Water Purification Effect of Ecological Floating Bed Combination Based on the Numerical Simulation

The Wuqing urban section of the North Canal Basin, Tianjin, is a significant gathering place for multisource pollution, showing the characteristics of a stagnant water body supplied by unconventional water sources. With the development of the economy and society, the water quality of the Wuqing urban section of the North Canal Basin, Tianjin, has been seriously polluted due to the discharge of sewage outlets and the influx of nonpoint source pollution from farmland. In this study, based on the results of special water experiments, a two-dimensional hydrodynamic water quality model was constructed. The concentrations of ammonia nitrogen (NH3-N), total phosphorus (TP), and chemical oxygen demand (COD) in the study area were simulated, and the model parameters were calibrated and verified with the measured values. Based on the model verification, the water quality improvement scheme of the ecological floating bed with different plant ratios was set up to simulate the water quality. The research results showed that the average concentrations of NH3-N, TP, and COD decreased by 10.4%, 15.7%, and of d 26.3%, respectively, after the ecological floating bed was arranged. During model parameter calibration and validation, the RMSE ranges of NH3-N, TP, and COD were 0.09-0.22 mg/L, 0.00-0.02 mg/L, and 0.37-2.42 mg/L, respectively. Other statistical indicators are also within a reasonable range, and the model accuracy and reliability are high. The simulation results of different scenarios showed that the optimal ratio of ecological floating bed plants was 700 m(2) of Scirpus validus Vahl and 700 m(2) of Canna in zone 1 of the floating bed combination, 430 m(2) of Scirpus validus Vahl, and 170 m(2) of Iris in zone 2 of the floating bed combination, and 200 m(2) of Iris and 200 m(2) of Lythrum salicaria in zone 3 of the floating bed combination. This study can provide a theoretical basis for the sustainable development of water purification in the North Canal. It can also provide a model approach for the implementation of river water purification schemes, exemplified by the North Canal.

Automated summary

Based on special water experiments and a hydrodynamic water quality model, a water quality improvement scheme using an ecological floating bed was developed to simulate and improve the water quality of the Wuqing urban section of the North Canal Basin in Tianjin. The results showed a significant decrease in ammonia nitrogen, total phosphorus, and chemical oxygen demand concentrations after the implementation of the ecological floating bed.