Enhanced nitrogen and phosphorus removal from mariculture water using immobilized bacteria and macroalgae.

With the vigorous development of the mariculture industry, the untreated wastewater from mariculture has exerted significant pressure on the water environment. The untreated N and P in the wastewater from mariculture can deteriorate the quality of the mariculture. In this study, a composite in situ treatment system involving macroalgae (Caulerpa lentillifera/Caulerpa sertularoides f. Longipes) and immobilized degrading bacteria was established to handle wastewater from shrimp culture. The changes in nutrients in aquaculture wastewater were studied by chemical analysis, and the microbial community structure was analyzed using molecular biology technology and high-throughput sequencing technology. The removal efficacy of nutrients in aquaculture wastewater and the composition of microorganisms in the wastewater were examined, and the primary causes for the alteration of the microbial community were analyzed. The results demonstrated that when the macroalgae in the system were Caulerpa lentillifera (CL), the removal efficiencies of TN, PO43--P, and COD from shrimp culture were 59.04%, 34.26%, and 68.61% respectively. When the macroalgae was Caulerpa sertularoides f. Longipes (CSF), the removal efficiencies of TN, PO43--P, and COD generated by experimental shrimp culture were 51.50%, 33.69%, and 50.88% respectively. The biomass (wet weight) of both macroalgae species also increased, facilitating the removal of nutrients from the wastewater. Additionally, both Proteobacteria and Bacteroidetes were the dominant bacteria in the three samples, and the addition of the composite in-situ treatment system had no impact on the dominant bacteria in the water. The results of FAPROTAX analysis indicated that compared with the untreated samples, the abundances of methyl-functional bacteria and amino acid-functional bacteria in the samples increased due to organic matter such as COD produced during shrimp culture and the addition of feed, suggesting that shrimp culture can influence the abundances of functional bacteria in the water. In conclusion, the combined in situ treatment system can effectively eliminate nutrients from aquaculture wastewater, and the combined effect of macroalgae and immobilized degrading bacteria plays a vital role in this process.

UV aging may enhance adsorption capacity of Poly (butylene adipate-co-terephthalate) (PBAT) to heavy metals and toxicity to zebrafish.

Compared with the fossil-based plastics, biodegradable plastics are more easily decomposed into small-sized particles (e.g., microplastics). However, the role of aged biodegradable plastics in being vector of co-existed pollutants and potential toxicological effects remain to be elucidated. The present study selected micro-sized biodegradable polymer Poly (butylene adipate-co-terephthalate) (PBAT) as the object, aiming to explore its aging process, environmental behavior with heavy metals (Cu and Pb), and the toxic effects on zebrafish. The results showed that distinct changes such as cracks and severe deformation can be observed on the surface of PBAT after 60 days of UV aging, and the functional groups changed consequently. The maximum adsorption capacity of aged PBAT for Cu and Pb reached 0.967 and 0.939 mg·g-1, which increased by 1.32 and 1.46 times, respectively. The results of 7-day acute toxicology experiments suggested that the adsorption behavior of aged PBAT may alleviate the toxic effects of heavy metals Cu and Pb on zebrafish in short-term exposure, however it could simultaneously cause a serious imbalance of intestinal microorganisms in zebrafish. As demonstrated, the coexistence of aged PBAT and heavy metals (Cu, Pb) can seriously reduce the intestinal microbial diversity and richness of zebrafish, which may induce more serious toxicity and disease in long-term exposure to pollutants. This study could provide fundamental data for better understanding on the adsorption behavior and ecological risk of aged biodegradable plastics with coexisted pollutants.

Feasibility of achieving advanced nitrogen removal via endogenous denitratation/anammox.

For achieving advanced nitrogen removal, a simultaneous endogenous denitratation/anammox (EDA) process was developed that could be undertaken in a sequencing batch reactor. The results indicated that, when the influent COD/TN ratio was 3.16, the advanced nitrogen removal was achieved with the effluent TN of 1.87 mg/L. Nitrogen removal by anammox accounted for 76% of TN removed in the EDA process. Microbial community analysis illuminated that anammox bacteria and denitrifying glycogen accumulating organisms (DGAOs) of 0.91% and 5.05% were detected, respectively. DGAOs could provide nitrite for anammox by using the intracellular carbon source to achieve advanced nitrogen removal. Additionally, based on the EDA process, a promising technique for achieving advanced nitrogen removal was proposed to reduce the consumptions of both the oxygen and the carbon sources.

[Mechanism of heavy-metal tolerance in Pseudomonas aeruginosa ZGKD2].

The cadmium-resistant bacterium Pseudomonas aeruginosa strain ZGKD2 exhibiting tolerance to various heavy-metals was isolated from gangue pile of coal area in our laboratory. This bacterium could serve as an effective metal sequestering and growth-promoting bioinoculant for plants grown in metal-contaminated soil. However, the mechanism of heavy-metal tolerance is still unclear. When the beef extract-peptone medium was supplemented with 200-3 000 micromol x L(-1) Cd2+, Cu2+, Zn2+, Ni2+, Pb2+ or Mn2+, the maximum biomass of strain ZGKD2 decreased with the increase of heavy-metal concentrations, while different concentrations of heavy-metals had no significant effect on its alkaline production. Stationary-phase cells of strain ZGKD2 were exposed to 0, 200, 600 and 1 000 micromol x L(-1) of Cd2+ , Cu2+, Zn2+ and Ni2+ or 0, 1 000, 2 000 and 3 000 micromol x L(-1) of Pb2+ and Mn2+ for 2 h, respectively. The activity of SOD and CAT increased in a heavy-metal-concentration-dependent manner, especially in the Cd2+ and Cu2+ treatments. The siderophore production of strain ZGKD2 in modified sugar-aspartic acid medium was enhanced by 200- 1 000 micromol x L(-1) of various heavy-metals. Cd2+ and Zn2+ strongly induced the siderophore production of strain ZGKD2, Ni2+ and Mn2+ had little effect, whereas Cu2+ led to significant inhibition. The siderophore production of strain ZGKD2 was positively related with its metal tolerance. These results indicated that alkaline production, siderophore production, and the increase of antioxidant enzyme activities in strain ZGKD2 might be the main mechanisms of heavy-metal tolerance.