Comparative Study on the Synergistic Effect of Suaeda salsa and Indigenous Microorganisms on Nitrogen and Phosphorus in Mariculture Wastewater

In order to explore the remediation effect of halophyte (Suaeda salsa) and indigenous microbial on the removal of nitrogen and phosphorus from mariculture wastewater at different pollution levels, two comparative experiments with and without microbial inhibitors were designed. The concentration changes of nitrate nitrogen, nitrite nitrogen, ammonia nitrogen and active phosphate, and the number of nitrifying and denitrifying bacteria before and after the repair of Suaeda salsa were determined respectively. The results showed that under the synergistic effect of halophyte and microbial remediation, the removal rates of ammonia nitrogen at high, medium and low levels were 65.11%, 51.06% and 77.82%, respectively. The removal rates of nitrate nitrogen were 91.47%, 81.98%, 52.42%, and the removal rates of active phosphate were 68.39%, 40.10%, and 28.96%, respectively. Under the action of adding microbial inhibitors to phytoremediation, which means with only the function of halophyte the removal rates of ammonia nitrogen were 94.56%, 48.22%, and 77.97%, the removal rates of nitrate nitrogen were 44.98%, 59.92%, and 47.71%, and the removeal rates of active phosphate were 33.12%, 45.41% and 54.21%, respectively, and the nitrite bacteria decreased by 1-2 orders of magnitude, while the nitrifying bacteria and denitrifying bacteria increased by 1-2 orders of magnitude. It is thus proved that the absorption by halophytes is the main way to remove ammonia nitrogen and active phosphate from saline mariculture wastewater, and the removal of nitrate nitrogen mainly depends on the combined action of denitrifying bacteria and halophyte absorption. With the increase of pollutant concentration, the presence of microorganisms can significantly promote the removal of pollutants.