Efficient recovery of phosphorus and sulfur from Anaerobic Membrane Bioreactor (AnMBR) permeate using chemical addition of iron and evaluation of its nutrient availability for plant uptake

Decomposing the molecular complexity and transformation of dissolved organic matter for innovative anaerobic bioprocessing

The sustainable transformation and management of dissolved organic matter (DOM) are crucial for advancing organic waste treatment towards resource-oriented processes. However, the intricate molecular complexity of DOM poses significant challenges, impeding a comprehensive understanding of the underlying biochemical processes. Here, we focus on the chemical "dark matter" mining using ultra-high resolution mass spectrometry technologies to elucidate the molecular diversity and transformation in anaerobic bioprocessing of food waste. We developed an analytical framework that reveals the persistence of DOM in the final effluent is mainly determined by its molecular properties, such as carbon chain length, aromaticity, unsaturation, and redox states. Our in-depth characterization and quantitative analysis of key biochemical reactions unveils the evolution of DOM composition, providing valuable insights into the targeted conversion of persistent molecules toward full utilization. Additionally, we establish a correlation between the redox state and energy density of a broad range of DOM molecules, enabling us to comprehend and evaluate their biodegradability. These insights enhance the mechanistic understanding of DOM transformation, guiding the rational design and regulation of sustainable organic waste treatment strategies.

Primary assessment of macronutrients in durian (CV Monthong) leaves using near infrared spectroscopy with wavelength selection

Farmers would be able to regulate fertilization and produce quality durian if they knew the nutrient concentration in durian leaves. A long period of time for traditional nutritional content determination is needed. Therefore, near-infrared spectroscopy is a good method for nondestructive and quick nutrient content evaluation. The leaf sample matrices (fresh leaves, dried ground leaves, and dried ground leaf pellets) were scanned by Fourier transform near-infrared (FT-NIR) with a wavelength of 12,500-3,600 cm-1. Regression models were developed using partial least squares (PLS) with full wavelength, short wavelength, and selected wavelength by successive projections algorithm (SPA). In this study, the model for N and K concentration was acceptable and the prediction was considered good but for P content not had succeeded. As a result, the PLS-SPA model using fresh leaf samples for evaluating N content in durian leaves exhibited performance of r2 = 0.852, SEP = 0.14%, RPD = 2.63 and bias = -0.020%. The PLS-SPA model using dried ground leaf samples for evaluating K content in durian leaves exhibited performance of r2 = 0.820, SEP = 0.13%, RPD = 2.36 and bias = 0.006%. This research found that it is possible to apply NIR waves to predict N and K concentrations in durian leaves. It is not necessary to predict directly from the wavelengths associated with -N or -K bonds. Instead, NIR can measure them indirectly from the bonding of proteins, which are products formed by N and K. In addition, selecting the wavelength that is related to the value to be measured can produce results that are not significantly different from using full or short wavelengths. These models can assist farmers in rapidly predicting N and K content in durian leaves for immediate fertilizer adjustment.

Anaerobic Wastewater Treatment and Potable Reuse: Energy and Life Cycle Considerations

Anaerobic secondary treatment has the potential to facilitate energy-positive operations at wastewater treatment plants, but post-treatment of the anaerobic effluent is needed to recover dissolved methane and nutrients and remove sulfide. In this study, a life cycle assessment was conducted to compare hypothetical full-scale wastewater treatment trains and direct potable reuse trains that combine the staged anaerobic fluidized membrane bioreactor (SAF-MBR) with appropriate post-treatment. We found that anaerobic wastewater treatment trains typically consumed less energy than conventional aerobic treatment, but overall global warming potentials were not significantly different. Generally, recovery of dissolved methane for energy production resulted in lower life cycle impacts than microbial transformation of methane, and microbial oxidation of sulfide resulted in lower environmental impacts than chemical precipitation. Use of reverse osmosis to produce potable water was also found to be a sustainable method for nutrient removal because direct potable reuse trains with the SAF-MBR consumed less energy and had lower life cycle impacts than activated sludge. Moving forward, dissolved methane recovery, reduced chemical usage, and investments that enable direct potable reuse have been flagged as key research areas for further investigation of anaerobic secondary treatment options.

Phosphorus Recovery by Adsorption from the Membrane Permeate of an Anaerobic Membrane Bioreactor Digesting Waste-Activated Sludge

The recovery of phosphorus (P) from waste activated sludge (WAS) is a promising approach for sustainable resource management. During the anaerobic digestion of WAS, orthophosphate is released, and this P species is favorable for adsorption recovery. In the present study, an anerobic membrane bioreactor (AnMBR) with a P-adsorption column was developed to generate biogas from WAS and to recover P from membrane permeate simultaneously. The effects of the hydraulic retention time (HRT) and solid retention time (SRT) of the AnMBR on P solubilization were investigated. As a result, the maximum P solubilization was 21% when the HRT and SRT were 45 days and 100 days, respectively. Orthophosphate in the membrane permeate was adsorbed and recovered using a mesoporous material called zirconium sulfate–surfactant micelle mesostructure (ZS) in the column. The adsorbed P could be desorbed from the ZS with a NaOH solution, and P was recovered as a concentrated solution by a factor of 25. When the HRT was 19 days, the biogas yield and biogas production rate were 0.26 L/g-VSinput and 0.123 L/L/d, respectively. The average methane content in the biogas was 80%. The developed membrane-based process may be effective for resource recovery from WAS.