In Situ Exploration of the Sulfidogenic Process at the Water-Sediment Interface in Sewers: Mechanism and Implications

Abstract

Corrosion and odor induced by sulfidogenic processes is a worldwide issue in environmental engineering. This study focuses on a neglected, but critical process, sulfidogenic conversion at the water-sediment interface, to optimize the prediction and control of sulfide in sewers. A novel in situ, high-resolution measurement method based on the diffusive gradients in thin films technique was established for the first time for use in sewer systems. The results showed that, at a critical shear velocity (i.e., ∼0.07 m/s), the key factor dominating sulfidogenic activity in the surface layer of sediment (i.e., ∼1 cm) switched to substrate diffusion resistance at the water-sediment surface. An increase in shear velocity from 0 to ∼0.07 m/s significantly activated the sulfidogenic process in this layer. The spatial variation in the functional microbial community further confirmed the sediment profile of sulfidogenic activity. A sewer model incorporating the substrate diffusion process at the water-sediment interface was developed and verified, which revealed the characteristic response of the diffusive boundary layer thickness at the water-sediment interface to shear velocity. The maximum sulfide production rates (k H2S) under varying water quality and shear velocity conditions were successfully simulated, improving the model’s predictive accuracy in gravity sewers. This study has certain engineering significance for optimizing sulfide prediction and control in sewers.

Stability and WBE biomarkers possibility of 17 antiviral drugs in sewage and gravity sewers

“…The bulk density of sediment was 1.45 g/cm 3 . The total solids (TS) and volatile solids (VS) contents were 69.3% and 3.1% (wet weight), respectively, which were comparable to previous studies ( Liu et al, 2015 ; Zuo et al, 2021 ). The wastewater pH in all reactors ranged at 7.2-7.7 during the batch test.…”

“…Additionally, to ensure representation and consistency of sediments across reactors, we analyzed the microbial community of surface sediments in reactor 1 and 2 with two biological replicates. The dominant phyla in reactor sediments were Proteobacteria, Halobacterota, Firmicutes, Chloroflexi and Bacteroidota (Figure S2), which were similar to sewer sediments in previous studies ( Shi et al, 2018 ; Zuo et al, 2021 ; Zuo et al, 2020b ). Combined with the genus-level structure (Figure S3), it further illustrated the similarity of sediments between two reactors and the presence of methanogens and sulfate-reducing bacteria ( Mohanakrishnan et al, 2009 ).…”

“…remdesivir, abacavir), primarily depending on whether their removal was controlled by mass transfer. In addition, another study reported that an increased shear velocity significantly changed the abundance of specific microbial phyla in different layers of sediments, which might also affect some biodegradation processes ( Zuo et al, 2021 ).…”

“…According to previous studies ( Li et al, 2020 ; Li et al, 2018 ), we employed four gravity sewer reactors ( Figure 1 ) to investigate the stability of antiviral drugs in gravity sewers. The laboratory reactors had an effective volume of 1.8L (14cm in diameter and 12cm in depth) ( Zuo et al, 2021 ). Sediment samples with an initial depth of approximately 5cm were added into reactor 1 and reactor 2.…”

“…Reactor 1, 2 and 3 were operated at a stirring speed of 24rpm while reactor 4 was operated at 54rpm, resulting in shear velocities of 0.07 and 0.17 m/s, respectively. The detailed conversion equations were obtained from previous studies and were listed in the SI, Section 1 ( Liu et al, 2016 ; Zuo et al, 2021 ). All four reactors have been in stable operation for over 300 days.…”