Naivy Dennise Rodal Morales
University of Califorina, Merced
Co-Authors: M. W. Beutel
Constructed wetlands use vegetation, sediment and biological processes to reduce pollutants in water which make them an effective treatment system. As an environmentally sustainability technique to improve water quality, the City of Newman, located in California’s Central Valley, aims to construct a 12-hectare surface-flow treatment wetland to treat irrigation runoff from surrounding agricultural fields. Our project involved modeling seasonal patterns of nutrient removal (total phosphorous (TP) and nitrate), and changes in salinity, in the proposed treatment wetland. Salinity is a main project concern as the City intends to reuse outflow from the wetland to dilute high-salinity water used to irrigate fodder crops. Hydrologic and water quality data in a “normal” water year were used to make water and mass balance calculations based on the P-k-C* model for the outlet concentration predictions of the wetland. The presentation discusses model development and the results of monthly outlet nutrient and salinity concentrations. In summary, nitrate concentration decreased on average 60%, but higher reduction was observed during the summer months of almost 90%. TP concentration decreased 20-35% and had two peaks in removal, one in April-May and another in September-October. The seasonality of the model results highlights the fact that nitrate is microbially mediated and temperature dependent (higher values in summer), while TP is agronomically mediated (peaks in spring and fall). Finally, salinity increased due to evapotranspiration by around 30% and mostly during warm summer months. The presentation concludes with a discussion of factors that play an important role in the effective operation of the wetland (e.g., residence time, number of cells, layout of cells) and a recommended wetland layout.