High Treatment Efficiency Research Articles

Growth of microalgae and cyanobacteria consortium in a photobioreactor treating liquid anaerobic digestate from vegetable waste

This research examines the biological treatment of undiluted vegetable waste digestate conducted in a bubble column photobioreactor. Initially, the bioreactor containing 3N-BBM medium was inoculated with Microglena sp., Tetradesmus obliquus, and Desmodesmus subspicatus mixture with a density of 1.0 × 104 cells/mL and the consortium was cultivated for 30 days. Then, the bioreactor was semi-continuously fed with liquid digestate with hydraulic retention time (HRT) of 30 days, and the treatment process was continued for the next 15 weeks. The change in the microalgal and cyanobacterial species domination was measured in regular intervals using cell counting with droplet method on a microscope slide. At the end of the experiment, Desmonostoc sp. cyanobacteria (identified with 16S ribosomal RNA genetical analysis) as well as Tetradesmus obliquus green algae along with Rhodanobacteraceae and Planococcaceae bacteria (determined with V3–V4 16sRNA metagenomic studies) dominated the microbial community in the photobioreactor. The experiment demonstrated high treatment efficiency, since nitrogen and soluble COD were removed by 89.3 ± 0.5% and 91.2 ± 1.6%, respectively, whereas for phosphates, 72.8 ± 2.1% removal rate was achieved.

Amino-functionalized UiO-66-doped mixed matrix membranes with high permeation performance and fouling resistance

For the reduction of bovine serum proteins from wastewater, a novel mixed matrix membrane was prepared by functionalizing the substrate material polyaryletherketone (PAEK), followed by carboxyl groups (C-SPAEKS), and then adding amino-functionalized UiO-66-NH2 (Am-UiO-66-NH2). Amino-functionalization of UiO-66 was accomplished by melamine, followed by an amidation reaction to immobilize Am-UiO-66-NH2, which was immobilized on the surface of the membrane as well as in the pore channels, which enhanced the hydrophilicity of the membrane surface while increasing the negative potential of the membrane surface. This nanoparticle-loaded ultrafiltration membrane has good permeation performance, with a pure water flux of up to 482.3 L·m−2·h−1 for C-SPAEKS/Am-UiO-66-NH2 and a retention rate of up to 98.7% for bovine serum albumin (BSA)-contaminated solutions. Meanwhile, after several hydrophilic modifications, the flux recovery of BSA contaminants by this series of membranes increased from 56.2% to 80.55% of pure membranes. The results of ultrafiltration flux time tests performed at room temperature showed that the series of ultrafiltration membranes remained relatively stable over a test time of 300 min. Thus, the newly developed mixed matrix membrane showed potential for high efficiency and stability in wastewater treatment containing bovine serum proteins.

Hybrid Membrane Camouflaged Chemodrug-Gene Nanoparticles for Enhanced Combination Therapy of Ovarian Cancer.

Recently, cell membrane camouflaged nanoparticles (NPs) endowed with natural cellular functions have been extensively studied in various biomedical fields. However, there are few reports about such biomimetic NPs used to codeliver chemodrug and genes for synergistic cancer treatment up to now. Herein, we first prepare chemodrug-gene nanoparticles (Mito-Her2 NPs) by the electrostatic interaction coself-assembly of mitoxantrone hydrochloride (Mito) and human epidermal growth factor receptor-2 antisense oligonucleotide (Her2 ASO). Then, Mito-Her2 NPs are coated by a hybrid membrane (RSHM), consisting of the red blood cell membrane (RBCM) and the SKOV3 ovarian cancer cell membrane (SCM), to produce biomimetic chemodrug-gene nanoparticles (Mito-Her2@RSHM NPs) for combination therapy of ovarian cancer. Mito-Her2@RSHM NPs integrate the advantages of RBCM (e.g., good immune evasion capability and long circulation lifetime in the blood) and SCM (e.g., highly specific cognate recognition) together and improve the anticancer efficacy of Mito-Her2 NPs. The results show that Mito-Her2@RSHM NPs can be devoured by SKOV3 ovarian cancer cells and effectively degraded to release Her2 ASOs and Mito simultaneously. Her2 ASOs can inhibit the expression of endogenous Her2 genes and recover cancer cells' sensitivity to Mito, which ultimately led to a high apoptosis rate of 75.7% in vitro. Mito-Her2@RSHM NPs also show a high tumor suppression rate of 83.33 ± 4.16% in vivo without significant damage to normal tissues. In summary, Mito-Her2@RSHM NPs would be expected as a versatile and safe nanodrug delivery platform with high efficiency for chemo-gene combined cancer treatment.

Iodate(V) activated ferrate(VI) for enhanced oxidation of micropollutants from water and sediment media

In this study, a new Fe(VI)/I(V) system was developed to efficiently strengthen utilization efficiency of generated Fe(IV)/Fe(V). This system could effectively degrade sulfamethoxazole, carbamazepine, bisphenol A and tetracycline within 4 min with k1 values of 0.60648 min−1, 1.39726 min−1, 0.65921 min−1 and 0.93298 min−1, which were 21–66 times higher than the sum of k1 values of I(V) alone and Fe(VI) alone systems, and also much better than H2O2, peroxydisulfate, and peroxymonosulfate strengthened Fe(VI) systems. In addition, Fe(VI)/I(V) exhibited favorable anti-interference, that high-salinity and high organic showed negligible inhibition on pollutant degradation. More importantly, I(V), as an excellent catalyst, hardly decayed during treatment process, which broadens the application field of Fe(VI)/I(V) in different contaminated environmental media and provides a distinguished efficiency for recycling use in contaminated sediment with only consumed Fe(VI) supplement. Fe(VI) consumption in Fe(VI)/I(V) system was not enhanced compared with Fe(VI) alone system, and thus saving agent costs is another significant advantage of Fe(VI)/I(V) system. Above multiple superiorities are still obvious even compared with the systems of other oxidants enhancing Fe(VI) developed in recent years. The main active species was identified as Fe(IV)/Fe(V). The mechanisms of I(V) strengthening Fe(VI) were determined as Fe(IV)/Fe(V) oxidation enhancement, rather than Fe(VI) decay enhancement. Utilization efficiency of Fe(IV)/Fe(V) was improved by oxidation reactivity modulation with I(V) complexes formation, thereby strengthening decontamination significantly. This study proposed a strategy for decontamination in different mediums with high treatment efficiency, high selectivity, satisfactory reusability, and low consumption of agents.

Optimization of Ceramic Filter for Greywater Treatment by using Horizontal Flow Constructed Wetland

Wetland technology is an effective and sustainable treatment process that relies on a combination of components. Media components, which vary based on the material used, play an important role in this technology. Ceramic-based filters are a natural and versatile water filtration method that can be used in combination with wetland systems to create a simple, low-cost, and efficient wastewater treatment technology. The aim of this study was to assess the performance and efficiency of two experimental scale horizontal flow constructed wetlands (HFCW) as a secondary stage for the treatment of household greywater. This was achieved by examining the untreated and treated greywater characteristics; evaluating the effectiveness of planted wetlands with ceramic addition in removing chemical oxygen demand (COD), biological oxygen demand (BOD5), nutrients, total suspended solids (TSS), and coliforms from the greywater; and monitoring the adaptation and growth of Bacopa monnieri L. in the treatment systems. The results showed that both treatment systems significantly improved all the greywater characteristics. The use of ceramic, gravel, and plants in wetlands enhanced the removal efficiency of Mg+2, TDS, and total hardness (TH). A higher treatment efficiency was observed in the ceramic-gravel bed than in the gravel bed.

Exploring optimal settings for safe and effective thulium fibre laser lithotripsy in a kidney model.

To explore the optimal laser settings and treatment strategies for thulium fibre laser (TFL) lithotripsy, namely, those with the highest treatment efficiency, lowest thermal injury risk, and shortest procedure time. An in vitro kidney model was used to assess the efficacy of TFL lithotripsy in the upper calyx. Stone ablation experiments were performed on BegoStone phantoms at different combinations of pulse energy (EP ) and frequency (F) to determine the optimal settings. Temperature changes and thermal injury risks were monitored using embedded thermocouples. Experiments were also performed on calcium oxalate monohydrate (COM) stones to validate the optimal settings. High EP /low F settings demonstrated superior treatment efficiency compared to low EP /high F settings using the same power. Specifically, 0.8 J/12 Hz was the optimal setting, resulting in a twofold increase in treatment efficiency, a 39% reduction in energy expenditure per unit of ablated stone mass, a 35% reduction in residual fragments, and a 36% reduction in total procedure time compared to the 0.2 J/50 Hz setting for COM stones. Thermal injury risk assessment indicated that 10 W power settings with high EP /low F combinations remained below the threshold for tissue injury, while higher power settings (>10 W) consistently exceeded the safety threshold. Our findings suggest that high EP /low F settings, such as 0.8 J/12 Hz, are optimal for TFL lithotripsy in the treatment of COM stones. These settings demonstrated significantly improved treatment efficiency with reduced residual fragments compared to conventional settings while keeping the thermal dose below the injury threshold. This study highlights the importance of using the high EP /low F combination with low power settings, which maximizes treatment efficiency and minimizes potential thermal injury. Further studies are warranted to determine the optimal settings for TFL for treating kidney stones with different compositions.

Biodegradation of human faecal sludge for photosynthetic bioelectricity generation and seawater desalination in a microbial desalination cell

ABSTRACT Inaccessibility and expensiveness of vital infrastructures are the main problems in some urban and rural areas to supply fresh water, sustainable energy, and wastewater treatment. An effective solution is the integration of several systems in an environmentally friendly technology of the photosynthetic microbial desalination cell (PMDC). The aim of this study is to assess the process characterisation of an algae-based PMDC, which was loaded with a high-strength mixture of human feces and urine (HFS). The PMDC was also able to efficiently remove COD and total nitrogen of HFS by 50% and 94%, respectively. The maximum power density, voltage, and desalination efficiency of 362.5 mW/m², 175.2 mV, and 60% were accomplished. Adequate parameter adjustment led to a remarkable maximum of 2.25 g/L.d in the ion removal rate. In addition, an energy balance was governed showing that zero or positive net energy in PMDC is feasible by replacing the main energy consumers. Based on the results, this type of MDC had a high efficiency for simultaneous saline water desalination and HFS treatment, which makes it attractive for further studies of upscaling and its application in remote areas.

Synergetic treatment of waste tantalum capacitors and polyvinyl chloride by subcritical water: Tantalum recovery, benzoic acid production and dechlorination

The rapid upgrading of electronic products led to the generation of a great deal of waste tantalum capacitors (WTCs). The recovery of WTCs is of great interest due to the high-value metal tantalum and resin materials. However, it is difficult to separate/recover the materials from WTCs because of the special structure and composition. Polyvinyl chloride (PVC) waste with high level of chlorine could result in severe corrosion and emission of chlorinated pollutants in the conventional disposal process. In this study, a synergetic and high-efficiency treatment of WTCs and PVC by subcritical water (SubCW) process was developed based on the interaction of the two kinds of wastes. The interaction between WTCs and PVC in SubCW could significantly reduce the treatment temperature and shorten the reaction time for recovering high-purity metal tantalum from WTCs, and it could also markedly improve the dechlorination efficiency (DE) of PVC. The optimized conditions for the synergetic treatment of WTCs and PVC were 325 ℃, 30 min, solid-to-liquid ratio of 1:5 g/mL, and PVC-to-WTCs ratio of 6:1 g/g. The resin conversion efficiency (RCE) of WTCs and the DE of PVC could reach 100% and 97.39% under the optimized conditions. The HCl released from PVC in SubCW could significantly promote the acid-catalytic hydrolysis of resin materials in WTCs and resulted in the production of abundant phenol/phenol derivates. In turn, hydroxyl functional group of phenol/phenol derivates could enhance the dechlorination of PVC by promoting the hydroxyl substitution reaction pathway. High level of benzoic acid (72.52%) could be obtained from the interaction between the decomposition products of WTCs and PVC by radical and oxidation reactions. The SubCW synergetic process developed in this study provided a high-efficiency and low-energy strategy for metal tantalum recovery, benzoic acid production, and dechlorination from WTCs and PVC wastes.

Enhancing biochar structure and removal efficiency of ammonium and microalgae in wastewater treatment through combined biological and thermal treatments

This study explored the efficiency of biological pre-treatment combined with thermal treatment to produce biochars, called E-biochars, for the removal of ammonium and microalgae without using chemical pre-treatment. The aim was to develop an environmentally sustainable approach for large-scale biochar production with high efficiency in wastewater treatment. The biological pre-treatment involved incubating the sawdust with Bacillus subtilis for 14 to 20 days and then subjected to pre-treatment at low temperatures (250-350 °C). This process broke down cellulose and altered its lignocellulosic structure, improving the biochar's morphology by leading to a more anisotropic pore structure. The thermal pre-treatment after that will help to open a broader range of pore sizes, spanning from macropores to micro-pores in the 1 μm to 5 μm dimension range. These alterations facilitated the efficient removal of ammonium and microalgae during adsorption experiments. The findings fit the Langmuir and the Freundlich models, according to the isotherm test of NH4+ and microalgae (R2 = 0.92÷0.99). The E-biochar termed EBH20, composted with Bacillus subtilis for 20 days at 350 °C, performed best, with Qmax equal to 40.2 mg/ g NH4+ under neutral conditions (pH = 7). Interestingly, the co-occurrence of ammonium and microalgae enhanced the removal of these contaminants. The interaction between microalgae cells and ammonium facilitated ammonium adsorption onto biochar and microalgae. The column breakthrough curves under NH4+ and NH4+ mixed microalgae adsorption were predicted using the Thomas model with the high agreement (R2 = 0.91÷0.99) for ammonium but for algae between prediction and running experimental column data.

High-efficient treatment of 4-nitrophenol wastewater in an upflow bubbling fluidized bed reactor based on Pickering emulsion

The Pickering emulsion continuous flow catalytic system is widely applied in chemical synthesis and catalytic reaction. However, the traditional system generally adopts top feeding method resulting in the tight bed, which greatly limits the flow and transport of reactant. Herein, a upflow bubbling fluidized bed reactor based on Pickering emulsion is successfully constructed to the treatment of 4-nitrophenol wastewater. Here, the stable and efficient O/W Pickering emulsion in the bed reactor benefits from the preparation of an emulsifier with highly active interfacial catalyst (Pd@SiO2). The flow configuration from bottom to top and H2 bubbles from the hydrolysis of NaBH4 can produce the obvious looseness of bed with Pickering emulsion in the continuous flow system, improving the flow and transport of reactant to catalyst surface and the reaction performance. Under the condition of low catalyst loading (0.2 wt%), the conversion of high concentration 4-NP (1 mM) wastewater remains more than 98.5 % for 60 h constantly, demonstrating the excellent catalytic efficiency of the bubbling fluidized bed reactor. Results show that a continuous flow catalytic system with the new flow configuration yields outstanding performance for wastewater treatment.

Catalytic valorization of Kraft lignin into feedstock chemicals with methyltrioxorhenium (MTO) catalyst in microbial electrochemical cell

In this study, the authors investigate a novel approach to valorize Kraft lignin using the catalyst Methyltrioxorhenium (MTO) in tandem with in-situ produced H2O2 in a Microbial Electrochemical Cell (MEC). This study demonstrates the in-situ oxidation of Kraft lignin using different concentrations of MTO catalyst (2 mM to 8 mM) and H2O2 (5.24 ± 0.40 mM to 8.91 ± 0.70 mM) in three MECs. The depolymerized Kraft lignin samples were characterized using FTIR, CHNS/O, and 1H NMR analysis. The MTO/H2O2 combination showed high selectivity towards the oxidation of Kraft lignin, resulting in both aromatic ring and side chain cleavage reactions and the production of valuable feedstock chemicals. The oxidation also led to a reduction of 68.42 % to 78.18 % in Chemical Oxygen Demand (COD) of lignin. The selective oxidation favored the recovery of Guaiacyl (G) unit-derived feedstock chemicals, with Guaiacol being the most abundant compound (45.04 mg/mL) among the quantified products by HPLC. Additionally, the system demonstrated high efficiency in anodic wastewater treatment, achieving BOD and COD removal rates ranging from 67.68 % to 72.55 %. This method showcases the use of a sustainable system in combination with a selective catalyst to produce valuable products from usually discarded Kraft lignin while simultaneously treating wastewater.

Synthesis of alkoxyphenols-rich bio-oil by microwave-assisted catalytic pyrolysis of wood over MoS2 catalyst

Microwave-assisted pyrolysis (MAP) is widely concerned as a high-efficiency treatment of forestry solid waste to produce value-added products. In this study, alkoxyphenols-rich bio-oil was selectively produced from wood powder through MAP process using self-made MoS2 catalysts. First of all, the yield of bio-oil was selectively controlled by changing the process parameters of microwave power, temperature and catalyst weight content. Under the conditions of 1200 W, 600 °C and 10 wt% of catalyst to feedstock, an optimal bio-oil yield of 54.3 wt% was achieved over the MoS2 catalysts. Notably, compared with commercial MoS2-catalyzed and non-catalyzed MAP, the self-made MoS2-catalyzed process realized the improvement for the content of both general phenol species and specific alkoxyphenols component, reaching up to 90.1 % and 77.3 %, respectively at 1200 W, 600 °C and 10 wt% of catalyst to feedstock, which was superior to most of the previously reported candidates. The contrast experiment evidenced the bifunctional roles of MoS2 as both microwave absorbent and catalyst. It could not only promote the production of bio-oil but also inhibit the carbonization, selectively upgrade non-condensable gas to bio-oil, and simultaneously limit the second pyrolysis of alkoxyphenols, which jointly leads to the efficient synthesis of alkoxyphenols-rich bio-oil. This work provides guidance for producing phenols-rich bio-oil and other highly value-added products through the microwave-assisted catalytic pyrolysis of biomass over transition metal dichalcogenides materials.

Effects of phytohormone on Chlorella vulgaris grown in wastewater-flue gas: C/N/S fixation, wastewater treatment and metabolome analysis

Chlorella vulgaris (C. vulgaris) can provide the means to fix CO2 from complicated flue gas, treat wastewater and reach a sustainable production of petrochemical substitutes simultaneously. However, a prerequisite to achieving this goal is to promote C. vulgaris growth and improve the CO2-to-fatty acids conversion efficiency under different conditions of flue gas and wastewater. Thus, the addition of indole-3-acetic acid (IAA) in C. vulgaris cultivation was proposed. Results showed that C. vulgaris were more easily inhibited by 100 ppm NO and 200 ppm SO2 under low nitrogen (N) condition. NO and SO2 decreased the carbon (C) fixation; but increased N and sulfur (S) fixation. IAA adjusted the content of superoxide dismutase (SOD) and malondialdehyde (MDA), improved the expression of psbA, rbcL, and accD, attenuated the toxicity of NO and SO2 on C. vulgaris, and ultimately improved cell growth (2014.64–2458.16 mgdw·L−1) and restored CO2 fixation rate (170.98–220.92 mg CO2·L−1·d−1). Moreover, wastewater was found to have a high treatment efficiency because C. vulgaris grew well in all treatments, and the maximal removal rates of both N and phosphorus (P) reached 100%. Metabonomic analysis showed that IAA, “NO and SO2” were involved in the down-regulated and up-regulated expression of multiple metabolites, such as fatty acids, amino acids, and carbohydrates. IAA was beneficial for improving lipid accumulation with 24584.21–27634.23 μg g−1, especially monounsaturated fatty acids (MUFAs) dominated by 16–18 C fatty acids, in C. vulgaris cells. It was concluded that IAA enhanced the CO2 fixation, fatty acids production of C. vulgaris and its nutrients removal rate.

The effectiveness of a new antiviral drug of plant origin in the form of eye drops in the complex therapy of ophthalmic herpes

Ophthalmic herpes is the most common infection-related cause of blindness in developing countries.Purpose: to evaluate the therapeutic efficacy, safety and tolerability of the drug Panavir® used as part of a combination therapy for herpetic superficial dendritic keratitis.Materials and methods. The study involved 106 patients aged 18 to 65 years divided into two groups. Group 1 (54 patients; 54 eyes) received treatment with Panavir® and Acyclovir ophthalmic ointment, whilst Group 2 (52 patients; 52 eyes) received a placebo of Panavir® and Acyclovir ophthalmic ointment. The primary parameter of the efficiency was the percentage of patients achieving clinical recovery, i.e. signs of complete epithelialization of the cornea.Results. In group 2 (monotherapy), a significantly greater number of patients with mild conjunctival hyperemia was registered than in the combination therapy group 1 — 59.26 vs. 23.08 %, p < 0.001. In group 1, the proportion of patients without corneal syndrome at visits 3 and 4 was, respectively, 11.11 and 61.11 %, while in group 2 it was only 3.85 and 19.61 %, respectively.Conclusion. The drug Panavir® eye drops 0.004 % showed a high therapeutic efficiency in the combined treatment of herpetic keratitis, and good tolerance. It also reduced the time required for corneal epithelialization and conjunctiva normalization.

Anaerobic digestion of thickened secondary sludge after microwave advanced oxidation pretreatment

A microwave-enhanced advanced oxidation process (MW-AOP) was used to treat thickened waste secondary sludge prior to anaerobic digestion (AD). A large amount of soluble chemical oxygen demand (SCOD) and volatile fatty acids (VFAs) was formed in the solution after pretreatment. Both single- and two-phase systems loaded up to 18.2 g volatile solids/(l day) while achieving high methane production, as well as high overall treatment efficiency. Both the upflow anaerobic blanket reactor and the continuous stirred tank reactor could operate at very short hydraulic retention times as short as 2 days without any evidence of souring. The results indicated that an acid reactor in the two-phase system was not required, due to very high levels of SCOD and VFAs produced in the MW-AOP-pretreated solution. As such, a single AD should be able to handle this easily biodegradable substrate following microwave pretreatment.

NO/SO2/HCl emissions from solid waste combustion via oxygen-carrier-aided combustion in rotary kiln

Rotary kiln incineration technology has become an important approach to achieve the harmless, reduced, and resourceful solid waste (SW) due to its wide range of fuel adaptability and high treatment efficiency. SW incineration through oxygen carrier (OC) aided combustion in the rotary kiln shows significant advantages in improving SW conversion and reducing CO emission. However, the impacts of introducing OC into the rotary kiln on the emissions of NO, SO2, and HCl, are still unknown. This research objective was to investigate the effects of OCs on the emission characteristics of NO, SO2, and HCl. Natural manganese and ilmenite ores as OCs, are added to a continuous-feeding rotary kiln during the combustion of biomass SW and hazardous SW. The results show that the introduction of OCs can significantly improve the uniformity of oxygen distribution in the furnace, and promotes the conversion of fuel N to NO. At high temperatures and low oxygen concentrations range, the reduction rate of NO by high-concentration CO or catalytic reduction by char and ash is faster than the oxidation of fuel N by OCs, which decreases NO concentration. Moreover, at high temperatures, when OCs are distributed in the bed of the rotary kiln, the fuel in the oxygen-poor zone can obtain O2 or lattice oxygen from the OCs, which promotes the decomposition and oxidation of S-containing compounds in fuels and increase the SO2 concentration. In addition, OCs in the bed provide more reaction sites for fuel conversion and promote the release of Cl as HCl at high temperatures. Specifically, during the oil sludge combustion at 900 °C, compared with the inert reference case, the addition of ilmenite ore increased the concentrations of NO, SO2, and HCl by 47.44%, 64.87%, and 20.28%, respectively, which is attributed to the better reactivity and redox cycle stability of ilmenite ore. This study highlights the potential of OC-aided combustion in rotary kilns as an approach to regulate SW combustion and offers a foundation for the future related research.

Electrochemical oxidation of phenol in a PtRu/NbC membrane-based catalytic nanoreactor

Electrochemical oxidation has attracted growing attention to treat organic in wastewater. However, achieving a high reactor efficiency and harmless treatment of the toxic organics is still a significant challenge. In this work, the bimetal Pt and Ru were firstly co-electrodeposited on the surface of nanoporous niobium carbide (NbC) membranes (∼8.3 nm pore size) applying for anode in flow-through reactor for phenol electrochemical oxidation. In a continuous flow-through reactor, the single-pass removals of phenol and chemical oxygen demand (COD) were 99.7 % and 74.2 %, respectively, with a short hydraulic retention time of 342 s, demonstrating rapid phenol degradation that is an order of magnitude shorter than those reported in other studies. This excellent reactor efficiency was ascribed to a large interfacial reaction area providing by the pollutant phase-catalytic membrane-green product phase. We compared the mass transfer of flow-through and flow-by reactor testifying the high efficiency of flow-through reactor. The excellent stability of PtRu/NbC anode enable this reactor to operate 50 h stably. Moreover, the presence of low or non-toxic (catechol and acetic acid) as the residues of phenol degradation resulting from the contribution of synergistic reaction between direct and indirect oxidation process.

Advanced degradation of refractory organic compounds in electroplating wastewater by an in-situ electro-catalytic biological coupling reactor: Removal performance, microbial community and possible mechanism

A high-efficiency treatment system for advanced degradation of refractory organic compounds such as saccharin sodium (SS) and polyethylene glycol 6000 (PEG 6000) in electroplating wastewater was proposed, which coupled ion exchange, electrocatalysis, and microbial interactions through ion exchange particle electrode (IEPE) in a reactor, named in-situ electro-catalytic biological coupling reactor (i-SECBCR). A small-scale experimental test system was established and a feasibility investigation was conducted under the condition of 1.248 L/h continuous flow. The results revealed that (1) the i-SECBCR showed higher average removal rates of SS, PEG 6000, COD and NH4+-N, i.e. 88.48 %, 41.26 %, 66.81 % and 51.61 %,which meant an increase by 5.04 %, 12.05 %, 0.46 %, and 34.50 %, respectively, compared with BAF; (2) the optimal current intensity (CI) of i-SECBCR for simultaneous removal of SS, PEG 6000, COD and NH4+-N was 0.40 mA cm−2; (3) Rhodobacter, Defluviimonas, unclassified_f__Microscillaceae, Pseudoxanthomonas, Novosphingobium, and unclassified_f__Xanthobacteraccae accounted for the main bacterial community in i-SECBCR; (4) the possible degradation mechanism was attributed mainly to the synergistic effect of ion exchange, electrocatalytic oxidation and biology. Therefore, the i-SECBCR was suitable to simultaneously advanced remove SS, PEG 6000, COD and NH4+-N in electroplating wastewater.

Research progress on using biological cathodes in microbial fuel cells for the treatment of wastewater containing heavy metals.

Various types of electroactive microorganisms can be enriched to form biocathodes that reduce charge-transfer resistance, thereby accelerating electron transfer to heavy metal ions with high redox potentials in microbial fuel cells. Microorganisms acting as biocatalysts on a biocathode can reduce the energy required for heavy metal reduction, thereby enabling the biocathode to achieve a lower reduction onset potential. Thus, when such heavy metals replace oxygen as the electron acceptor, the valence state and morphology of the heavy metals change under the reduction effect of the biocathode, realizing the high-efficiency treatment of heavy metal wastewater. This study reviews the mechanisms, primary influencing factors (e.g., electrode material, initial concentration of heavy metals, pH, and electrode potential), and characteristics of the microbial community of biocathodes and discusses the electron distribution and competition between microbial electrodes and heavy metals (electron acceptors) in biocathodes. Biocathodes reduce the electrochemical overpotential in heavy metal reduction, permitting more electrons to be used. Our study will advance the scientific understanding of the electron transport mechanism of biocathodes and provide theoretical support for the use of biocathodes to purify heavy metal wastewater.

Removing nutrients in recirculating aquaculture system wastewater from Nile tilapia culture via Spirulina cultivation: Optimizing sodium bicarbonate concentration and micronutrient supplementation

Recirculating aquaculture system (RAS) wastewater from Nile tilapia (Oreochromis niloticus) culture raises environmental concerns, necessitating proper treatment prior to discharge. Phytoremediation using Spirulina offers a promising solution by enabling the simultaneous removal of nutrients from wastewater while also producing valuable biomass. This study aimed to optimize the sodium bicarbonate (NaHCO3) concentrations (3.36, 8.40, and 16.80 g/L) for achieving maximum nutrient treatment efficiency and Spirulina production in RAS wastewater from Nile tilapia culture, without external nitrogen and phosphorus supplementation. Additionally, this study examined the effect of different concentrations of nitrate (10 to 120 mg NO3-N/L) that are naturally present in RAS wastewater and Zarrouk's micronutrient supplementation on Spirulina production and nutrient treatment efficiency. The optimal NaHCO3 concentration for achieving maximum Spirulina production and effective nutrient treatment efficiency was found to be 8.40 g/L. At this concentration, high nitrate treatment efficiencies, reaching up to 80%, were observed specifically in RAS wastewater containing 10 to 50 mg NO3-N/L, while excellent phosphate treatment efficiencies, up to 99%, were found across all nitrate concentrations. Moreover, Spirulina biomass (X) reach a saturated growth of 0.398 g DW/L (6.09 mg Chl a/L) in RAS wastewater with a nitrate concentration of 50 to 120 mg NO3-N/L. Furthermore, the Pearson correlation coefficients revealed that the factor determining Spirulina growth in RAS wastewater with nitrate 10–50 mg NO3-N/L was nitrate, whereas in RAS wastewater with nitrate 80–120 mg NO3-N/L, it was NaHCO3. By supplementing Zarrouk's micronutrient at 25% to RAS wastewater containing 120 mg NO3-N/L and 16.80 g/L of NaHCO3, Spirulina biomass could be enhanced to reach 1.525 g DW/L (6.09 mg Chl a/L), while achieving a nitrate treatment efficiency of 86%.