Electrocoagulation using Ti/Ti for the remediation and reuse of aqueous Dispersive Blue-79

The entire ecology is contaminated by the synthetic dyes that are widely utilised in the textile industries. They can be handled using a variety of technologies, but an eco-friendly method called electrocoagulation has been used to prevent additional contamination. Textile wastewater containing disperse dyes are successfully treated in Electrocoagulation (EC) utilizing Al, Fe, and Stainless Steel (SS), but it is not cost effective, also the treated water contains certain mg/L of the metals used, along with dye components, which obstructs the reuse of the same. The effects of initial pH, applied voltage, dye concentration, supporting electrolyte, and treatment time on the colour removal efficiency (CRE) and consumption of energy were examined in EC process followed by activated charcoal filtration (hybrid process) with a monopolar Ti/Ti electrode on the remediation of aqueous solution of Dispersive Blue-79 (dye 3G). The maximum CREobtained was 99.4%, chemical oxygen demand (COD) 93%, and biological oxygen demand (BOD) 85%, under the following optimized operating conditions, applied voltage 15 V, pH = 7, concentration of dye, electrolyte 110 mg/L, 0.2 g/L and time = 15 min. The overall operating cost for the treatment of aqueous dye 3G was 0.455US/m3. The mechanism of EC was studied using XPS analysis in the sludge obtained. For the purpose of the reuse, FTIR, AAS, and ICP-OES analysis were done and compared with the aqueous dye 3G, after EC and hybrid process to ensure the maximum removal of the degraded dye components and metal. ICP-OES results showed that there were no traces of metal in the treated aqueous dye 3G using this method. Throughout the study, the experimental outcomes indicated that the hybrid process upgraded the quality of the treated aqueous dye 3G.

Photocatalytic O2 activation by metal-free carbon nitride nanotube for rapid reactive species generation and organic contaminants degradation

Advanced oxidation processes (AOPs) using oxygen (O₂) as an oxidant represent a low-cost and sustainable wastewater treatment process. Herein, a metal-free nanotubular carbon nitride photocatalyst (CN NT) was prepared to activate O₂ to degrade organic contaminants. The nanotube structure allowed for sufficient O₂ adsorption, while the optical and photoelectrochemical properties enabled photogenerated charge to be efficiently transferred to the adsorbed O₂ to trigger the activation process. The developed CN NT/Vis-O₂ system based on O₂ aeration degraded various organic contaminants and mineralized 40.7% of chloroquine phosphate within 100 min. In addition, the toxicity and environmental risk of treated contaminants were reduced. Mechanistic studies suggested that the enhanced O₂ adsorption capacity and fast charge transfer behavior on CN NT surface led to reactive·O₂^-, ¹O₂ and h⁺ generation, each of which played a distinct role in contaminants degradation. Importantly, the proposed process could overcome the interference from water matrices and outdoor sunlight, and the energy and chemical reagent savings reduced the operating cost to about 1.63 US$·m^-3. Altogether, this work provides insights into the potential application of metal-free photocatalysts and green O₂ activation for wastewater treatment.

Granulated biomass fly ash coupled with fenton process for pulp and paper wastewater treatment

The work describes the combination of granulated biomass fly ash (G_BFA) with Fenton process to enhance the removal of adsorbable organic halides (AOX) from pulp bleaching wastewater. At optimal operating conditions, wastewater's chemical and biochemical oxygen demand (COD and BOD₅, respectively) and colour were also quantified, and operating cost of treatment assessed. For the first time, raw pulp bleaching wastewater was used to granulate BFA, instead of water, reducing the water footprint of the treatment. Five wastewater treatment setups were studied: (i) conventional Fenton process; (ii) G_BFA application; (iii) simultaneous application of G_BFA and Fenton process; (iv) sequential treatment by G_BFA followed by Fenton process; (v) sequential treatment by Fenton process followed by G_BFA. The latter yielded the highest AOX removal (60-70%), whilst COD was also reduced (≈15%) and wastewater biodegradability (BOD₅/COD) was enhanced from 0.075 to a maximum of 0.134. Another positive feature of the proposed solution was that G_BFA were successfully recovered and reused without regeneration, yielding similar AOX removal compared with fresh G_BFA. The operating cost of removing 1 g of AOX from the pulp bleaching wastewater by the optimal treatment setup (60-70% removal of AOX) was 14-26% lower than the operating cost of conducting Fenton process alone (50% removal of AOX).

Valorisation of residual iron dust as Fenton catalyst for pulp and paper wastewater treatment

In this work, the performance of residual iron dust (RID) from metallurgic industry was assessed as Fenton catalyst for the treatment of real pulp bleaching wastewater. The focus was on the removal of recalcitrant pollutants AOX (adsorbable organic halides), by a novel, cleaner, and cost-effective circular solution based on a waste-derived catalyst. The behaviour of RID as iron source was firstly assessed by performing leaching tests at different RID:wastewater w/v ratios and contact time. Afterwards, RID-catalysed homogeneous and heterogeneous Fenton processes were conducted to maximise AOX removal from the pulp bleaching wastewater. Reusability of RID was assessed by a simple collect-and-reuse methodology, without any modification. Similar AOX removal under less consumption of chemicals was achieved with the novel heterogeneous Fenton process. Reaction in the bulk solution was the main pathway of AOX removal, given that the low surface area and porosity of the material did not allow for a high contribution of surface reaction to the overall performance. Moreover, AOX removal was similar over two consecutive treatment cycles, with Fenton process being responsible for 56.7-62.1% removal of AOX from the wastewater, and the leaching step adding 11.4-13.2%. At the end of treatment, COD either decreased (1^st cycle) or remained unchanged (2^nd and 3^rd cycle). The operating cost of the optimised heterogeneous Fenton was 3-11% lower than under conventional Fenton process. This work presented a novel, circular solution based on a low-cost waste-derived catalyst, advancing the knowledge needed to foster industrial application of such technologies to increase industrial environmental performance and efficiency.

Treatment of printing ink wastewater using a continuous flow electrocoagulation reactor

Printing ink wastewater from printing facilities is difficult to treat because of its heavy pollutant load (chemical oxygen demand - COD, color and total suspended solids - TSS). In this study undiluted printing ink wastewater with high COD (i.e., 20,000 mgL^-1) was treated using a highly efficient, continuous flow electrocoagulation reactor with aluminum electrodes. The parameters investigated were: initial COD concentration (4000, 10,000 and 20,000 mgL^-1), current density (21, 42 and 83 mAcm^-2), and inlet flow rate (6, 8 and 10 mLmin^-1). All parameters showed great efficiency in terms of pollutant removal for diluted printing ink wastewater. For undiluted printing ink wastewater treatment, COD, color, and TSS removal were maximized at 6 mLmin^-1 flow rate reaching 82%, 98%, and 85% COD, color, and TSS removal, respectively, by applying the lower tested current density 21 mAcm^-2. COD, color and TSS removal increased with increasing current density. For undiluted printing ink wastewater and a flow rate of 8 mLmin^-1, COD removal was between 42 and 88%, color reduction between 85 and 99%, and TSS reduction between 83 and 98% when the applied current was increased (from 21 to 83 mAcm^-2). Lower pollutant removal was observed at the highest flow rate of 10 mLmin^-1 for all current densities tested. Process cost calculations in terms of electrical energy, electrode material consumption and sludge disposal, showed that the use of continuous flow electrocoagulation reactor (with flow rate 6 mLmin^-1, and at 21 mAcm^-2) is an affordable and effective treatment method for printing ink wastewater streams with very high COD. Sludge characterization showed Al-silicate-rich sludge. Particle sizes increased after treatment and Cu and Ti were detected in the sludge. A post-treatment stage is necessary before discharging effluent into water bodies.

Relation analysis on emission control and economic cost of SCR system for marine diesels

In order to meet the IMO Tier III emissions regulations and reduce environmental pollution, many ocean-going vessels have installed the marine SCR system to reduce NOx emissions. However, the investment cost and operation cost of the marine SCR system, as well as the factors affecting the SCR cost are still the problems that need to be studied. In this paper, MAN S46 diesel engine matched SCR system was taken as the research object, and a cost calculation model of Marine SCR system based on cost analysis method has been proposed. The relationship between SCR system cost and some factors such as unit capacity, unit running time and inlet NOx concentration have been analyzed. The research we have done suggests that operating time, NOx inlet concentration, and emission limits are the three main important factors in the operating cost of an SCR system. Among the various secondary costs of operating costs, the reducing agent cost, fuel increase cost, and indirect annual cost account for 60%, 24%, and 7%, respectively. Moreover, the results suggest that the unit denitration cost of the matched SCR system is highly affected by the power of the diesel engine and annual running time. This study demonstrated clearly the relationship between emission control and economic cost of SCR system for marine diesels and was expected to provide a theoretical basis for sustainable development in marine environmental protection policies.

Sulfur autotrophic denitrification filter and heterotrophic denitrification filter: Comparison on denitrification performance, hydrodynamic characteristics and operating cost

Sulfur autotrophic denitrification (SAD) process, as an alternative to heterotrophic denitrification (HD) filter, receives growing interest in polishing the effluent from secondary sewage treatment. Although individual studies have indicated several advantages of SAD over HD, rare study has compared these two systems under identical condition and by using real secondary effluent. In this study, two small pilot scale filters (SAD and HD) were designed with identical configuration and operated parallelly by feeding the real secondary effluent from a WWTP. The results showed SAD filter can be started up without the addition of soluble electron donor, although the time (14 days) was about 3 times longer than that of HD filter. The nitrate removal rate of SAD filter at HRT of 1.4 h was measured as 0.268 ± 0.047 kg N/(m³∙d). Similar value was observed in HD filter with supplementing 90 mg/L COD. The COD concentration of effluent always kept lower than that of influent in SAD filter but not in HD filter. In addition, SAD filter could maintain a stable denitrification performance without backwash for 15 days, while decline of nitrate removal rate was observed in HD filter just 2 days after stopping the backwash. This different behavior was further confirmed as the SAD filter had a better hydraulic flow pattern. Analysis according to high-throughput 16S rRNA gene-based Illumina MiSeq sequencing clearly showed the microbial community evolution and differentiation among the samples of seed sludge, SAD and HD filters. Finally, the economic assessment was carried out, showing the operation cost of SAD filter was over 50% lower than that of HD filter.

Escherichia coli inactivation using a hybrid ultrasonic-electrocoagulation reactor

In the current study, a new hybrid ultrasonic-electrocoagulation reactor (U-E reactor) has been used to inactivate Escherichia coli in water. The new hybrid reactor consists of an ultrasonic bath fitted with four perforated aluminium electrodes. These perforated electrodes are designed to act as baffle-plates to enhance the water-mixing process. The electrodes eliminate the need for external mixing devices, which in turn, enhances the cost-effectiveness of the unit. Initially, the ability of the electrocoagulation to inactivate E. coli was optimised for different operating parameters such as electrolysing time (T_e), electrodes spacing (ES) and current density (CD). The ultrasonic field was then applied over different time periods (T_u), during the course of the electrolysing process. Statistical analyses have been conducted to assess the relative effect of each operating parameter on the inactivation of E. coli. An economic study has also been conducted to assess the operating costs of the U-E reactor. The results revealed that the new U-E reactor inactivated 100% of the E. coli within 11 min of electrolysis at ES of 5 mm, CD of 1.5 mA/cm², and an operation cost of 0.212 US $/m³. It was been established that the relative effect of operating parameters on E.coli inactivation followed the order: T_e>T_u>CD>ES.

Operating cost analysis of a concentric aluminum tubes electrodes electrocoagulation reactor

Energy consumed by the electrochemical treatment of wastewater has more responsibility in designing such a process. The objective of the present study was to investigate the effect of electrodes geometry used in the electrocoagulation cell on the operating cost that required to remove lead from the industrial wastewater. The studied operating variables in the present study were the initial concentration of lead (10–300)ppm, electrolysis time (5–60)minutes, applied electric current (0.5–2.5)Amps., pH (2–12), and stirring speed (0–300)rpm. It has shown that cost was affected by the configuration of aluminum electrodes as well as other studied parameters. Statistical methods and programs were used to estimate an empirical correlation of the operating cost as well as the consumption of aluminum electrodes and energy.

Treatment of printing ink wastewater using electrocoagulation

The present study investigates the treatment of real printing ink wastewater by using the electrocoagulation (EC) process. Effects of initial chemical oxygen demand (COD) concentrations, electrode materials and current densities were examined to determine the maximum COD and color removal from the wastewater. In parallel, raw and treated printing ink wastewater toxic potential was further estimated via the application of toxicity tests using the freshwater crustacean Thamnocephalus platyurus for assessing EC process efficiency. According to the results, it was observed that the EC is efficient under most of the operating conditions used, as COD and color removal ranged between 72.03 to 85.81% and 98.7-100%, respectively. The total cost of the EC process, considering the treatment time, applied current, applied voltage and the total anode electrode mass consumption was also estimated. The Fe electrode proved to be of lower cost than the Al electrode, however the use of Al electrode produced better decolorization results in the solutions. Moreover, toxicity tests currently performed with the use of larvae of the fairy shrimp Thamnocephalus platyurus revealed a substantial decrease in the toxic potential of printing ink wastewater, thus indicating the efficiency of the proposed EC process.

Evaluation of direct and alternating current on nitrate removal using a continuous electrocoagulation process: Economical and environmental approaches through RSM

This study aims to investigate the effects of alternating current (AC) and direct current (DC) for nitrate removal and its operating costs by using a continuous electrocoagulation (CEC) process. For this purpose, two series of 31 experiments, which were designed by response surface method (RSM), were carried out in both cases of the AC and the DC modes. In each series, the effect of selected parameters, namely, initial nitrate concentration, inlet flow rate, current density and initial pH along with their interactions on the nitrate removal efficiency as well as its operating costs, as responses, were investigated separately. According to the analysis of variance (ANOVA), there is a reasonable agreement between achieving results and the experimental data for both responses. The nitrate removal in the AC mode was slightly more efficient than that of the DC mode. In addition, the average operating costs of the DC mode, including the energy and the electrode consumption for the CEC process were achieved 54 US$/(kg nitrate removed); whereas this amount was calculated 29 US$/(kg nitrate removed) for the AC mode. Therefore, the average of the operating costs was improved more than 40% using the AC mode, which was mainly related to reduction of aluminum electrode consumption.

Removal of phosphate from River water using a new baffle plates electrochemical reactor

During the last 50 years, the human activities have significantly altered the natural cycle of phosphate in this planet, causing phosphate to accumulate in the freshwater ecosystems of some countries to at least 75% greater than preindustrial levels, which indicates an urgent need to develop efficient phosphate treatment methods. Therefore, the current study investigates the removal of phosphate from river water using a new electrochemical cell (PBPR). This new cell utilises perforated baffle plates as a water mixer rather than magnetic stirrers that require power to work. This study investigates the influence of key operational parameters such as initial pH (ipH), current density (Ј), inter-electrode distance (ID), detention time (t) and initial phosphate concentration (IC) on the removal efficiency, and influence of the electrocoagulation process on the morphology of the surface of electrodes.

Overall, the results showed that the new reactor was efficient enough to reduce the concentration of phosphate to the permissible limits. Additionally, SEM images showed that the Al anode became rough and nonuniform due to the production of aluminium hydroxides. The main advantages of the electrocoagulation technique are:

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The EC method does not produce secondary pollutants as it does not required chemical additives, while other traditional treatment methods required either chemical or biological additives [[1], [2], [3], [4]].

•

It has a large treatment capacity and a relatively short treatment time in comparison with other treatment methods, such as the biological methods [1,[5], [6], [7]].

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The EC method produces less sludge than traditional treatment traditional chemical and biological treatment methods [8,9].

EC technology, like any other treatment method, has some drawbacks that could limit its performance. For instance, it still has a clear deficiency in the variety of reactor design, and the electrodes should be periodically replaced as they dissolve into the solution due to the oxidation process [2,10].

Electrochemical treatment of carwash wastewater using Fe and Al electrode: Techno-economic analysis and sludge characterization

The present study was conducted to investigate the electrochemical treatment of carwash wastewater using electrocoagulation (EC) process with Fe and Al electrodes. The effects of operating conditions such as initial pH (2-10), current density (0.1-5 mA/cm²) and operating time (5-50 min) on chemical oxygen demand (COD), oil-grease, chloride removal efficiencies as well as total operating costs were studied. The optimum conditions that achieve higher removal efficiencies were found as pH: 8, current density: 3 mA/cm², operating time: 30 min for Fe electrode and pH: 6, current density: 1 mA/cm², operating time: 30 min for Al electrode. The removal efficiencies for COD, oil-grease and chloride were obtained as 88%, 90% and 50% for Fe and 88%, 68% and 33% for Al electrodes under the optimum conditions. The total operating costs at the optimum conditions were calculated as 0.6 $/m³ and 0.3 $/m³ for Fe and Al electrodes, respectively. The sludge samples generated after EC process were characterized with Fourier transform infrared (FTIR) spectroscopy and zeta potential measurements for both electrodes. The analyses showed the presence of hydroxides and oxyhydroxides in the sludge samples and the surface of the sludge samples was negatively charged in the wide range of pH. As a conclusion, this study revealed that EC process using Fe electrode should be a feasible technology for higher COD and oil-grease removals from carwash wastewaters.

Defluoridation of drinking water using a new flow column-electrocoagulation reactor (FCER) - Experimental, statistical, and economic approach

A new batch, flow column electrocoagulation reactor (FCER) that utilises a perforated plate flow column as a mixer has been used to remove fluoride from drinking water. A comprehensive study has been carried out to assess its performance. The efficiency of fluoride removal (R%) as a function of key operational parameters such as initial pH, detention time (t), current density (CD), inter-electrode distance (ID) and initial concentration (C₀) has been examined and an empirical model has been developed. A scanning electron microscopy (SEM) investigation of the influence of the EC process on morphology of the surface of the aluminium electrodes, showed the erosion caused by aluminium loss. A preliminary estimation of the reactor's operating cost is suggested, allowing for the energy from recycling of hydrogen gas hydrogen gas produced amount. The results obtained showed that 98% of fluoride was removed within 25 min of electrolysis at pH of 6, ID of 5 mm, and CD of 2 mA/cm². The general relationship between fluoride removal and operating parameters could be described by a linear model with R² of 0.823. The contribution of the operating parameters to the suggested model followed the order: t > CD > C₀ > ID > pH. The SEM images obtained showed that, after the EC process, the surface of the anodes, became non-uniform with a large number of irregularities due to the generation of aluminium hydroxides. It is suggested that these do not materially affect the performance. A provisional estimate of the operating cost was 0.379 US $/m³. Additionally, it has been found that 0.6 kW/m³ is potentially recoverable from the H₂ gas.

Simultaneous arsenic and fluoride removal from synthetic and real groundwater by electrocoagulation process: Parametric and cost evaluation

Co-existence of arsenic and fluoride in groundwater has raised severe health issues to living being. Thus, the present research has been conducted for simultaneous removal of arsenic and fluoride from synthetic groundwater by using electrocoagulation process with aluminum electrode. Effects of initial pH, current density, run time, inter electrode distance and NaCl concentration over percentage removal of arsenic and fluoride as well as operating cost have been studied. The optimum experimental conditions are found to be initial pH: 7, current density: 10 A/m², run time: 95 min, inter electrode distance: 1 cm, NaCl concentration: 0.71 g/l for removal of 98.51% arsenic (initial concentration: 550 μg/l) and 88.33% fluoride (initial concentration: 12 mg/l). The concentration of arsenic and fluoride in treated water are found to be 8.19 μg/l and 1.4 mg/l, respectively, with an operating cost of 0.357 USD/m³ treated water. Pseudo first and second order kinetic model of individual and simultaneous arsenic and fluoride removal in electrocoagulation have also been studied. Produced sludge characterization studies also confirm the presence of arsenic in As(III) form, and fluoride in sludge. The present electrocoagulation process is able to reduce the arsenic and fluoride concentration of synthetic as well as real groundwater to below 10 μg/l and 1.5 mg/l, respectively, which are maximum contaminant level of these elements in drinking water according to WHO guidelines.

Iron removal, energy consumption and operating cost of electrocoagulation of drinking water using a new flow column reactor

The goal of this project was to remove iron from drinking water using a new electrocoagulation (EC) cell. In this research, a flow column has been employed in the designing of a new electrocoagulation reactor (FCER) to achieve the planned target. Where, the water being treated flows through the perforated disc electrodes, thereby effectively mixing and aerating the water being treated. As a result, the stirring and aerating devices that until now have been widely used in the electrocoagulation reactors are unnecessary. The obtained results indicated that FCER reduced the iron concentration from 20 to 0.3 mg/L within 20 min of electrolysis at initial pH of 6, inter-electrode distance (ID) of 5 mm, current density (CD) of 1.5 mA/cm², and minimum operating cost of 0.22 US $/m³. Additionally, it was found that FCER produces H₂ gas enough to generate energy of 10.14 kW/m³. Statistically, it was found that the relationship between iron removal and operating parameters could be modelled with R² of 0.86, and the influence of operating parameters on iron removal followed the order: C₀>t>CD>pH. Finally, the SEM (scanning electron microscopy) images showed a large number of irregularities on the surface of anode due to the generation of aluminium hydroxides.

Cost Analysis of Spinal Versus General Anesthesia for Lumbar Diskectomy and Laminectomy Spine Surgery

BACKGROUND

Lumbar spine surgery can be performed using various anesthetic modalities, most notably general or spinal anesthesia. Because data comparing the cost of these anesthetic modalities in spine surgery are scarce, this study asks whether spinal anesthesia is less costly than general anesthesia.

METHODS

A total of 542 patients who underwent elective lumbar diskectomy or laminectomy spine surgery between 2007 and 2011 were retrospectively identified, with 364 having received spinal anesthesia and 178 having received general anesthesia. Mean direct operating cost, indirect cost (general support staff, insurance, taxes, floor space, facility, and administrative costs), and total cost were compared among patients who received general and spinal anesthesia. Linear multiple regression analysis was used to identify the effect of anesthesia type on cost and determine the factors underlying this effect, while controlling for patient and procedure characteristics.

RESULTS

When controlling for patient and procedure characteristics, use of spinal anesthesia was associated with a 41.1% lower direct operating cost (-$3629 ± $343, P < 0.001), 36.6% lower indirect cost (-$1603 ± $168, P < 0.001), and 39.6% lower total cost (-$5232 ± $482, P < 0.001) compared with general anesthesia. Shorter hospital stay, shorter duration of anesthesia, shorter duration of operation, and lower estimated blood loss contributed to lower costs for spinal anesthesia, but other factors beyond these were also responsible for lower direct operating and total costs.

CONCLUSIONS

When comparing the benefits of spinal and general anesthesia, spinal anesthesia is less costly when used in patients undergoing lumbar diskectomy and laminectomy spine surgery.

Accelerated carbonation using municipal solid waste incinerator bottom ash and cold-rolling wastewater: Performance evaluation and reaction kinetics

Accelerated carbonation of alkaline wastes including municipal solid waste incinerator bottom ash (MSWI-BA) and the cold-rolling wastewater (CRW) was investigated for carbon dioxide (CO2) fixation under different operating conditions, i.e., reaction time, CO2 concentration, liquid-to-solid ratio, particle size, and CO2 flow rate. The MSWI-BA before and after carbonation process were analyzed by the thermogravimetry and differential scanning calorimetry, X-ray diffraction, and scanning electron microscopy equipped with energy dispersive X-ray spectroscopy. The MSWI-BA exhibits a high carbonation conversion of 90.7%, corresponding to a CO2 fixation capacity of 102g perkg of ash. Meanwhile, the carbonation kinetics was evaluated by the shrinking core model. In addition, the effect of different operating parameters on carbonation conversion of MSWI-BA was statistically evaluated by response surface methodology (RSM) using experimental data to predict the maximum carbonation conversion. Furthermore, the amount of CO2 reduction and energy consumption for operating the proposed process in refuse incinerator were estimated. Capsule abstract: CO2 fixation process by alkaline wastes including bottom ash and cold-rolling wastewater was developed, which should be a viable method due to high conversion.