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To investigate the treatment effect of a bacteria-algal symbiosis system on farmland drainage with low carbon,and high nitrogen soft fiber bio-rope (polyolefin polyamide composite), Vallisneria natans (Lour.)Hara and Cyperus rotundus L. were used to construct a symbiotic carrier system for the bacteria and algae. The results showed that when the fiber rope was used as the carrier and the filling density was in the range of 10%~30%, the concentration of algae in the system increased with the increase in density, and the removal effect of total nitrogen (TN), total phosphorus (TP), and ammonia nitrogen (NH+ 4-N)was significantly improved, with the 30% fiber rope system exhibiting the best effect. When the hydraulic retention time (HRT) was 2 d, the average temperature was 25 ℃, the average concentrations of influent chemical oxygen demand (COD), TN, TP, and NH + 4 - N were 73.69, 15.45, 0.73 mg · L-1 and 6.32 mg · L-1, respectively. The average effluent mass concentrations were 19.17, 1.76, 0.14 mg·L-1, and 1.48 mg·L-1, respectively, which reached the class Ⅴ standard stipulated by the surface water environmental quality standard. The C. rotundus L. system showed a good treatment effect on COD, with a removal rate of up to 77%. The removal effect of these pollutants by the V. natans (Lour.) Hara system was mediocre. In addition, a significant negative correlation was found between the chlorophyll concentration and NH+ 4-N content in the effluent water. The introduction of carriers, such as nitrifying bacteria, would proliferate bacteria with long generation cycles in the system. The results indicated that when 30% fiber rope was used as the carrier, the effect of the bacteria-algal symbiosis system on farmland drainage was optimally improved. [ABSTRACT FROM AUTHOR]

Under the background of the construction and application of the national virtual simulation experimental teaching center, the paper elaborates the construction strategy of the virtual simulation laboratory for iron and steel production, describes the construction achievements of the hardware and software environments, discusses the building of the virtual simulation practice teaching system of “one flow, four levels, six factors and eight combinations” and the application of the system in practice teaching. Practices show that the construction strategy and the system building have important practical value and guiding significance for the construction, application and sustainable development of the virtual simulation practice teaching laboratory, and provide reference and suggestion for the reform of the engineering practice teaching mode based on virtual simulation. [ABSTRACT FROM AUTHOR]