWs was primarily driven by stochastic processes under increasing influent CNR conditions. Furthermore, HFCWs with more stochastic microbial communities exhibited better denitrification performance (NO3--N removal). Overall, this study enhances our understanding of nutrient removal, microbial co-occurrence, and assembly mechanisms in CWs under varying influent CNRs.

Supplementation of micro-nutrients to growth media of microalgae-induced biomass and fatty acids composition for clean energy generation.

The presence of harmful heavy metals (HMs) in the aquatic environment can damage the environment and threaten human health. Traditional remediation techniques can have secondary impacts. Thus, more sustainable approaches must be developed. Microalgae have biological properties (such as high photosynthetic efficiency and growth), which are of great advantage in the HMs removal. In this study, the effect of various concentrations (2×, 4×, and 6×) of copper (Cu), cobalt (Co), and zinc (Zn) on microalgae (C. sorokiniana GEEL-01, P. kessleri GEEL-02, D. asymmetricus GEEL-05) was investigated. The microalgal growth kinetics, HMs removal, total nitrogen (TN), total phosphor (TP), and fatty acids (FAs) compositions were analyzed. The highest growth of 1.474 OD680nm and 1.348 OD680nm was obtained at 2× and 4×, respectively, for P. kessleri GEEL-02. P. kessleri GEEL-02 showed high removal efficiency of Cu, Co, and Zn (38.92-55.44%), (36.27-68.38%), and (32.94-51.71%), respectively. Fatty acids (FAs) analysis showed that saturated FAs in C. sorokiniana GEEL-01 and P. kessleri GEEL-02 increased at 2× and 4× concentrations while decreasing at 6×. For P. kessleri GEEL-02, the properties of biodiesel including the degree of unsaturation (UD) and cetane value (CN) increased at 2×, 4×, and 6× as compared to the control. Thus, this study demonstrated that the three microalgae (particularly P. kessleri GEEL-02) are more suitable for nutrient and HMs removal coupled with biomass/biodiesel production.

Prediction of biological nutrients removal in full-scale wastewater treatment plants using H2O automated machine learning and back propagation artificial neural network model: Optimization and comparison.

The effective control of total nitrogen (ETN) and total phosphorus (ETP) in effluent is challenging for wastewater treatment plants (WWTPs). In this work, automated machine learning (AutoML) (mean square error = 0.4200 âˆ¼ 3.8245, R2 = 0.5699 âˆ¼ 0.6219) and back propagation artificial neural network (BPANN) model (mean square error = 0.0012 âˆ¼ 6.9067, R2 = 0.4326 âˆ¼ 0.8908) were used to predict and analyze biological nutrients removal in full-scale WWTPs. Interestingly, BPANN model presented high prediction performance and general applicability for WWTPs with different biological treatment units. However, the AutoML candidate models were more interpretable, and the results showed that electricity carbon emission dominated the prediction. Meanwhile, increasing data volume and types of WWTP hardly affected the interpretable results, demonstrating its wide applicability. This study demonstrated the validity and the specific advantages of predicting ETN and ETP using H2O AutoML and BPANN model, which provided guidance on the prediction and improvement of biological nutrients removal in WWTPs.

Enhanced biological wastewater treatment supplemented with anaerobic fermentation liquid of primary sludge.

The wastewater treatment performance in an inverted A2/O reactor supplemented with fermentation liquid of primary sludge was explored comparing to commercial carbon sources sodium acetate and glucose. Similar COD removal rate was observed with the effluent COD stably reaching the discharge standard for those 3 carbon sources. However, the fermentation liquid distributed more carbon source in the anaerobic zone. Fermentation liquid and sodium acetate tests achieved better nitrogen removal rate than glucose test. The fermentation liquid test showed the best biological phosphorus removal performance with the effluent phosphorus barely reaching the discharge standard. The microbial community characterization revealed that the fermentation liquid test was dominated by phylum Proteobacter in all the anoxic, anaerobic and aerobic zones. Denitrifying phosphorus accumulating organisms (PAOs) (i.e., genera Dechloromonas and unclassified_f__Rhodocyclaceae) were selectively enriched with high abundances (over 20%), which resulted in improved phosphorus removal efficiency. Moreover, the predicted abundances of enzymes involved in nitrogen and phosphorus removal were also enhanced by the fermentation liquid.

Microbial community dynamics and metagenomics reveal the potential role of unconventional functional microorganisms in nitrogen and phosphorus removal biofilm system.

The conventional functional microorganisms for nitrogen and phosphorus removal, such as Nitrosomonas, Nitrobacter, Nitrospira and Candidatus Accumulibacter, were hotspots in past research. However, the role of diverse unconventional functional microorganisms was neglected. In this study, a biofilm system was developed to explore the potential role of unconventional functional microorganisms in nutrients removal. According to the results of microbial community dynamics and metagenomics, complete ammonia oxidizing (comammox) bacteria was 20 times more abundant than ammonia-oxidizing bacteria (AOB) at day 121 and its abundance of amoA gene was almost the same as AOB. Although Nitrospira dominated the nitrite-oxidizing bacteria (NOB), diverse unconventional nxrB-containing microorganisms, particularly Chloroflexi, also significantly contributed to the nitrite oxidation. Binning analysis showed that Myxococcota-affiliated Haliangium had the necessary genes owns by phosphorus-accumulating organisms (PAO) and was likely to be the primary PAO since its abundance (6.38 %) was much higher than other conventional PAO (0.70 %). Comparing metagenome-assembled genomes of comammox bacteria with AOB and ammonia-oxidizing archaea (AOA), it possessed potential metabolic versatility in hydrogen and phosphorus, which may be the primary reason for the positive effect of the alternating anaerobic and aerobic conditions on the enrichment of comammox bacteria. Collectively, our findings broaden the understanding on the microbial mechanism of nitrogen and phosphorus removal in biofilm system.

Insights into simultaneous nitrogen and phosphorus removal in biofilm: The overlooked comammox Nitrospira and the positive role of glycogen-accumulating organisms.

Simultaneous nitrogen and phosphorus removal (SNPR) biofilm system is an effective wastewater treatment process. However, the understanding on the mechanism of functional microorganisms driving SNPR is still limited, especially the role of complete ammonia oxidation (comammox) Nitrospira and glycogen-accumulating organisms (GAO). In this study, a sequencing batch biofilm reactor (SBBR) performing SNPR was operated for 249 d. Based on the 16S rRNA gene, comammox amoA amplicon sequencing, metagenomics and batch experiment, we found that comammox Nitrospira was the main ammonia-oxidizing microorganisms (AOM) and provided nitrite for anaerobic ammonia oxidation (anammox) bacteria (AnAOB). Besides, GAO was dominated by the bacteria of genus Defluviicoccus and played a primary role in reducing nitrate rather than nitrite. Fluorescent in situ hybridization (FISH) analysis confirmed that Nitrospira was enriched in the inner layer of the biofilm. Thus, we put forward a novel insight into the mechanism of SNPR biofilm system. Comammox Nitrospira was responsible for nitrite and nitrate production in the inner biofilm, and AnAOB consumed the produced nitrite during the anammox process. While GAO reduced nitrate to nitrite and polyphosphate-accumulating organisms (PAO) converted nitrite to dinitrogen via denitrifying phosphorus removal in the outer biofilm. These findings provide a new understanding in SNPR biofilm system.

Improving nutrients removal of Anaerobic-Anoxic-Oxic process via inhibiting partial anaerobic mixture with nitrite in side-stream tanks: Role of nitric oxide.

A side-stream tank which was in parallel with the anoxic tank was used to improve the performance of an Anaerobic-Anoxic-Oxic process. The partial mixtures from the anaerobic tank were injected into the side-stream tank with the initial nitrite nitrogen (NO2--N) concentrations of 10 mg/L and 20 mg/L. When the initial NO2--N concentration in the tank was 20 mg/L, total nitrogen and total phosphorus removal efficiencies of the A2/O process increased from 72% and 48% to 90% and 89%, respectively. 2.23 mg/L of nitric oxide (NO) were observed in the side-stream tank. The abundance of Nitrosomonas sp. and Nitrospira sp. were varied from 0.98% and 6.13% to 2.04% and 1.13%, respectively. The abundances of Pseudomonas sp. and Acinetobacter sp. were increased from 0.81% and 0.74% to 6.69% and 5.48%, respectively. NO plays an important role for improving the nutrients removal of the A2/O process in the side-stream nitrite-enhanced strategy.

Removal of parabens from wastewater by Chlorella vulgaris-bacteria co-cultures.

Anthropogenic activities have increased the dispersal of emerging contaminants (ECs), particularly of parabens, causing an escalation of their presence in wastewater (WW). Current WW technologies do not present satisfactory efficiency or sustainability in removing these contaminants. However, bioremediation with microalgae-based systems is proving to be a relevant technology for WW polishing, and the use of microalgae-bacteria consortia can improve the efficiency of WW treatment. This work aimed to study dual cultures of selected bacteria (Raoultella ornithinolytica, Acidovorax facilis, Acinetobacter calcoaceticus, Leucobacter sp. or Rhodococcus fascians) and the microalga Chlorella vulgaris in microbial growth and WW bioremediation - removal of methylparaben (MetP) and nutrients. The association with the bacteria was antagonistic for C. vulgaris biomass productivity as a result of the decreased growth kinetics in comparison to the axenic microalga. The presence of MetP did not disturb the growth of C. vulgaris under axenic or co-cultured conditions, except when associated with R. fascians, where growth enhancement was observed. The removal of MetP by the microalga was modest (circa 30 %, with a removal rate of 0.0343 mg/L.d), but increased remarkably when the consortia were used (> 50 %, with an average removal rate > 0.0779 mg/L.d), through biodegradation and photodegradation. For nutrient removal, the consortia were found to be less effective than the axenic microalga, except for nitrogen (N) removal by C. vulgaris w/ R. fascians. The overall results propose that C. vulgaris co-cultivation with bacteria can increase MetP removal, while negatively affecting the microalga growth and the consequent reduction of sludge production, highlighting the potential of microalgae-bacteria consortia for the effective polishing of WW contaminated with parabens.

Deciphering three-dimensional bioanode configuration for augmenting power generation and nitrogen removal in air-cathode microbial fuel cells.

In this study, the engineering-oriented three-dimensional (3D) bioanode concept was applied, demonstrating that spiral-stairs-like/rolled carbon felt (SCF/RCF) configurations achieved good performances in air-cathode microbial fuel cells (ACMFCs). With the 3D anodes, ACMFCs generated significantly higher power densities of 1535 mW/m3 (SCF) and 1800 mW/m3 (RCF), compared with that of a traditional flat carbon felt anode (FCF, 315 mW/m3). The coulombic efficiency of 15.39 % at SCF anode and 14.34 % at RCF anode also is higher than the 7.93 % at FCF anode. The 3D anode ACMFCs exhibited favorable removal of chemical oxygen demand (96 % of SCF and RCF) and total nitrogen (97 % of SCF, 99 % of RCF). Further results show that three-dimensional anode structures could enrich more electrode surface biomass and diversify the biofilm microbial communities for promoting bioelectroactivity, denitrification, and nitrification. These results demonstrate that three-dimensional anodes with active biofilm is a promising strategy for creating scalable MFCs-based wastewater treatment system.

Under-loaded operation of an anaerobic-anoxic-aerobic system in dry and wet weather dynamics to prevent overflow pollution: Impacts on process performance and microbial community.

Effects of low hydraulic loading rate (HLR) in dry weather and high HLR in wet weather on pollutant removal, microbial community, and sludge properties of a full-scale wastewater treatment plant (WWTP) were extensively studied to explore the risk of under-loaded operation for overflow pollution control. Long-term low HLR operation had an insignificant effect on the pollutant removal performance of the full-scale WWTP, and the system could withstand high-load shocks in wet weather. Low HLR resulted in higher oxygen and nitrate uptake rate due to the storage mechanism under the alternating feast/famine condition, and lower nitrifying rate. Low HLR operation enlarged particle size, deteriorated floc aggregation and sludge settleability, and reduced sludge viscosity due to the overgrowth of filamentous bacteria and inhibition of floc-forming bacteria. The remarkable increase in Thuricola and the contract morphology of Vorticella in microfauna observation confirmed the risk of flocs disintegration in low HLR operation.

Environmentally relevant level of perfluorooctanoic acid affect the formation of aerobic granular sludge.

The growing increasing occurrence of perfluorooctanoic acid (PFOA) in wastewater has raised concerns about its potential impact on the environment. Nevertheless, the impact of PFOA at environmentally relevant level on the formation of aerobic granular sludge (AGS) is still a 'black box'. This study thus aims to fill this gap by comprehensive investigation of sludge properties, reactor performance and microbial community during the formation of AGS. It was found that 0.1 mg/L PFOA delayed the formation of AGS, causing relatively lower proportion of large size AGS at the end of operation process. Interestingly, the microorganisms contribute to the reactor's tolerance to PFOA by secreting more extracellular polymeric substances (EPS) to slow or block the entry of toxic substances into the cells. During the granule maturation period, the reactor nutrient removal especially chemical oxygen demand (COD) and total nitrogen (TN) were affected by PFOA, decreasing the corresponding removal efficiencies to ∼81.2% and ∼69.8%, respectively. Microbial analysis further revealed that PFOA decreased the abundances of Plasticicumulans, Thauera, Flavobacterium and Cytophagaceae_uncultured, but it has promoted Zoogloea and Betaproteobacteria_unclassified growth, which maintained the structures and functions of AGS. The above results revealed that the intrinsic mechanism of PFOA on the macroscopic representation of sludge granulation process was revealed, and it is expected to provide theoretical insights and practical support for direct adoption of municipal or industrial wastewater containing perfluorinated compounds to cultivate AGS.

Stimulating carbon and nitrogen metabolism of Chlorella pyrenoidosa to treat aquaculture wastewater and produce high-quality protein in plate photobioreactors.

Wastewater treatment by microalgae is the economical and environmentally friendly strategy, but is still challenged with the strict discharge standards and valuable biomass exploitations. The carbon and nitrogen metabolism of Chlorella pyrenoidosa was improved by the red LED light and starch addition to treat Tilapia aquaculture wastewater (T-AW) and produce protein simultaneously in a plate photobioreactor. The red LED light was applied to improve the nutrient removals at an outdoor temperature, but the concentrations except total nitrogen did not satisfy the discharge standards. After starch addition, the removal efficiencies of total phosphorus, total nitrogen, chemical oxygen demand, and total ammonia nitrogen were 85.15, 96.96, 88.53, and 98.01 % in a flat-plate photobioreactor, respectively, which met the discharge standards and the protein production reached 0.60 g/L. At a molecular level, the metabolic flux and transcriptome analyses showed that red light promoted carbon flux of the Embden-Meyerhof-Pranas pathway and tricarboxylic cycle, and upregulated the levels of genes encoding α-amylase, glutamine synthetase, glutamate dehydrogenase, nitrate transporter, and ammonium transporter, which facilitated nutrients removal and provided nitrogen sources for protein biosynthesis. The harvesting C. pyrenoidosa possessed the 62 % essential amino acids and great lipid composition for biofuels. This study provided a new orientation for outdoor wastewater treatment and protein production by collaboratively regulating the carbon and nitrogen metabolism of microalgae.