Industrial Wastewater Research Articles

Associative analysis of sludge microbiota and wastewater degradation efficacy within swine farm sludge systems

Industrial wastewater management is a significant global challenge. Sludge microbiota from swine farms may play a crucial role in enhancing wastewater treatment processes, thereby reducing water pollution from industrial activities. A deeper understanding of this complex community could lead to innovative approaches for improving wastewater treatment methods. Sludge samples were collected from the anaerobic, sedimentation, and thickening tanks of ten swine farms. The microbiota communities were analyzed using 16S rRNA full-length sequencing on the PacBio platform, with subsequent data analysis conducted on the QIIME2 platform utilizing the SILVA database. Compared to anaerobic and thickening tanks, the sedimentation tanks exhibited a unique profile of sludge microbiota, with higher abundances of the phyla Proteobacteria, Bacteroidota, and Caldatribacteriota. Additionally, sludges from farms already utilized in processing industrial water—specifically farms B, G, and J—contained higher concentrations of bacteria (>20 ng/μL), indicating the robustness of the bacterial load for practical industrial use. Furthermore, sludge from farms with higher alpha diversity, such as E, G, I, and J, exhibited enriched degradation profiles, including the degradation of aromatic compounds, polymers, industrial compounds, toluene, and vanillin. The farms were categorized based on wastewater ammonia nitrogen degradation levels, revealing a clustering effect of the microbiota from the sedimentation tanks in the Principal Coordinates Analysis (PCoA) plot. A higher relative abundance of the families Rhodocyclaceae, AKYH767, and Comamonadaceae, and a lower abundance of the families Anaerolineaceae and Christensenellaceae, were found in groups with high ammonia nitrogen reduction, suggesting potential targets for bioaugmentation strategies. In conclusion, this study underscores the critical role of microbial abundance, composition, and biodiversity in optimizing wastewater treatment and advocates for comprehensive microbiota analysis to identify suitable sludge for industrial applications.

Controlling synthesis of defect state lignin-derived carbon and application for U(VI) removal from aqueous solution: Effects of oxygen-defect and grain-size

Lignin has deemed to be the main polluting component of paper industry wastewater. But developing a potential strategy for utilization of lignin is a challenges problem. Lignin derived materials present potential performance for heavy metal wastewater treatment due to their unique physicochemical properties, and were found to be promising candidate materials in U(VI) removal. However, it is still lacking of a comprehensive understanding that the influences of surface oxygen-defect and grain-size on U(VI) removal processes. Here, using lignin as the raw material, combining plasma treatment technology to prepare defect states Lignin Derived Carbon (LDC), and exploring the influences of surface oxygen-defect and grain-size on their removal U(VI) process. The results indicated that with the reducing of LDC particle size (from ∼4 to ∼ 1 μm), the removal performance of U(VI) was improved. And the U(VI) removal performance of LDC was further improved by introducing of oxygen defect via H2 plasma etch. The characterization analysis of defect states LDC before and after reaction with U(VI) shown that the U(VI) removal mechanism was dominated by defects site complexation. These finding provide deep insight into the recycling of industrial solid wastes lignin and improving of U(VI) removal performance via defect controlling technology.

A sustainable lignin-clay nano-absorbent for highly efficient methylene blue removal

Water pollution caused by toxic dyes such as methylene blue (MB) has become a bottleneck for recycling or reusing enormous industrial wastewater. Designing a green and cost-effective bio-absorbent for the highly efficient removal of MB from wastewater is crucial but remains a great challenge. In this study, abundant, inexpensive, and environmentally benign lignin and bentonite were used as starting materials, and quaternary and amphiphilic lignin as a network macromolecule was designed to be inserted into the galleries of the stacked bentonite clay to prepare lignin-bentonite nanohybrids. The specific surface area of the modified nano-absorbent was significantly increased to 45.60 m2/g and owned a type II-like isothermal mechanism. The absorbent showed a maximum removal of MB of 99.7 % at neutral pH and room temperature with a maximum adsorption capacity of 822.22 mg/g, demonstrating the potential of an excellent adsorbent. The MB adsorption process fits well with both Langmuir and Freundlich isotherm models, the adsorption mechanism includes strong electrostatic attraction between absorbent and MB, and physical adsorption in a complicated monolayer and multiple macroporous structures. This study leverages the economic and environmental benefits of lignin and bentonite clay to prepare a cost-effective bio-absorbent for efficient removal of MB from aqueous solutions.

The adsorption of p-hydroxybenzoic acid on graphene oxide under different pH and in-situ desorption in direct current electric field

The development and ongoing optimization of measures to reduce and eliminate p-hydroxybenzoic acid (p-HBA) in industrial wastewater are significant due to its potential carcinogenic effect and bio-recalcitrant. Graphene oxide (GO) is an ideal adsorbent for removing aromatic acids and achieving adsorbent recovery and resource conservation. In this study, the adsorption properties of p-HBA onto GO at different pH values and the regeneration mechanism of adsorbent under varying electric field intensities were analyzed using molecular dynamics (MD) simulation. The simulation results demonstrate that GO exhibits preferable adsorption capabilities for p-HBA at low pH, and van der Waals (vdW) interaction plays a leading role. However, the adsorption stability decreases at high pH (particularly pH > 9.3) with most p-HBA desorption from the GO surface. When an electric field of 1.0 V/nm is applied to the acidic system (HGO_HBA_HBA−), the total adsorption interaction energy between GO and p-HBA decreases but remains high (−1836.93 kJ/mol). When a 0.6 V/nm electric field is added to the alkaline system (GO2−_HBA2−), the vdW and electrostatic interaction energies are recorded as −35.34 kJ/mol and 3546.97 kJ/mol. The vdW interaction is weak, and electrostatic repulsion increases, facilitating the desorption of p-HBA from the GO surface. This work aims to share insights into the microscopic removal mechanism of p-HBA on the GO surface under different pH values and provide a theoretical perspective on the regeneration mechanism of GO.

Metal‐Organic Framework (Cu@ZIF) for Photocatalytic Reduction of p‐Nitrophenol and its Toxicological Evaluation using Zebrafish (Danio Rerio)

AbstractGlobal food security depends on agricultural development, yet excessive fertilizer and pesticide usage is harmful to the environment. These substances have a role in human health problems, environmental changes, and erosion of the soil. Although p‐nitrophenol, an organic pollutant and other organophosphorous compounds are utilised in agriculture, their usage raises major health and environmental issues. These synthetic pesticides are quite effective at getting rid of pests, but they have also been linked to serious health problems for people and animals, degraded soil, and contaminated water. One typical persistent pollutant present in industrial wastewater is the organic pollutant, which is produced by organophosphorous compounds. The primary objective of this work is to use Cu@ZIF for photoreduction of p‐nitrophenol (PNP). A UV‐visible spectrophotometer test revealed that the deterioration peak after 60 mins. An analyzer for total organic carbon (TOC) was utilised to assess the PNP mineralization. The catalyst remained same and continued in the same behaviour even after four cycles. This study evaluated the acute toxicity of PNP on the development of early‐stage zebrafish, paying particular attention to the embryonic developmental deformities. The technique of photocatalytic decontamination is safe for the environment, financially practical, and technically achievable.

Construction and structural of p-CeCuO3/n-CeO2 hybrid nanostructures for the photocatalysis driven by LED light system and industrial textile wastewater remediation

The application of photocatalytic nanomaterials in industrial wastewater is essential for removing toxic dyes. To address this issue, various noble single nanomaterials (CeCuO3 and CeO2) and CeCuO3/CeO2 were synthesized using a chemical method. These nanomaterials were characterized through advanced analytical techniques. The degradation response was evaluated by the removal of methyl orange dye solution with a wastewater sample. Among the materials tested, CeCuO3/CeO2 showed superior performance, achieving high degradation efficiencies for methyl orange (95.72%) solutions compared to CeO2 and CeCuO3. This efficiency is primarily attributed to the formation of a high-quality heterojunction between CeCuO3 and CeO2, which enhances charge carrier transfer and the separation of generated electron-hole pairs, thereby significantly improving catalytic performance. The investigation into the effects of reactive species confirmed the critical roles of •OH and •O2– species in the dye removal process. Furthermore, recyclability tests indicated that the excellent reusability properties of CeCuO3/CeO2 nanocomposites.

Simplex-lattice design and decision tree optimization of endophytic Trichoderma-multi-walled carbon nanotube composite for enhanced methylene blue removal

This study investigates a novel approach for enhancing methylene blue (MB) removal from water using a composite of endophytic Trichoderma mate and multi-walled carbon nanotubes (MWCNTs). For the first time, a unique combination of simplex-lattice design and decision tree learning algorithm was employed to optimize MB removal. This innovative approach effectively identified the optimal composite ratio of hyphal mate (0.5354 g/L) and MWCNTs (0.4646 g/L) for maximizing MB removal, which achieved remarkable removal efficiency ranging from 63.50 to 95.78 % depending on the combination used. The DT model further demonstrated promising potential for predicting MB removal efficiency. SEM revealed a unique hybrid material formed by the intertwining or entrapment of MWCNTs within the hyphal network of Trichoderma mate. FT-IR analysis confirmed the presence of novel functional groups on the MWCNTs' surface at 2438.79 and 528.25 cm−1, likely due to interactions with the endophytic fungi's biomolecules. These functional groups presumably act as reducing and stabilizing agents, promoting efficient MB adsorption. This research paves the way for utilizing the combined biological and chemical approach (fungal biomass and MWCNTs) in bioremediation applications. The findings suggest significant potential for practical applications in wastewater treatment, providing an eco-friendly and cost-effective method for dye removal. Furthermore, the proposed method shows promise for scaling up to industrial wastewater treatment and applicability in resource-limited settings, offering a sustainable solution for global water pollution challenges. Further investigations with larger datasets incorporating additional influencing factors are necessary to refine the predictive power of the DT model for practical applications.

Electrocoagulation treatment of wastewater collected from Haldia industrial region: Performance evaluation and comparison of process optimization

This study investigates the treatment of oil-contaminated wastewater with high levels of inorganic substances, suspended solids and turbidity, collected from the Haldia industrial region of India in February 2023. The wastewater, originating from industries such as chemical, petrochemical, textile, and battery manufacturing, presents a complex pollutant load that challenges traditional treatment methods. Electrocoagulation was employed as the treatment technique, with process optimization conducted using Box-Behnken design (BBD) and central composite design (CCD) for key parameters: pH, initial oil concentration, current density, and electrolysis time. The study comprehensively examined the effects of these parameters on turbidity removal. The optimal conditions were determined to be a pH of 7.5, an initial oil concentration of 275 mg/L, a current density of 17.5 mA/cm², and an electrolysis time of 20 min. Under these conditions, CCD outperformed BBD, achieving a desirability score of 93 % compared to 80 % for BBD. The process successfully reduced turbidity from 450 NTU to 56 NTU and total suspended solids (TSS) from 300 mg/L to 102 mg/L. The operation cost of the process was found to range from ₹0.904/m³ to ₹2.71/m³ as the electrolysis time increased from 0.17 to 0.5 h. The study presents a viable solution for industrial wastewater treatment in this region, aligning with the United Nations Sustainable Development Goal (UN SDG) 2030. Additionally, combining electrocoagulation with membrane filtration may enhance comprehensive pollutant removal.

Utilization of Coffee Grounds as an Adsorbent in Reducing the Levels of Naphthol Dyes of Weaving Industry Wastewater

Naphthol dye is one of the synthetic dyes contained in weaving industry waste. One method that can be used to reduce the disadvantageous effects of these substances is by adsorption using activated charcoal adsorbent from coffee grounds. This research aims to determine the character of activated charcoal from coffee grounds and the effect of adsorbent dosage and stirring time on the adsorption of naphthol dye levels. Making activated charcoal from coffee grounds goes through 3 stages, namely the dehydration stage, carbonization stage at 350 oC for 3.5 hours, and activation stage using a 0.1 M HCl activator for 48 hours. The characterization of activated charcoal obtained complies with SNI 06-3730-1995 with results of water content of 3.74%, ash content of 2.12%, and iodine adsorption capacity of 758.29 mg/g, and functional group testing was carried out by varying the adsorbent dosage at 0.125; 0.250; 0.500; 0.750; 1 g (per 100 mL sample) and stirring time for 10; 20; 30; 40; 50 minutes. From the research results, it was obtained the best adsorbent dose and mixing time were 0.5 g and 40 minutes with adsorption efficiency of 98.68% and 99.63%.

Construction of magnetically separable S-scheme BiFeO3/Cl-g-C3N4 heterostructure photocatalyst for simultaneous removal of Cr(Ⅵ) and tetracycline in aqueous solution: Performance and mechanism insight

A green, efficient and recyclable magnetic BiFeO3/Cl-g-C3N4 photocatalyst was prepared for the simultaneous removal of Cr(Ⅵ) and tetracycline (TC) from water by wet chemical and thermal synthesis methods. Experimental results revealed that BiFeO3/Cl-g-C3N4 achieved a removal efficiency of 96.1 % for Cr(Ⅵ) and 98.2 % for TC under visible light irradiation for 50 min at pH 6. The results of the work function, charge density difference, UV–vis DRS, PL, PC and EIS tests indicate the formation of S-scheme heterojunctions between BiFeO3 and Cl-g-C3N4, which exhibits superior carrier separation and migration efficiency. The evidence for interfacial charge transfer from BiFeO3 to Cl-g-C3N4 within BiFeO3/Cl-g-C3N4 was further corroborated by means of ISIXPS, EPR and KPFM. Moreover, calculations of the density of states demonstrate that the introduction of Cl enhances the reduction capability of BiFeO3/Cl-g-C3N4. Results from ESR tests and trapping experiments has demonstrated that the singlet oxygen (1O2) and electrons are the primary active species. Furthermore, the high removal rates of TC and Cr(VI) from industrial wastewater and groundwater, coupled with the lower ecotoxicity of TC degradation intermediates, indicate that BiFeO3/Cl-g-C3N4 has the potential for practical applications. After five cycles, the BiFeO3/Cl-g-C3N4 still removed 90.5 % of TC and 96 % of Cr(Ⅵ).

Cr3+doped α-Fe2O3 nanoparticles for photodegradation of organic pollutants with their disinfection efficacy

Pristine and Cr-doped α-Fe2O3 nanoparticles were synthesized using a low-cost and simple one-step hydrothermal method without any precipitating agent. Cr-doped α-Fe2O3 was found to be a promising candidate for recyclable photocatalytic application for Tetracycline (TC) and Congo-red (CR) degradation under normal sunlight irradiation along with excellent antibacterial properties. Addition of Cr shows a significantly improved degradation efficiency from 20% to 91% in just 25 min for CR, while the degradation rate reached to 81% for TC, which was also monitored in real-time using internet of things (IoT). Also, a high degree of mineralization was achieved (∼87.9%), which was confirmed using total organic carbon (TOC) content. In parallel, the biochemical oxygen demand/chemical oxygen demand (BOD5/COD) ratio confirmed the fast degradation efficiency using a small amount of catalytic dosage (∼ 0.40 g/L). Also, degradation of multiple dyes provides a promising avenue for addressing complex waste water treatment challenges. Moreover, Cr-doped α-Fe2O3 displays excellent antibacterial activity towards E.coli and E.Faecium. Major factors involved in sunlight driven photocatalytic activity for example absorbance range, porosity, separation between e--h+, and charge transfer property were surprisingly improved by Cr doping and henceforth increased photocatalytic activity and antibacterial properties. This work highlights the potential utilization of Cr-doped α-Fe2O3 for the purification and disinfection of industrial waste water.

Current regulates electron donors for heterotrophic and autotrophic microorganisms to enhance sulfate reduction in three-dimensional electrode biofilm reactors

The variability in industrial production often generates wastewater with an unstable carbon-to-sulfur ratio, challenging the concurrent removal of sulfate and organic compounds. Three-dimensional biofilm electrode reactor (3D-BER) technology offers a promising solution, compatible with both autotrophic and heterotrophic sulfate reduction. In this study, four up-flow 3D-BERs with gradient current levels were operated for nearly 400 days to treat simulated high-concentration sulfate wastewater. The effects of current intensity, hydraulic retention time (HRT), and influent carbon-to-sulfur ratio on sulfate and organic removal were investigated. The composition and functions of microbial communities were analyzed by metagenomic sequencing. The synergistic mechanism between heterotrophic and autotrophic sulfate reduction was examined by delineating their individual contributions to sulfate removal. Under optimized conditions (HRT 60 h, influent carbon-to-sulfur ratio of 1.7, and current intensity of 50 mA), the highest removal efficiencies for SO42- and COD reached 70.47 % and 85.58 %, respectively. Elevated current intensity increased the abundances of Desulfuromonadaceae, Desulfovibrionaceae and Methanobacteriaceae, while decreasing Anaerolineaceae and Geobacteraceae. Key genes involved in carbon fixation and hydrogen-relied sulfate reduction showed lower abundances at high current levels, whereas genes for direct electron uptake from the electrode were more abundant. Batch experiments demonstrated a synergistic effect between autotrophic and heterotrophic sulfate reduction, most pronounced at 50 mA. Our work successfully regulates electron donors for microbial reduction of high-concentration sulfate in 3D-BERs by manipulating current intensity, providing new insights into the application of bioelectrochemical technology for complex industrial wastewater treatment.

Biological decolorisation of the anionic Dye Acid Blue 9 by bacterial consortium: A sustainable and ecofriendly approach for the treatment of textile wastewater

Industrialization has led to the proliferation of dye waste, posing significant environmental challenges due to the structural complexity of dyes. Various industries discharge untreated toxic waste into water bodies, posing severe environmental hazards to humans as well as aquatic ecosystem. Synthetic dyes from textiles exacerbate this issue due to their toxicity, making the management of industrial wastewater a significant environmental challenge. This study offers a potential solution by investigating the degradation of hazardous Acid Blue-9 (AB9) dye using bacterial consortium containing Pseudomonas fluorescens and Bacillus subtilis. The experiments were conducted in minimal salt media with varying concentrations of different parameters (pH, temperature, initial dye concentration, size of inoculum, carbon and nitrogen sources) used for optimization process. Using the One-Factor-At-A-Time method, the consortium in the study was able to decolorize at a noteworthy rate of decolorisation about 85–87.2 %. This rate was notably increased to around 90.02 % with the implementation of Response Surface Methodology. Additionally, the decolorisation process was further confirmed by using UV-Visible Spectroscopy and Fourier Transform InfraRed Spectroscopy. Additionally, a phytotoxicity assessment test on crops of agricultural significance supports the potential of this bacterial consortium for the bioremediation of AB9 contaminated water. The dye samples treated with bacterial consortium showed significantly higher seed germination rates (∼82.9 %), along with increased shoot (∼9.13 cm) and root lengths(∼3.01 cm), compared to the untreated samples. This promising finding suggests the potential for reusing treated water in agriculture and industry, offering a sustainable solution to water pollution.

Prospects of Effective Microorganisms (EM) in bioremediation of textile industrial wastewater

Prospects of Effective Microorganisms (EM) in bioremediation of textile industrial wastewater

Development and performance of microalgae-based symbiotic systems for high-strength chemical oxygen demand wastewater treatment from the sugar mills

Agricultural and agro-industrial activities have risen exponentially to meet the ever-growing demand for food, energy, and other important resources. High freshwater consumption occurs in these sectors and is discharged as effluent containing excessive organic loads that require treatment. In this study, microalgal, bacterial, and fungal (yeast) isolates native to the sugar industry effluent were screened for effective chemical oxygen demand (COD) removal from wastewater when co-cultured. The microalgae-bacteria consortium (MBC) comprised Chlorella sorokiniana A7 and three bacterial strains including Rhodococcus sp. B009, Bacillus sp. B010, and B013; whilst the microalgae-yeast consortium (MYC) consisted of Chlorella sorokiniana A7 and Saccharomyces cerevisiae Y2. When the Chlorella sorokiniana-based symbiotic systems were characterized in sugar industry wastewater, excellent COD removal efficiencies were achieved compared to the axenic Chlorella sorokiniana A7. The COD removal efficiencies were 86 %, and 71 % after 96 h of cultivation for MBC, and MYC, respectively. After 168 h of cultivation in wastewater, ≥90 % of COD removal efficiency was observed in both MBC and MYC systems. The MYC also showed improved chlorophyll-a content, photosynthesis, and respiration in Chlorella sorokiniana A7. This study has demonstrated the efficiency of Chlorella sorokiniana-based consortium systems that could be used as eco-friendly and sustainable bioremediation tools for high-strength COD wastewater streams. An insight into mechanisms of interactions between Chlorella sp., and co-cultured microbial strains grown in sugar industry wastewater still needs further studies.

PERFORMANCE OF FREE WATER SURFACE FLOW CONSTRUCTED WETLAND FOR LEAD AND CADMIUM IONS REMOVAL USING AZOLLA PINNATA PLANT

Phytoremediation is the ability of some plants to bio accumulate, decompose, or transformation of pollutants in soils, water, or air. In the current study, an effort is made to study the effectiveness of free-floating plants to treat simulated industrial wastewater polluted with Lead and Cadmium ions using Azolla Pinnata plant in a lab condition. Free water surface flow constructed wetland were fed with simulated Cd and Pb ions in different concentrations (5, 10 and 20) mgl-1. Different operating conditions were studied such as; pH, dissolved oxygen, electrical conductivity, temperature, and sodium adsorption ratio to find out the possibility of using treated wastewater for irrigation. Results showed that, Azolla plant had a higher removal efficiency to extract Lead ions (90.1%, 86.67%, and 81.3%) than Cadmium (79.3%, 78.4%, and 69.7%) when the initial concentration is (5, 10, 20) mgl-1 respectively, during 5 days. A slight reducing in pH (8.3 to 7.4) and dissolved oxygen (8.7 to 7.2) mgl-1 observed, all these values mentioned satisfied with the Iraqi standards and World Health Organization. From values of electrical conductivities (250- 750) (µScm-1) and the sodium adsorption ratios (0- 10) it was found that treated wastewater falls into class C2S1 which mean that water has good quality and can be used to irrigate moderately salt-tolerant crops on soils with good permeability.

Long-lived superhydrophobic micro/nano-locked fiber membranes for long-lasting oil-water separation effectiveness

Superhydrophobic/superoleophilic oil-water separation membranes have great potential for treating industrial, domestic, and marine oily wastewater. However, the robustness of these membranes remains a challenge that restricts their ability to maintain long-lasting oil-water separation effectiveness. Inspired by the adhesion mechanisms of snail and tree frog, exploiting the synergistic effects of interfacial hydrogen bonding and mechanical interlocking, we herein achieved strong adhesion between hydrophobicized in-situ nanoparticles and textile fibers to fabricate a long-lived superhydrophobic micro/nano-locked fiber membrane (LSMFM). LSMFM maintains excellent superhydrophobicity even when exposed to mechanical and chemical damage, such as continuous sandpaper abrasion, tape-peeling, weight impact, water jet, and acid/alkali/salt erosion. Additionally, LSMFM efficiently separates various light/heavy oil-water mixtures, achieving a remarkable separation flux of >10,000 L·m−2·h−1 and an efficiency >98 %, even after 200 cycles with n-hexane. Importantly, such membranes still maintain a high separation flux >19,000 L·m−2·h−1 and efficiency >97 % after sequentially being subjected to acids, alkalis, freezing, and high temperatures, and even the adsorption bag formed by wrapping LSMFM with superhydrophilic wood pulp cotton can adsorb oil at fixed-point and continuously recover pure oil from oily wastewater. This study paves a new way for the sustainable purification of oily wastewater in extreme environments.

Simultaneous removal of Pb(II) and Cr(VI) from a steel company wastewater using various green adsorbents: Material characterization and numerical optimization

ABSTRACT This study focuses on the simultaneous uptake of Pb(II) and Cr(VI) from industrial wastewater by walnut shell (WS), almond shell (AS), peanut shell (PS), and coconut shell (CS) adsorbents. Among the used adsorbents, the CS adsorbent exhibited the greatest BET surface area of 18.97 m2/g and porosity of 63.17% and the WS adsorbent also had the highest pore volume of 0.3536 m3/g. Lead and chromium removal were optimized using response surface methodology via a central composite design (CCD) approach. The efficiency of lead and chromium uptake from the wastewater was enhanced by increasing the concentration of WS, AS, PS, and CS adsorbents (Cads.) and decreasing the flow rate (Q) of the wastewater. Under the optimal conditions (Cads. = 0.85 g/L and Q = 2.5 mL/min), the maximum lead and chromium uptake from steel company wastewater was achieved using CS (92%) and WS (97.2%) adsorbents, respectively. The actual lead and chromium removal values were well-fitted based on a high Rpred2, confirming the validity of the CCD model. The acceptable performance of these green adsorbents in the simultaneous removal of chromium and lead from the wastewater introduces the WS, AS, PS, and CS adsorbents as inexpensive and available candidates for industrial wastewater treatment containing heavy metals.

A fluorescent sensor for rapid and quantitative aquatic bacteria detection based on bacterial reactive oxygen species using Ag@carbon dots composites.

A novel fluorescent sensor based on silver nanoparticle-carbon dot composites (Ag@CDs) has been developed for the rapid and quantitative detection of aquatic bacteria. The sensor operates on the principle of plasmon-enhanced resonance energy transfer, where the fluorescence of CDs is quenched by Ag nanoparticles and restored upon bacterial interaction due to the generation of reactive oxygen species. The Ag@CDs exhibit a linear response to bacterial concentration over the range 7 × 104 ~ 4 × 107 CFU·mL-1, with a low detection limit of 4 × 104 CFU·mL-1. The fluorescence recovery is rapid, reaching maximum intensity within 5 min. The method demonstrates high selectivity, with minimal interference from common ions and compounds found in municipal and industrial wastewater. The Ag@CDs-based 96-well plate assay for quantitative measurement of bacteria was developed. The assay's performance was further validated through the analysis of real water samples, showing a recovery of 94.0 ~ 102% for domestic wastewater and 97.6 ~ 106% for industrial wastewater. Also, Ag@CDs-based test strips assay for semi-quantitation were developed for rapid in-field aquatic bacteria detection. Ag@CDs can be conveniently integrated into 96-well plates and test strips, providing rapid on-site aquatic bacteria testing.

Ammonium Removal and Recovery from Industrial Wastewater Using Distillation Method

:Industrial wastewater contains high ammonium concentration, leading to difficulties in the treatment process using conventional methods. This study used the heat distillation method following the alkalization of wastewater to remove and recover ammonium from the wastewater of an industrial plant. The influent wastewater has a pH 6.41 and a very high ammonium concentration (28000 mgN/L). The distillation system was designed to consist of heating, cooling, and recovery units. After alkalinization, the wastewater sample was boiled using an electric stove, the ammonia vapor passed through the cooler and condensed into liquid ammonia, and was recovered. The controlling factors for the removal efficiency including solution pH (7-12) and distillation time (0.5, 10, 15, 30, 60 and 90 min) were investigated. Experimental results show that the optimal conditions for ammonium treatment from wastewater are at pH 12 and distillation time of 30 min, corresponding to 100% of removal efficiency. In terms of liquid ammonia recovery, the ice cooling mode was more efficient than the tap water cooling and vacuum evaporating modes. Final ammonia concentration reached 215 mgN/L that has potential for industrial production.