Helping WWTP managers to address the volatile methylsiloxanes issue-Behaviour and complete mass balance in a conventional plant

Francisco Sánchez-Soberón; Gabriel F Pantuzza; Madalena Fernandes; Vera Homem; Arminda Alves; Milton Fontes; Magda André; Joana Cunha; Nuno Ratola

doi:10.1016/j.envres.2023.116564

Helping WWTP managers to address the volatile methylsiloxanes issue-Behaviour and complete mass balance in a conventional plant

Environ Res. 2023 Oct 1:234:116564. doi: 10.1016/j.envres.2023.116564. Epub 2023 Jul 6.

Authors

Francisco Sánchez-Soberón¹, Gabriel F Pantuzza², Madalena Fernandes², Vera Homem³, Arminda Alves³, Milton Fontes⁴, Magda André⁵, Joana Cunha⁵, Nuno Ratola⁶

Affiliations

¹ LEPABE - Laboratory for Process Engineering, Environment, Biotechnology and Energy, Faculty of Engineering, University of Porto, Rua Dr. Roberto Frias, 4200-465, Porto, Portugal; Department of Atmospheric Pollution, National Center for Environmental Health, Instituto de Salud Carlos III, Ctra. Majadahonda - Pozuelo, Km. 2., 28220, Madrid, Spain.
² LEPABE - Laboratory for Process Engineering, Environment, Biotechnology and Energy, Faculty of Engineering, University of Porto, Rua Dr. Roberto Frias, 4200-465, Porto, Portugal.
³ LEPABE - Laboratory for Process Engineering, Environment, Biotechnology and Energy, Faculty of Engineering, University of Porto, Rua Dr. Roberto Frias, 4200-465, Porto, Portugal; ALiCE - Associate Laboratory in Chemical Engineering, Faculty of Engineering, University of Porto, Rua Dr. Roberto Frias, 4200-465, Porto, Portugal.
⁴ AdRA - Águas da Região de Aveiro, S.A., Travessa Rua da Paz 4, 3800-587 Cacia, Aveiro, Portugal.
⁵ AdCL - Águas Do Centro Litoral, S.A., ETA da Boavista, Av. Dr. Luís Albuquerque, 3030-410, Coimbra, Portugal.
⁶ LEPABE - Laboratory for Process Engineering, Environment, Biotechnology and Energy, Faculty of Engineering, University of Porto, Rua Dr. Roberto Frias, 4200-465, Porto, Portugal; ALiCE - Associate Laboratory in Chemical Engineering, Faculty of Engineering, University of Porto, Rua Dr. Roberto Frias, 4200-465, Porto, Portugal. Electronic address: nrneto@fe.up.pt.

PMID: 37422117
DOI: 10.1016/j.envres.2023.116564

Abstract

Volatile methylsiloxanes (VMSs) are a group of additives employed in different consumer products that can affect the quality of the biogas produced in wastewater treatment plants (WWTPs). The main objective of this study is to understand the fate of different VMSs along the treatment process of a WWTP located in Aveiro (Portugal). Thus, wastewater, sludge, biogas, and air were sampled in different units for two weeks. Subsequently, these samples were extracted and analyzed by different environment-friendly protocols to obtain their VMS (L3-L5, D3-D6) concentrations and profiles. Finally, considering the different matrix flows at every sampling moment, the mass distribution of VMSs within the plant was estimated. The levels of ∑VMSs were similar to those showed in the literature (0.1-50 μg/L in entry wastewater and 1-100 μg/g dw in primary sludge). However, the entry wastewater profile showed higher variability in D3 concentrations (from non detected to 49 μg/L) than found in previous studies (0.10-1.00 μg/L), likely caused by isolated releases of this compound that could be related to industrial sources. Outdoor air samples showed a prevalence of D5, while indoor air locations were characterized by a predominance of D3 and D4. Differences in sources and the presence of an indoor air filtration system may explain this divergence. Biogas was characterized by ∑VMSs concentrations (8.00 ± 0.22 mg/m³) above the limits recommended by some engine manufacturers and mainly composed of D5 (89%). Overall, 81% of the total incoming mass of VMSs is reduced along the WWTP, being the primary decanter and the secondary treatment responsible for the highest decrease (30.6% and 29.4% of the initial mass, respectively). This reduction, however, is congener dependant. The present study demonstrates the importance of extending sampling periods and matrices (i.e., sludge and air) to improve sample representativity, time-sensitivity, and the accuracy of mass balance exercises.

Keywords: Biogas; Green chemistry; Indoor air; Mass balance; Volatile methylsiloxanes; Wastewater treatment plants.

Publication types

Research Support, Non-U.S. Gov't

MeSH terms

Biofuels
Environmental Monitoring
Sewage
Siloxanes / analysis
Wastewater*
Water Purification*

Substances

Wastewater
Sewage
Biofuels
Siloxanes