Hydraulic characterization and start-up of a novel circulating flow bio-carriers.

High-quality biofilm carriers are crucial for the formation of biofilm, but problems such as slow biofilm growth on the carrier surface have been troubling a large number of researchers. The addition of a carrier changes the flow state in the reactor, which in turn affects the microbial attachment and the quantity of microorganisms. Also, aerobic microorganisms need to use dissolved oxygen in the water to remove water pollutants. In this paper, a novel recirculating flow carrier with a hollow cylinder structure is proposed, with a certain number of hollow inverted circular plates placed at equal distances inside. In this paper, the hydraulic residence time, aeration volume, and the spacing of the inflow plates of the recirculating flow biofilm carrier, which are three important factors affecting the hydraulic characteristics of the reactor, are first investigated. At the same time, it was compared with the common combined carrier to find the optimal operating conditions for the hydraulic characteristics. Secondly, a reactor start-up study was carried out to confirm that the new recirculating flow biofilm carrier could accelerate the biofilm growth by changing the hydraulic characteristics. The results showed that under the same conditions, the hydraulic properties of the reactor were better with the addition of the recirculating flow carrier, with an effective volume ratio of 98% and a significant reduction in short flows and dead zones. The stabilized removal of COD, NH3-N, and TN in the reactor with the addition of the recirculating flow carrier reached about 94%, 99%, and 91% respectively, at the beginning of the 15th day, which effectively proved the feasibility of the recirculating flow carrier.

Research progress of anaerobic ammonium oxidation (Anammox) process based on integrated fixed-film activated sludge (IFAS).

The integrated fixed-film activated sludge (IFAS) process is considered one of the cutting-edge solutions to the traditional wastewater treatment challenges, allowing suspended sludge and attached biofilm to grow in the same system. In addition, the coupling of IFAS with anaerobic ammonium oxidation (Anammox) can further improve the efficiency of biological denitrification. This paper summarises the research progress of IFAS coupled with the anammox process, including partial nitrification anammox, simultaneous partial nitrification anammox and denitrification, and partial denitrification anammox technologies, and describes the factors that limit the development of related processes. The effects of dissolved oxygen, influent carbon source, sludge retention time, temperature, microbial community, and nitrite-oxidising bacteria inhibition methods on the anammox of IFAS are presented. At the same time, this paper gives an outlook on future research focus and engineering practice direction of the process.

Sustainability and affordability of Chinese-funded renewable energy project in sub-Saharan Africa: a hybridized solid oxide fuel cell, temperature sensors, and lithium-based solar system approach.

Renewable energy projects are at the crux of all Chinese-funded investment in sub-Saharan Africa, which accounts for some 56% of all Chinese-led investments globally. However, the prevailing problem is that about 568 million people were still without electricity access in 2019 across urban and rural areas in sub-Saharan Africa, which does not commensurate with the United Nations Sustainable Development Goal (SDG7) of ensuring affordable and clean energy for all. Previous studies have assessed and improved the efficiency of integrated power generation systems often combined on three levels, power plant, solar panel, and fuel cells, and integrated into national grids or off-grid systems for a sustainable supply of power. This study has included a lithium-ion storage system as a key component in a hybridized renewable energy generation system for the first time that has proven to be efficient and investment worthy. The study also examines the operational parameters of Chinese-funded power plant projects in sub-Saharan Africa and their effectiveness in achieving SDG-7. The novelty of this study is evident in the proposed integrated multi-level hybrid technology model of solid oxide fuel cells, temperature point sensors, and lithium batteries powered by a solar system and embedded in thermal power plants as an alternative electrical energy system for domestic and industrial use in sub-Saharan Africa. Performance analysis of the proposed power generation model indicates its complementary capacity of generating additional energy output with thermodynamics energy and exergy efficiencies of 88.2% and 67.0% respectively. The outcome of this study draws the attention of Chinese investors, governments in sub-Saharan African countries, and top industry players to the following: to consider refocusing their energy sector policy initiatives and strategies towards exploring the lithium resource base in Africa, optimizing energy generation cost, recouping optimal profit from their renewable energy technology investments, and making electricity supply clean, sustainable, and affordable for use in sub-Saharan Africa.

Application of ZIF-8 nanocomposite membrane in microbial desalination cells for simultaneous heavy metal removal and biofouling prevention.

Microbial desalination cells (MDC) syndicate the advantage of physical separation by using membranes to create conditions required for Bioelectrochemical processes for the treatment of various domestic and industrial wastewater, while simultaneously desalinating saline water and generating bioenergy. However, since the introduction of this technology, heavy metal removal has been a challenge, and membrane fouling has become a major bottleneck limiting the optimum performance and efficiency of this technology. This study incorporated the use of ZIF-8 nanocomposite membrane via phase inversion mechanism in MDC for simultaneous heavy metal removal and membrane biofouling prevention. The study was conducted in two MDC systems; MDC-Control (without the ZIF-8 nanocomposite membrane) and MDC with ZIF-8 nanocomposite membrane. The results from the experiment shown that maximum removal efficiency of 85.7%, 84.3%, 84.0%, and 90.61% was obtained for Cu2+, Zn2+, Pb2+, and Cd2+ respectively in MDC-ZIF-8, while MDC control showed 54.17%, 59.71%, 51.94%, and 54.17%. The results were well fitted to the Langmuir adsorption isotherm with correlation coefficients (R2) > 0.99 in all cases for MDC-ZIF-8. A maximum adsorption capacity (Qmax) of 292 mg g-1 was attained for all four metal ions in MDC-ZIF-8. Besides, after 38 days of continuous operation with two complete desalination for both systems, the SEM-EDS characterization analysis, polarization characteristics, and power generation revealed antifouling characteristics of ZIF-8 nanocomposite membrane incorporated in MDC. The integration of the ZIF-8 nanocomposite membrane proved to be simultaneously efficient in biofouling prevention and heavy metal removal without jeopardizing the system's ability for wastewater treatment, bioelectricity generation, and desalination processes.

Scaled-up multi-anode shared cathode microbial fuel cell for simultaneous treatment of multiple real wastewaters and power generation.

Microbial fuel cell (MFC) is lauded for its capacity to valorize organic substrates in wastes, providing a solution to environmental pollution and energy crisis. While different types of organic substrates affect removal efficiency and current output, most MFCs are designed to only be able to utilize one type of wastewater. However, many real wastewater treatment sites generate more than one type of wastewater which hinders the installation of most MFCs. This study aimed to investigate the performance of the novel-designed multi-anode shared cathode MFC (MASC-MFC) compared with a standard single anode/cathode MFC (SAC-MFC) and the simultaneous treatment of different types of real wastewaters (sewage, slaughterhouse, and hospital) in one MFC unit. The MASC-MFC (9025 mW/m2 at 23.332 mA/m2) produced 1.7 times and 1.6 times higher in power density and current density and 2.2 times lower in internal resistance than the standard single anode/cathode MFC (SAC-MFC). A maximum COD removal efficiency of 62.7% was achieved with synthetic wastewater. Feeding the MASC-MFC with multiple real wastewaters decreased maximum power density 3.5 (2599 mW/m2) times and increased internal resistance 2.7 times. Stable current generation 1.575 mA was achieved over 300 h despite the different and complex wastewater physio-chemical compositions. The MASC-MFC achieved over 40% and approximately 30% coulombic efficiency independently in all the anode chambers irrespective of the type of real wastewater used, demonstrating the MASC-MFC's capacity to treat different real wastewaters with the added benefit of electricity production.

Comparative Studies of Recirculatory Microbial Desalination Cell-Microbial Electrolysis Cell Coupled Systems.

The recirculatory microbial desalination cell-microbial electrolysis cell (MDC-MEC) coupled system is a novel technology that generates power, treats wastewater, and supports desalination through eco-friendly processes. This study focuses on the simultaneous efficient removal of Fe2+ and Pb2+ in the MEC and ammonium ions in the MDC. It also evaluates the performances of dual-chambered MEC (DCMEC) and single-chambered MEC (SCMEC), coupled with MDC with Ferricyanide as catholyte (MDCF) in heavy metals (Pb2+ and Fe2+) removal, in addition to the production of voltage, current, and power within a 48-h cycle. The SCMEC has a higher Pb2+ (74.61%) and Fe2+ (85.05%) removal efficiency during the 48-h cycle than the DCMEC due to the simultaneous use of microbial biosorption and the cathodic reduction potential. The DCMEC had a higher current density of 753.62 mAm-2 than that of SCMEC, i.e., 463.77 mAm-2, which influences higher desalination in the MDCF than in the SCMEC within the 48-h cycle. The MDCF produces a higher voltage (627 mV) than Control 1, MDC (505 mV), as a power source to the two MECs. Stable electrolytes' pH and conductivities provide a conducive operation of the coupled system. This study lays a solid background for the type of MDC-MEC coupled systems needed for industrial scale-up.

A multi-emission analysis of organic and inorganic pollutants during the combustion of sludge with high and low calorific value coals.

To achieve allowable gas emission limits and eliminate the high cost and challenges associated with pre-treatment of sludge before incineration, a new technique was proposed to co-incinerate wet printing and dyeing sludge with different calorific values of coal while conducting a full evaluation of organic and inorganic emission of pollutants. Different proportions (0%, 10%, 20%, 30%, 40%) of the wet sludge-coal slurry (peat) were incinerated using a commercialized fluid bed (circulating) incinerator. The results showed the that flue gas emitted contained sulfur oxides (SOx), nitrogen oxides (NOx), polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs), polychlorinated biphenyls (PCBs), and heavy metals in bottom ash. The ΣPCBs content produced from the 7 congeners was 6.4014 µg/m3 with more than 65% below tetra-chlorinated biphenyls which are the most harmful and persistent. An increment in the sludge (peat) ratio caused the content of SOx to decrease drastically, while the content of NOx exhibited two maxima. The heavy metal concentrations of Cd, Zn, Mn, Pb, Fe, Ni, Cr, and Cu decreased with increasing sludge ratio. The leaching toxicity of heavy metals in the bottom ash proved to be lower than the limit values for hazardous waste. The PCDD/F 1-TEQ emissions of the flue gas increased from 0.06844 to 0.10779 ng/m3 as the proportion of sludge increased in peat. The I-TEQ values of the PCDD/Fs showed a slight increment with increasing sludge ratio. The sum of the PCDD/Fs (ideally at 20-30%) does not exceed the 0.1ng/Nm3 of the EU and the 0.5 ng TEQ/Nm3 of the new Chinese emissions standard. Statement of novelty Different calorific values of coal of different proportions were incinerated with wet printing and dyeing sludge in order to achieve the new allowable gas emission limits, tap heat energy and eliminate high cost.