Microalgal-bacterial granular sludge (MBGS) process has a gorgeous prospect for municipal wastewater treatment, but the research on the treatment of complex organic wastewater by MBGS process with ...CO2 addition under outdoor conditions is not enough. Therefore, this paper evaluated the feasibility of CO2-added MBGS process for complex organic wastewater disposal under natural day-night cycles. The results showed that the addition of CO2 overall improved the removal efficiency of pollutants. Typically, the removal efficiency of total phosphorus increased averagely from 88.5 % to 95.0 % in 12-h day cycle and from 26.2 % to 45.3 % in 12-h night cycle. The addition of CO2 increased the size of MBGS from 1.0 mm to 16.5 mm within 30 days due to extracellular polymeric substances secretion and the dominant filamentous microalgae on granules. The decrease of catalase activity and malondialdehyde content indicated that CO2 reduced oxidative damage and maintained the normal growth of MBGS. Further estimates of the collected gas showed that CO2-added MBGS process could reduce global CO2 emissions by one hundred million tons per year. This study is expected to contribute to the goal of carbon neutrality in the area of wastewater treatment by MBGS process.
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•CO2-added microalgal-bacterial granular sludge (MBGS) was evaluated outdoors.•CO2 addition promoted the phosphorus removal for both day and night cycles.•CO2 favored the MBGS growth with filamentous microalgae on the granule surface.•CO2 -added MBGS process contributed to the global carbon neutrality.
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•A continuous-flow microalgal-bacterial granular tubular reactor was developed.•Daytime was favorable for ammonia removal while nighttime for nitrate removal.•Phosphate-P removal was ...highly reliable on the weather condition.•Nitrite-N maintained high removal efficiency of over 99% under varied conditions.•Superb nitrite removal relied mainly on nitrite reduction instead of denitrification.
This study developed a continuous-flow non-aerated microalgal-bacterial granular tubular reactor for aquaculture wastewater treatment under natural day-night conditions. Results showed that daytime was favorable for ammonia removal while nighttime for nitrate removal. Over 99% of nitrite-N could be removed over the day-night cycles at a hydraulic retention time of 6 h. However, the phosphorus removal was found to be sensitive to the weather condition, ranging from 35.0% to 96.6%. It was also observed that dissolved oxygen produced by microalgae in daytime was sufficient for creating a 6-h aerobic condition in nighttime for sustaining heterotrophic activity. Chlorella and Leptolyngbya were identified as the most abundant algae related to weather changes. Metagenomics analysis revealed that the high nitrite removal relied mainly on nitrite reduction. These experimental findings offer new insights into the non-aerated microalgal-bacterial granular sludge for environmentally sustainable aquaculture wastewater treatment.
In this study, a eukaryotic microalgae dominated microalgal-bacterial granular sludge process was explored for municipal wastewater treatment under simulated natural diel cycles. Different from ...previous studies with constant illumination, the excellent performances were obtained in terms of organics, ammonia-N and phosphate-P removal under simulated natural day-night conditions. It was found that about 94.9% of organics, 69.5% of ammonia-N and 90.6% of phosphate-P could be removed on average over a day-night cycle at a shorter hydraulic retention time of 2 h in the daytime, while 93.1% of organics, 62.5% of ammonia-N and 80.8% of phosphate-P removed at a hydraulic retention time of 4 h during the nighttime. Chlorophyceae were identified as the dominant microalgae, with Alphaproteobacteria and Sphingobacteriia being the major bacteria in MBGS. It was further revealed that microbial assimilation by microalgae and bacteria could serve as the main mechanism for the observed removal of organics, ammonia and phosphate, while the corresponding key metabolic pathways were also elucidated. Chlorophyceae were found to be the main player for the phosphorus removal via H+-exporting ATPase and H+-transporting two-sector ATPase, while Alphaproteobacteria were potentially responsible for the observed ammonia removal mediated by glutamine synthetase and glutamate dehydrogenase. It is expected that this study can offer an environmentally sustainable option for municipal wastewater treatment.
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•Microalgal-bacterial granular sludge process was demonstrated under day-night cycles.•85% of organics and P were removed during diel cycles.•Ammonia removal was organic source-dependent, with 75% removed for acetate.•The removal mechanisms of organics, N and P were identified with key metabolic pathways.•Metabolic pathways of organics, N and P were related to the functions of microbial taxa.
Flowering control of field-cultivated summer-to-autumn flowering chrysanthemums was established using light culture and selecting appropriate cultivars. In order to make the technique applicable in ...wider areas, we attempted to stabilize the period from light-off to anthesis. The effects of natural day-length after light-off on flowering were studied. Long days, especially near the summer solstice in the northern part of Japan, inhibited floral development of some cultivars selected in mid-latitude regions. We characterized and selected cultivars suitable for light culture and that flower stably under longer photoperiods. The use of cultivars with a longer critical day-length for flowering could reduce the delay of anthesis.
Fine particulate matter (PM
) is directly associated with smog and has become the primary factor that threatens air quality in China. In order to investigate the variation patterns of PM
...concentrations in various regions of Wuhan city across different time spans, we analyzed continuous monitoring data from six monitoring sites in Wuhan city from 2013 to 2017. The results showed that the PM
concentration from the various monitoring sites in the five-year period showed a decreasing trend. January, October, and December are the three months with relatively high mean monthly PM
concentrations in the year, while June, July, and August are the three months with relatively low mean monthly PM
concentrations in the year. The number of days with a daily mean concentration of 35⁻75 μg/m³ was the highest, while the number of days with a daily mean concentration of more than 250 μg/m³ was the lowest. PM
accounted for a large proportion of the major pollutants and is the main source of air pollution in Wuhan city, with an average proportion of over 46%.
We assessed runner production in everbearing strawberry cultivars (Fragaria × ananassa Duch.) ‘Natsuakari’ and ‘Dekoruju’, which exhibit poor ability to produce runners, thus limiting their ...propagation and use. Both cultivars required 1,000 h of chilling (< 5°C) to induce runner production when grown under a long day length (LD); however, they required longer chilling under a short day length (SD). Plants chilled for 2,000 h tended to produce more runners under SD than under LD. During spring and summer, the overwintered ‘Natsuakari’ plants produced the fewest runners under SD. In contrast, the overwintered ‘Dekoruju’ plants produced the fewest runners under LD. Thus, a longer day length did not always enhance runner production in these cultivars. In autumn, 90-day cold storage at −2°C was substituted for natural chilling for plants that were rooted in summer. For both cultivars, the production of runners by plants that were rooted in July was similar to or greater than that by plants that were rooted in May. The rooting of mother plants in July, which are more available than plants rooted in May, did not have a detrimental effect on runner production during the next early summer period. Considering total runner production till July, we concluded that it is appropriate to initiate cold storage in December for the ‘Natsuakari’ cultivar and in November or December for the ‘Dekoruju’ cultivar.
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