ACS ES&T engineering最新文献

This study presents the simultaneous conversion of food waste and CO₂ into volatile fatty acids (VFAs) using a 6 L tubular microbial electrosynthesis cell (MES). The MES reactor uses a bioanode to convert food waste into current and CO₂, while on the cathode, H₂ is produced and subsequently consumed by cathode microbes for the conversion of CO₂ to VFAs. The study reveals that system performance is impacted by organic loading, applied voltage, and flow rate, and optimal operational conditions achieve a VFA titer of 1763 mg/L with the Coulombic efficiency (CE) exceeding 90% at the anode, highlighting efficient electron recovery from food waste. Resistance analysis indicates that the cathode contributed most to system resistance, while microbial community analysis shows a synergy between fermentative and electroactive bacteria in the anode and dominant acetogens in the cathode, facilitating efficient electron recovery and VFA synthesis, respectively. The research underscores the tubular MES’s potential for sustainable food waste treatment and CO₂ valorization into valuable VFAs, contributing to waste management and greenhouse gas mitigation strategies.

The coexistence of microplastics (MPs) and oil contaminants in soil has led to a new pollution scenario around the oil-production region, yet how to cost-effectively remediate soil with combined pollutants has rarely been explored. Herein, we propose a fast pyrolysis technique to perfectly remediate MP_S-oil copresence soil (MPs-oil-soil). The experimental data showed that pyrolysis at 500 °C for 15 min is a key threshold for the complete removal of MPs and petroleum contaminants from soil. Above this threshold, seed germination and the growth of wheat in the soil increased, and the rhizosphere microbial population decreased with increasing abundance of beneficial microbial flora, such as Proteobacteria, Actinobacteria and Bacteroidetes (which promote the circulation of nutrients and help to strengthen plant resistance). Structural equation modeling revealed that temperature had a more significant positive effect on the remediation effect than did time. Two-dimensional correlation spectroscopy combined with synchronous fluorescence spectroscopy showed that the presence of MPs was the main factor affecting the pyrolysis threshold. Three-dimensional excitation–emission matrix and UV–visible absorption spectroscopy revealed large differences in the aromaticity and relative molecular weight of dissolved organic matter before and after the pyrolysis threshold. These findings shed light on the mechanistic understanding of the pyrolytic remediation of microplastics and oil-contaminated soils.

Human urine is considered a major stream of nitrogen mass flow in domestic wastewater, which is widely available and rich in valuable nutrient resources for hydroponic cultivation. In this study, a promising concept of nutrient recovery from real urine was proposed, including urine alkalinization by Ca(OH)₂, full nitrification in a trickling filter, and chemical supplementations. The steady performance of urine nitrification among different urine-collecting batches indicates the robustness of the trickling filter. An optimal hydraulic loading rate of 2.1 m³ m^–2 h^–1 sufficed the dissolved oxygen and urine circulation in the trickling filter, achieving a nitrate production rate of 223 ± 2 mg N L^–1 d^–1 with an efficiency of 90 ± 2% at pH 6 and 21 °C. The electrical energy consumption was only 1.15 kWh kg^–1 NO₃^–-N production at a short hydraulic retention time of 1 day. Among all of the three types of pH control reagents (i.e., Ca(OH)₂, CaCO₃, and K₂CO₃), K₂CO₃ could enhance the activity of ammonium-oxidizing bacteria by raising the inorganic carbon level in the trickling filter and subsequently result in the lowest supplementation of extra macronutrients (i.e., nitrogen, phosphorus, and magnesium) to the urine-sourced nutrient solution. Batch tests showed that the highest activity of ammonium-oxidizing and nitrite-oxidizing bacteria was in the bottom compartment of the trickling filter, consistent with the vertical stratification of their relative abundance. Overall, the proposed novel concept was demonstrated to be robust and energy-efficient in nutrient recovery from real urine for hydroponics.