Chemical Oxygen Demand Removal Performance Research Articles

Effect of Green synthesized iron nanoparticles by Azardirachta Indica in different proportions on antibacterial activity

Green synthesis of iron nanoparticles has accumulated an ultimate interest over the last few years to their distinctive properties, applicable in various fields of science and technology. In the present study, synthesis of iron nanoparticles using Azadirachta Indica leaf extract is performed. Different proportions of precursor (ferrous sulphate) to leaf extract were prepared by varying the volume quantity of leaf extract from 1:1 to 1:5. Their morphology, structure and size distribution is confirmed by Scanning Electron Microscope along with X-ray energy dispersive spectroscopy and Fourier Transform Infrared spectroscopy analysis. Presence of accountable polyphenols such as total phenolic content by Folin-Ciocalteau(FC) method (20 mg per gram of leaf extract) and gallic acid(0.280 mg/g), caffeic acid(0.278 mg/g) &catechin(0.532 mg/g) for synthesis conciliation and were quantified by High Performance Liquid Chromatography. Its performance is evaluated on treatment of petrochemical refinery waste water to assess Chemical Oxygen Demand(COD) and nitrate removal for different proportions. The performance of COD removal (77%) and nitrate removal(74%) for 1:5 on 5th day is observed to be efficient. To further study this effect, size of FeNPs formed and concentration of polyphenols were taken into consideration. Antibacterial activity of synthesized iron nanoparticles from AI leaf extract on bacteria (Escherichia Coli, Pseudomonas Aeruginosa, and Staphylococcus Aureus) is accomplished by well diffusion method. Size of FeNPs achieved for 1:2 ratio was 98–200 nm and for all proportions varying between 120 and 600 nm due to agglomeration enhanced bacterial decay. It was portrayed that there was an increase in the inhibition zone as the proportions increased from 1:2 to 1:5. Hence for the contact time of 48 h, 1:5 found to be effective in inhibiting more number of bacterial cells compared to other proportions.

Modeling of expanded granular sludge bed reactor using artificial neural network

In present study, a three-layer backpropagation neural network (BPNN) model was developed to predict the performance of an expanded granular sludge bed (EGSB) reactor. Six related variables such as influent chemical oxygen demand (COD) concentration, hydraulic retention time (HRT), alkalinity (ALK) concentration, pH, volatile fatty acid (VFA) concentration and oxidation reduction potential (ORP), were selected as inputs of the model. All input values were converted to the range (−1, 1) before passing them into the network. Activation function of hidden layer and output layer were “tansig” and “purelin” individually. Several comparisons were conducted to obtain an optimal network structure. Dividerand function was chosen to divide the operating data into training group, testing group and validation group. The Levenberg Marquardt algorithm (trainlm) was found as the best of the ten training algorithms. Other model parameters such as number of neurons in the hidden layer (X1), initial adaptive value (X2) and initial value of weights and biases (X3) were optimized using response surface methodology (RSM). The optimum conditions for minimum mean squared error (MSE) were as follows: X1 (12), X2 (6.0) and X3 (1.0). The precision of optimum ANN model was assessed by means of various statistics such as MSE, determination coefficient (R2), coefficient of variation (CV) and MSE. The result indicated that the proposed ANN model exhibited superior predictive accuracy for the forecast of COD removal performance by EGSB system. Finally, the results of connection weights method demonstrated that VFA concentration (50.37%) had a remarkable impact on reactor performance.

Removal of organic and inorganic substances from industry wastewaters using modified aluminosilicate‐based polyethersulfone ultrafiltration membranes

Membrane separation processes are attracting increasing interest for the treatment of industrial wastewaters owing to its high organic and inorganic content removal efficiency and material stability. Herein, we have presented an approach to modify polyethersulfone (PES) membrane using aluminosilicate particles (ASPs) for high permeability and separation performance against tannery and distillery wastewater. PES:ASPs ultrafiltration membrane was developed by phase inversion technique at different weight ratios of 0:100, 10:90, 20:80, 30:70, and 40:60 of PES:ASPs. The functional groups and hydrophilicity were analyzed by X‐ray diffraction (XRD) and contact angle, respectively. The modified membranes displayed improved wastewater permeability and higher flux compared to the neat PES membrane. The moderate removal of biochemical oxygen demand (BOD), chemical oxygen demand (COD), total dissolved solids, chlorides, and sulfates from tannery and distillery wastewaters were attained for all ASPs‐based PES membranes. In the case of tannery effluent treatment, high BOD reduction of 92% was observed for 80:20 weight ratio of PES:ASPs membrane and 75% BOD reduction for the pure PES membrane. The sulfides removal was 2.21 mg L−1 for 90:10 weight ratio of PES:ASPs membrane when compared with the initial quantity of 42 mg L−1 distillery wastewater. The PES:ASPs membrane with 80:20 weight ratios presented the best COD and BOD removal performance. © 2017 American Institute of Chemical Engineers Environ Prog, 36: 1612–1620, 2017

Membrane Aerated Biofilm Reactors for Thermomechanical Pulping Pressate Treatment

Abstract A comparative study on the treatment of thermomechanical pulping (TMP) pressate between thermophilic (55 °C) and mesophilic (30 °C) membrane aerated biofilm reactors (MABRs) was conducted under different cycle lengths (CLs) for over 114 days. The performance of the MABRs was evaluated in terms of soluble chemical oxygen demand (COD) removal and biofilm detachment. With a total influent COD of 3,700–4,100 mg/L, the soluble COD removal efficiency of thermophilic MABR (40–65 %) was slightly lower than that of mesophilic MABR (50–80 %) under different CLs. The level of effluent suspended solids (ESS) in treated effluent of the thermophilic MABR was generally higher than that of the mesophilic MABR, suggesting a more significant biofilm detachment from membrane surfaces in the thermophilic MABR. The performance of COD removal improved at the time five to ten days after each significant biofilm detachment. The results suggest that MABR is a promising technology for TMP pressate treatment and biofilm thickness control is important for achieving better performance.

Roughness and temperature effects on the filter media of a trickling filter for nitrification

The performance of trickling filters using two types of plastic media with the same material, the same shape and different roughness was evaluated during a temperature-decreasing period to understand the roughness and temperature effects on the filter media. Real restaurant wastewater was used for the experiments. The chemical oxygen demand (COD) removal and nitrification performance of plastic media with a rough surface (LT-15) was superior to that with a smooth surface (KT-15). Because the biomass of microorganisms attached on the LT-15 was twice that attached on the KT-15, the larger biomass attached on the LT-15 was thought to be responsible for the higher performance. During the operation, the COD loading and water temperature varied in the range from 0.37 to 1.9 kg m −3 d −1 and 17.0−10.0°C, respectively. However, the COD removal performance was not dependent on the COD loading or water temperature. On the contrary, the COD loading and the water temperature influenced the nitrification performance. Although a nitrification efficiency of 100% was recorded at a COD loading of 0.37 kg m −3 d −1, it deteriorated to 17–28% at higher COD loading. Moreover, a decline in the water temperature decreased the nitrification performance. The temperature-activity coefficient for nitrification was estimated to be 1.096. Based on this value, it was inferred that the COD loading should be set at less than 0.20 kg m −3 d −1 for the complete nitrification of the restaurant wastewater in winter, when the water temperature usually drops to around 10°C.

Potential of KMnO4 and H2O2 in treating semi-aerobic landfill leachate

Treatment of recalcitrant landfill leachate was carried out using hydrogen peroxide (H2O2) and potassium permanganate (KMnO4). The treatment performance was reported in terms of colour, chemical oxygen demand (COD) and ammoniacal nitrogen (NH4-N). The effect of oxidant dosages and pH was determined and optimum conditions were determined considering the removal of parameters of interest. The optimum dosage of both oxidants was similar in terms of COD removal; however, H2O2 gave better removal (42 %) and similar results were obtained for NH4-N (24 %). KMnO4 proved better in terms of colour with a reduction of 74 % compared to 43 % by hydrogen peroxide at pH 7. Acidic conditions (pH 2–5) proved conducive towards the removal of all parameters with the exception of COD removal by KMnO4 that exhibited a low removal at pH 5 and increased with increasing pH. The COD reduction at pH 3 was ~38 % for KMnO4 and H2O2, whereas the reduction in NH4-N was 22 and 28 % for KMnO4 and H2O2, respectively. The COD and NH4-N removal performance of H2O2 was better compared with KMnO4; however, consistently higher colour removal was obtained for KMnO4.

Enhanced removal of contaminant using the biological film, anoxic–anaerobic–aerobic and electro-coagulation process applied to high-load sewage treatment

In order to explore a new treatment process applying to decentralized domestic sewage treatment, and enhance removal of total nitrogen (TN), total phosphorus (TP) and chemical oxygen demand (COD), a novel system integrating anoxic–anaerobic–aerobic (reversed A2O) and electro-coagulation (EC) process was studied, and complex biological media (CMB) was used as suspended carrier for biofilm development. In this work, TN, TP and COD removal performance were investigated with consideration of three major factors, hydraulic retention time (HRT), organic loading rate (OLR) and sludge recycle ratio (SRR). Results showed that (1) The optimum HRT was between 8 and 12 h. The removal efficiencies of TN, TP and COD were about 68%, 95% and 95%, respectively. (2) With the increase of OLR, the removal efficiency of TN increased slowly. But it increased first and then declined for COD and TP removal. Their maximum were attained when OLR was 1.8 g(COD)/(L d), and they were 96% and 93%, respectively. (3) The optimum SRR was 75%. The COD, TN and TP removal efficiencies were about 95%, 72% and 98%, respectively. In this system, the maximum TN and COD removal were achieved in anoxic tank, but it was achieved in aerobic tank for TP removal. The EC bed enhanced the effluent quality, especially the efficiency in advanced P removal. From these results, it was concluded that the new process could be a reliable option for providing excellent effluent quality.

Mineralization and Kinetics of Reactive Brilliant Red X-3B by a Combined Anaerobic–Aerobic Bioprocess Inoculated with the Coculture of Fungus and Bacterium

Mineralization of Reactive Brilliant Red X-3B by a combined anaerobic-aerobic process which was inoculated with the co-culture of Penicillium sp. QQ and Exiguobacterium sp. TL was studied. The optimal conditions of decolorization were investigated by response surface methodology as follows: 132.67g/L of strain QQ wet spores, 1.09g/L of strain TL wet cells, 2.25g/L of glucose, 2.10g/L of yeast extract, the initial dye concentration of 235.14mg/L, pH 6.5, and 33°C. The maximal decolorization rate was about 96% within 12h under the above conditions. According to the Haldane kinetic equation, the maximal specific decolorization rate was 89.629mg/g˙h. It was suggested that in the anaerobic-aerobic combined process, decolorization occurred in the anaerobic unit and chemical oxygen demand (COD) was mainly removed in the aerobic one. Inoculation of fungus QQ in the anaerobic unit was important for mineralization of X-3B. Besides, the divided anaerobic-aerobic process showed better performance of COD removal than the integrated one. It was suggested that the combined anaerobic-aerobic process which was inoculated with co-culture was potentially useful for the field application.

Contaminant removal performances on domestic sewage using modified anoxic/anaerobic/oxic process and micro-electrolysis

The objective of this study was to enhance removal of chemical oxygen demand (COD), total nitrogen (TN) and total phosphorus (TP) from domestic sewage in a sequencing batch reactor with added new materials. A modified anoxic/anaerobic/oxic (MAAO) process, integrating a micro-electrolysis (ME) bed in an anoxic tank, and complex biological media (CBM) in anoxic, anaerobic and oxic tanks to treat domestic sewage, and their performances were investigated. The MAAO system was operated at controlled hydraulic reTENTion time (HRT) of 8 h and mixed liquor recirculation (MLR) at 75%. The results showed that the MAAO system could effectively remove COD, TN and TP with average rates of 93%, 80% and 94%, respectively, in March, and 94%, 76% and 91%, respectively, in August. In this system, TP was primarily removed from the anoxic tank regardless of the operational conditions; removal contribution ratios to TP of the anoxic tank reached 56% both in March and August, indicating that the ME bed can effectively enhance phosphorus removal. TN was primarily removed from the anoxic and anaerobic tanks; removal contribution ratios to TN of anoxic and anaerobic tanks reached 36–38% and 37–38%, respectively. The oxic tank had the highest share of COD removal (56% both in March and August) in the removal of phosphorus. The outflow concentrations of COD, TN and TP were 3–46, 7–14 and 0.3–0.5 mg/L, respectively, in March, and 26–49, 9–15 and 0.04–0.1 mg/L, respectively, in August. COD and TN removal performances indicated that the innovative materials of the ME bed and CBM can effectively enhance COD and TN removal.

Enhancement of Coagulation Process with Floatation for the Treatment of Dyeing Wastewater

Coagulation process enhanced with floatation was applied to treat dyeing wastewater generated from the production process of textile. The efficiency was mainly evaluated in terms of the chemical oxygen demand (COD) removal of mixed wastewater. Comparing the coagulation experiment with coagulation-floatation experiment on the performance of COD removal for the dyeing wastewater, we can find that floatation promote the effect of coagulation. The results show that: the COD removal of the dyeing wastewater in the coagulation-floatation experiment can reach 68% after floatation with the speed of 1.2 L/min for 4 min and maintaining standstill for 90 min, which is 17% more than the result appeared in coagulation experiment, under the conditions of the dosage of AlCl3and PAM is 100 mg/L and 15 mg/L, respectively.

Biodegradation characteristics and size fractionation of landfill leachate for integrated membrane treatment

The fate of organics and nitrogen during the biological treatment with MBR and subsequent membrane filtration processes (nano filtration, NF; reverse osmosis, RO) were investigated for a landfill leachate. The chemical oxygen demand (COD) and total Kjeldahl nitrogen (TKN) removal performances of membrane bioreactor (MBR) were obtained to be around 89% and 85%, respectively. The effluent COD of MBR was measured to be 1935mg/L (30kDa) which is much lower than experimentally determined soluble inert COD of 3200mg/L using 0.45μm filter. The readily and slowly biodegradable COD fractions were estimated to be 17% and 52% of raw influent COD, respectively. The respirometry based modeling test performed on raw leachate exhibited much slower degradation kinetics compared to municipal wastewater. A unique subset of model parameters was extracted from batch respirometry by using acclimated MBR sludge. The sequential ultrafiltration (UF) experiments (particle size distribution, PSD) revealed that most of the organics was below 2nm filter mesh size. In addition, NF/RO post treatment after MBR system was required to increase COD and total nitrogen (TN) removal performances up to 99%. Relatively lower salt rejection rates around 94% was obtained for RO system as a post treatment of MBR system.

Improving the settling properties of activated sludge by gradually decreasing the settling time

The study aims at evaluating the impact of gradually decreasing the settling time on settling properties of activated sludge removing organic matter. For that, a lab-scale sequencing batch reactor (SBR), fed with soluble starch and acetate, was seeded with floccular biomass. As the selected strategy to washout slowly settling flocks and retain biomass with improved settling capacity, settling time (Ts) was decreased gradually from 45 to 30, 15, 5 and 1 min. Long-term monitoring showed that each time the Ts was decreased to the next lower level, there was biomass washout. Yet high amount of biomass (10 g MLVSS/L) with improved settling properties (sludge volume index ⩽ 16 mL/g) and high chemical oxygen demand (COD) removal performance (97%) was maintained with a Ts as low as 5 min. Further decreasing Ts to 1 min did not impose any negative effect. Biomass maintenance, settling properties, and COD removal performance of the system were comparable with those of aerobic granular biomass. Yet, minimum settling velocities corresponding to 5 and 1 min settling times applied at the last two phases of operation (0.4 and 2.0 cm/min) were lower than those reported for granular biomass systems, hence the biomass remained floccular but the system had an exceptionally good settling capacity and COD removal efficiency.

Optimal performance of COD removal during aqueous treatment of alazine and gesaprim commercial herbicides by direct and inverse neural network

A direct and inverse artificial neural network (ANN and ANNi) approach was developed to predict the chemical oxygen demand (COD) removal during the degradation of alazine and gesaprim commercial herbicides under various experimental conditions. The configuration 9–9–1 (9 inputs, 9 hidden and 1 output neurons) presented an excellent agreement (R 2 = 0.9913) between experimental and simulated COD value considering the hyperbolic tangent sigmoid and linear transfer function in the hidden layer and output layer. The sensitivity analysis showed that all studied input variables (reaction time, pH, herbicide concentration, contaminant, US ultrasound, UV light intensity, [TiO 2] o,[K 2S 2O 8] o, and SR solar radiation) have strong effect on the degradation of the commercial herbicide in terms of COD removal. In addition, reaction time is the most influential parameter with relative importance of 33.49%, followed by initial herbicide concentration. COD optimal performance was carried out by inverting artificial neural network. Now, ANNi could calculate the optimal unknown parameter (reaction time) to obtain a COD required. Very low percentage of error and short computing makes this methodology attractive to be applied to the on-line control of Advanced Oxidation Process (AOP) over the degradation of commercial herbicide.

Effects of selected pharmaceutically active compounds on treatment performance in sequencing batch reactors mimicking wastewater treatment plants operations

The impact of four pharmaceutically active compounds (PhACs) introduced both individually and in mixtures was ascertained on the performance of laboratory-scale wastewater treatment sequencing batch reactors (SBRs). When introduced individually at concentrations of 0.1, 1 and 10 μM, no significant differences were observed with respect to chemical oxygen demand (COD) and ammonia removal. Microbial community analyses reveal that although similarity index values generally decreased over time with an increase in PhAC concentrations as compared to the controls, no major microbial community shifts were observed for total bacteria and ammonia-oxidizing bacteria (AOB) communities. However, when some PhACs were introduced in mixtures, they were found to both inhibit nitrification and alter AOB community structure. Ammonia removal decreased by up to 45% in the presence of 0.25 μM gemfibrozil and 0.75 μM naproxen. PhAC mixtures did not however affect COD removal performance suggesting that heterotrophic bacteria are more robust to PhACs than AOB. These results highlight that the joint action of PhACs in mixtures may have significantly different effects on nitrification than the individual PhACs. This phenomenon should be further investigated with a wider range of PhACs so that toxicity effects can more accurately be predicted.

Impacts of cell surface characteristics on population dynamics in a sequencing batch yeast reactor treating vegetable oil-containing wastewater

Ten yeast strains acquired from different sources and capable of utilizing vegetable oil or related compounds (fatty acid or oleic acid) as sole carbon sources were inoculated into a sequencing batch reactor (SBR) for the treatment of high-strength vegetable oil-containing wastewater. The SBR system stably removed >89% of chemical oxygen demand (COD) and >99% of oil when fed with wastewater containing 15g/L COD and 10g/L oil in average. Denaturing gradient gel electrophoresis of polymerase chain reaction-amplified 26S rRNA genes showed that among the ten yeast strains, only Candida lipolytica, Candida tropicalis, and Candida halophila were dominant in the system. To elucidate the major factors affecting the selection of yeast strains in the SBR system, the three dominant strains were compared with two non-dominant strains in terms of COD removal performance, biomass yield, cell settleability, cell flocculation ability, cell emulsification ability, and surface hydrophobicity. Results showed that hydrophobicity and emulsification ability of yeast cells were the two most important factors determining the selection of yeast strains in the treatment of high-strength oil-containing wastewater.

Influence of elevated pH shocks on the performance of a submerged anaerobic membrane bioreactor

The effects of elevated pH shocks on the performance and membrane fouling of a submerged anaerobic membrane bioreactor (SAnMBR) treating thermomechanical pulping (TMP) whitewater was studied over a 120-day period. Changes in chemical oxygen demand (COD) removal, biogas production, sludge and cake layer properties, and their correlations to membrane fouling – before and after pH shocks – were systematically studied using various analytical tools. The results showed that a pH 8.0 shock had a minor impact, while pH 9.1 and 10.0 shocks exerted significant long-lasting negative impacts on COD removal, biogas production and membrane filtration performance of the SAnMBR. When the normal pH (7.0) was resumed, it took approximately 1, 6, and 30 days for the performance to recover for pH 8.0, 9.1 and 10.0 shocks, respectively. The elevated pH shocks induced the dispersion of sludge flocs and resulted in the accumulation of colloids and solutes or biopolymers in the sludge suspension, and thus deteriorated membrane performance. Statistical analysis showed that the ratio of proteins (PN) to polysaccharides (PS) in extracellular polymeric substances (EPS) had a strongly negative effect on the membrane fouling rate. There were smaller size particles deposited on the membrane surface and a more compact and denser cake layer was formed after being exposed to an alkaline shock at pH 10, resulting in higher membrane fouling rates.

Performance of COD removal from oxide chemical mechanical polishing wastewater using iron electrocoagulation

This study investigated the feasibility of chemical oxygen demand (COD) abatement from oxide chemical mechanical polishing (oxide-CMP) wastewater. The process variables, including applied voltage, electrolyte concentration and temperature, were evaluated in terms of COD removal efficiency. In addition, the effects of applied voltage, supporting electrolyte, and temperature on electric energy consumption were evaluated. Under the optimum balance of variables, satisfactory COD removal efficiency and relatively low energy consumption were achieved. The optimum electrolyte concentration, applied voltage, and temperature were found to be 200 mg/L NaCl, 20 V, and 25°C, respectively. Under these conditions, the COD concentration in oxide-CMP wastewater decreased by more than 90%, resulting a final wastewater COD concentration that was below the Taiwan discharge standard (100 mg/L). Since the processed wastewater quality exceeded the direct discharge standard, the effluent could be considered for reuse. COD removal rates obtained during the electrocoagulation process can be described using a pseudo-kinetic model. The present study results show that the kinetic data fit the pseudo first-order kinetic model well. Finally, the morphology and composition of the sludge produced were characterized using scanning electron microscopy (SEM) and energy dispersion spectra (EDS).

Decolorisation of H‐acid manufacturing process wastewater by anion exchange resin

Anion exchange resin was employed to examine the feasibility to treat the H‐acid manufacturing wastewater by column experiment. Besides the acidity recovery, the decoloring efficiency and chemical oxygen demand (COD) removal efficiency of the anion exchange resin was investigated in the experiments. The results revealed that the anion exchange resin was able to remove colourful pollutants and degrade a part of COD effectively, and at the same time reserve acidity in the wastewater solution. The resin regenerated by a 10% NaCl aqueous solution had the same ability to discolour and remove the COD from the wastewater as the new resin had. The resin regenerated by 3% w/w NaCl aqueous solution, which was the same concentration as seawater, also had, to some extent, the same effect on decolorisation and the removal of COD; however, its colour and COD removal performance was not as efficient as the resin regenerated by 10% w/w NaCl and the new resin. H‐acid (0.25%) was also successfully recovered from the regenerating solutions.

Determination of Schulze Equation for Chemical Oxygen Demand Reduction Using Stabilized Landfill Refuse Media

Three columns each with 770 cm2 of surface area and 60–105 cm effective depth were set up for this study. These columns were filled with compacted, stabilized refuse. High-strength brewery wastewaters were uniformly trickled down the medium. Overall, 16 runs with various organic loadings were tested and the results demonstrated that the stabilized refuse had excellent capability in removing chemical oxygen demand (COD). The COD removal efficiency reached 95% at a depth of 60 cm at Q = 8 L/day for the initial COD of ∼6000 mg/L and the efficiency increased to >99% at a depth of 90 cm (organic loading of 0.69 kg/m3/day). As would be expected, the filter performance is a function of flow rate, influent COD concentration, and bed depth. The Schulze equation is able to predict the COD removal performance well. The variations of pH, oxidation reduction potential, and volatile fatty acids indicated that the acidogenesis reaction occurred in the upper layers.

Comparison of various advanced oxidation processes and chemical treatment methods for COD and color removal from a polyester and acetate fiber dyeing effluent

In this paper, a comparison of various advanced oxidation processes (O 3, O 3/UV, H 2O 2/UV, O 3/H 2O 2/UV, Fe 2+/H 2O 2) and chemical treatment methods using Al 2(SO 4) 3 · 18H 2O, FeCl 3 and FeSO 4 for the chemical oxygen demand (COD) and color removal from a polyester and acetate fiber dyeing effluent is undertaken. Advanced oxidation processes (AOPs) showed a superior performance compared to conventional chemical treatment, which maximum achievable color and COD removal for the textile effluent used in this study was 50% and 60%, respectively. Although O 3/H 2O 2/UV combination among other AOPs methods studied in this paper was found to give the best result (99% removal for COD and 96% removal for color), use of Fe 2+/H 2O 2 seems to show a satisfactory COD and color removal performance and to be economically more viable choice for the acetate and polyester fiber dyeing effluent on the basis of 90% removal.