Characterization of trace metal impact on organic acid metabolism and functional microbial community in treating dairy processing wastewater with thermophilic anaerobic membrane bioreactor

Using amino acid waste liquid as functional supplement to change microbial community in up-flow anaerobic sludge blanket treatment of methanolic wastewater

In this study, amino acid waste liquid was employed as a functional supplement (designated as amino acid-rich FS) in the up-flow anaerobic sludge blanket (UASB) treatment of methanolic wastewater. The effect of amino acid-rich FS was evaluated through repeated batch tests, showing that a 0.5% and 1% dosage increased the maximum methane production rate by 93.60% and 123.04%, respectively, by promoting faster methanol degradation. Additionally, long-term operation of the UASB reactor was conducted with increased dosages of amino acid-rich FS, resulting in improved performance. Microbial community analysis demonstrated that the addition of amino acid-rich FS enhanced microbial diversity, with the abundance of Sporomusa increasing by 47.5 times. Beyond the original cooperative relationships, an additional synergy between Sporomusa and Methanosarcina was observed. These findings could address the key challenge of limited microbial diversity in the anaerobic treatment of methanolic wastewater.

In-sewer iron dosing enhances bioenergy recovery in downstream sewage sludge anaerobic digestion: The impact of iron salt types and thermal hydrolysis pretreatment

Dosing iron salts is a widely adopted strategy for sewer odor and corrosion management, and it can affect bioenergy recovery during anaerobic digestion (AD) of sludge in downstream wastewater treatment plants. However, the different impacts of in-sewer iron salt dosing on AD, depending on the types of iron and digestion conditions, remain unclear. Therefore, this study investigated the impact of in-sewer ferrous (Fe(II)) and ferrate (Fe(VI)) dosing on bioenergy recovery in both conventional AD and AD with thermal hydrolysis pretreatment (THP). The results showed that in-sewer Fe(VI) dosing notably enhanced methane production in AD more than in-sewer Fe(II) dosing, with cumulative methane yields of 197.1±1.9 mLCH4∙gVSadded-1 for Fe(VI) and 186.5±10.4 mLCH4∙gVSadded-1 for Fe(II), respectively. Microbial analyses and iron particle characterizations suggested that the superior promotion with Fe(VI) dosing may be attributed to the smaller particle sizes and higher iron oxide content of Fe(VI) resultant products. This led to a greater enhancement in direct interspecies electron transfer (DIET) between syntrophic bacteria and methanogens, as indicated by the upregulation of Methanosaeta and key functional genes involved in CO2-utilizing methanogenesis. Additionally, in THP-AD, the methane production enhancement caused by in-sewer iron dosing (35.5 mLCH4∙gVSadded-1) exceeded that in conventional AD (26.9 mLCH4∙gVSadded-1), although organic degradation during THP was unaffected. As THP-AD gains popularity for improved bioenergy recovery from sludge, our findings suggest that in-sewer iron dosing supports this advancement. Furthermore, in-sewer Fe(VI) dosing appears more promising within integrated wastewater management strategies, facilitating energy- and carbon-neutralization of urban water systems.

Enhancing physico-chemical water quality in recycled dairy effluent through microbial consortium treatment

The dairy industry, notorious by generating wastewater rich in organic and nitrogenous content, necessitates sustainable recycling solutions. Biological treatment emerges as a cost-effective and chemical-free alternative. This study delves into the potential of microbial consortium, a microbial consortium, for recycling dairy effluent, aiming at water reclamation and environmental sustainability. Effluent samples from Madurai's Dairy Industry underwent microbial consortium treatment in a recycling prototype, with treatment efficacy assessed through physicochemical parameters and contaminant removal efficiency. Guided by a biodegradability index of 4.51, the study showcased EM's impact, revealing a notable decrease in pH levels, fostering an alkaline environment (2.35 ± 0.06 ppt). Dissolved oxygen increased significantly to 4.50 ppm, indicating improved aerobic conditions. EM treatment led to substantial reductions in calcium (53 %), magnesium (95 %), nitrogen (22 %), sulfate (79 %), phosphate (86 %), BOD (78 %), and COD (82 %). In contrast, dairy effluent treated without microbial consortium during the sludge activation process exhibited negligible water quality improvement. These findings underscore microbial consortium efficacy in advancing biological treatment of dairy effluent, demonstrating a significant reduction in contaminants and showcasing its potential for sustainable water reclamation. Improved alkalinity, dissolved oxygen, and nutrient content further signify positive impacts on ecosystem health. Microbial consortium emerges as a promising avenue for recycling dairy effluent, offering an economically viable and environmentally friendly solution. The study emphasizes the crucial role of microbial treatments in achieving efficient water reclamation, contributing to a cleaner and sustainable environment. Future research and broader implementation of microbial consortium in dairy industry wastewater management are recommended for enhanced environmental benefits.

Case specific: Addressing co-digestion of wastewater sludge, cheese whey and cow manure: Kinetic modeling

The study investigated the methane production efficiency in a semi-continuous laboratory experiment with periodic feeding of wastewater sludge (WWS) as primary substrate and addition of whey (CW) and cow manure (CM). The short-term behavior of a real-scale anaerobic digester with WWS and the methane production improvements with different feeding mixtures of WWS, CW and CM were addressed. Gradual addition of CW to WWS (WWS:CW:CM = 70:20:0 to 70:55:0) increased the average daily methane production to 48.6 mL CH4/g COD/day and prevented reactor failure, but high VOA/TIC values showed that the reactors were conditionally stable evolution at an OLR of 8 g COD/L/day. Reactors that were additionally supplemented with CM (WWS:CW:CM = 70:55:10) achieved at least 12.3 % more methane than the reactors supplemented with WWS and CW alone. The highest methane production and process evolution in the reactors were achieved at OLRs between 7.5 and 8.7 g COD/L per day. After day 50, the addition of double the amount of CW further increased the methane production and VOA/TIC ratios. In this case, the OLR increased from 6.3 to 9.3 g COD/L/day. The concentration of propionic and acetic acid in all reactors increased above the recommended values and caused inhibition and instability. A strong positive Pearson correlation was found between the trace elements (Fe, Cu, Zn, Mn) detected by XRF. TE contributed to methane production, but to a lesser extent than TIC and NH4+-N. The simplified model successfully predicted methane production under a periodic feeding regime.

Iron Recycle-Driven Organic Capture and Sidestream Anaerobic Membrane Bioreactor for Revolutionizing Bioenergy Generation in Municipal Wastewater Treatment

The practicality of intensifying organic matter capture for bioenergy recovery to achieve energy-neutral municipal wastewater treatment is hindered by the lack of sustainable methods. This study developed innovative processes integrating iron recycle-driven organic capture with a sidestream anaerobic membrane bioreactor (AnMBR). Iron-assisted chemically enhanced primary treatment achieved elemental redirection with 75.2% of chemical oxygen demand (COD), 20.2% of nitrogen, and 97.4% of phosphorus captured into the sidestream process as iron-enhanced primary sludge (Fe-PS). A stable and efficient biomethanation of Fe-PS was obtained in AnMBR with a high methane yield of 224 mL/g COD. Consequently, 64.1% of the COD in Fe-PS and 48.2% of the COD in municipal wastewater were converted into bioenergy. The acidification of anaerobically digested sludge at pH = 2 achieved a high iron release efficiency of 96.1% and a sludge reduction of 29.3% in total suspended solids. Ultimately, 87.4% of iron was recycled for coagulant reuse, resulting in a theoretical 70% reduction in chemical costs. The novel system evaluation exhibited a 75.2% improvement in bioenergy recovery and an 83.3% enhancement in net energy compared to the conventional system (primary sedimentation and anaerobic digestion). This self-reliant and novel process can be applied in municipal wastewater treatment to advance energy neutrality at a lower cost.

Technical and financial feasibility of a chemicals recovery and energy and water production from a dairy wastewater treatment plant

Due to the high volume of wastewater produced from dairy factories, it is necessary to integrate a water recovery process with the treatment plant. Today, bipolar membrane electrodialysis units (BMEUs) are increasingly developed for wastewater treatment and reutilizing. This article aims to develop and evaluate (technical and cost analyses) a combined BMEU/batch reverse osmosis unit (BROU) process for the recovery of chemicals and water from the dairy wastewater plant. The combined BROU/BMEU process is able to simultaneously produce water and strong base-acid, and reduce power consumption due to the injection of concentrated feed flow into the BMEU. A comprehensive comparative analysis on the performances of two combined and stand-alone BMEU configurations are developed. The proposed combined technology for dairy factory wastewater treatment is designed on a new structure and configuration that can address superior cost analysis compared to similar technologies. Further, the optimal values of permeate flux and current density as two vital and influencing parameters on the performance of the studied dairy wastewater treatment process were calculated and discussed. From the outcomes, the total cost of production in the combined configuration has been reduced by approximately 26% compared to the stand-alone configuration. Increasing the feed concentration rate using the batch reverse osmosis process for the dairy wastewater treatment process can be an ideal solution from an economic point of view. Moreover, point (current density, feed concentration rate, total unit cost) = 328.9 , 7 , 14.37 can be considered as an optimal point for the economic performance of the studied wastewater treatment process.

Evaluation of anaerobic membrane bioreactor treating dairy processing wastewater: Elemental flow, bioenergy production and reduction of CO2 emission

The management of dairy processing wastewater (DPW) must address water pollution while delivering renewable energy and recovering resources. A high-rate anaerobic membrane bioreactor (AnMBR) was investigated for treating DPW, and the system was evaluated in terms of elemental flow, nutrient recovery, energy balance, and reduction of CO2 emission. The AnMBR system was superior in terms of both methanogenic performance and efficiency of bioenergy recovery in the DPW treatment, with a high net energy potential of 51.4-53.2 kWh/m3. The theoretical economic values of the digestate (13.8 $/m3) and permeate (4.1 $/m3) were assessed according to nutrient transformation and price of mineral fertilizer. The total CO2 emission equivalent in the AnMBR was 44.7 kg CO2-eq/m3, with a significant reduction of 54.1 kg CO2-eq/m3 compared to the conventional process. The application of the AnMBR in the DPW treatment is a promising approach for the development of carbon neutrality and a circular economy.

A review of iron use and recycling in municipal wastewater treatment plants and a novel applicable integrated process

Chemical methods are expected to play an increasingly important role in carbon-neutral municipal wastewater treatment plants. This paper briefly summarises the enhancement effects of using iron salts in wastewater and sludge treatment processes. The costs and environmental concerns associated with the widespread use of iron salts have also been highlighted. Fortunately, the iron recovery from iron-rich sludge provides an opportunity to solve these problems. Existing iron recovery methods, including direct acidification and thermal treatment, are summarised and show that acidification treatment of FeS digestate from the anaerobic digestion-sulfate reduction process can increase the iron and sulphur recycling efficiency. Therefore, a novel applicable integrated process based on iron use and recycling is proposed, and it reduces the iron salts dosage to 4.2 mg/L and sludge amount by 80%. Current experimental research and economic analysis of iron recycling show that this process has broad application prospects in resource recovery and sludge reduction.

Syntrophic Propionate Oxidation: One of the Rate-Limiting Steps of Organic Matter Decomposition in Anoxic Environments

Syntrophic propionate oxidation is one of the rate-limiting steps during anaerobic decomposition of organic matter in anoxic environments. Syntrophic propionate-oxidizing bacteria (SPOB) are members of the "rare biosphere" living at the edge of the thermodynamic limit in most natural habitats. Hitherto, only 10 bacterial species capable of syntrophic propionate oxidization have been identified. SPOB employ different metabolisms for propionate oxidation (e.g., methylmalonyl-CoA pathway and C6 dismutation pathway) and show diverse life strategies (e.g., obligately and facultatively syntrophic lifestyle). The flavin-based electron bifurcation/confurcation (FBEB/C) systems have been proposed to help solve the thermodynamic dilemma during the formation of the low-potential products H2 and formate. Molecular ecological approaches, such as DNA stable isotope probing (DNA-SIP) and metagenomics, have been used to detect SPOB in natural environments. Furthermore, the biogeographical pattern of SPOB has been recently described in paddy soils. A comprehensive understanding of SPOB is essential for better predicting and managing organic matter decomposition and carbon cycling in anoxic environments. In this review, we described the critical role of syntrophic propionate oxidation in anaerobic decomposition of organic matter, phylogenetic and metabolic diversity, life strategies and ecophysiology, composition of syntrophic partners, and pattern of biogeographic distribution of SPOB in natural environments. We ended up with a few perspectives for future research.

Methanogenic treatment of dairy wastewater: A review of current obstacles and new technological perspectives

Methanogenic treatment can effectively manage wastewater in the dairy industry. However, its treatment efficiency and stability are problematic due to the feature of wastewater. This review comprehensively summarizes the dairy wastewater characteristics and reveals the mechanisms and impacts of three critical issues in anaerobic treatment, including ammonia and long-chain fatty acid (LCFA) inhibition and trace metal (TM) deficiency. It evaluates current remedial strategies and the implementation of anaerobic membrane bioreactor (AnMBR) technology. It assesses the use of nitrogen-removed effluent return to dilute the influent for solving protein-rich dairy wastewater treatment. It explores the methodology of TM addition to dairy wastewater in accordance with microbial TM content and proliferation. It analyzes the multiple benefits of applying high-solid AnMBR to lipid-rich influent to mitigate LCFA inhibition. Finally, it proposes a promising low-carbon treatment system with enhanced bioenergy recovery, nitrogen removal, and simultaneous phosphorus recovery that could promote carbon neutrality for dairy industry wastewater treatment.