Effect of different aeration rates on total nitrogen and cod removal in intermittently aerated horizontal subsurface flow constructed wetlands

Abstract

The aim of the present research was to evaluate the effect of different aeration rates on chemical oxygen demand (COD) and total nitrogen (TN) removal in five constructed wetlands with horizontal subsurface flow, intermittently aerated for 1 hour three times a day. Each constructed wetland will be evaluated using different aeration rates: 0, 2, 5, 10 and 20 L min^-1. Wetlands will receive a daily flow of 8.7 L of synthetic domestic wastewater, resulting in 3 days of hydraulic retention time. The following parameters will be evaluated: COD, dissolved oxygen, pH, TN, nitrate, nitrite, electrical conductivity, temperature and flow rate. After an analysis of the results and statistic conclusions, it was possible to determine that aeration plays a main role in the improvement of nitrogen and COD removal in the systems. However, the different aeration rates in this case were not decisive for this purpose, but statistically enough for good and similar performance. Regarding the analysis of the efficiency of the parameters, the COD removal had a 3% higher performance in the wetlands with intermittent aeration when compared to the non-aerated system, in a mean percentage of 97.5% to 98.24% efficiency. The NT also had a 30% higher efficiency in the aerated wetlands, reaching an average of 80% to 83.6% of removal.