Biological neutralization and biosorption of dyes of alkaline textile industry wastewater

Rapid catalytic reduction of environmentally toxic azo dye pollutant by Prussian blue analogue nanocatalyst

The release of toxic azo dyes pollutants in the environment from different industries represents a public health concern and a serious environmental problem. Therefore, the conversion of hazardous methyl orange (MO) azo dye to environmentally benign products is a critical demand. In this work, an eco-friendly Prussian blue analogue (PBA) was synthesized and its catalytic activity toward the reduction of MO was investigated. The PBA copper(ii) hexacyanocobaltate(III) (Cu3[Co(CN)6]2) was synthesized by a facile inexpensive chemical coprecipitation method without using hazardous solvents. The nanocatalyst was characterized using XPS, Raman, FTIR spectroscopy, and XRD. The chemical reduction of MO using NaBH4 and the PBA as nanocatalyst was monitored by UV-VIS spectroscopy. Toxic MO was completely reduced in 105 s with a rate constant (k) 0.0386 s-1 using only 10 μg of the PBA nanocatalyst. Besides the powerful catalytic activity, the nanocatalyst also showed excellent stability and recyclability for ten consecutive cycles, with no significant decrease in the catalytic performance. Therefore, the proposed PBA is a promising, stable, cost-effective, and eco-friendly nanocatalyst for the rapid elimination of hazardous azo dyes.

Pineapple wastewater as co-substrate in treating real alkaline, non-biodegradable textile wastewater using biogranulation technology

This study was to develop biogranules using a sequencing batch reactor (SBR) and to evaluate the effect of pineapple wastewater (PW) as a co-substrate for treating real textile wastewater (RTW). The biogranular system cycle was 24 h (2 stages of phase), with an anaerobic phase (17.8 h) followed by an aerobic phase (5.8 h) for every stage of the phase. The concentration of pineapple wastewater was the main factor studied in influencing COD and color removal efficiency. Pineapple wastewater with different concentrations (7, 5, 4, 3, and 0% v/v) makes a total volume of 3 L and causes the OLRs to vary from 2.90 to 0.23 kg COD/m3day. The system achieved 55% of average color removal and 88% of average COD removal at 7%v/v PW concentration during treatment. With the addition of PW, the removal increased significantly. The experiment on the treatment of RTW without any added nutrients proved the importance of co-substrate in dye degradation.

Ecotoxicological response surface analysis of salt and pH in textile effluent on Bacillus subtilis and Lactuca sativa

Textile effluents, although their composition can vary considerably, typically contain high levels of dissolved salts and exhibit wide variations in pH. Ecotoxicological studies regarding the effects of these parameters, however, have been limited owing to the need for sensitive and easy-to-handle bioindicators that require low amounts of sampling, are cost-effective, time-efficient, and ethically endorsed. This kind of study, additionally, demands robust multi-factorial statistical designs that can accurately characterize the individual and combined relationship between variables. In this research, Response Surface Methodology (RSM) was used to calculate the individual and interaction effects of NaCl concentration and pH value of a Simulated Textile Effluent (STE) on the development rate (DR) of the bioindicators: Bacillus subtilis bacteria and Lactuca sativa lettuce. The results demonstrated that the bioindicators were sensitive to both NaCl and pH factors, where the relative sensitivity relationship was B. subtilis > L. sativa. The quadratic equations generated in the experiments indicated that increased concentrations of 50-250 mg L-1 of NaCl caused a perturbance of 1.40%-34.40% on the DR of B. subtilis and 0.50%-12.30% on L. sativa. The pH factor at values of 3-11 caused an alteration of 27.00%-64.78% on the DR of the B. subtilis and 51.37%-37.37% on the L. sativa. These findings suggest that the selected bioindicators could serve as effective tools to assess the ecotoxicological effects of textile effluents on different ecological systems, and the RSM was an excellent tool to consider the ecotoxicological effects of the parameters and to describe the behavior of the results. In conclusion, the NaCl and pH factors may be responsible for disrupting different ecosystems, causing imbalances in their biodiversity and biomass. Before discharge or reuse, it is suggested to remove salts and neutralize pH from textile effluents and, mostly, develop novel, eco-friendlier textile processing techniques.

Adaptive growth and acidogenic fermentation performance of haloalkaliphilic bacterial communities enriched from biofilms colonising strongly alkaline and saline bauxite residue

The present study aimed to characterise the adaptive growth and acidogenic fermentation performance of haloalkaliphilic bacteria sourced from field biofilms colonising seawater-treated bauxite residue, under moderate and extremely alkaline pH conditions (8.5 to 10.8) and coupled saline (EC ≈ 50 mS/cm) conditions. The haloalkaliphilic bacterial communities demonstrated strong adaptiveness to the increasing pH from 8.5 to 10.8. The dominant groups were Exiguobacterales and Bacillales at pH 8.5 and 10, but Lactobacillales and Bacillales at pH 10.8. The exposure to pH 10.8 initially delayed bacterial growth in the first 24 h, but which rapidly recovered to a peak rate at 48 h similar to that in the pH 10 treatment. Correspondingly, lactic acid concentration at pH 10.8 rapidly rose to as high as >2000 mg/L at 48 h. Bacterial growth and organic acid production were positively related to carbohydrate supply. Overall, these bacterial groups fermented glucose to produce mainly lactic acid (>80 %) and other acids (such as acetic acid, formic acid, and succinic acid), leading to 0.5-2.0 units of pH reduction, despite the strong buffering capacity in the culture solution. The bacteria could up-regulate their phosphatase activity to mineralise the organic P in the basal nutrient broth, but increasing soluble phosphate-P at a 1:10 of glucose-C was beneficial. The biofilm-sourced bacteria communities contained redundant fermentative haloalkaliphilic groups which were adaptive to strongly alkaline pH and saline conditions.

Instant pH sensor based on the functionalized cellulose for detecting strong acid leaks

Acid spills cause large-scale environmental damage and casualties. To respond to such incidents, a sensor capable of detecting acid leaks is required. Cellulose is a useful substrate material for the fast detection of acid leaks because it has high hydrophilicity and porosity. On the other hand, methods of manufacturing cellulose-based sensors are still complicated or time-consuming. Thus, in this study, a simple and rapid synthesis method for a cellulose-based pH sensor was proposed. The functionalization of α-cellulose was achieved via chloroacetyl chloride, and Congo red was covalently immobilized to the functionalized cellulose for detecting strong acids. The manufacturing process was composed of two steps as above and finished within 8 h. The developed sensor exhibited absorbance changes in the pH range of 0.2 to 3.0, and response time was shorter than 1 s. A prototype system using this sensor was manufactured and tested, and it detected acid leaks easily and quickly.

Comprehensive characterization of industrial wastewaters using EEM fluorescence, FT-IR and 1H NMR techniques

The organic matter present in six industrial wastewaters (pulp and paper mill, brewery, textile, dairy, slaughterhouse effluents and a municipal landfill leachate) has been studied in this work using three analytical techniques: excitation-emission matrix fluorescence (EEMF), proton nuclear magnetic resonance spectroscopy (¹H NMR) and Fourier transform infrared spectroscopy (FTIR). The pulp and paper mill effluent shows characteristic signals of the presence of lignins, carbohydrates and carboxylic acids, as well as sulfate, carbonate and sulfonates (coming from surfactants used in the cleaning of tanks). The main constituents of the brewery effluent are peptides and proteins coming mainly from spent yeast and diatomite filters (the presence of the latter was confirmed by SiO bands in the FTIR spectrum). The municipal landfill leachate is characterized by the majority presence of humic substances (typical of an old landfill) and a residual presence of small peptides, amino acids and carboxylic acids. Additionally, several inorganic compounds were identified by FTIR, such as nitrate, sulfate, phosphate and cyanide ions. The textile effluent from a cotton-based industry contains carbohydrates, carboxylic acids and sulfonates, which can act as auxochromes in the textile industry. The dairy effluent comprises amino acids and small peptides coming from the biodegradation of milk and whey in addition to carbohydrates (lactose) and carboxylic acids (mainly lactic acid). The presence of tyrosine-like peaks B in the EEMF spectrum of the slaughterhouse effluent indicates the existence of small peptides and amino acids coming from the biodegradation of blood proteins. Additionally, residual glucose, fatty acids, phosphate and sulfate were also identified in this effluent.

Nitrate removal by alkali-resistant Pseudomonas sp. XS-18 under aerobic conditions: Performance and mechanism

To improve poor nitrate removal by microorganisms under strong alkaline conditions, a new type of aerobic nitrification-reducing bacteria was isolated in this study. Using nitrogen balance and genome information, the capacity of Pseudomonas XS-18 to remove nitrate and the mechanism of alkali tolerance were analyzed. At pH 11.0, XS-18 could remove 12.17 mg N/(L·h) nitrate. At C/N ratios of 13.0 and 25 °C, nitrite and ammonia nitrogen were barely enriched. XS-18 could reduce nitrate through dissimilation and assimilation, and 21.74% and 77.39% of nitrate was converted into cellular components and organic nitrogen, respectively. Meanwhile, functional genes (nirBD, nasAB, gdhA, glnA, and gltBD) associated with nitrogen metabolism were determined. In addition, Na⁺/H⁺ antiporters (MnhACDEFG, PhaACDEFG, NhaCD and TrkAH) and a cell surface protein (SlpA) from the XS-18 genome, as well as compatible solutes that help stabilize intracellular pH, were also characterized. XS-18 possessed significant potential in alkaline wastewater treatment.

Carbon flow conversion induces alkali resistance and lipid accumulation under alkaline conditions based on transcriptome analysis in Chlorella sp. BLD

Alkaline environments are abundant globally and cause damage to most organisms, while some microalgae can grow well and accumulate lipids under those conditions. Here the mechanisms of alkali resistance and lipid accumulation in the alkaliphilic microalgae Chlorella sp. BLD were explored using physiological-biochemical and transcriptome analysis. When cultivated at alkaline pH, Chlorella sp. BLD exhibited good alkali-resistance ability and increased biomass (0.97 g L^-1). The biochemical composition of Chlorella sp. BLD changed significantly (lipid content increased 39% and protein content decreased 19.5%) compared with pH 7.5. Through transcriptome analysis, we found that pathways related to carbon metabolism such as photosynthesis, glycolysis, and the TCA cycle were significantly regulated under alkaline conditions. Genes that encoding the key enzyme in carbon-related metabolism such as Rubisco, AMY, PK, ME, CS, ACAT, KAS, and DGAT were identified. Transcriptional regulation of these genes results in carbon flow switching from starch and protein to cell wall metabolism, organic acid synthetic and lipid accumulation in response to alkaline conditions. These results reveal the alkali resistance mechanism of Chlorella sp. BLD and provide a theoretical basis for microalgae oil production under alkaline conditions.

Assessing environmental impact of textile production with water alkalization footprint

The dyeing process contributes most to the water consumption and wastewater emission associated with the textile industry, leading to water depletion and degradation. The water footprint is an effective concept for evaluating the environmental impact of textile production processes on water bodies, and serves as a reference for practitioners seeking to develop suitable water management strategies. Water degradation can be quantified in terms of several sub-indicators, such as aquatic eutrophication, acidification, and ecotoxicity. However, some processes (such as the production of viscose fiber and dyeing) produce significant quantities of alkaline wastewater that can alkalize the receiving water bodies. In this study, we proposed the concept of water alkalization footprint to assess the potential impact of water alkalization caused by textile production. To achieve this, we constructed an evaluation framework and calculated the relevant characterization factors by considering the mechanisms of chemical reaction. A dyeing mill was selected as a case study to demonstrate the feasibility of the concept. The results indicate that the dyeing of 1 ton of viscose fabric produces a water alkalization footprint of 15.478 kg OH^- equiv, and that NaOH in the wastewater from the desizing and dyeing phases was the largest contributor at 97.23%.

Efficient degradation method of emerging organic pollutants in marine environment using UV/periodate process: Case of chlorazol black

Sea has historically been subject to high anthropogenic pressures of direct and indirect loads of emerging organic pollutants (EOPs) from intensive industrial and agricultural activities. Photoactivated periodate (UV/IO₄^-) is an innovative oxidation technique that was never tested in seawater as pollutants matrix. In this work, we attempted to investigate the treatment of seawater contaminated with chlorazol black (CB) dye, as a model of EOPs, using photoactivated periodate process. It was found that periodate (0.5mM) assisted-UV treatment of CB (20mgL^-1) in seawater resulted in 13.16-fold increase in the initial degradation rate, compared to UV alone, and 82% of CB was removed after 40min face to 38% under UV alone. The beneficial effect of UV/IO₄^- treatment is strongly dependent on operational parameters. More interestingly, SDS surfactant, as an organic matter, did not affect the degradation process, making UV/IO₄^- a promising technique for treating seawater contaminated with EOPs.

Supercritical water oxidation treatment of textile sludge

In this work, we studied the supercritical water oxidation (SCWO) of the textile sludge, the hydrothermal conversion of typical textile compounds and the corrosion properties of stainless steel 316. Moreover, the influence mechanisms of NaOH during these related processes were explored. The results show that decomposition efficiency for organic matter in liquid phase of the textile sludge was improved with the increment of reaction temperature or oxidation coefficient. However, the organic substance in solid phase can be oxidized completely in supercritical water. Serious coking occurred during the high pressure water at 250-450°C for the Reactive Orange 7, while at 300 and 350°C for the polyvinyl alcohol. The addition of NaOH not only accelerated the destruction of organic contaminants in the SCWO reactor, but effectively inhibited the dehydration conversion of textile compounds during the preheating process, which was favorable for the treatment system of textile sludge. The corrosion experiment results indicate that the stainless steel 316 could be competent for the body materials of the reactor and the heat exchangers. Furthermore, there was prominent enhancement of sodium hydroxide for the corrosion resistance of 316 in subcritical water. On the contrary the effect was almost none during SCWO.

Y2O3 functionalized natural palygorskite as an adsorbent for methyl blue removal

The methyl blue adsorption isotherm on Y₂O₃/Palygorskite obeys the Langmuir model, with the maximum adsorption capacity greatly enhanced to 1579.06 mg g⁻¹, exhibiting potential applications in wastewater treatment.

Characterizing treated wastewaters of different industries using clustered fluorescence EEM-PARAFAC and FT-IR spectroscopy: implications for downstream impact and source identification

The quantity and spectroscopic features of dissolved organic matter (DOM) in treated wastewaters were studied for up to 57 facilities across 12 industrial categories to evaluate the potential influences of the effluents on downstream ecosystems and the feasibility of spectroscopic techniques in discriminating pollution sources. The average dissolved organic carbon (DOC) concentration was 3.30±0.70-73.4±14.0 mg L(-1) for each category, high enough to pollute downstream waterbodies. The average specific UV absorbance at 254 nm (SUVA) for each category spanned a broad range between 0.79±0.24 and 5.35±1.41 L(mg m)(-1), suggesting a variable aromaticity of DOM. Fluorescence excitation emission matrix-parallel factor analysis (EEM-PARAFAC) identified four humic-like and two protein-like components. The EEMs were grouped into seven clusters, five of which were dominated by a single PARAFAC component in each cluster. Fourier transform infrared (FT-IR) spectroscopy revealed notable variations in relative intensities of several characteristic absorbance bands among different wastewaters. The large variability in SUVA, PARAFAC and FT-IR features indicated that the chemical composition of DOM greatly differ among industrial wastewaters, and further implied variable biogeochemical reactivity in downstream waterbodies. The results also suggested the potential of DOM features in discriminating different wastewaters, although the variations within each industrial category were also significant.