Redução de micropoluentes por sistema de tanque séptico e wetland construído vertical com recirculação

Abstract

Constructed wetlands are well-established systems known worldwide for the treatment of domestic effluents. In Brazil they are still little used, and in-depth studies are needed on the removal of carbonaceous and nitrogenous organic matter, as well as the so-called emerging contaminants present in the sewage system. Therefore, it is necessary to seek the removal of drugs and endocrine disrupters from wastewater, in order to ensure that they are not released into the environment, which may cause adverse effects to aquatic organisms and reach human water supply. These chemical compounds can be found in surface water, groundwater and even in water for consumption in water treatment plants, due to their high consumption and because the existing treatment systems do not allow complete removal. The objective of this research was to evaluate the presence of drugs and endocrine disrupters and to study the reduction of the pollutants found in an experimental system of treatment of domestic effluents near the University Student House on the campus of the Federal University of Santa Maria (UFSM) septic (TS) followed by vertical flow wetland (WCFV). The reduction of emergent pollutants in four operational phases, using different rates of hydraulic application and different plants (Heliconia psittacorum and Canna ssp.), called phases I, II, III and IV, were evaluated. The flow measurement was performed at four points using ultrasonic and electromagnetic meters. Samples of crude sewage, treated sewage in the TS and WCFV sewage were collected for the physical-chemical and microbiological analyzes of the parameters BOD, COD, solids series, ammoniacal nitrogen, nitrite, nitrate and temperature. A total of 38 samples were collected for the determination of micropollutants using UHPLC/MS-MS, including: 17α-ethinylestradiol, acetylsalicylic acid, bisphenol A, caffeine diclofenac, estriol, estrone, ibuprofen, paracetamol and progesterone between January 2016 and July 2017. It was possible to detect the pollutants in 100% of samples: caffeine, ibuprofen and paracetamol. The efficiency of the reduction of emergent pollutants was relative according to the operation and the seasonality. The highest reductions of the classical parameters and of the emergent pollutants occurred in the operational phase IV, using the recirculation strategy of 50% of the effluents and the Canna ssp plant. Despite the greater removals obtained in phase IV, no significant statistical difference was observed in comparison with phase I. However, phase IV stands out due to the good development of Canna spp. in comparison to Heliconia psittacorum, among other important points, such as the higher occurrence of nitrification using 50% of recirculation, as determined in previous research in this same experiment. The mean reduction of caffeine and paracetamol in Phase IV was 99.2 and 86.3%, respectively. Due to the mode of operation of WCFV, with low TDH, there was no significant relationship between caffeine, ibuprofen and paracetamol reductions with WCFV sample temperatures. The experimental wastewater treatment system composed of septic tank and vertical flow Constructed wetland showed high efficiencies in the reduction of microcontaminants, with emphasis on the application of 50% effluent recirculation to TS. The mean reductions obtained were 86.3%, 83.3% and 91.6% for caffeine, ibuprofen and paracetamol, respectively. The reduction of caffeine and paracetamol by chlorination was -36.0 and 75.4%.