An integrated smartphone-based electrochemical detection system for highly sensitive and on-site detection of chemical oxygen demand by copper-cobalt bimetallic oxide-modified electrode.

A portable and integrated electrochemical detection system has been constructed for on-site and real-time detection of chemical oxygen demand (COD). The system mainly consists of four parts: (i) sensing electrode with a copper-cobalt bimetallic oxide (CuCoOx)-modified screen-printed electrode; (ii) an integrated electrochemical detector for the conversion, amplification, and transmission of weak signals; (iii) a smartphone installed with a self-developed Android application (APP) for issuing commands, receiving, and displaying detection results; and (iv) a 3D-printed microfluidic cell for the continuous input of water samples. Benefiting from the superior catalytic capability of CuCoOx, the developed system shows a high detection sensitivity with 0.335 µA/(mg/L) and a low detection limit of 5.957 mg/L for COD determination and possessing high anti-interference ability to chloride ions. Moreover, this system presents good consistency with the traditional dichromate method in COD detection of actual water samples. Due to the advantages of cost effectiveness, portability, and point-of-care testing, the system shows great potential for water quality monitoring, especially in resource-limited remote areas.

Factors affecting the performance of a pharmaceutical wastewater treatment plant: Characterization of effluent and environmental risk.

Pharmaceutical industries produce a huge volume of emerging pollutants (EPs) that pose a threat to the aqueous environment. Biological processes have shown their inefficacy in treating many pharmaceutical products. The study assessed physicochemical parameters, EPs, heavy metals in pharmaceutical industrial wastewater, and the removal efficiency (RE) of an aerobic biological treatment plant. The study also assessed the contamination levels and risk using several indices, such as the Canadian Council of Ministers of the Environment Water Quality Index (CCME-WQI), heavy metal pollution index (HPI), heavy metal evaluation index (HEI), and risk quotients index (RQs). The study found that the treated water quality was poor, having antibiotics, nonsteroidal anti-inflammatory drugs, and others, along with several transformation products (TPs) and heavy metals, which were unsafe for consumption with high environmental risk. The analysis results showed that the RE for TSS, BOD5, COD, TDS, and EC were found to be 91.80%, 86.81%, 72.29%, 72.20%, and 65.60%, respectively, where the values of BOD5, COD, NO3-, and PO43- in the effluent were still higher than the permissible limits of the ECR (2023). However, the RE for heavy metals was in the order of Cu (84.62%) > Fe (65.04%) > Mn (63.3%) > Zn (60.58%) > Cd (53.85%) > Ni (54.12%) > Pb (42.42%) > Cr (38%), where Cr and Cd concentrations were still higher than the permissible limit of DoE (2019). The Pearson correlation and PCA suggested that EC, TDS, TSS, DO, BOD5, and COD were the most correlating and contributing variables. This study argued that metal-ligand behaviors mainly affect the removal efficiency of the treatment plant by lowering the removal rate of heavy metals and pharmaceutical products.

Efficient treatment of tannery wastewater through aeration, coagulation, and algal pond.

BACKGROUND: Tannery wastewater effluents contain many toxic and carcinogenic heavy metals and physiochemical parameters that need to be removed before these effluents enter in the main water bodies or rivers. In this study, the effluents from the tannery industry are treated through aeration, coagulation, and Chlorella vulgaris pond treatment processes for the removal of physiochemical: parameters only. METHODS: The effect of removal efficiencies (%) was studied on the physicochemical parameters, including salinity, electrical conductivity (EC), total dissolved solids (TDS), turbidity, total suspended solids (TSS), biochemical oxygen demand (BOD), and chemical oxygen demand (COD). RESULTS: The key results showed that the removal of EC, TDS, turbidity, TSS, BOD, and COD was 80.2%, 67%, 81%, 80.8%, 68.6%, and 100%, respectively, in raw wastewater treatment having 25, 50, and 70 g of algae C. vulgaris doses. The removal efficiencies (%) of salinity, EC, TDS, turbidity, TSS, BOD, and COD were 83%, 87.1%, 77.1%, 80%, 40%, 97%, and 98%, respectively, during coagulated wastewater treatment with three doses of algae. The observed improvement in treated wastewater indicated that the removal efficiencies (%) of salinity, EC, TDS, turbidity, TSS, BOD, and COD were 85.7%, 39.3%, 81.3%, 67.8%, 50.3%, 97%, and 98%, with C. vulgaris. CONCLUSION: This study confirmed that the treatment of tannery wastewater by these processes increased the pollutant removal efficiencies as all the physiochemical parameters were exceeding the permissible limits. RESULTS CONTRIBUTION IN FUTURE: This research will be helpful to treat the industrial wastewaters or effluents before it further mixes up in the main water streams. In this way, water quality will be better, aquatic life will be saved, and further researchers can analyze more ways for efficient treatments as they have a baseline data through this study findings. PRACTITIONER POINTS: One of the most pollutant sources in terms of both physical and chemical parameters is the produced wastewater from tannery industries. The effluents from tannery industry are treated through aeration, coagulation, and algae ponds treatment processes. These treatment made the tannery wastewater as environmental friendly.

Study on H2SO4-modified corn straw biochar as substrate material of constructed wetland.

The high value resource utilization of corn straw is a long-term problem at present and in the future. Biochar preparation is an important utilization way of corn straw. The research on city tail water treated by constructed wetland (CW) with biochar was carried out to further increase the wastewater treatment capacity of the CW. Surface characterization, structural characteristics, and adsorption of straw biochar modified by different acids were measured. The study found that the ability of H2SO4 to remove ash from biochar was stronger than other acids and H2SO4-biochar was easy to be cleaned without H2SO4 residue. The performance of biochar modified by H2SO4 was obviously better than other acids, and the biochar adsorption was enhanced. The modification of biochar substrate modified by H2SO4 in CW reduced the change of electrical conductivity (EC) and promoted denitrification. H2SO4-modified biochar promoted the absorption of N and P by Iris pseudacorus L. The compound modification effect of straw biochar was obvious. The results revealed the acid modification characteristics of straw biochar, which were beneficial for increasing the wastewater treatment rate by CW. This study will promote the sustainable development of CW.

[Chemical Oxygen Demand(COD) Composition and Contribution in Typical Waters of Baiyangdian Lake].

Chemical oxygen demand (COD) is an important index used to assess organic oxygen consumption pollution. To explore COD composition in the natural water in Baiyangdian Lake, the main composition, source, and influencing factors of oxygen-consuming organic substances in the water body were revealed through physical continuous classification, three-dimensional fluorescence, and other methods. The results showed that the COD of the two waters was affected by dissolved organic substances (protein-like and humus-like organic matters) with size of less than 220 nm (59%-93%), and inorganic substances had little effect on COD. The source of organic matter in overlying water was primarily affected by endophytic vegetation decomposition, sediment release (the release flux of TOC was in the range of 1.55-2.28 mg·(m2·d)-1), and other endogenous sources (biological index>0.8), as well as by land-based sources such as reed platform and artificial pollution (1.4

Sensing of chemical oxygen demand (COD) by amperometric detection-dependence of current signal on concentration and type of organic species.

The standard method to determine chemical oxygen demand (COD) with K2Cr2O6 uses harmful chemicals, has a long analysis time, and cannot be used for on-site online monitoring. It is therefore necessary to find a fast, cheap, and harmless alternative. The amperometric determination of COD on boron-doped diamond (BDD) electrodes is a promising approach. However, to be a suitable alternative, the electrochemical method must at least be able to determine the COD of water samples independently of the contained substances. Therefore, the current signal as a function of various organic materials was investigated for the first time. It was shown that the height of the signal current depended on the type of organic matter in single-substance solutions and that this substance dependency increases with the amount of COD. Those findings could be explained by the mechanism proposed for this reaction, showing that the selectivity of the reaction depends on the ratio of the concentration of hydroxyl radicals and organic species. We give an outlook on how to improve the method in order to increase the linear working range and avoid signal variance and how to further explain the signal variance.

Electrochemical treatment of electroplating wastewater using synthesized GO/TiO2 nanotube electrode.

The graphene oxide (GO) deposited TiO2 nanotube (GO/TiO2) electrode on a titania plate was prepared using a simple anodization method. The morphological and structural properties of TiO2 and GO/TiO2 electrodes have been studied using field emission scanning electron microscopy energy dispersive spectroscopy (FESEM-EDS), X-ray diffraction (XRD), UV-vis diffuse reflectance spectroscopy (UV-vis DRS), Raman spectroscopy, Fourier transform infrared spectra (FT-IR), and X-ray photoelectron spectroscopy (XPS). FESEM-EDS analysis confirmed that the 13.56% wt of GO nanoparticles was formed over the TiO2 substrate, with the thickness of the wall to be ∼300 nm. The crystallite size of GO/TiO2, i.e., 19.53 nm, was confirmed by XRD analysis. Analysis of the UV-DRS spectrum showed the bandgap of the synthesized GO/TIO2 nanotube electrode to be 3.052 eV. Box-Behnken design (BBD) under response surface methodology (RSM) was used to design the experiments. The effect of operating input parameters like pH, current (i), and degradation time (t) on % COD degradation (X1) and energy consumed (X2) were also examined. At optimum process parameters, the value of X1 and X2 were 57.61% and 15.00 kWh/m3, respectively. Possible intermediates were identified based on the GC-MS data analysis. Scavenger tests showed that •OH radical plays a major role in electroplating effluents degradation. Based on the results, the EO process using GO/TiO2 electrodes could be considered a promising technique for electroplating effluent degradation due to high degradation efficiency.

Study on the Treatment of Refined Sugar Wastewater by Electrodialysis Coupled with Upflow Anaerobic Sludge Blanket and Membrane Bioreactor.

In this paper, refined sugar wastewater (RSW) is treated by electrodialysis (ED) coupled with an upflow anaerobic sludge blanket (UASB) and membrane bioreactor (MBR). The salt in RSW was first removed by ED, and then the remaining organic components in RSW were degraded by a combined UASB and MBR system. In the batch operation of ED, the RSW was desalinated to a certain level (conductivity < 6 mS·cm-1) at different dilute to concentrated stream volume ratios (VD/VC). At the volume ratio of 5:1, the salt migration rate JR and COD migration rate JCOD were 283.9 g·h-1·m-2 and 13.84 g·h-1·m-2, respectively, and the separation factor α (defined as JCOD/JR) reached a minimum value of 0.0487. The ion exchange capacity (IEC) of ion exchange membranes (IEMs) after 5 months of usage showed a slight change from 2.3 mmol·g-1 to 1.8 mmol·g-1. After the ED treatment, the effluent from the tank of the dilute stream was introduced into the combined UASB-MBR system. In the stabilization stage, the average COD of UASB effluent was 2048 mg·L-1, and the effluent COD of MBR was maintained below 44-69 mg·L-1, which met the discharge standard of water contaminants for the sugar industry. The coupled method reported here provides a viable idea and an effective reference for treating RSW and other similar industrial wastewaters with high salinity and organic contents.

An optimized sono-heterogeneous Fenton degradation of olive-oil mill wastewater organic matter by new magnetic glutarlaldehyde-crosslinked developed cellulose.

The present study highlights the olive mill wastewater (OMW) treatment characteristics through a sono-heterogeneous Fenton process using new designed [GTA-(PDA-g-DAC) @Fe3O4] and characterized by Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), thermogravimetric analysis (TGA), magnetic properties measurements, and point of zero charge (pH pzc) analysis. A preliminary removal study showed significant degradation efficiency (75%) occurred combining the magnetic synthesized catalyst [GTA-(PDA-g-DAC)@Fe3O4] ([catalyst] = 2 g/L) with US /H2O2 and maintaining 500WL-1 ultrasonic power (US). The values obtained by US only were (13%), H2O2/US (18%), US/Fe3O4 (28%), and US /Fe3O4/H2O2(35%). The catalytic findings have shown that [GTA-(PDA-g-DAC)@Fe3O4] exhibited good properties for OMW compound's degradation. The sonocatalytic process coupling and extra oxidant addition resulted in the degradation substantial levels. For instance, the concomitant effect of degradation optimized parameters; H2O2 10 mM, [GTA-(PDA-g-DAC) @Fe3O4] nanocomposites 2.5 g/L, at pH 3, and T 35 °C for 70 min resulted in an almost complete mineralization of aqueous OMW solution followed by a significant decolorization. Oxidation results exhibited efficient degradation rates in total phenolic compounds (TPC), total amino compounds (TAC), and chemical oxygen demand (COD) oxidation rate were 89.88, 92.75, and 95.66 respectively following the optimized sono-heterogeneous catalytic Fenton process. The prepared magnetic catalyst exhibited a good stability during repeated cycles. The gathered findings gave the evidence that sono-heterogeneous catalytic Fenton process is a promising treatment technology for OMW effluents.

Impact of reactor configuration on pilot-scale microbial fuel cell performance.

Different microbial fuel cell (MFC) configurations have been successfully operated at pilot-scale levels (>100 L) to demonstrate electricity generation while accomplishing domestic or industrial wastewater treatment. Two cathode configurations have been primarily used based on either oxygen transfer by aeration of a liquid catholyte or direct oxygen transfer using air-cathodes. Analysis of several pilot-scale MFCs showed that air-cathode MFCs outperformed liquid catholyte reactors based on power density, producing 233% larger area-normalized power densities and 181% higher volumetric power densities. Reactors with higher electrode packing densities improved performance by enabling larger power production while minimizing the reactor footprint. Despite producing more power than the liquid catholyte MFCs, and reducing energy consumption for catholyte aeration, pilot MFCs based on air-cathode configuration failed to produce effluents with chemical oxygen demand (COD) levels low enough to meet typical threshold for discharge. Therefore, additional treatment would be required to further reduce the organic matter in the effluent to levels suitable for discharge. Scaling up MFCs must incorporate designs that can minimize electrode and solution resistances to maximize power and enable efficient wastewater treatment.

An approach to removing COD and BOD based on polycarbonate mixed matrix membranes that contain hydrous manganese oxide and silver nanoparticles: A novel application of artificial neural network based simulation in MATLAB.

This study aimed to determine the efficacy of novel ultrafiltration and mixed matrix membrane (MMM) composed of hydrous manganese oxide (HMO) and silver nanoparticles (Ag-NPs) for the removal of biological oxygen demand (BOD) and chemical oxygen demand (COD). In the polycarbonate (PC) MMM, the weight percent of HMO and Ag-NP has been increased from 5% to 10%. A neural network (ANN) was used in this study to compare PC-HMO and Ag-NP. MMM was evaluated in combination with HMO and Ag-NP loadings in order to assess their effects on pure water flux, mean pore size, porosity, and efficacy in removing BOD and COD. HMO and Ag-NPs can decrease membrane porosity in the casting solution while increasing mean pore size. According to the study's findings, the artificial neural network model appears to be highly appropriate for predicting the removal of BOD and COD. To develop a successful model, a suitable input dataset was selected, which consisted of BOD and COD. An ideal model architecture for MMM was proposed based on an optimal number of hidden layers (2 layers) and neurons (5-8 neurons). Experiments and predicted data show a strong correlation between the developed models. BOD was predicted with an excellent R2 and a low root mean square error (RMSE) of 0.99 and 0.05%, respectively, while COD was predicted with an excellent R2 and a low RMSE of 0.99 and 0.09%, respectively. Based on the results, Ag-NP was found to be an excellent candidate for the preparation of MMMs as well as convenient for the removal of BOD and COD from polluted water sources.

Sulfur(IV) assisted oxidative removal of organic pollutants from source water.

The removal of organic pollutants presents a major challenge for drinking water treatment plants. The chemical oxygen demand (COD) is essentially the measure of oxidizable organic matter in source waters. In this study, we report that COD can efficiently be decreased by adding Fe(II)/Fe(III) and sulfite ion to the source water while purging it with air. In this process, oxygen is activated to oxidize the main constituents of COD, i.e. organic substrates, via the generation of reactive inorganic oxysulfur radical ions. In the end, the total amount of sulfur(IV) is converted to the non-toxic sulfate ion. It has been explored how the COD removal efficiency depends on the concentration of S(IV), the total concentration of iron species, the concentration ratio of Fe(II) and Fe(III), the purging rate and the contact time by using source water from a specific location (Királyhegyes, Hungary). The process has been optimized by applying the Response Surface Methodology (RSM). Under optimum conditions, the predicted and experimentally found COD removal efficiencies are in excellent agreement: 85.4% and 87.5%, respectively. The robustness of the process was tested by varying the optimum values of the parameters by ± 20%. It was demonstrated that the method is universally applicable because a remarkable decrease was achieved in COD, 62.0-88.5%, with source waters of various compositions acquired from 9 wells at other locations using the same conditions as in the case of Királyhegyes.

Effects of biochar on water quality and rice productivity under straw returning condition in a rice-wheat rotation region.

Straw returning is helpful to improve soil properties and realize the reutilization of agricultural waste. However, wheat straw returning may result in paddy water quality deterioration in rice-wheat rotation regions. This study conducted pot experiments of rice planting with different biochar application rates (0, 5, 20, and 40 t/hm2) under wheat straw returning conditions. The purposes are to investigate the applicability of biochar mixed with wheat straw returning to paddy fields and explore the effects of biochar on water quality, leaching losses of nitrogen (N) and phosphorus (P), and rice yield components. Results indicated that total straw returning reduced the water quality in paddy surface water and aggravated the leaching losses of N and P. Fortunately, the biochar application improved the negative effects caused by straw returning. 40 t/hm2 biochar mixed with straw returning significantly reduced the concentrations of COD and N in paddy surface water and N leaching loss than straw returning treatment (ST), decreased by 48.33%, 41.01%, and 45.73%, respectively. Meanwhile, applying biochar at a rate of 20 t/hm2 with straw returning is suitable to control the diffusion of P. In addition, the ST treatment had no significant effect on rice yield, while the proper application rate of biochar under straw returning condition can improve rice yield and promote N utilization. 20 t/hm2 biochar treatment is more effective to improving rice yield (16.89%) and N use efficiency (NUE) (10.14%). These findings can provide a new method to solve the negative effects of total straw returning on the water environment and rice growth and guide the utilization of straw resources in the rice-wheat rotation regions.

Treatment of Poultry Slaughterhouse Wastewater (PSW) Using a Pretreatment Stage, an Expanded Granular Sludge Bed Reactor (EGSB), and a Membrane Bioreactor (MBR).

This study presents the biological treatment of poultry slaughterhouse wastewater (PSW) using a combination of a biological pretreatment stage, an expanded granular sludge bed reactor (EGSB), and a membrane bioreactor (MBR) to treat PSW. This PSW treatment was geared toward reducing the concentration of contaminants present in the PSW to meet the City of Cape Town (CoCT) discharge standards and evaluate an alternative means of treating medium- to high-strength wastewater at low cost. The EGSB used in this study was operated under mesophilic conditions and at an organic loading rate (OLR) of 69 to 456 mg COD/L·h. The pretreatment stage of this laboratory-scale (lab-scale) plant played an important role in the pretreatment of the PSW, with removal percentages varying between 20% and 50% for total suspended solids (TSS), 20% and 70% for chemical oxygen demand (COD), and 50% and 83% for fats, oil, and grease (FOG). The EGSB further reduced the concentration of these contaminants to between 25% and 90% for TSS, 20% and 80% for COD, and 20% and >95% for FOG. The last stage of this process, i.e., the membrane bioreactor (MBR), contributed to a further decrease in the concentration of these contaminants with a peak removal performance of >95% for TSS and COD and 80% for the FOG. Overall, the system (pretreatment-EGSB-MBR) exceeded 97% for TSS and COD removal and 97.5% for FOG removal. These results culminated in a product (treated wastewater) meeting the discharge standards.

The Removal of Selected Inorganics from Municipal Membrane Bioreactor Wastewater Using UF/NF/RO Membranes for Water Reuse Application: A Pilot-Scale Study.

Membrane technology has advanced substantially as a preferred choice for the exclusion of widespread pollutants for reclaiming water from various treatment effluent. Currently, little information is available about Ultrafiltration (UF)/Nanofiltration (NF)/Reverse Osmosis (RO) performance at a pilot scale as a practical engineering application. In this study, the effluent from a full-scale membrane bioreactor (MBR) municipal wastewater treatment works (MWWTWs) was treated with an RO pilot plant. The aim was to evaluate the effect of operating conditions in the removal of selected inorganics as a potential indirect water reuse application. The influent pH, flux, and membrane recovery were the operating conditions varied to measure its influence on the rejection rate. MBR/RO exhibited excellent removal rates (>90%) for all selected inorganics and met the standard requirements for reuse in cooling and irrigation system applications. The UF and NF reduction of inorganics was shown to be limited to meet water standards for some of the reuse applications due to the high Electron Conductivity (EC > 250 µS·cm-1) levels. The MBR/NF was irrigation and cooling system compliant, while for the MBR/UF, only the cooling system was compliant.

Performance of Salvinia molesta plants in tertiary treatment of domestic wastewater.

The objective of this study was to investigate the performance of different weight of Salvinia molesta plants in biological treatment of domestic wastewater. Three treatment systems containing 280g (GS1), 140g (GS2) and 70g (GS3) of S. molesta plants were used for the phytoremediation process. Physicochemical analysis such as pH, colour, chemical oxygen demand (COD), and biological oxygen demand (BOD5) of the influent and effluent water samples were performed according to spectrophotometric methods. The outcome of the study demonstrated that the different weight of S. molesta plants played a significant role in improving the quality of the wastewater samples, in which GS1 removed 96.8% (colour), 91% (BOD5), and 82.6% (COD). While up to 88.6% (colour), 87.1% (BOD5), and 81.1% (COD) reduction was observed for GS2 treatment systems, and GS3 was efficient in removing 85.5% (colour), 86.1% (BOD5), and 68.3% (COD). Also, a pH value of 6.29-7.19, 5.97-7.07, and 6.17-7.42 was obtained from GS1, GS2 and GS3 treatment systems, respectively. Thus, the treatment system with the highest quantity of S. molesta (GS1) demonstrated better performance compared to the other two systems (GS2 and GS3). The findings of this research can be applied in addressing the goals of sustainable development through the use of green technology to reduce the threat of water pollution in natural water bodies. Perhaps existing and future water scarcity can be resolved through the use of phytoremediation technology.

Estimating the chemical oxygen demand of petrochemical wastewater treatment plants using linear and nonlinear statistical models - A case study.

In this research, twelve linear and nonlinear regression models were performed and evaluated to formulate the best one for the estimation of chemical oxygen demand level in the effluent of the clarifier unit of a petrochemical wastewater treatment plant. The input variables measured twice a day in the influent of the biological unit over a period of 13 months using standard methods. The piece-wise linear regression with breakpoint method, with a mean squared error value equal to 0.041, mean absolute error of 0.144, and correlation coefficient equal to 0.835 was found to estimate the output chemical oxygen demand parameter more sustainable rather than other linear and nonlinear methods. However, some of the other applied models such as radial basis function neural network and gene expressing programming models achieved good performance considering their correlation coefficient, robustness in presence of outliers, mean squared error and mean absolute error test. Mathematical and intelligent modeling proved useful as an accurate alternative to estimate the amount of chemical oxygen demand rather than spending time and cost for its laboratory tests.

An electro-Fenton process to treat waste liquor of a hyperaccumulator that contains potentially toxic elements and the COD.

Rapid and safe treatment of harvested fresh biomass of hyperaccumulators is essential for phytoremediation of metal-contaminated soils. Here, an electro-Fenton (EF) process was used to remove cadmium (Cd) and chemical oxidation demand (COD) from waste liquor from the dewatering of biomass of the hyperaccumulator Sedum plumbizincicola after flocculation precipitation. The results showed that the order of impact of the factors on the removal rate of COD and Cd was pH > electrical current density > H2O2 dosage. Increasing pH promoted Cd removal but hindered COD removal. As current density and H2O2 dosage increased the removal rates of both Cd and COD initially increased and then decreased. Compared to an electrocoagulation process, the addition of H2O2 in EF process greatly enhanced Cd and zinc (Zn) removal. Speciation analysis showed that most of the Cd and Zn in the initial liquor were organically and inorganically complexed. At optimal conditions, e.g., pH 5, current density 15 mA cm-2 and H2O2 dosage 9 g L-1, the removal efficiencies of Cd, Zn and COD reached 99.4, 99.9 and 55.5% after 80 min of EF treatment. Electro-Fenton process can therefore be used to quickly remove trace metals from the waste liquor of the hyperaccumulator.

Electrocoagulation pre-treatment to simultaneously remove dissolved and colloidal substances and Ca2+ in old corrugated container wastewater.

An effective electrocoagulation pre-treatment (ECP) method was proposed to simultaneously solve the problems of the micro stickies deposition and high Ca2+ content in old corrugated container (OCC) papermaking wastewater during the recycling process. The optimal ECP condition was investigated. The results indicated that the effect of an Al electrode on wastewater treatment was superior to that of a Fe or Mg electrode. The optimal treatment conditions of the current density, electrode distance and reaction time were 115 A m-2, 5 cm and 60 min, respectively. After the ECP, the chemical oxygen demand (COD) and Ca2+ removal rates were 75.33% and 64.53%, respectively, and the turbidity and dissolved and colloidal substance (DCS) content decreased by 97.1% and 43.68%, respectively. The particle size of flocs in the liquid increased from 1.675 µm to 31.97 µm, and the floc content was 0.78 g L-1 after ECP. The anode material and energy consumption were 0.1846 kg m-3 and 4.56 kWh m-3, respectively, and the cost of treatment was estimated to be 1.11 $ m-3. The results demonstrate that ECP can effectively remove the micro stickies, COD, and Ca2+ in the OCC wastewater, which is conducive to reducing the cost of wastewater treatment and conform to the requirements of sustainable development.

Molecular and culture-based surveys of metabolically active hydrocarbon-degrading archaeal communities in Sundarban mangrove sediments.

Archaea remain important players in global biogeochemical cycles worldwide, including in the highly productive mangrove estuarine ecosystems. In the present study, we have explored the diversity, distribution, and function of the metabolically active fraction of the resident archaeal community of the Sundarban mangrove ecosystem, using both culture-independent and culture-dependent approaches. To evaluate the diversity and distribution pattern of the active archaeal communities, RNA based analysis of the 16S rRNA gene was performed on an Illumina platform. The active Crenarchaeal community was observed to remain constant while active Euryarchaeal community underwent considerable change across the sampling sites depending on varying anthropogenic factors. Haloarchaea were the predominant group in hydrocarbon polluted sediments, leading us to successfully isolate eleven p-hydroxybenzoic acid degrading haloarchaeal species. The isolates could also survive in benzoic acid, naphthalene, and o-phthalate. Quantitative estimation of p-hydroxybenzoic acid degradation was studied on select isolates, and their ability to reduce COD of polluted saline waters of Sundarban was also evaluated. To our knowledge, this is the first ever study combining culture-independent (Next Generation sequencing and metatranscriptome) and culture-dependent analyses for an assessment of archaeal function in the sediment of Sundarban.