An anaerobic osmotic membrane bioreactor coupled with membrane distillation for removal of organic micropollutants and estrogenic activity from municipal sewage

• Ano de defesa: 2021
• Autor(a) principal: Arcanjo, Gemima Santos
• Tipo de documento: Tese
• Tipo de acesso: Acesso aberto
• Idioma: eng
• Instituição de defesa: Universidade Federal de Viçosa
• Palavras-chave em Português: Águas residuais - Purificação; Esgotos; Águas residuais - Microbiologia; Avaliação de riscos ambientais; Tratamento de Águas de Abastecimento e Residuárias
• Link de acesso: https://locus.ufv.br//handle/123456789/28156

The contamination of water sources by pharmaceutically active compounds (PhACs) and their effect on aquatic communities and human health have become an environmental concern worldwide. Municipal sewage is the major source of organic micropollutants in the environment. Even when there is a sewage treatment plant present, conventional biological treatment cannot remove recalcitrant compounds. Membrane bioreactors (MBRs), due to their high solids concentrations and retention times, improve biological treatment removal of nutrients and recalcitrant organic compounds. Forward osmosis (FO) and membrane distillation (MD), which present high rejection of dissolved compounds, even at concentrations of µg L -1 and ng L -1 , are an alternative for use in MBRs treating municipal sewage. Thus, this research aimed to evaluate the performance of an anaerobic osmotic membrane bioreactor coupled with membrane distillation (AnOMBR-MD) in treatment of municipal sewage containing PhACs (17α- ethinylestradiol, betamethasone, ketoprofen, fenofibrate, fluconazole, loratadine e prednisone). The AnOMBR-MD was operated with NaCl as draw solute in a hybrid submerged FO-MD module. The removal efficiencies of dissolved organic carbon (DOC) and P-PO 43- were 97.2% and 98.0%. N-NH 4+ accumulated in the bioreactor and reached the draw solution (DS) and distillate. Changes in the microbial community were observed due to salinity build-up and the presence of PhACs, while the system removed more than 96.4% of the compounds evaluated. Estrogenic activity was not detected in distillate samples and the environmental and human health risks sharply declined. A second study was conducted to select the best DS salt in the integrated FO-MD hybrid module. The technique to order preference by similarity to the ideal solution was used in in multicriteria decision making, that considered results of water and salt flux, energy consumption, costs, and FO and global rejection of micropollutants for each draw solute tested (NaCl, MgCl 2 , sodium acetate (NaOAc), magnesium acetate (MgOAc 2 ), and EDTA-Na 2 ). MgCl 2 was selected as the best salt for the DS in the FO-MD system and could be used to mitigate salinity build-up in the mixed liquor, followed in order of rank by NaCl, NaOAc, EDTA-Na 2 and MgOAc 2 . In the third study, MgCl 2 was used as draw solute of the AnOMBR-MD in treatment of synthetic municipal sewage containing PhACs and estrogenic activity. Due to organic and inorganic fouling, permeate fluxes declined 82 and 67%, for FO and MD, respectively. MD salt rejection was higher than 99.6% and more than 90% of dissolved organic carbon was removed. P-PO 43- rejection by the FO-MD module was greater than 99.98%, which led to accumulation of this nutrient in the mixed liquor (ML). N-NH 4+ concentration in the ML also increased, and with the reverse flux of Mg 2+ , precipitation of struvite, magnesite and monetite may have occurred. Salinity build-up was lower than when NaCl was used as DS. The ML conductivity increased until day 21 and then stabilized. Biological removal of estrogenic activity was reduced with salt accumulation, but increased after salinity stabilization. AnOMBR-MD removal of estrogenic activity was higher than 99.97%, with reduction in environmental and non-carcinogenic human risks from high to low, while incremental lifetime carcinogenic risk decreased to negligible. On the other hand, risk assessment showed that a better removal of ketoprofen and loratadine is needed, since the acute environmental risk of the distillate was still high, due to the presence of these substances. The results of the present research demonstrated that permeate fluxes in FO and MD are still low and some strategies to overcome this drawback are needed, such as physical and chemical cleaning. Furthermore, the use of the YES assay combined with detection and identification of micropollutants allowed an effective assessment of overall treatment performance. Keywords: Microbial community. Concentration polarization. Reverse salt flux. YES assay. Risk assessment.