Chemical Oxygen Demand Reduction Efficiency Research Articles

Phytoremediation capabilities of Salvinia molesta, water hyacinth, water lettuce, and duckweed to reduce phosphorus in rice mill wastewater

The objective of this study was to investigate the reduction of phosphorus from rice mill wastewater by using free floating aquatic plants. Four free floating aquatic plants were used for this study, namely water hyacinth, water lettuce, salvinia, and duckweed. The aquatic plants reduced the total phosphorus (TP) content up to 80% and chemical oxygen demand (COD) up to 75% within 15 days. The maximum efficiency of TP and COD reduction was observed with water lettuce followed by water hyacinth, duckweed, and salvinia. The study also aims to predict phosphorus removal by three modeling techniques, for example, linear regression (LR), artificial neural network (ANN), and M5P. Prediction has been done considering hydraulic retention time (HRT), hydraulic loading rate (HLR), and initial concentration of phosphorus (Cin) as input variables whereas the reduction rate of TP (R) has been considered as a predicted variable. ANN shows promising results as compared to M5P tree and LR modeling. The model accuracy is analyzed using three statistical evaluation parameters which are coefficient of determination (R2), root mean square error (RMSE), and means absolute error (MAE).

OPTIMIZATION OF THE ELECTRO-FENTON PROCESS FOR COD REDUCTION FROM REFINERY WASTEWATER

This study shows the results of the experimental investigation of refinery wastewater treatment by the electro-Fenton process. The experiments were designed using Taguchi design approach with an orthogonal array (OA) of L16 runs. Four process variables (current density (CD), temperature (T), Fe2+ concentration (Fe2+), and time (t)) at four different levels were considered for the present design. Regression analysis was performed to predict a correlation for the response function (chemical oxygen demand (COD) reduction efficiency) of the treatment process by the electro-Fenton technique. Analysis of variance (ANOVA) was carried out to verify the significant variables that control COD reduction. Moreover, a linear model analysis was implemented for the signal to noise (S/N) ratios with larger the better and for means. Based on S/N ratios and means responses, the operating conditions for optimum COD reduction were: CD = 8 mA/cm2, T = 60 C, Fe2+ = 0.4 mM, and t = 6 h, at which 87.35% of COD was reduced. ANOVA shows that the operating temperature had the most significant impact on COD reduction efficiency. The R-square value for the predicted COD reduction correlation was 90.00%. Considering ranks based on delta statistics, the relative magnitude of effects of the process variables were: T, Fe2+, t, and CD.

Phycoremediation of textile effluent-contaminated water bodies employing microalgae: nutrient sequestration and biomass production studies

Combinatorial process development for rationalized recycling of nutrients employing microalgae may provide realistic solutions to both environment management and energy generation. The present study was performed to investigate nutrient recycling potential of microalgal strains viz. Anabaena ambigua, Chlorella pyrenoidosa and Scenedesmus abundans in terms of biomass productivity and specific growth rate using textile wastewater as a nutrient source at different dilutions (25, 50, 75, 100%). Biomass production kinetics revealed that alga could grow even up to 100% textile wastewater. Comparative phycoremediation potential was evaluated for 25 days employing 75% textile wastewater under batch conditions. The microalgal species were observed to effectively reduce the chloride, nitrate and phosphate concentrations up to 61%, 74.43% and 70.79%, respectively. Maximum chemical oxygen demand reduction efficiency was observed employing S. abundans (< 85%). Spectral analysis revealed potentiality of applying microalgae for textile wastewater remediation and also provided insight into the possible mechanism involved.

Efficiency of activated carbon from palm kernel shell for treatment of greywater

The potential of activated carbon from palm kernel shell (PKS-AC) to improve the quality of surface water and greywater based on the measurements of the parameters pH, turbidity, chemical oxygen demand (COD), total dissolved oxygen (TDS) and total suspended solids (TSS) was investigated in the present study. The PKS was acid treated with aqueous H3PO4 (1 N) for overnight at room temperature and then subjected to heat treatment at 550 °C for 2 h. The efficiency of the PSK-AC samples of 30 and 40 mm thicknesses was examined for reduction of the above parameters in surface water and greywater samples for 5, 15, 30 and 60 min of the filtration process. The efficiency of COD reduction by 50 and 56.44%, that of TDS by 57.81% and 22%, and that of TSS by 83.11 and 42.11% were detected using the PSK-AC samples above, respectively. The OH group contributed most to the removal of pollutants among the OH, N–H, C=O, C=C, C–O–C, C–O–H main functional groups pointed out via Fourier Transform Infra-red (FTIR) analysis on the surface. The scanning electron microscopy (SEM) images revealed that the surface of the raw PSK-AC appeared smooth with holes on the external surface, while the grains were filled in the PSK-AC after the adsorption process.

Advanced Oxidation Processes and Nanofiltration to Reduce the Color and Chemical Oxygen Demand of Waste Soy Sauce

Currently, the ozone (O3) oxidation efficiency in the treatment of waste soy sauce provides 34.2% color removal and a 27.4% reduction in its chemical oxygen demand (COD). To improve the O3 oxidation efficiency, hydrogen peroxide (H2O2) is used to cause a H2O2/O3 process. In H2O2/O3 process experiments, a previously optimized pH of 11 and applied O3 dose of 50 mg L−1 were used and the H2O2/O3 ratio was varied between 0.1 and 0.9 in intervals of 0.2. The results show that an H2O2/O3 ratio of 0.3 results in the highest efficiencies in terms of color removal (51.6%) and COD reduction (33.8%). Nanofiltration (NF) was used to pretreat the waste soy sauce to improve color removal and COD reduction. The results showed that NF with an NE-70 membrane results in 80.8% color removal and 79.6% COD reduction. Finally, the combination of NF and H2O2/O3 process resulted in the best treatment efficiency: 98.1% color removal and 98.2% COD reduction. Thus, NF &amp; H2O2/O3 process can be considered as one of the best treatment methods for waste soy sauce, which requires high intrinsic color removal and COD reduction efficiencies.

Decolorization and mineralization of Amaranth dye using multiple zoned aerobic and anaerobic baffled constructed wetland

ABSTRACTThe objective of this study is to determine the reduction efficiency of Chemical Oxygen Demand (COD) as well as the removal of color and Amaranth dye metabolites by the Aerobic–anaerobic Baffled Constructed Wetland Reactor (ABCW). The ABCW reactor was planted with common reed (Phragmite australis) where the hydraulic retention time (HRT) was set to 1 day and was fed with synthetic wastewater with the addition of Amaranth dye. Supplementary aeration was supplied in designated compartments of the ABCW reactor to control the aerobic and anaerobic zones. After Amaranth dye addition the COD reduction efficiency dropped from 98 to 91% while the color removal efficiency was 100%. Degradation of azo bond in Amaranth dye is shown by the UV–Vis spectrum analysis which demonstrates partial degradation of Amaranth dye metabolites. The performance of the baffled unit is due to the longer pathway as there is the up-flow and down-flow condition sequentially, thus allowing more contact of the wastewater with the rhizomes and micro-aerobic zones.

Microbial fuel cell operation using nitrate as terminal electron acceptor for simultaneous organic and nutrient removal

A double-chambered biocathode microbial fuel cell with carbon felt employed as electrodes was developed for wastewater treatment and bioelectricity generation simultaneously. The system was operated in fed-batch mode for over eight batches. The effect of circuit connections on organic and nitrate reduction was investigated. The maximum power density recorded was 21.97 mW/m2 at current density of 88.57 mA/m2. The Coulombic efficiency and internal resistance of the system were 5% and 100 Ω. Up to 89.9 ± 5.9% of chemical oxygen demand reduction efficiency achieved with an influent of 1123 ± 28 mg/L. There was no significant difference in the chemical oxygen demand reduction when system operated in either open or closed circuit. This study clearly showed that higher nitrate reduction efficiency obtained in closed circuit (74.7 ± 7.0%) due to bio-electrochemical denitrification compared to only 41.7% in the open circuit. The result also successfully demonstrated nitrate as terminal electron acceptor for the cathodic nitrate reduction.

Electrochemical treatment of tannery wastewater—Raw, coagulated, and pretreated by AOPs

ABSTRACTThis study on tannery wastewater treatment showed that indirect electrooxidation by chlorine generated at a Ti/SnO2/PdO2/RuO2 (SPR) anode led to full ammonia removal, and a decrease in chemical oxygen demand (COD) of up to 77.0%. A combined process of coagulation + H2O2/UV + electrooxidation allowed us to achieve a decrease in COD of up to 97.5%. Equations describing the kinetics of the decrease in COD, the relationship between the decrease in COD and current, and the relationship between the current efficiency of COD reduction and the initial concentrations of the reagents were established. The changes in the Adsorbable Organically Bound Halogen (AOX) value were determined, and the individual compounds, including chloroorganics, present in raw and treated wastewater were identified by gas chromatography mass spectrometry (GC-MS). Values of AOX increased in the initial phase of electrooxidation, while afterwards they decreased.

Optimized Removal of Sodium Dodecylbenzenesulfonate by Fenton-Like Oxidation Using Response Surface Methodology

This study investigates the degradation of sodium dodecylbenzenesulfonate (SDBS) in aqueous solution by the Fenton-like oxidation process. The effects of different parameters such as concentrations of ferric chloride and hydrogen peroxide, pH and reaction time on the SDBS removal and Chemical Oxygen Demand (COD) reduction were evaluated. Response Surface Methodology (RSM) with Central Composite Design (CCD) was used to study and optimize the oxidation process. A quadratic polynomial equation could accurately model the SDBS removal with an R2 of 0.98. The results showed that pH and time were the most significant parameters affecting SDBS removal and COD reduction, respectively. A high SDBS (90.5%) and COD (70.7%) reduction efficiency were obtained at the optimal conditions of 60 min, pH 4 and 8.82 mM of H2O2 and 3.67mM of Fe+3. In this work, the effects of some organic compounds on the degradation of SDBS by the Fenton-like process were examined. The results showed that 50 mgL-1of oxalic acid slightly enhanced the SDBS degradation efficiency while acetic acid and Ethylenediaminetetraacetic acid (EDTA) reduced it.

Reuse the pulp and paper industry wastewater by using fashionable technology

This proposed method is a promising way, which can be implemented in pulp and paper industries by effective removal of the color and chemical oxygen demand (COD) and the resulting treated water may surely reuse to the other streams. Fourier Transformer Infra Red spectra confirmed the presence of the respective functional groups in the removed pollutants from the wastewater. The efficiency of Non-ferric Alum (NF Alum) and cationic polyacrylamide (C-PAM) with and without power boiler fly ash was also studied. The reduction efficiency of color and chemical oxygen demand (COD) is evaluated at the optimum dosage of NF Alum, fly ash, and C-PAM. At the optimized pH attained from these coagulants using to treat the wastewater, the flocs formation/settling and the pollutant removal efficiency are encouraging and the resulting color of the wastewater is to 40 PtCo units from 330 PtCo units and COD to 66 mg/L from 218 mg/L. While using NF Alum alone with C-PAM for the treatment of wastewater, the highest reduction efficiency of COD is 97 mg/L from 218 mg/L and the color is 60 from 330 PtCo units at pH 4.8 was noted. From these observations, NF Alum and power boiler fly ash with C-PAM can effectively remove the pollutants from the pulp and paper mill wastewater and the water can be reused for other streams.

Application of Ultrasonication and Hybrid Bioreactor for Treatment of Synthetic Textile Wastewater

AbstractThis study explores the influence of ultrasonic pretreatment on the performance of a hybrid bioreactor treating synthetic textile wastewater. The study primarily focuses on assessing the decolorization and chemical oxygen demand (COD) reduction efficiency of a hybrid bioreactor. The hybrid bioreactor provided anaerobic-aerobic sequential treatment to the ultrasonically pretreated textile wastewater containing two new generation diazo dyes namely, reactive black 5 (RB5) and reactive red (RR120), along with other chemical constituents. Ultrasonic pretreatment produced approximately 52% color and 48% COD reduction efficiency at an optimized power of 200 W and 180 min sonication time. For the hybrid reactor treating ultrasonically pretreated textile wastewater, a maximum of 98% COD and 92% color removal efficiencies were obtained at an HRT of 32 h [organic loading rate (OLR)=0.74 kg COD m−3d−1] and 24 h (OLR=1.0 kg COD m−3 d−1), respectively. Significant levels of aromatic amines formation were obse...

Multiple aerobic and anaerobic baffled constructed wetlands for simultaneous nitrogen and organic compounds removal

The objective of this study is to determine the reduction efficiency of chemical oxygen demand (COD) as well as the removal of NH4+-N and NO3--N by the Aerobic–anaerobic Baffled Constructed Wetland Reactor (ABCW). The ABCW reactor was planted with common reed (Phragmite australis), where the hydraulic retention times was set to 1 d and was fed with synthetic wastewater. Supplementary aeration was supplied in designated compartments of the ABCW reactor to control the aerobic and anaerobic zones. The COD reduction efficiency was 98%, while the NO3--N and NH4+-N removal was 36–98%, respectively, which was due to nitrification and denitrification processes. The outstanding performance of the baffled unit was due to the longer pathway as there is the up-flow and down-flow condition sequentially, thus allowing more contact of the wastewater with the rhizomes and micro-aerobic zones.

Evaluation of flocculating performance of a thermostable bioflocculant produced by marine Bacillus sp.

ABSTRACTThis study assessed the bioflocculant (named MBF-W7) production potential of a bacterial isolate obtained from Algoa Bay, Eastern Cape Province of South Africa. The 16S ribosomal deoxyribonucleic acids gene sequence analysis showed 98% sequence similarity to Bacillus licheniformis strain W7. Optimum culture conditions for MBF-W7 production include 5% (v/v) inoculum size, maltose and NH4NO3 as carbon and nitrogen sources of choice, medium pH of 6 as the initial pH of the growth medium. Under these optimal conditions, maximum flocculating activity of 94.9% was attained after 72 h of cultivation. Chemical composition analyses showed that the purified MBF-W7 was a glycoprotein which was predominantly composed of polysaccharides 73.7% (w/w) and protein 6.2% (w/w). Fourier transform infrared spectroscopy revealed the presence of hydroxyl, carboxyl and amino groups as the main functional groups identified in the bioflocculant molecules. Thermogravimetric analyses showed the thermal decomposition profile of MBF-W7. Scanning electron microscopy imaging revealed that bridging played an important role in flocculation. MBF-W7 exhibited excellent flocculating activity for kaolin clay suspension at 0.2 mg/ml over a wide pH range of 3–11; with the maximal flocculation rate of 85.8% observed at pH 3 in the presence of Mn2+. It maintained and retained high flocculating activity of over 70% after heating at 100°C for 60 min. MBF-W7 showed good turbidity removal potential (86.9%) and chemical oxygen demand reduction efficiency (75.3%) in Tyume River. The high flocculating rate of MBF-W7 makes it an attractive candidate to replace chemical flocculants utilized in water treatment.

Integrated process of fungal membrane bioreactor and photocatalytic membrane reactor for the treatment of industrial textile wastewater

In this study, fungal membrane bioreactor (FMBR) and semiconductor photocatalytic membrane reactor (PMR) were used in order to test the efficiency of integrated fungal biodegradation and photocatalytic degradation of textile wastewater from reactive washing processes. It was found that color removal and chemical oxygen demand (COD) reduction efficiencies were 88% and 53% for photocatalytic degradation, respectively. TiO2 and ZnO were tested as semiconductor catalysts in the PMR and TiO2 showed better efficiencies than ZnO for both color and COD removal. However, it was attained that color removal and COD reduction efficiencies were about 56% and 60% for fungal biodegradation using Phanerochaete chrysosporium, respectively. Moreover, integrated system in which photocatalytic degradation was employed as a post-treatment application after fungal biodegradation process achieved high removal efficiencies for color and COD removal as 93% and 99%, respectively.

Using response surface methodology to evaluate electrocoagulation in the pretreatment of produced water from polymer-flooding well of Dagang Oilfield with bipolar aluminum electrodes

The wide use of polymers to enhance oil recovery can make pumping and rejecting oilfield produced water difficult because of the high viscosity of the treated water. To deal with this problem, this study proposed an electrocoagulation method that is time saving, highly efficient, and easy to apply. A Box–Behnken design coupled with the response surface methodology (RSM) was used to construct a model of the electrocoagulation process that considers three key variables: current density, inter-electrode gap, and operation time. The optimized operational conditions were obtained using second-order polynomial models; they were a current density of 45.6 mA/cm2, an inter-electrode of 3.2 cm, and an operation time of 22.8 min. The results under these conditions were a viscosity reduction of 90.9% and a chemical oxygen demand (COD) reduction of 74.9%. These data strongly correlated with the predicted values of the RSM models. Based on the single and interactive effect analysis, it showed that viscosity and COD reduction efficiency enhanced with increasing operation time. The efficiencies were increased when current density was raised from 20 to 40 mA/cm2 and subsequently decreased from 40 to 60 mA/cm2. They were also increased while inter-electrode gap was enlarged from 2.0 to 4.0 cm and then decreased from 4.0 to 6.0 cm. Furthermore, the practicability of the polymer-flooding produced water treatment under the optimized conditions was proved by UV–vis, zeta potential, and particle size measurement.

Removal Efficiency of Faecal Indicator Organisms, Nutrients and Heavy Metals from a Peri-Urban Wastewater Treatment Plant in Thohoyandou, Limpopo Province, South Africa.

Wastewater treatment facilities are known sources of fresh water pollution. This study was carried out from January to June 2014 to assess the reduction efficiency of some selected contaminants in the Thohoyandou wastewater treatment plant (WWTP). The pH and electrical conductivity of the effluent fell within the South African wastewater discharge guidelines. The WWTP showed the chemical oxygen demand reduction efficiency required by the Department of Water Affairs (DWA) guidelines of 75 mg/L for the months of April and June, although it was below this standard in March and May. Free chlorine concentration varied between 0.26–0.96 mg/L and exceeded the DWA guideline value of 0.25 mg/L. The concentration of nitrate-nitrogen (NO3− N) in the influent and effluent varied between 0.499–2.31 mg/L and 7.545–19.413 mg/L, respectively. The concentration of NO3− N in the effluent complied with DWA effluent discharge standard of 15 mg/L, except in April and May. Phosphate concentrations in the influent and effluent were in the ranges of 0.552–42.646 mg/L and 1.572–32.554 mg/L, respectively. The WWTP showed reduction efficiencies of E. coli and Enterococci during some sampling periods but the level found in the effluent exceeded the recommended guideline value of 1000 cfu/100 mL for faecal indicator organisms in wastewater effluents. Consistent removal efficiencies were observed for Al (32–74%), Fe (7–32%) and Zn (24–94%) in most of the sampling months. In conclusion, the Thohoyandou WWTP is inefficient in treating wastewater to the acceptable quality before discharge.

Characterization of a bioflocculant produced from the consortium of three marine bacteria of the genera Cobetia and Bacillus and its application for wastewater treatment

In this study, we purified and characterized bioflocculant from a mixed culture of three marine bacteria (Cobetia sp. OAUIFE, Bacillus sp. MAYA, and Bacillus sp. Gilbert with accession number JF799092, JF799093, and HQ537128, respectively) isolated from the sediment sample of Algoa Bay South Africa. The bioflocculant from the consortium showed high flocculation of river water, brewery wastewater, and dairy wastewater, with resultant flocculating activities of 96.4%, 93.7%, and 82.2%, respectively. The applicability of the bioflocculant for removing turbidity and reducing chemical oxygen demand (COD) from these real wastewaters was excellent. The bioflocculant turbidity removal efficiency for brewery wastewater was 92%, while its COD reduction efficiency for dairy wastewater was 99%. A scanning electron microscopy (SEM) image of the purified bioflocculant revealed an amorphous morphology, while Fourier transform infra-red (FTIR) analysis also revealed the presence of amino, hydroxyl, and carboxyl functional groups among others, which could be responsible for the high-flocculating activity of the bioflocculant. This environmental-friendly bioflocculant holds promise for application in the field of biotechnology.

Membrane treatment of the bleaching plant (EPO) filtrate of a kraft pulp mill

The objective of this study was to evaluate the use of membrane technology to treat oxygen and peroxide-reinforced extraction stage (EPO) filtrate from a kraft pulp mill bleach plant. Three different types of tubular membranes were tested in a pilot plant: (i) tight ultrafiltration (UF); (ii) open UF followed by nanofiltration (UF+NF); and (iii) nanofiltration (NF). According to the separation performance, considering the chemical oxygen demand (COD) and colour removal, permeate flux, operational simplicity and cost, the results indicated that the best option for treatment of (EPO) filtrates was the tight UF membrane. This membrane obtained a COD removal of 79% with a colour reduction of 86%. The effect of (EPO) filtrate UF treatment on the mill effluent treatment plant was evaluated. Compared with the actual mill effluent, the results indicated that if the UF permeate was recycled in the bleaching area, the COD reduction efficiency increased by 7%, the final effluent colour decreased by 8%, the biological sludge production decreased by 18%, and the energy consumption decreased by 40%. In the tertiary treatment plant, the coagulant dosage decreased by 40%, and the tertiary sludge production decreased by 46%.

Chemical oxygen demand, total organic carbon and colour reduction in slaughterhouse wastewater by unmodified and iron-modified clinoptilolite-rich tuff

In this study, reduction of chemical oxygen demand (COD), colour, and total organic carbon in effluents from a slaughterhouse in central Mexico was performed using clinoptilolite-rich tuff. The experimental parameters considered were initial concentration of the adsorbate, pH, adsorbent dosage, and contact time. Surface morphology of the materials was tested by using scanning electron microscopy. Specific surface area was analysed by using Brunauer–Emmett–Teller (BET) and phase composition was analysed by using X-ray diffraction. The experimental adsorption data were fitted to the first- and pseudo-second-order kinetic models. The highest COD removal was observed in slightly acidic pH conditions. The maximum reduction efficiency of COD was accomplished with unmodified clinoptilolite-rich tuff at a contact time of 1440 min. In these conditions, the adsorbent was efficient for treating wastewater from a slaughterhouse. Moreover, after several regeneration cycles with Fenton reagent or hydrogen peroxide, the regenerated zeolite with H2O2(3%) showed the best reduction efficiencies.

Applicability of a new pre-hydrated industrial grade polyaluminium salt for the decolourisation of textile wastewater

This study was conducted to assess the decolourisation and chemical oxygen demand (COD) reduction efficiency of a novel pre-hydrated aluminium salt as aluminium chlorohydrate (ACH) for the treatment of textile wastewater using coagulation/flocculation technology. Though, ACH belongs to the same group of polyaluminium salts, it is significantly different from polyaluminium chloride (PACl) in terms of the degree of hydration and alumina content and was used for the first time as a coagulant for the decolourisation of synthetic as well as real textile wastewater. The experimental results revealed that ACH is highly effective for the treatment of synthetic textile wastewater producing more than 99% of colour removal and 45% of COD reduction efficiency at a very low dosage of 200 mg L−1. The decolourisation of real textile wastewater was found to be very much in line with the results obtained for the treatment of synthetic textile wastewater. Superior decolourisation efficiency at a very low dosage as compared to that of the pre-established studies for real textile wastewater and least volume of easily dewatered sludge production makes ACH a novel and very promising coagulant for the treatment of industrial textile wastewater.