Capabilities and mechanisms of microalgae on nutrients and florfenicol removing from marine aquaculture wastewater.

The regulations governing the discharge of marine aquaculture wastewater are becoming increasingly stringent, and the problems of nitrogen and phosphorus pollution and antibiotic residues in wastewater are serious. Microalgae-based treatment with the dual benefits of wastewater purification and microalgae resource recycling was regarded as the most promising technology in aquaculture wastewater treatment. Isochrysis galbana and Chlorella sp. were chosen to investigate antibiotic and nutrient removal mechanisms from aquaculture wastewater. FLO addition stimulated microalgae growth at low FLO concentrations (0.1 and 1 mg/L) but inhibited growth at 10 mg/L. The removal efficiency of DIN by Chlorella sp. and I. galbana after 7 days of cultivation was 66.4% and 25.8%, respectively. Linear curves were obtained between DIN concentration and cultivation duration, remove constant (k) increased as FLO concentration increased from 0 to 10 mg/L, and the highest value of k was obtained in both the Chlorella sp. and I. galbana groups at 10 mg/L. DIP concentrations in FLO-contained simulated aquaculture wastewater decreased sharply with the cultivation of Chlorella sp. and I. galbana, and DIP removal rate increased as FLO concentration increased. When the initial concentration of FLO was 0.1 mg/L, biodegradation by I. galbana accounted for 86.67% of FLO removal. In contrast, FLO removal with biodegradation and biosorption by Chlorella sp. was 89.74% and 3.72%, respectively. Furthermore, Chlorella sp. grown in MPBR demonstrated superior capability for antibiotic-containing marine aquaculture wastewater purification, with average removal rates of DIN and DIP of 81.2% and 100%, respectively. The high removal rate is related to membranes which can improve microalgae performance by decoupling SRT and HRT. For microalgae-based aquaculture wastewater, ammonia was the most crucial nitrogen source, followed by nitrate. These findings serve as a theoretical foundation for developing microalgae-based aquaculture wastewater treatment technology and eliminating antibiotics in aquaculture.

Novel nitrogen removal process in marine aquaculture wastewater treatment using Enteromorpha ferment liquid as carbon.

The process performance of partial denitrification of a novel anaerobic fermentation integrated fixed-film activated sludge (IFAS-AFPD) of Enteromorpha was studied. The response surface method was used to determine the optimal reaction conditions, and the operation experiment was carried out under the optimal conditions. The results showed that the nitrogen removal effect was the best when the salinity was 12.2 g•L-1, the Carbon-Nitrogen ratio (C/N) was 4, the pH was 8.5, and the Nitrite Accumulation Rate, Nitrate Removal Rate, Chemical Oxygen Demand Utilization Rate could reach 77%, 89% and 51%. Experimental results have shown that the NAR of the Enteromorpha ferment liquid system could be maintained at about 74%, which was noteworthy higher than that of the sodium acetate (CH3COONa) system at 42%; Microbial community analysis showed that Enteromorpha ferment liquid was more beneficial to the growth of Bacteroidetes than CH3COONa.

Investigation into the Novel Microalgae Membrane Bioreactor with Internal Circulating Fluidized Bed for Marine Aquaculture Wastewater Treatment.

A microalgae membrane bioreactor (MMBR) with internal circulating fluidized bed (ICFB) was constructed at room temperature to study the removal efficiency of marine aquaculture wastewater pollutants and continuously monitor the biomass of microalgae. Within 40 days of operation, the removal efficiency of NO3--N and NH4+-N in the ICFB-MMBR reached 52% and 85%, respectively, and the removal amount of total nitrogen (TN) reached 16.2 mg/(L·d). In addition, the reactor demonstrated a strong phosphorus removal capacity. The removal efficiency of PO43--P reached 80%. With the strengthening of internal circulation, the microalgae could be distributed evenly and enriched quickly. The maximum growth rate and biomass concentration reached 60 mg/(L·d) and 1.4 g/L, respectively. The harvesting of microalgae did not significantly affect the nitrogen and phosphorus removal efficiency of ICFB-MMBR. The membrane fouling of the reactor was investigated by monitoring transmembrane pressure difference (TMP). Overall, the membrane fouling cycle of ICFB-MMBR system was more than 40 days.