Showing papers on "Bioreactor published in 2021"

Comammox Nitrospira Species Dominate in an Efficient Partial Nitrification–Anammox Bioreactor for Treating Ammonium at Low Loadings

Abstract: Bacteria capable of complete ammonia oxidation (comammox) are widespread and contribute to nitrification in wastewater treatment facilities. However, their roles in partial nitrification-anaerobic ammonium oxidation (anammox) systems remain unclear. In this study, a bench-scale bioreactor with continuous stirring was operated for more than 1000 days with limited oxygen supply to achieve efficient nitrogen removal (70.1 ± 2.7%) at a low ammonium loading of 35.2 mg-N/L/day. High-throughput amplicon sequencing analysis of the comammox ammonia monooxygenase subunit A (amoA) gene revealed seven sequence types from two clusters in clade A of comammox Nitrospira. Quantitative polymerase chain reaction analyses suggested that the comammox species dominated the ammonia-oxidizing community, with an abundance as high as 89.2 ± 7.9% in total prokaryotic amoA copies. Multiple linear regression further revealed the substantial contribution of the comammox Nitrospira to ammonia oxidation in the bioreactor. The investigation with bioreactor and batch experiments consistently showed that activities of comammox Nitrospira were inhibited by free ammonia far more severely than other ammonia-oxidizing microbes. Overall, this study provided new insight into the ecology of comammox Nitrospira under hypoxic conditions and suggested comammox-associated partial nitrification-anammox as a potential method for treating low-strength ammonium-containing wastewater.

A review on membrane fouling control in anaerobic membrane bioreactors by adding performance enhancers

Abstract: Anaerobic membrane bioreactors (AnMBRs), the combination of anaerobic digestion and membrane technology, have gained increasing popularity due to their remarkable advantages over aerobic membrane bioreactors, such as biogas production and potential energy use. However, membrane fouling remains a challenging issue that deteriorates the performance of membrane and shortens its lifespan. Pretreatment of feed wastewater by adding fouling reduction enhancers, such as adsorbents and flocculants, into anaerobic membrane bioreactor can effectively mitigate membrane fouling by altering the feed properties. Activated carbon, such as powdered activated carbon (PAC) and granular activated carbon (GAC), has been widely applied as an adsorbent to aerobic and anaerobic membrane bioreactors for membrane fouling control. Organic enhancers such as biochar and waste yeast, and inorganic enhancers like polyaluminum chloride and zeolite have also been applied to AnMBRs promoting flocculation and coagulation. Thus, this review discusses the impacts of different fouling reduction enhancers under anaerobic conditions as well as AnMBR system. In addition, the mechanisms of the enhancers mitigating the membrane fouling are also summarized for better understanding of the effects of the enhancers in AnMBRs.

Trends and progress in AnMBR for domestic wastewater treatment and their impacts on process efficiency and membrane fouling

Abstract: Anaerobic membrane bioreactor has emerged as an innovative technology in treating domestic wastewater due to its excellent produced effluent quality and high potential of neutral or positive energy balance. One of the biggest challenges in positive energy objective is fouling mitigation which contributes towards 70% of the total energy requirement of MBR-based domestic wastewater treatment. Numerous studies were carried out to address this issue, utilizing various reactor design configurations and operating conditions for energy minimization as well as membrane performance enhancement. The latest research trend in this sector is the establishment of hybrid processes like Granular Anaerobic Membrane Bioreactors (G-AnMBR), Forward Osmosis Anaerobic Membrane Bioreactor (FO-AnMBR) and Microbial Electrolysis Cell-Anaerobic Membrane Bioreactor (MEC-AnMBR) for domestic wastewater treatment which not only provides efficiency in treatment but also improves fouling mitigation. Also, the application of techniques developed particularly for fouling mitigation like quorum quenching and sensing, cell entrapment and membrane module vibrations in AnMBRs were assessed. This paper reviews the latest trends in anaerobic membrane bioreactors research with regards to water quality produced, removal efficiencies and fouling mitigation.

Anoxic/oxic membrane bioreactor assisted by electrocoagulation for the treatment of azo-dye containing wastewater

Abstract: This study investigated the use of an anoxic-oxic electro-membrane bioreactor (A/O-EMBR) for the treatment of an azo-dye containing wastewater. The reactor performance and the bacterial community structure were assessed and compared without (Period I) and with (Period II) the application of the electrocoagulation process under the current density of 10 A m−2. The dye removal performance was substantially improved as the electrocoagulation was applied, increasing from 52% (Period I) to 94.9% (Period II). Respirometric tests showed that the nitrifying activity increased when the membrane bioreactor was exposed to electrocoagulation. Likewise, activity batch tests indicated that both anoxic and anaerobic dye removal rates increased when the electrocoagulation was applied, while aerobic decolorization was not affected and remained invariant. DNA sequencing analysis revealed significant shifts in the microbial community composition upon implementation of electrocoagulation. Janibacter and Lactococcus genus, recognized as azo dye-degrading bacteria, were the most abundant in Period II and accounted for almost 60% and 16% of the classified sequences, respectively. Filtration batch tests revealed better filterability conditions of the mixed liquor when the reactor was assisted by the electrocoagulation. However, the membrane fouling rate became more intense in this period, a result that was attributed to the substantial increment in total suspended solids content. The average energy consumption per mass of dye removed decreased by 17.2% (from 580 to 480 kWh kgdyeremoved−1) when the electrocoagulation was applied, indicating that A/O-EMBR configuration was able to achieve a better energy efficiency in terms of dye removal.

Effectiveness of Denitrifying Bioreactors on Water Pollutant Reduction from Agricultural Areas

Abstract: Highlights Denitrifying woodchip bioreactors treat nitrate-N in a variety of applications and geographies. This review focuses on subsurface drainage bioreactors and bed-style designs (including in-ditch). Monitoring and reporting recommendations are provided to advance bioreactor science and engineering. Abstract. Denitrifying bioreactors enhance the natural process of denitrification in a practical way to treat nitrate-nitrogen (N) in a variety of N-laden water matrices. The design and construction of bioreactors for treatment of subsurface drainage in the U.S. is guided by USDA-NRCS Conservation Practice Standard 605. This review consolidates the state of the science for denitrifying bioreactors using case studies from across the globe with an emphasis on full-size bioreactor nitrate-N removal and cost-effectiveness. The focus is on bed-style bioreactors (including in-ditch modifications), although there is mention of denitrifying walls, which broaden the applicability of bioreactor technology in some areas. Subsurface drainage denitrifying bioreactors have been assessed as removing 20% to 40% of annual nitrate-N loss in the Midwest, and an evaluation across the peer-reviewed literature published over the past three years showed that bioreactors around the world have been generally consistent with that (N load reduction median: 46%; mean ±SD: 40% ±26%; n = 15). Reported N removal rates were on the order of 5.1 g N m-3 d-1 (median; mean ±SD: 7.2 ±9.6 g N m-3 d-1; n = 27). Subsurface drainage bioreactor installation costs have ranged from less than $5,000 to $27,000, with estimated cost efficiencies ranging from less than $2.50 kg-1 N year-1 to roughly $20 kg-1 N year-1 (although they can be as high as $48 kg-1 N year-1). A suggested monitoring setup is described primarily for the context of conservation practitioners and watershed groups for assessing annual nitrate-N load removal performance of subsurface drainage denitrifying bioreactors. Recommended minimum reporting measures for assessing and comparing annual N removal performance include: bioreactor dimensions and installation date; fill media size, porosity, and type; nitrate-N concentrations and water temperatures; bioreactor flow treatment details; basic drainage system and bioreactor design characteristics; and N removal rate and efficiency.

An Insight into Biological and Chemical Technologies for Micropollutant Removal from Wastewater

Abstract: Over the last few decades, the occurrence of micropollutants (MPs) in wastewater has emerged as a challenging task for the scientific community. Biological treatment technologies (BTTs) are most widely used for MPs removal, including activated sludge, constructed wetland, membrane bioreactor (MBR), aerobic bioreactor, anaerobic bioreactor, microalgae bioreactor, fungal bioreactor, trickling filter, rotating biological reactor, nitrification, and biosorption. Results showed that during biological treatment some of the non-biodegradable MPs are not efficiently removed. Chemical treatment technologies (CTTs) including Fenton, ozonation, photolysis, photo-Fenton, photocatalysis, and electro-Fenton process have been widely used. However, the complete mineralization of MPs by CTTs is usually expensive. Therefore, a cost and resource-efficient alternative are to direct biological treatment in combination with a chemical treatment to convert the hazardous pollutants into more biodegradable compounds. This chapter provides an insight into the removal of micropollutants from wastewater treatment plants (WWTPs) by biological, chemical, and hybrid technologies. Further studies are needed for optimizing these processes, especially in terms of technical and economic perspectives.

Textile wastewater bioremediation using immobilized Chlorella sp. Wu-G23 with continuous culture

Abstract: Immobilized microalga Chlorella sp. Wu-G23 (G23) was entrapped inside a polymer matrix or appended on the surface of a strong solid carrier. Alginates then formed a microalgae/polymeric matrix granule within the cross-linking solution. The textile wastewater bioremediation technology using immobilized G23 in textile wastewater effectively removed chemical oxygen demand (COD), ammonium nitrogen (NH4+-N) and color after 7 days of cultivation. Batch model results show that the optimal cultivation parameters for simultaneously removing textile wastewater pollutants and accumulating lipids were initial pH 10 with extra urea 1 g/L and K2HPO4 8 mg/L added without aeration. A bioreactor cultivated the immobilized G23 at hydraulic retention time of 48 h with continuously fed textile wastewater for 440 h. Peak removal efficiencies of NH4+-N 80.2%, COD 70.8% and color 77.9% with fatty acid methyl esters 10% were achieved. The color removal occurred through the biosorption mechanism using nonviable suspended and immobilized microalgae biomass. The NH4+-N and COD could be degraded in the cell-free, nonviable microalgae because the microorganism in the textile wastewater could utilize them as a nutrient source.

A digital light processing 3D printed magnetic bioreactor system using silk magnetic bioink.

Abstract: Among various bioreactors used in the field of tissue engineering and regenerative medicine, a magnetic bioreactor is more capable of providing steady force to the cells while avoiding direct manipulation of the materials. However, most of them are complex and difficult to fabricate, with drawbacks in terms of consistency and biocompatibility. In this study, a magnetic bioreactor system and a magnetic hydrogel were manufactured by single-stage three-dimensional printing with digital light processing (DLP) technique for differentiation of myoblast cells. The hydrogel was composed of a magnetic part containing iron oxide and glycidyl-methacrylated silk fibroin, and a cellular part printed by adding mouse myoblast cell (C2C12) to gelatin glycidyl methacrylate, that was placed in the magnetic bioreactor system to stimulate the cells in the hydrogel. The composite hydrogel was steadily printed by a one-stage layering technique using a DLP printer. The magnetic bioreactor offered mechanical stretching of the cells in the hydrogel in three-dimensional ways, so that the cellular differentiation could be executed in three dimensions just like the human environment. Cell viability, as well as gene expression using quantitative reverse transcription-polymerase chain reaction, were assessed after magneto-mechanical stimulation of the myoblast cell-embedded hydrogel in the magnetic bioreactor system. Comparison with the control group revealed that the magnetic bioreactor system accelerated differentiation of mouse myoblast cells in the hydrogel and increased myotube diameter and length in vitro. The DLP-printed magnetic bioreactor and the hydrogel were simply manufactured and easy-to-use, providing an efficient environment for applying noninvasive mechanical force via FDA-approved silk fibroin and iron oxide biocomposite hydrogel, to stimulate cells without any evidence of cytotoxicity, demonstrating the potential for application in muscle tissue engineering.

Direct Medium-Chain Carboxylic Acid Oil Separation from a Bioreactor by an Electrodialysis/Phase Separation Cell

Abstract: Medium-chain carboxylic acids (MCCAs) are valuable platform chemicals and can be produced from waste biomass sources or syngas fermentation effluent through microbial chain elongation. We have previously demonstrated successful approaches to separate >90% purity oil with different MCCAs (MCCA oil) by integrating the anaerobic bioprocess with membrane-based liquid-liquid extraction (pertraction) and membrane electrolysis. However, two-compartment membrane electrolysis unit without pertraction was not able to separate MCCA oil. Therefore, we developed a five-compartment electrodialysis/phase separation cell (ED/PS). First, we tested an ED/PS cell in series with pertraction and achieved a maximum MCCA-oil flux of 1.7 × 103 g d-1 per projected area (m2) (19 mL oil d-1) and MCCA-oil transfer efficiency [100% × moles MCCA-oil moles electrons-1] of 74% at 15 A m-2. This extraction system at 15 A m-2 demonstrated a ∼10 times lower electric-power consumption (1.1 kWh kg-1 MCCA oil) than membrane electrolysis in series with pertraction (9.9 kWh kg-1 MCCA oil). Second, we evaluated our ED/PS as a stand-alone unit when integrated with the anaerobic bioprocess and demonstrated that we can selectively extract and separate MCCA oil directly from chain-elongating bioreactor broth with just an abiotic electrochemical cell. However, the electric-power consumption increased considerably due to the lower MCCA concentrations in the bioreactor broth compared to the pertraction broth.