Remoção de nutrientes em wetland construído do tipo francês

Abstract

Filters with macrophytes (built wetlands) are decentralized sewage treatment systems, which have the advantages of low operating costs, low power consumption, operational simplicity and significant efficiency. In this context, this research aimed to evaluate the efficiency of a French wetland system with a saturated filtering mass in the removal of total nitrogen from sanitary sewage from the university restaurant of the Universidade Tecnológica Federal do Paraná. The experimental unit is located in the dependencies of UTFPR - Campus Londrina, monitoring of the system occurred within 8 weeks. The saturation height was 25 cm, the system was fed intermittently, with 4 pulses per day. Samples of raw sewage (system inlet), stage I and stage II (system exit) were collected, the samples were submitted to physical-chemical analysis, being they pH, alkalinity, nitrogen series and phosphate. At the entrance of the system, the alkalinity (mgCaCO3 L-1) and average pH were 37.42 and 5.13, stage I presented 73.29 and 6.34 and the system output (stage II) 48.89 and 6.65. In relation to the nitrogen series, the concentration of ammoniacal nitrogen underwent a reduction throughout the system, proving the existence of the nitrification process, being the concentration at the entrance of the system of 16.1 mg L−1 and at the exit of 2,8 mg L−1. The presence of nitrite in the samples was not observed and the nitrate concentrations of the system output were higher than those found at the entrance of the system. As results, mean NTK removals ranging from 58.7% to 92% were obtained. In stage II, maximum nitrogen removal efficiency of 90.2% was observed, and it was concluded that the saturation height of the filtering mass was essential for the occurrence of denitrification. The rates of phosphate removal were high, and the presence of this parameter was not detected in any of the samples referring to the system output. The results showed that the proposed treatment system is an excellent alternative for treatment of effluents, in addition it has been shown to be effective in the removal of total nitrogen.