Abstract:

The aim is to provide a theoretical basis for purifying aquaculture wastewater by biological methods and managing plant cultivation mode. Ammonium chloride (NH₄Cl), potassium nitrate (KNO₃), and potassium dihydrogen phosphate (KH₂PO₄) were used to provide ammonia nitrogen, nitrate nitrogen, and total phosphorus. A completely random outdoor experiment was conducted. The growth law of green Myriophyllum verticillatum under the variation of the three factors of ammonia nitrogen, nitrate nitrogen and total phosphorus was studied. The length and fresh weight of green Myriophyllum verticillatum after 30 days increased first and then decreased with the increase of ammonia nitrogen concentration. The ammonia nitrogen concentration of 25 mg/L was the most suitable concentration for the growth. When the concentration of nitrate changed from 5 mg/L to 35 mg/L, its fresh weight and length generally increased first and then decreased. The most suitable nitrate concentration for growth was 15 mg/L. When the total phosphorus concentration changed from 5 mg/L to 35 mg/L, its growth status was positively correlated with the concentration, and the concentration threshold suitable for its growth was unknown, needing to be further studied. The growth of green Myriophyllum verticillatum was significantly affected by the changes of ammonia nitrogen and total phosphorus concentration, and was less affected by the changes of nitrate nitrogen concentration compared to the first two factors. The research results can provide a theoretical basis for purifying the wastewater in the sewage, managing and maintaining the ecological water purification system of green Myriophyllum verticillatum.

Key words: green Myriophyllum verticillatum, ammonia nitrogen, nitrate nitrogen, total phosphorus, growth law