Hydrogen peroxide production in a pilot-scale microbial electrolysis cell

The final publication is available at Elsevier via https://dx.doi.org/10.1016/j.btre.2018.e00276 © 2018. This manuscript version is made available under the CC-BY-NC-ND 4.0 license https://creativecommons.org/licenses/by-nc-nd/4.0/A pilot-scale dual-chamber microbial electrolysis cell (MEC) equipped with a carbon gas-diffusion cathode was evaluated for H2O2 production using acetate medium as the electron donor. To assess the effect of cathodic pH on H2O2 yield, the MEC was tested with an anion exchange membrane (AEM) and a cation exchange membrane (CEM), respectively. The maximum current density reached 0.94–0.96 A/m2 in the MEC at applied voltage of 0.35–1.9 V, regardless of membranes. The highest H2O2 conversion efficiency was only 7.2 ± 0.09% for the CEM-MEC. This low conversion would be due to further H2O2 reduction to H2O on the cathode or H2O2 decomposition in bulk liquid. This low H2O2 conversion indicates that large-scale MECs are not ideal for production of concentrated H2O2 but could be useful for a sustainable in-situ oxidation process in wastewater treatment.Ontario Early Researcher Awar

The Development of a Low-Cost Particulate Matter 2.5 Sensor Calibration Model in Daycare Centers Using Long Short-Term Memory Algorithms

Particulate matter (PM) pollution is a crucial environmental issue. Considering its adverse health impacts, especially on children’s immune systems, Korean regulations require annual PM2.5 measurements in daycare centers. Therefore, we developed a low-cost PM2.5 sensor calibration model for measuring the indoor PM concentrations in daycare centers using long short-term memory (LSTM) algorithms. Moreover, we trained the model to predict the PM2.5 based on temperature and humidity, and optimized its hyperparameters. The model achieved a high accuracy and outperformed traditional calibration methods. The optimal lookback period was 76, which led to a high calibration performance with root mean and mean squared errors, a coefficient of determination, and mean absolute errors of 3.57 and 12.745, 0.962, and 2.7, respectively. The LSTM model demonstrated a better calibration performance than those of the linear (r2 = 0.57) and multiple (r2 = 0.75) linear regression models. The developed calibration model provided precise short-term measurement values for the optimal management of indoor PM concentrations. This methodology can be applied to similar environments to obtain new learning and hyper-parameters. Our results will aid in improving the accuracy of low-cost sensors for measuring indoor PM concentrations, thereby providing cost-effective solutions for enhancing children’s health and well-being in daycare centers and other multiuse facilities

Forest management practice for enhancing carbon sequestration in national forests of Korea

This paper examines forest management planning and its possible outcomes using linear programing (LP). More specifically, the most appropriate forest harvesting schedule was selected that can maximize the carbon sequestration in the current forest areas considering forest manager’s income. The LP model allows the managers to segment forests into cutting units under rotation basis logging activities. Through harvest prescription from LP, we derived the balanced age-class distribution that constitutes improved conditions for sustainable use of forest resource. However, the solutions from LP did not achieve normal forests with perfectly even aged distribution. Instead, it produced a left-skewed age-class distribution due to the cost restriction of management ruling out the achievement of a normal forest as an optimal solution. The results from our LP model also confirm that the forest management activities will enhance yearly carbon sequestration in forests for all scenarios compared to baseline, and the shorter rotation ages tend to call for more carbon sequestration and economic profit. However, it is difficult to ensure that 50 years rotation is the optimal rotation age for the target forests, since we do not consider the benefit of biodiversity conservation

Increased Power in Sediment Microbial Fuel Cell: Facilitated Mass Transfer via a Water-Layer Anode Embedded in Sediment.

We report a methodology for enhancing the mass transfer at the anode electrode of sediment microbial fuel cells (SMFCs), by employing a fabric baffle to create a separate water-layer for installing the anode electrode in sediment. The maximum power in an SMFC with the anode installed in the separate water-layer (SMFC-wFB) was improved by factor of 6.6 compared to an SMFC having the anode embedded in the sediment (SMFC-woFB). The maximum current density in the SMFC-wFB was also 3.9 times higher (220.46 mA/m2) than for the SMFC-woFB. We found that the increased performance in the SMFC-wFB was due to the improved mass transfer rate of organic matter obtained by employing the water-layer during anode installation in the sediment layer. Acetate injection tests revealed that the SMFC-wFB could be applied to natural water bodies in which there is frequent organic contamination, based on the acetate flux from the cathode to the anode

Contribution of Liquid/Gas Mass-Transfer Limitations to Dissolved Methane Oversaturation in Anaerobic Treatment of Dilute Wastewater

The mechanisms controlling the accumulation of dissolved methane in anaerobic membrane bioreactors (AnMBRs) treating a synthetic dilute wastewater (a glucose medium) were assessed experimentally and theoretically. The AnMBR was maintained at a temperature of 24–26 °C as the organic loading rate increased from 0.39 to 1.1 kg COD/m³-d. The measured concentration of dissolved methane was consistently 2.2- to 2.5-fold larger than the concentration of dissolved methane at thermodynamic equilibrium with the measured CH₄ partial pressure, and the fraction of dissolved methane was as high as 76% of the total methane produced. The low gas production rate in the AnMBR significantly slowed the mass transport of dissolved methane to the gas phase. Although the production rate of total methane increased linearly with the COD loading rate, the concentration of dissolved methane only slightly increased with an increasing organic loading rate, because the mass-transfer rate increased by almost 5-fold as the COD loading increased from 0.39 to 1.1 kg COD/m³-d. Thus, slow mass transport kinetics exacerbated the situation in which dissolved methane accounted for a substantial fraction of the total methane generated from the AnMBR

Change of current density and acetate concentration on SMFC-FB by injection of acetate.

<p>Arrow indicates acetate injection into the catholyte at the water-sediment interface in SMFC-wFB. No acetate injected SMFC-wFB was also operated as a control set.</p

Aceate injection tests for the SMFC-woFB and SMFC-wFB constructed with sediement-woAc; OCV and CCV evolution (2 kΩ) in the MFCs (A), development of cathode potential (B) and anode potential (C) in the MFCs; the arrows with the letters “A” and “B” mark the acetate injection points and the resulting current response points respectively.

<p>Aceate injection tests for the SMFC-woFB and SMFC-wFB constructed with sediement-woAc; OCV and CCV evolution (2 kΩ) in the MFCs (A), development of cathode potential (B) and anode potential (C) in the MFCs; the arrows with the letters “A” and “B” mark the acetate injection points and the resulting current response points respectively.</p

Voltage measurements of SMFC-woFB and SMFC-wFB under closed circuit mode at a 5 knd SMFC-wFBls CHas CHteas analyzed by conver The arrow indicates when the operation mode was changed to CCV.

<p>Voltage measurements of SMFC-woFB and SMFC-wFB under closed circuit mode at a 5 knd SMFC-wFBls CHas CHteas analyzed by conver The arrow indicates when the operation mode was changed to CCV.</p