Construction of symbiotic system of filamentous algae and submerged plants and its application in wastewater purification

Application of symbiotic system of filamentous algae and submerged plants in constructed wetlands is expected to further improve the sewage treatment performance. Unfortunately, due to the complexity of their relationship, researches on the combined purification of water quality by filamentous algae and submerged plants are still in the initial stage, and relative results are quite different. Herein, we chose Spirogyra as the model filamentous algae to construct a symbiotic system of Spirogyra - Ceratophyllum demersum on the basis of screening suitable submerged plants. According to the monitoring of multiple physiological indicators of filamentous algae and submerged plants in the symbiotic system, under the conditions of biomass of filamentous algae 3.5–4 g/L, NH3-N concentration 6.22 mg/L, TP concentration 0.66 mg/L, neutral or weakly alkaline pH value, the inhibition effect between filamentous algae and submerged plants was minimal. Based on the optimization, the removal rate of NH3-N and TP could reach 91.53% and 86.52%, which were higher than systems consisted of several submerged plants or submerged plant and other species. In addition, under the dynamic water condition which was closer to the real environment, the system operated in proper flow rate could still efficiently treat the pollutants. Moreover, the improvement effect on DO of sewage in system was better compared with that of the static water system. The research results provided a new idea for further improving the treatment efficiency of constructed wetland and theoretical basis for the combined purification by submerged plants and algae in eutrophic water.