Utilization of nitrogen from surface and subsurface applied wastewater

A pilot test was conducted to determine the difference in nitrogen removal between surface and subsurface applied wastewater systems in soil columns topped with Bermuda grass (cynodon dactylon). Six columns were set up, three with water applied to the surface, and three with water applied in the subsurface through a positive-displacement pump. The concentration of nitrogen was kept uniform within the system with variable loading rates to ensure leaching occurred. The water added and the water leached were tested with HACH(R) test-n-tube kits for total nitrogen, ammonia, and nitrate-N concentrations. A statistical analysis was performed to determine if there were any significant differences in the concentrations of these constituents in the effluents between the two systems. The analysis showed that there was virtually no difference (Pr>F = 0.657) between the two systems in regards to percent of nitrogen removed from the system. The test also showed that subsurface applied systems performed marginally better that surface applied systems in total nitrogen and nitrate-N concentrations in the effluent. There were also virtually no differences (Pr>F = 0.209) in the total Kjeldahl Nitrogen concentrations in the plant tissue.