NUTRIENT REMOVAL RATE FROM THE WASTEWATER IN THE SAN JOSÉ DEL CABO WETLAND, BAJA CALIFORNIA, MÉXICO

Wetlands have a great diversity of animals and plants and one of their capability is that they retain nutrients and “clean” wastewater. The San José del Cabo wetland (México) is a riparian system and its pollution is a key issue in Mexico, due to the variety of bird species and because some are in risk. This wetland receives clean water from the aquifer San Jose del cabo, and wastewater discharges of the San Jose del Cabo town, which is located beside it, which diminishes the quality of the water (Mendez Suriano, 2017), nevertheless, stop the saline intrusion (CONAGUA, 1998).

It is important to quantify how much nitrogen the wetland can manage to keep the natural balance in the ecosystem. This work will review how much nutrient (nitrogen & phosphorus) percentage can be retained by the San José del Cabo wetland, from 2013 -2018.

San José del Cabo wetland is located in the San José del Cabo basin which is considered to be a half graben basin produced by the San José del Cabo fault (Figure 7). Sedimentary deposits reach approximately 1.6 km thickness in the center of the basin overlaying Cretaceous crystalline basement (granite). The information provided by CONAGUA, was mapped and the inlet and outlet points were defined to start the calculations. The assumptions in the method are a constant flux throughout the year and that the water flows through a homogeneous material. Average concentrations were done from 2013 to 2018 and spatial distribution to calculate percentage removal, loading rate and Ratio N:P.

The percentage removal efficiency of the nitrogen in ammonia is 77%, the total phosphorus percentage removal found was 45%. The San Jose del Cabo wetland can take 53 kg/d of ammonia and 179 kg/d of Total Nitrogen, and retain 41 kg/d of ammonia and 103 kg/d of Total Nitrogen. For phosphates, the wetland can receive 20 kg/d approximately and 28. kg/d of total phosphorus.

For the hydraulic retention time was calculated of 48 days and the estimated hydraulic loading rate was 0.023 m³/m²*d.

The Ratio N:P was calculated between the division of Nitrates mg N/L for the inlet was 3.4:1 and for the outlet was 2.1:1.

Wetland contamination and eutrophication are directly linked to an imbalance of the relationship between nitrogen and phosphorus. This study sets the antecedent and support for stricter legislation in the country to counter such contamination.