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Post-hydrothermal liquefaction wastewater (PHWW), which contains approximately 80% of original feedstock resources, shows great potential to achieve sustainable development of an environment-enhancing energy system. A combination of anaerobic digestion and algae cultivation was proposed for methane recovery and nutrient supply from PHWW. Granular activated carbon (GAC) and ozone were used to enhance energy recovery from the PHWW. The results indicated that with GAC addition, the maximum methane yield increased by 67.7%–228 mL/g CODremoval. In addition, Chlorella vulgaris displayed optimal growth in a 5-fold diluted digestate with a 2.32 g/L maximum biomass content and 180 mg/(L·d) biomass production rate. The total energy yield was 565 kJ/g COD, which was 27.4 times higher than that without GAC. Integration of anaerobic digestion and algae cultivation, particularly with GAC addition during fermentation, is a feasible and advantageous process for energy recovery from PHWW.

Miscanthus is a promising source of bioenergy with high lignocellulose content. This paper studied the effect of hydrothermal pretreatment on Miscanthus biogas production. Different pretreatment temperature from 125 to 200°C was tested. After pretreatment, hemicellulose was partially removed and this led to a change in cellulose accessibility. Enzymatic hydrolysis was used to examine the digestibility of different samples. There was no obvious enhancement in low temperature (125 and 150°C) conditions. According to the results, 200°C hydrothermal pretreatment was the optimal condition saving 50% on the digestion time and increasing glucose production 13.2 times compared with the raw material. Although the cellulose crystallinity increased after the pretreatment, its effect on biogas production and enzymatic hydrolysis was limited.

The submerged aeration membrane (SAM) system and axial vibration membrane (AVM) system can mitigate membrane fouling. In this study, both systems were investigated to compare the performance of filtration and the membrane fouling in algae filtration. In 5-h filtration, the transmembrane pressure (TMP) of SAM reached to 70.0 kPa, while there was almost no increase in TMP for AVM. After continuous filtration, it could be found that there was hardly any algae cells on the membrane of AVM (0.11 g/m2), which was about 32.4 times less than that of SAM (3.56 g/m2). Compared with the SAM system, AVM had a lesser membrane fouling, regardless of the reversible fouling or irreversible fouling. By SEM, FTIR and EEM, it could be found there was less irreversible extracellular organic matter (EOM) on the membrane of AVM. By MW distribution, it could be observed that less EOM with high-MW adhered to membrane of AVM.

Microalgae-based technology is an environmental-friendly and cost-effective method for biofuel production and pollutants removal. In this study, Scenedesmus obliquus (S. obliquus) was cultured with varying concentrations of ofloxacin (OFL) in BG11 medium. In the algae-antibiotics culture system, S. obliquus could effectively remove OFL with a concentration of 10 mg/L; however, the removal efficiency was restricted under higher doses (20–320 mg/L). Meanwhile, the lipid content significantly increased by 21.10–49.63%, which was caused by carbon being converted from carbohydrate to lipid. The greatest lipid productivity (7.53 mg/L/d) occurred at an OFL concentration of 10 mg/L, which was approximately 1.5-fold greater than the control. Moreover, S. obliquus cultured with OFL was able to improve the biodiesel quality due to an increase of saturated fatty acids and a decrease of unsaturated fatty acids. This study demonstrates that an algae-antibiotics system is a promising solution to simultaneously achieve antibiotics removal and biofuel production.

It has been proven that extrusion can change the structure of rice straw and increase biogas production, but the effect of a single pretreatment is limited. Ca(OH)2 pretreatment was used to enhance the enzyme hydrolysis and biogas production of extruded rice straw. After Ca(OH)2 pretreatment, the glucose and xylose conversion rates in enzymatic hydrolysis increased from 36.0% and 22.4% to 66.8% and 50.2%, respectively. The highest biogas production observed in 8% and 10% Ca(OH)2 pretreated rice straw reached 564.7mL/g VS and 574.5mL/g VS, respectively, which are 34.3% and 36.7% higher than the non-Ca(OH)2-loaded sample. The Ca(OH)2 pretreatment can effectively remove the lignin and increase the fermentable sugar content. The structural changes in the extruded rice straw have also been analyzed by XRD, FTIR, and SEM. Considering all of the results, an 8% Ca(OH)2 loading rate is the best option for the pretreatment of extruded rice straw.

Alcohol wastewater (AW) as carbon source for enhancing Chlorella pyrenoidosa growth and lipid accumulation in anaerobically digested starch wastewater (ADSW) was performed in outdoor cultivation. The biomass and lipid production significantly increased while adding optimal amount of AW (AW/ADSW=1:15) during exponential phase. In comparison with blank ADSW culture, the optimal AW addition increased the biomass production, lipid content and productivity by 35.29%, 102.68% and 227.91%, respectively. However, AW addition caused severe bacterial contamination and the total bacterial increased by 4.62-fold. Simultaneously, the optimal consortia of microalgae/bacteria effectively removed nutrients from the wastewater, including 405.18±36.47mgCODCr/L/day, 49.15±5.54mgN/L/day and 6.72±1.24mgP/L/day.

Recently, anaerobic digestion of lignocellulosic biomass for methane production has attracted considerable attention. However, there is little information regarding methane production from asparagus stem, a typical lignocellulosic biomass, by anaerobic digestion. In this study, alkaline pretreatment of asparagus stem was investigated for its ability to increase hydrolysis rate and methane production and to improve biodegradability (BD). The hydrolysis rate increased with increasing NaOH dose, due to higher removal rates of lignin and hemicelluloses. However, the optimal NaOH dose was 6% (w/w) according to the specific methane production (SMP). Under this condition, the SMP and the technical digestion time of the NaOH-treated asparagus stem were 242.3 mL/g VS and 18 days, which were 38.4% higher and 51.4% shorter than those of the untreated sample, respectively. The BD was improved from 40.1% to 55.4%. These results indicate that alkaline pretreatment could be an efficient method for increasing methane production from asparagus stem.

The inhibitory effects and biotransformation potential of the fluoroquinolone antibiotic ciprofloxacin (CIP) under anoxic (i.e., nitrate reducing) and anaerobic (i.e., sulfate reducing and methanogenic) conditions were investigated. Fermentation and sulfate reduction was inhibited in 10-80 mg/L CIP-amended sulfate-reducing cultures but recovered with prolonged incubation. Methanogenesis in the mixed culture was significantly inhibited at 80-100 mg CIP/L. No significant decrease of CIP concentration was observed under both sulfate-reducing and methanogenic conditions. However, a low degree of CIP biotransformation was observed in a fed-batch denitrifying culture after a lag time even though the microbial, denitrifying activity was gradually inhibited at 24-40 mg CIP/L. Furthermore, the degradation of CIP was accelerated with a CIP reamendment of the denitrifying culture. Two CIP biotransformation products in the denitrifying culture were detected and their proposed chemical structures suggest that the antibiotic quinolone moiety of CIP was intact.

The adsorption, inhibition, and biotransformation of the fluoroquinolone antibiotic ciprofloxacin (CIP) under aerobic conditions were investigated in this study. The maximum adsorption capacity and the Langmuir constant were 37.9 mg CIP/g VSS and 37 L/g, respectively. A glucose-fed aerobic culture was inhibited by CIP at 10mg/L or higher and the degree of inhibition increased with increasing CIP concentration. However, the microbial activity recovered to some extent with prolonged incubation under a semi-continuous feeding mode. A low extent of CIP biotransformation was observed in an aerobic, glucose-fed culture derived from poultry litter extract. LC/UV/MS analysis of the biotransformation product showed that only the piperazine ring was oxidized, while the antibiotic quinolone part of CIP was intact.

A freshwater algae Chlorella pyrenoidosa was cultured outdoors using anaerobically digested activated sludge effluent. The effects of pH variations were evaluated. The coupled pH variations and free ammonia toxicity significantly affected the algal growth, lipids accumulation and contamination control during every season. The free ammonia toxicity at high pH levels actually inhibited the algal growth. Compared to an optimal algal growth at a pH of 5.7-6.5, biomass productivity at a high pH of 8.3-8.8 was reduced by 67.15±6.98%, 54.39±6.42% and 83.63±5.71% in the spring, fall and summer, respectively. When the pH rose above 9.1-9.6, algae were unable to grow in the wastewater. However, high pH levels reduced contamination (e.g., bacteria and microalgae grazers) and triggered lipids accumulation in algal cells. These findings suggest that pH control strategies are essential for this type of algal wastewater system, where ammonia is the dominant nitrogen source.

A freshwater green algae Chlorella pyrenoidosa (C. pyrenoidosa) was cultured in outdoors using the diluted anaerobically digested activated sludge (ADAS). The outdoors batch culture in every season showed that C. pyrenoidosa can grow normally under natural conditions in the diluted ADAS (STE/ADAS=1.5/1, 3/1 and 5/1, v/v). Seasonal changes of environmental conditions significantly affected biomass growth and nutrient removal. Optimal biomass growth and nutrient removal was achieved at STE/ADAS=1.5/1 during summer culture, harvesting a maximum biomass concentration of 1.97 ± 0.21 g/L, average biomass productivity of 291.52 ± 33.74 g/m(3)/day (maximum value of 573.10 ± 41.82) and average lipids productivity of 37.49 ± 5.26 g/m(3)/day (maximum value of 73.70 ± 9.75); simultaneously, the microalgae growth effectively removed nutrients from the wastewater, including 105.6 ± 17.1 mg CODCr/L/day, 36.8 ± 6.1mg N/L/day and 6.1 ± 1.1 mg P/L/day.

Microalgae cultivation using wastewater might be a suitable approach to support sustainable large-scale biomass production. Its compelling characteristics included the recycling of nutrients and water resources, reducing carbon emissions and harvesting available biomass. In outdoor batch and continuous cultures, Chlorella pyrenoidosa completely adapted to anaerobic digested starch processing wastewater and was the dominant microorganism in the photobioreactor. However, seasonal changes of environmental conditions significantly influenced biomass growth and lipid production. The long-term outdoor operation demonstrated that the biomass concentration and productivity in continuous operations at different hydraulic retention times (HRTs) can be successfully predicted using the kinetic growth parameters obtained from the batch culture. A moderate HRT (4days) in the summer provided the best microalgae and lipid production and achieved relatively high biomass concentrations of 1.29-1.62g/L, biomass productivities of 342.6±12.8mg/L/d and lipids productivities of 43.37±7.43mg/L/d.

The cultivation of microalgae Chlorella pyrenoidosa ( C. pyrenoidosa ) using anaerobic digested starch wastewater (ADSW) and alcohol wastewater (AW) was evaluated in this study. Different proportions of mixed wastewater (AW/ADSW = 0.176:1, 0.053:1, 0.026:1, v/v) and pure ADSW, AW were used for C. pyrenoidosa cultivation. The different proportions between ADSW and AW significantly influenced biomass growth, lipids production and pollutants removal. The best performance was achieved using mixed wastewater (AW/ADSW = 0.053:1, v/v), leading to a maximal total biomass of 3.01 ± 0.15 g/L (dry weight), lipids productivity of 127.71 ± 6.31 mg/L/d and pollutants removal of COD = 75.78 ± 3.76%, TN = 91.64 ± 4.58% and TP = 90.74 ± 4.62%.

Supplementing proper nutrients could be a strategy for enhancing algal biomass, nutrients uptake and lipid accumulation in the coupling system of biodiesel production and municipal wastewater treatment. However, there is scant information reporting systematic studies on screening and optimization of key supplemented components in the coupling system. The main factors were scientifically screened and optimized using statistical methods. Plackett–Burman design (PBD) was used to explore the roles of added nutrient factors, whereas response surface methodology (RSM) was employed for optimization. Based on the statistic analysis, the optimum added TP and FeCl 3 ·6H 2 O concentrations for Scenedesmus obliquus -like microalgae growth, nutrients uptake and lipid accumulation were 4.41 mg L −1 and 6.48 mg L −1 , respectively. The corresponding biomass, lipid content and TN/TP removal efficiency were 1.46 g L −1 , 36.26% and >99%. The predicted value agreed well with the experimental value, as determined by validation experiments, which confirmed the availability and accuracy of the model.

To explore the integration of microalgae cultivation and anaerobic processing for wastewater treatment, we utilized an airlift circulation photobioreactor and a dynamic membrane reactor for microalgae cultivation in combination with an upflow anaerobic sludge bed (UASB) reactor for starch processing wastewater (SPW) treatment. Chlorella pyrenoidosa completely adapted to the digested SPW without any chemical additives, and it grew normally under a wide temperature range in different seasons. C. pyrenoidosa was always the dominant microorganism in the photobioreactors although bacteria and some wild type microalgae were observed. Optimal biomass growth and pollutants removal was achieved at temperatures between 35 and 38°C in summer, removing 65.99% of COD, 83.06% of TN, 96.97% of TP and a biomass productivity of 0.37gL(-1)d(-1). Temperature fluctuation significantly influenced lipid contents and FAMEs compositions in biomass. The results demonstrate the successful integration of microalgae biomass production and anaerobic processing for wastewater treatment.

The aim of this study was to evaluate the effect of different inoculum sources on the rice straw anaerobic digestion. Six different digestates (DM, SM, CM, MS, AGS and PS) were applied as inoculums and their effects were evaluated in batch reactors. The results indicated that digested manures were more suitable than sludge. Reactors inoculated with digested manures achieved higher, biogas production and lignocellulose degradation. The better adaptability of digested manures had relationship with its higher cellulase and xylanase activities and sufficient nutrients content. DM had the best effect among all three digested manures. Reactors inoculated with DM achieved the highest biogas production (325.3 mL/g VS) and enzymes activities. The synergism between cellulase and xylanase activities played an important role in lignocellulose degradation.

Airlift loop reactors (ALRs) are important bioreactors for wastewater treatment. However, few studies have investigated the application of an ALR for simultaneous carbon and nutrient removal, especially for activated sludge systems. This study evaluated the performance of integrated nitrogen, phosphorus and COD removal in an ALR with a low height-to-diameter ratio in a limited filamentous bulking (LFB) state (SVI of 180–220 mL/g). The average removal efficiencies for COD, NH 4 + – N , TN and TP were 91%, 92%, 86% and 94%, respectively. Additional research showed that only under the LFB state, the appropriate distribution of dissolved oxygen inside the ALR was established to promote a well-balanced aerobic and anoxic/anaerobic state. In addition, the macro-gradient of the substrate concentration at the inlet and the heavier bio-P sludge density compensated for the proliferation of filaments. Hence, the stable LFB state was achieved by balancing the floc-forming bacteria and the filamentous bacteria in the ALR.