Garrafas pet amassadas como meio suporte em sistemas alagados construídos de escoamento subsuperficial horizontal não plantados: forma de disposição no leito,desempenho e potencial de liberação de microplásticos no esgoto sanitário

Abstract

Different support media have been evaluated in Horizontal Subsurface Flow Constructed Wetland Systems(HSSF-CWs), aiming to provide good performance in sewage treatment, increasing the use ful life of the bed and having low costs. Previous research has demonstrated the potential of using PET bottles as a support medium, making it important to assess their disposal in the bed and the risk of releasing microplastics into the treated wasterwater, which is a current concern. With this, with the accomplishment of the present work, the objective was to evaluate non-planted HSSF-CWs and filled with closed and opened crushed PET bottles, regarding the performance, presence of interstitial solids (inference about biofilm formation), clogging and release of microplastics, compared to a bed filled with gravel. To achieve the purpose, physical, chemical and biochemical analyzes were carried out on the influent and effluent to the units, evaluation of the presence of microplastics in sanitary sewage (raw and treated), and release into water and sewage, as in contact with PET bottles. For this, three CWSs-HSF were made on an experimental scale with Hidraylic Retention Time (HRT) of 1.5 d, refered to as HSSF-CW GR, OP and CP, respectively, filled with gravel, opened PET and closed PET. Weekly analyzes of pH, electrical conductivity (EC), BOD, total Kjeldahl nitrogen (TKN), total phosphorus (TP) and total solids (TS). The removal efficiencies for HSSF-CW GR, OP and CP achieved respectively, reached 67, 67, 64% BOD, 66, 38 and 21% NTK, 31, -34 and -44% PT and 14, 19 and 9% for ST. Based on the results obtained, it was observed that there was no significant difference between the treatments, suggesting that it is possible to use both open and closed PET bottles in SACs-EHSS, replacing gravel. In relation to the microplastic, it was verified that there was no trend of greater biofilm formation in the bed filled with crushed and opened PET bottles, nor of greater accumulation of solids from the wear of the support medium in the CWS containing gravel (despite the smaller final porosity provided). The detected presence of microplastics is very low, and plastic materials can be used in the treatment of wastewater without risk of contamination of the treated efluente, at least a short monitoring time.