Treatment Of Alkaline Wastewater Research Articles

Artificial intelligence-driven control for enhancing carbon dioxide-based wastewater pH regulation in tubular reactor

Alkaline wastewater treatment using carbon dioxide can reduce chemical costs and provide a safer alternative to traditional methods. However, complex gas-liquid reactions and narrow operating pH ranges present challenges. This research develops an artificial intelligence-driven control system for treating alkaline wastewater using carbon dioxide in a bench-scale tubular reactor. The proposed control system employs an inverse neural network to regulate the carbon dioxide gas based on the desired setpoint, along with a Smith predictor and a linear controller to compensate for natural delays, model mismatches, and pH disturbances. The inverse neural controller was trained using experimental data from a bench-scale reactor pH treatment of synthetic alkaline wastewater and verified on real influent from an electroplating wastewater treatment plant. The results show that the proposed method efficiently enforces the desired reactor outlet pH setpoint with up to 51.36% faster settling time than a proportional-integral controller while improving pH-adjusting efficiency by 72.24%.

Enhanced conversion from H2O2 to 1O2 on Cu–N centers: Investigation of mechanisms and application in alkaline wastewater treatment

Heterogeneous Fenton-like systems using H2O2 as an oxidant have been extensively investigated in acidic and neutral conditions, but usually, they become ineffective under alkaline conditions. In this study, a cuprous graphitic carbon nitride material (Cu–CN) was prepared that can generate singlet oxygen (1O2) from H2O2. The results demonstrate that at pH 11, 95 % of 50 mg/L p-chlorophenol (4-CP) can be effectively eliminated within 120 min. Through semi-quantitative analysis and density functional theory calculations, it has been confirmed that 1O2 is the dominant reactive oxygen species in this system under alkaline conditions. The main pathway for 1O2 generation involves the formation of a complex between ·O2– and Cu(II)-N sites, and the subsequent intramolecular electron transfer. To enhance the stability and separation performance of this catalyst, polyethylene glycol (PEG) was employed as a binder to combine Cu–CN with Fe3O4. The terminal hydroxyl groups in PEG were cross-liked by metals, thus forming a solid and magnetic composite (CuFe@PEG). Compared to Cu–CN, CuFe@PEG exhibited remarkable performance with 93 % retention of its original capacity for 4-CP removal at pH 11. Furthermore, after seven cycles, the degradation efficiency only decreased by 6.36 %. This study introduces a novel approach for utilizing Fenton-like reactions in treating alkaline wastewater.

NiCo layered double hydroxides/NiFe layered double hydroxides composite (NiCo-LDH/NiFe-LDH) towards efficient oxygen evolution in different water matrices

Engineering robust non-noble metal electrocatalysts towards efficient impure water (e.g., seawater, wastewater) oxidation is a prospective approach to achieve carbon neutrality via accelerating green hydrogen energy development. Herein, a NiCo layered double hydroxides (LDH)/NiFe LDH composite (NiCo-LDH/NiFe-LDH) was developed for oxygen evolution reaction (OER) via a hydrothermal process-electrodeposition method. The optimal NiCo-LDH/NiFe-LDH-30 composite only needed an overpotential (η) of 240 mV to drive 100 mA/cm2 in alkalized freshwater, with a low Tafel slope of 16.6 mV/dec and good stability for over 90 h. Further analyses suggested that the strong interface interaction between NiCo-LDH and NiFe-LDH accelerated the oxygen gas bubble evolution and boosted interfacial charge transfer, and the formed built-in electric field and higher oxidation state species (metal oxyhydroxides) contributed to the high intrinsic catalytic activity. The NiCo-LDH/NiFe-LDH-30 composite also held excellent OER activities in different impure water environments, including alkaline 0.5 M NaCl solution (η100 = 333 mV), alkaline lake water (η100 = 345 mV), and alkaline wastewater treatment plant (WWTP) effluent (η100 = 320 mV). More importantly, the potential effects of Cl− and CO32− in impure water were revealed during the OER process. This work elaborates on the role of built-in electric field and the strong coupling interaction in composite catalysts, which pave the way for the design of cost-effective catalysts with excellent adaptability in different water environments.

Evaluation of synergistic approach of spinel cadmium–copper nanoferrites as magnetic catalysts for promoting wastewater decontamination: Impact of Ag ions doping

Metal substitution is an efficient strategy to improve the catalytic activity of ferrite-based catalysts. In this study, Cd0.5Cu0.5−xAgxFe2O4 (where 0 ≤ x ≤ 0.5) ferrites were fabricated via a simple co-precipitation method. The influence of the silver ions on the structural, magnetic, and catalytic characteristics of the spinel nanoparticles, as well as on their morphology, was examined. X-ray diffractograms revealed a crystalline cubic spinel structure with crystallite sizes in the nanoregime (7–15 nm). The saturation magnetization reduced from 29.8 to 2.80 emu as the Ag+ doping increased. Two prominent absorption bands were visible in Fourier-transform infrared spectra at 600 cm−1 and 400 cm−1, respectively, and they belonged to the tetrahedral (A) and octahedral (B) sites. The samples were then used as catalysts for the oxidative breakdown of the typical organic contaminant indigo carmine dye (IC). The catalytic process followed the first-order kinetic model, and the rate constant increased from 0.007 to 0.023 min−1 with increasing of Ag+ doping. Cd0.5Cu0.5-xAgxFe2O4 exhibited excellent catalytic performance in the pH range of 2–11, which means that they are promising efficient and stable materials for Fenton-based alkaline wastewater treatment. Finally, the pathway includes, HO•, HO2−•, and O2−• as oxidants resulted from the synergistic effects of Fe3+, Cu2+, and Ag+, with H2O2 and surface hydroxyl groups have been proposed.Graphical

Membrane Separation Used as Treatment of Alkaline Wastewater from a Maritime Scrubber Unit.

Since 1 January 2020, the sulfur content allowed in exhaust gas plume generated by marine vessels decreased to 0.5% m/m. To be compliant, a hybrid scrubber was installed on-board, working in closed loop and generating a high volume of alkaline wastewater. The alkaline water suspension was treated by a silicon carbide multitubular membrane to remove pollutants, and to allow the water discharge into the natural environment. In this paper, membrane filtration behavior was analyzed for the maritime scrubber wastewater. A range of operating parameters were obtained for several feedwater quality-respecting industrial constraints. The objective was an improvement of (I) the water recovery rate, (II) the filtration duration, and (III) the permeate quality. Thus, in high-fouling water, a low permeate flow (60 L h−1 m−2) with frequent backflushing (every 20 min) was used to maintain membrane performance over time. In terms of water quality, the suspended solids and heavy metals were retained at more than 99% and 90%, respectively. Other seawater discharge criteria in terms of suspended solids concentration, pH, and polyaromatic hydrocarbons were validated. The recommended operating conditions from laboratory study at semi-industrial scale were then implemented on a vessel in real navigation conditions with results in agreement with expectations.

Peracetic Acid Enhances Micropollutant Degradation by Ferrate(VI) through Promotion of Electron Transfer Efficiency.

Ferrate(VI) and peracetic acid (PAA) are two oxidants of growing importance in water treatment. Recently, our group found that simultaneous application of ferrate(VI) and PAA led to much faster degradation of micropollutants compared to that by a single oxidant, and this paper systematically evaluated the underlying mechanisms. First, we used benzoic acid and methyl phenyl sulfoxide as probe compounds and concluded that Fe(IV)/Fe(V) was the main reactive species, while organic radicals [CH3C(O)O•/CH3C(O)OO•] had negligible contribution. Second, we removed the coexistent hydrogen peroxide (H2O2) in PAA stock solution with free chlorine and, to our surprise, found the second-order reaction rate constant between ferrate(VI) and PAA to be only about 1.44 ± 0.12 M-1s-1 while that of H2O2 was as high as (2.01 ± 0.12) × 101 M-1s-1 at pH 9.0. Finally, further experiments on ferrate(VI)-bisulfite and ferrate(VI)-2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic)acid systems confirmed that PAA was not an activator for ferrate(VI). Rather, PAA could enhance the oxidation capacity of Fe(IV)/Fe(V), making their oxidation outcompete self-decay. This study, for the first time, reveals the ability of PAA to promote electron transfer efficiency between high-valent metals and organic contaminants and confirms the benefits of co-application of ferrate(VI) and PAA for alkaline wastewater treatment.

Carbon dioxide-hardened sodium silicate-bonded sand regeneration using calcium carbide slag: The design and feasibility study

Wet regeneration of sodium silicate sand (SBS) can yield a high regeneration rate. However, its large-scale implementation is limited by high cost of reagents and required alkaline wastewater treatment. Therefore, excessive SBS is extensively piled-up or buried, causing a huge waste of resources and environmental pollution. This study aimed to mitigate this problem by regenerating CO2-hardened SBS using a cheap regeneration reagent, namely calcium carbide slag (CCS), which is an easily available industrial waste, and considering the alkaline substance recovery. The regeneration mechanism was explored by macro-tests and micro-analysis. The results proved that CCS causticized the regenerated wastewater, forming a strong alkaline environment and speeding up the sodium silicate film peeling-off. In 20 min, a 92% regeneration rate was reached. The compressive strength of the sand core prepared by regenerated sand (RS) exceeded that of the new sand nearly twice if the same binder is used. At the same time, the regenerated wastewater flocculated after adding CCS, and there was no need to add other reagents. After natural precipitation, an alkaline solution with NaOH purity of 84% was obtained, which could be reused in chemical industry. This method has the advantages of low regeneration energy consumption, small secondary pollution, and excellent regeneration effect, making lucrative implying its large-scale implementation. It also substantiates the further SBS application in construction and chemical industry.

Application of fuzzy analytic hierarchy process and linear goal programing for selection of best available techniques of the cold rolled coil manufacturing processes: A case study in Binh Duong, Vietnam

The cold rolled coil manufacturing is one of the steel making processes with great environmental concerns due to the high energy consumption and greenhouse gas emissions, significant wastewater discharge, and hazardous waste disposal. A large number of technical solutions have been introduced to improve energy efficiency and environmental sustainability in the steel rolling sub-sector, particularly the best available techniques (BATs) adopted by European IPPC Bureau (2001). In this study, fuzzy analytic hierarchy process and linear goal programing are combined in the development of a multi-criteria decision support system for evaluating and selecting best available techniques (BATs) in the cold rolled coil manufacturing industry. The proposed approach comprises of four steps and results in the rankings of the potential BATs for the cold rolled coil installations. In a case study of a cold rolling mill in Vietnam, amongst eleven BATs that were recommended for the installation, two BATs of the highest priority were further analyzed, including: (1) improving the spent degreasing baths and the alkaline wastewater treatment system using membrane technology; and (2) recovering spent emulsion to supply fuels for the steam boiler. It is expected that the application of these BATs can enhance environmental performances and significantly reduce energy cost for the steam boiler during its operation.

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.

Preparation of alkali-resistant PVDF membranes via immobilization of sodium lauryl sulfate (SDS) on surface

A novel strategy was proposed to fabricate alkali-resistant PVDF membrane via sodium lauryl sulfate (SDS) attached to the surface of membrane and immobilized by UV-curable polyester acrylate and tri(propylene glycol) diacrylate (TPGDA). The attached anionic surfactant, SDS, on the membrane surface can resist the alkali corrosion by NaOH, and the curing of the resin can immobilize the SDS on the membrane firmly. Due to the unique alkali resistance of SDS and resin formed, the UV-curable resin-modified PVDF membrane showed greatly enhanced alkali-resistant ability. Characterization of SEM and FTIR showed that polyester acrylate and TPGDA were cured successfully under the action of 1-hydroxycyclohexyl phenyl ketone (184) and ultraviolet light. Whiteness, differential scanning calorimeter and X-ray photoelectron spectrometer characterization showed that the modified PVDF membrane had a lower degree of dehydrofluorination than the pristine PVDF membrane after alkali treatment. Results of the detailed alkali-resistant analysis indicated that the F/C ratio of the UV-curable resin-modified PVDF membrane decreased by 2.6% after alkali treatment compared to pristine PVDF membrane decreased by 19.28%. The alkali-resistant performance was mainly attributed to the immobilized SDS. This study provided a facile and scalable method for designing alkali-resistant PVDF membrane, which shows a promising potential in the treatment of alkaline wastewater and alkaline-cleaning PVDF membrane.

Lanthanum-doped α-Ni(OH)2 1D-2D-3D hierarchical nanostructures for robust bifunctional electro-oxidation

The development of advanced electrocatalysts for electro-oxidation reactions has attracted much attention because of the critical role of such electrocatalysts in improving the overall efficiency of coupled hydrogen production. We have developed an efficient lanthanum-doped α-Ni(OH)2 bifunctional catalyst with a 1D-2D-3D hierarchical nanostructure. It shows superior activity and stability in the anodic oxygen evolution reaction (OER) and urea oxidation reaction (UOR). Enrichment of the edge sites and conducting La doping in α-Ni(OH)2 phase enable formation and stabilization of abundant local Ni3+ ions. This guarantees ultralow onset potentials in electro-oxidation reactions. The 1D-2D-3D hierarchical nanostructure significantly boosts the in situ generation of high-valence active species, which results in efficient and stable OER and UOR performances, and the synergistic merit of doping-induced facile reaction kinetics. Because of the structural benefits of a large surface area, charge-transfer promotion, good structural stability, and bifunctionality, a 1% La-doped α-Ni(OH)2 hierarchical nanostructure gives superior OER and UOR performances with low overpotentials, large catalytic current densities, and excellent operational stability. It is therefore a promising catalyst for use in simultaneous alkaline wastewater treatment and hydrogen production.

Band-gap-energy-adjustable and noble-metal-free modified NiS-ZnxCd1-xS for highly efficient visible-light-driven Cr6+ photoreduction in alkaline wastewater

Industrial wastewater containing heavy metal ions can cover the full pH range according to the manufacturing process. Alkaline wastewater treatment is still a great challenge because Cr6+ therein has a more negative reduction potential (Cr2O72− + 14H+ + 6e− = 2Cr3+ + 7H2O (ECr6+(Cr2O72−/Cr3+) = Eθ−RTnFln[OH]−) than in acid solution, in which it can be easily reduced by numerous reagents. In this study, weakly alkaline Cr6+ solution has been used to simulate weakly alkaline industrial wastewater, and a reagent capable of excellent reduction efficiency therein has been developed. A series of band-gap-energy-adjustable NiS-ZnxCd1-xS composites has been synthesized by a one-pot hydrothermal method. A more negative conduction band position for ZnxCd1-xS has been achieved by doping and changing the amount of Zn2+ ions to ensure a superior photoreduction ability. All modified samples show excellent photocatalytic efficiency. For example, the reduction efficiency of 10%NiS–Zn0.25Cd0.75S sample is threefold higher than that of Zn0.25Cd0.75S and sixfold higher than that of CdS when deployed at a catalytic level for 30 min. Multiple characterization methods have been applied, and the results show that the improved efficiency can be ascribed to intimate contact between Zn0.25Cd0.75S and NiS. Photoluminescence (PL) and photocurrent measurements and electrochemical impedance spectroscopy (EIS) further elucidate the catalytic mechanism and imply an enhanced charge-carrier separation efficiency between Zn0.25Cd0.75S and NiS.

The alkaline photo-sulfite system triggers Fe(IV/V) generation at hematite surfaces

The formation of high-valent iron-oxo species (i.e., Fe(IV) = O, Fe(V) = O) is of vital importance in iron-mediated advanced oxidation processes (AOPs) for the rapid removal of organic contaminants, and it is mainly derived from the reduction of ferrate(VI) or the oxidation of homogeneous Fe(II). In this study, we have shown Fe(III) in the hematite surfaces under light illumination in the presence of sulfite can generate high-valent iron-oxo species that efficiently degrade refractory organics under alkaline conditions. Interactions between hematite and sulfite under xenon lamp irradiation in aqueous solution were investigated by combination of quenching experiments, electron spin resonance (ESR), high-performance liquid chromatography coupled with mass spectrometer (HPLC-MS), and X-ray photoelectron spectroscopy (XPS) techniques, and a possible mechanism was proposed. Importantly, this work demonstrates a novel and fundamental breakthrough toward the design synthesis and understanding of the high-valent iron-oxo species, and also might provide potential applications in the treatment of alkaline wastewaters.

Starch-Modifying Enzymes.

Starch is a carbohydrate polymer found abundantly on earth. It is synthesized in plants as a short-term storage compound for respiration in the leaves and for long-term storage in the tubers, seeds and roots of plants. A wide variety of enzymes modify or convert starch into various products. The classes of enzymes that act on starch include endoamylases, exoamylases, debranching enzymes and transferases. Starch-modifying enzymes of microbial origin are utilized in a wide variety of industrial applications. Alkaline-active amylases are diverse in terms of optimum reaction conditions, substrate and product specificity. Amylases that are active at lower temperatures and alkaline conditions are most suited for detergent formulation. Other notable starch-modifying enzymes from alkaliphiles include maltooligosaccharide-forming amylases and cyclodextrin glycosyltransferases (CGTases), which produce a variety of maltooligosaccharides and cyclodextrins, respectively. Such compounds are used in the food, fine chemical, pharmaceutical and cosmetic industries, among others. Alkaline-active amylases are also applicable in the paper, textile and leather industries and also in bioremediation and alkaline waste water treatment. Their application in these fields is further enhanced through stabilization and improving their specificity and catalytic action by employing nanotechnology and genetic engineering. Graphical Abstract *Alkaline alpha-amylase AmyK from Bacillus sp. KSM-1378. Shirai T, Igarashi K, Ozawa T, Hagihara H, Kobayashi T, Ozaki K, Ito S (2007) Proteins 66:600-610. Source: Protein Data Bank in Europe (PDBe).

Bentonite/carbon composite as highly recyclable adsorbents for alkaline wastewater treatment and organic dye removal

Alkaline wastewater is high-concentrated and refractory organic wastewater from oil refinery, and its chemical oxygen demand (COD) ranged from tens of thousands to more than 100,000 mg L−1. This kind of wastewater is very difficult to deal with. In this study, natural bentonite (BT) was used as the adsorbent to treat the alkaline wastewater. Subsequently, the used BT containing numerous organic compounds was calcined in inert atmosphere to prepare BT/carbon composite (BTCC). This adsorption-calcinations process can be repeated for 9 times and the adsorption performance does not decrease. The characterization results confirmed that as-prepared BTCC has irregular flake-shaped structures, and the carbon content of samples was increased with increased recycle. The adsorbents can be recycled to deal with alkaline wastewater and reduce the COD value of alkaline wastewater. The percentage removal of COD was 91% after recycling 9 times. Moreover, the recycling BTCC also showed superior adsorption behavior for methylene blue (MB). The equilibrium adsorption isotherms were better fitted by the Freundlich isotherm, and the kinetics model of MB adsorption was ideally conformed to pseudo-second-order model. This process realized the principle of “using waste to treat waste”, and obtained excellent recyclable adsorbent material for organic wastewater treatment.

A novel bioflocculant produced by a salt-tolerant, alkaliphilic and biofilm-forming strain Bacillus agaradhaerens C9 and its application in harvesting Chlorella minutissima UTEX2341

A novel bioflocculant MBF-C9 produced by a salt-tolerant, alkaliphilic Bacillus agaradhaerens C9 was investigated in this study. The effects of culture conditions such as initial pH, carbon source, nitrogen source, C/N ratio, and NaCl concentrations on MBF-C9 production were studied. The result showed that 4.65g/L purified MBF-C9 was extracted with the following optimized conditions: 10g/L glucose as carbon source, 10g/L yeast extract as nitrogen source and initial pH 10.2. The MBF-C9 contained 65.42% polysaccharides, 4.70% proteins, and 1.65% nucleic acids. The highest flocculating rate of 95.29% for kaolin suspension was achieved at a dosage of 1.5mg/L, pH 6.53 and 29°C, and the highest flocculating rate of 80.63% for Chlorella minutissima UTEX2341 cells was observed at a dosage of 8mg/L, which is much lower than that used in previous study. In addition, C9 could form biofilm under alkaline condition. Therefore, C9 has the potentials to be used in harvesting microalgae or as a bacterial agent to strengthen the treatment of alkaline wastewater.

Treatment of Alkaline Waste Water Generated by the Hydrolysis of Rice Husk

This article shows the results of research on finding ways to purify waste water produced by alkaline hydrolysis of rice waste - rice husk. Two methods were used: baromembrane filtration and electrochemical oxidation of organic substances. It was found that in the results of baromembrane processing of hydrolyzate on the membranes mainly stay silicon compounds partially sorbing organic substances contained in the feedstock. Through the membranes there pass the major part of microbiologically oxidated organic matter, so its difficult to reach the required waste water treatment stage. The use of electrochemical oxidation of organic substances extracted by alkaline hydrolysis of rice husks into a solution allows more qualitatively treat the solution. A range of indicators (chemical oxygen demand, permanganate demand, polyphenols) evaluating the content of organic compounds in the desilicated solution showed that in order to remove them effectively enough electrolyte concentration of sodium chloride is 4 g L-1, formed by the desilication and dilution of the solution with the distilled water 1:10.

Efficient degradation of Rhodamine B in microwave-H2O2 system at alkaline pH

Microwave-H2O2 (MW-H2O2) technology, one of the environmental treatment methods, was reported to usually prefer acidic and neutral circumstances in substrates’ degradation. In this work, degradation of Rhodamine B (RhB) and methylene blue (MB) in MW-H2O2 system was found to be very competitive at extreme alkaline pH. This is a new finding and few studies have noticed it yet. Through radical species’ tests and control experiments, degradation of RhB at strong alkaline pH in MW-H2O2 system was considered to mainly undergo oxygen oxidation, and the enhancement of MW thermal effect. This work provided a possible effective way to study the degradation at highly alkaline circumstances, and might promote the development of MW-H2O2 technology in alkaline wastewater treatment.

The Examination of the Boundary Layer Formed on the Nickel Electrode/Solution Interface in the Boundary Layer Separation Method in Plastic Industrial Wastewaters

Strict environmental laws limit the emission of wastewaters formed in the manufacturing of plastics. We have developed a new method for the treatment of alkaline wastewaters, which we have given the name Boundary Layer Separation Method (BLSM). We have utilized the phenomenon that on the surface of an electrically charged electrode, ions can be enriched in the boundary layer, as compared to the liquid phase. The essence of the method is that – with an appropriately chosen velocity – the boundary layer can be removed from the wastewater, and the boundary layer, which is rich in ions, can be recycled. Electrosorption is a surface phenomenon, thus the formation of the boundary layer requires appropriate electrodes. Nickel pastille electrodes prepared with powder metallurgical methods and nickelized nickel electrodes prepared with electrolysis were used for the experiments. The phenomena on the electorde/solution interface were examined in flowing systems. The discharge of the diffuse part of the boundary layer was examined as the function of the flow rate. It is concluded that it is pointless to exceed the relative velocity of 25 cm/s in the case of nickel pastille electrodes and 10 cm/s in the case of nickelized nickel electrodes. Lastly, the ion transport with BLSM and the experimental device is presented. Electrochemical methods, such as BLSM have the advantage of not utilizing dangerous chemicals, only inert electrodes. An additional advantage is that they do not generate further pollutants.

Neutralization of alkaline industrial wastewaters using Exiguobacterium sp.

A facultatively alkaliphilic bacterium capable of lowering the pH of highly alkaline wastewater from 12.0 to 7.5 within just 2.0 h was isolated from industrial wastewater drained sludge of a local beverage industry. The metabolic product which the bacterium produces in order to neutralize alkaline wastewater was found to be carboxylic acid in nature by Fourier Transform- Infrared (FT-IR) spectroscopy. The isolate belongs to genus Exiguobacterium as determined by 16S rRNA gene sequencing and biochemical characterization. It was found to be gram-positive, nonspore-forming, nonmotile, rod shaped, growing aerobically and anaerobically at a wide range of temperatures (5–40 °C), pH (6.5–12.0) and NaCl concentrations(0–9.5%). The strain was able to hydrolyze starch and was catalase positive but lacked oxidase or aminopeptidase activity. Acid was produced from glycerol, cellobiose, d-mannose, mannitol, methyl α- d-glucoside, amygladin and arbutin. From the 16S rRNA gene sequence analysis, the strain appeared to be most similar (99%) to the sequence from Exiguobacterium aurantiacum strain DSM 6208.Neutralization of highly alkaline wastewater without addition of any external carbon source highlights the potential use of the isolate as an alternative to the conventional acid neutralization method for treatment of alkaline wastewater.