Characterization of Oxidation-Reduction Potential Variations in Biological Wastewater Treatment Processes: A Study from Mechanism to Application

Constructed wetland systems employing submerged macrophytes are increasingly utilized for treating municipal and industrial wastewater, as well as odoriferous and eutrophic water bodies. However, the pollutant removal efficiency of these systems needs further enhancement. In this study, we examined the impact of the gas-to-water ratio on the treatment efficiency of the constructed wetland of Vallisneria. We also examined the extracellular polymeric substances (EPSs) of the floating biofilm and the structure of the microbial community in this system. Our findings showed that the gas-to-water ratio significantly affects the total nitrogen (TN) removal rate within the Vallisneria wetlands, with an optimum removal at a gas-to-water ratio of 15:1, while the removal efficiencies for chemical oxygen demand (COD), NH4+-N, and total phosphorus (TP) remain relatively unaffected. Increased gas-to-water ratios corresponded to a notable decrease in biofilm EPSs. High-throughput sequencing analysis demonstrated a shift in biofilm-denitrifying bacteria from anoxic heterotrophic to aerobic denitrifiers, alongside a significant rise in the abundance of denitrifying bacteria, whereas excessively high gas-to-water ratios inhibited the growth of these bacteria. A gas-to-water ratio of 15:1 constituted the optimal condition for ecological restoration of the water body within the Vallisneria wetland systems. These results could contribute to the optimization of submerged-macrophyte constructed wetland system design and the enhancement of treatment efficiency.

Section: Microbial Community Diversitymentioning

confidence: 99%

Impact of Gas-to-Water Ratio on Treatment Efficiency of Submerged-Macrophyte Constructed Wetland Systems

Mao,

Lu,

Huang

et al. 2024

“…This meant that there was a more oxidizing environment. ORP measurements are influenced by the activity of oxidizing (oxygen) and reducing (oxygen, hydrogen) species in the water [31]. The ORP of each oxidant system increased with increasing oxidant concentration to a maximum.…”

Section: Ros Formation From Ufbs Generatormentioning

confidence: 99%

Hydroxyl Radical-Based Advanced Oxidation Processes of Red Reactive Dyes by Ultrafine Bubbles Method

Sofia,

Hanam,

Sunardi

et al. 2024

The breakdown of dyes, which are environmentally hazardous substances and notoriously difficult to degrade, presents the main treatment challenge for wastewater from textile industries. Most advanced oxidation processes (AOPs) for dye degradation usually use costly decolorizing agents, whose residue from Wastewater Treatment Plants may be hazardous to the environment. The present study aimed to apply ultrafine bubbles (UFBs) for water AOPs to degrade textile dyes. Our most recent innovation, ultrafine bubbles, enables the production of reactive oxygen species recently introduced as oxidants in AOPs. First, the disc diffuser was optimized by introducing various flow rates of 1–5 L Per Minute (LPM) to generate UFBs with unique characteristics observed from Zeta Potential, pH, Dissolved Oxygen (DO), and Oxidation–Reduction Potential (ORP). The air UFBs using a disc diffuser with 3 LPM were selected to degrade the Navacron Ruby S-3B dye solution (1000 Pt-Co). The treatment was optimized on the coagulant dosage (0.25, 0.5, 0.75, and 1 ppm) and bubbling times (0–120 min). As a result, the UFBs were successful in degrading the Navacron Ruby S-3B dye solution, resulting in a 45% reduction in Pt-Co color scale with a bubbling time of only 120 min and minimal coagulant dosage (0.5 ppm) compared to the Navacron Ruby S-3B dye solution treatment commonly using a coagulant dosage of 1.5 ppm without UFBs. Based on FTIR, XRF, and PL analysis, we propose the AOP mechanism of hydroxyl radicals for the Navacron Ruby S-3B dye solution. It is emphasized that UFB water AOPs (UFBs–WAOPs) represent a promising alternative technology for treating textile wastewater without chemicals or decolorizing agents. Thus, the UFBs-WAOPs are economical and environmentally benign textile wastewater treatment methods.

“…This oxygen deficit and the presence of the reducing agents such as ammonium and sulfate ions in the minimum salt media culture could, therefore, be attributed to the steep gradient in ORP reduction in the first 24 h, which led to the reduced biodegradation rates afterward [42]. Previous studies have shown that ORP measurement is more accurate and sensitive than the direct measurement of dissolved oxygen (DO) to monitor the oxidizing and/or reducing the strength of wastewater effluents and, thus, can be used to determine the onset of the aerobic to anaerobic shifts and vice versa in biological processes [26]. The ORP slowly increased towards the positive side after 24 h, and this could be explained by the fact that the log phase, which is associated with high oxygen consumption, had ended, and the remaining oxygen-demanding process was the catabolic breakdown of the short chain hydrocarbons, which required relatively lesser oxygen consumption.…”

Section: Oxidation-reduction Potential (Orp) Variationsmentioning

confidence: 99%

“…These chemical parameters change as organic pollutants are biodegraded into intermediate and dead-end metabolites and possibly mineralized into carbon and water. Wang et al [26] (2022) established a direct correlation between ORP and other process parameters such as COD, DO, and nitrate content in an anoxic denitrification process. The results obtained indicated that under low nitrate concentrations of about 3 mg/L, there was a direct relationship between ORP and COD, and this relationship could be used in process surveillance and control of the carbon dosage in anoxic denitrification processes.…”

Section: Introductionmentioning

confidence: 99%

Insights into the Physicochemical Parameters, Microbial Community Structure, and Functional Variations in Biodegradation of N-Alkane Derivatives from Fischer–Tropsch Wastewater

Koloti,

Nkuna,

Matambo

2023

This study provides a theoretical baseline on the application of chemical and microbiological indicators as rapid system performance monitoring tools that will allow for timely corrective measures to maintain and improve the bioremediation performance of the Fischer–Tropsch wastewater (FTWW) treatment plants. Microorganisms isolated from the sediments and water samples collected from site 1 of Blesbokspruit wetland exhibited the highest biodegradation efficiency of up to 98.04% and 92.85%, respectively, in 96 h reaction time using batch culture media spiked with 300 ppm short chain n-alkane derivatives. The highest COD reduction rate was observed during the first 24 h of biodegradation, and it steadily declined thereafter. The decline in pH from 7.0 to 6.3 was observed in the 96 h reaction time and was attributed to the production of acidic secondary metabolites and the entrapment of the produced CO2 within the batch media. The ORP also declined from the aerobic zone to the anaerobic zone within 24 h (day 1) reaction time. The EC and TDS results were also indicative of the rate of consumption of essential nutrients during the biodegradation process, which could be related to biochemical reactions involved in biodegradation of n-alkane derivatives. Proteobacteria and Firmicutes were the prevalent phyla during the biodegradation of the n-alkane derivatives. Enterococcus and Escherichia genera were more dominant on most days of biodegradation, therefore, indicating that these genera were actively involved in the biodegradation process of the n-alkane derivatives. These genera displayed a positive correlation with EC, ORP, pH and TDS in the four days of biodegradation for batch cultures inoculated with microorganisms from the water and sediments samples collected from the Blesbokspruit wetland. The results obtained demonstrated that physicochemical and microbiological indices can be used to infer the biodegradation rates, patterns and system operations in FTWW bioremediation.