THE USE OF CONSTRUCTED WETLANDS FOR THE TREATMENT OF AQUACULTURE WASTEWATER IN THE MEXICAN HIGHLANDS

Constructed wetlands (CW) have been widely used in the treatment of aquaculture wastewater. However, the study of constructed wetlands in cold climates has been limited. Four artificial wetlands with four different combinations of vegetation were built to treat wastewater from a 3000 juvenile rainbow trout (Oncorhynchus mykiss) recirculating aquaculture system. The CWs were monitored for 6 months to assess their ability to remove various aquatic pollutants under cold climatic conditions. The highest performance in the removal of nitrogen species (TAN 30%, NO₂-N, 22% and NO₃-N: 56%) was achieved by the wetland with a combination of two plant species (Echinochloa crus-galli and Hydrocotyle ranunculoides). The same situation happened in the removal of Total Phosphates (23%), Total Suspended Solids (60%) and Chemical Oxygen Demand (50%). However when these two plants operated individually in different wetlands their performance was consistently lower compared to the wetland with the combination of plants. In contrast the wetland with zero vegetation had the lowest development of all the CW, and in some cases the outlet water had worst quality than in the inlet.