Chemical Oxygen Demand Removal Of Wastewater Research Articles

Effect of bio-electrochemical systems on the removal of organic and inorganic membrane fouling from anaerobic membrane bioreactors

To alleviate the fouling of membrane bioreactors, a coupling system was constructed in which a conductive membrane served as the anode of a bio-electrochemical system, whereas ordinary carbon felt served as the cathode. The membrane module showed approximately 90 % performance for wastewater chemical oxygen demand removal. As the external resistance increased from 50 to 1500 Ω, the number of operating days increased from 25 to 62. The respective concentrations of polysaccharide and protein on R-1500 membrane surface were 6.81- and 2.05-fold greater than the concentrations on the R-50 membrane, and the concentration of Ca2+ on the surface of the R-50 membrane was 1.48-fold greater than the concentration on the R-1500 membrane. Therefore, inorganic fouling is the main type of membrane fouling in coupled systems with low external resistance. For coupled systems with higher external resistance, severe organic fouling eventually causes membrane blockage. Variance partitioning analysis showed that the micro-electric field contributed to 95.34 % of the effect on the control of membrane fouling, significantly greater than the 67.19 % contributed by the current. Therefore, in the system where organic and inorganic fouling coexists, appropriate enhanced field strength (increase in external resistance) is particularly important for membrane fouling control.

Enhancement of photosynthetic bacteria biomass production and wastewater treatment efficiency by zero-valent iron nanoparticles

Photosynthetic bacteria (PSB) wastewater treatment is a novel technology for wastewater purification and resources recovery but is restricted by low efficiency. This paper applied zero-valent iron nanoparticles (Fe0 NPs) to enhance its performance. Results showed that 20mg/L Fe0 NPs under light-anaerobic condition significantly increased the PSB biomass production and wastewater chemical oxygen demand removal by 122% and 164.3%, and shortened the time required for wastewater purification by 33%; these effects were far more better than the addition of Fe2+. The mechanism was because the addition of Fe0 NPs promoted the intracellular ATP content and pigments (carotenoid and bacteriochlorophyll) contents, and up-regulated dehydrogenase and succinate dehydrogenase activity; the increase rate reached 38.7%, 39.6%, 22.0%, 23.9% and 218.2%, respectively.

Application of wastewater with high organic load for saline-sodic soil reclamation focusing on soil purification ability

Fresh water source scarcity in arid and semiarid area is limitation factor for saline-sodic soil reclamation. The reusing of agricultural drainage and industrial wastewater are preferred strategies for combating with this concern. The objective of current study was evaluation in application of industrial sugar manufacture wastewater due to high soluble organic compounds in saline-sodic and sodic soil. Also soil ability in wastewater organic compounds removal was second aim of present study. Saline-sodic and sodic soil sample was leached in soil column by diluted wastewater of amirkabir sugar manufacture in Khuzestan Province of Iran at constant water head. Sodium, electric conductivity and chemical oxygen demand of soil column leachate were measured per each pore volume. The experimental kinetics of wastewater organic compounds on two saline-sodic and sodic soil were also investigated by three pseudo second order, intra particle diffusion and elovich model. The results of current study showed that electric conductivity of saline-sodic soil was decreased to 90% during 3 initial pore volumes, from other side exchangeable sodium percent of saline-sodic and sodic soil decreased 30 and 71 percent, respectively. There were no significant different between wastewater chemical oxygen demand removal by saline-sodic and sodic soil in both batch and column studies. Wastewater chemical oxygen demand was decreased to 35% during pass through soil column. The results showed that the adsorption kinetics of wastewater organic compounds were best fitted by the pseudo-second order model with 99 percent correlation coefficient (r2=0.99%).

Integrated Ultrafiltration Membranes and Chemical Coagulation for Treatment of Baker’s Yeast Wastewater

An integrated system ultrafiltration membrane-coagulation has been employed for removal of chemical oxygen demand (COD) and turbidity from baker's yeast effluents. Fouling in the membrane is a common problem; chemical coagulation has been used as a pre-treatment method to mitigate fouling. Poly aluminum chloride (PACl), aluminum sulfate and lime had been used as coagulants. The results indicated that PACl exhibited higher removal efficiency than other coagulants. Two-stage coagulation and combination of coagulants were also investigated. The removal efficiency of COD and turbidity were achieved 68% and 81% by two-stage coagulation by PACl-lime, respectively. The effects of operating conditions on the ultrafiltration process for two types of hollow fiber membranes polyvinylidene fluoride (PVDF) and polypropylene (PP) on permeate flow rate, turbidity and COD removal of wastewater were further investigated. The results showed that by increasing the feed pressure, flow rate and feed temperature the permeate flow rate increased and the removal efficiency decreased. Under optimum conditions, PVDF membrane showed higher performance but compromised the flux compared to PP membrane.

Biodiesel production potential of oleaginous Rhodococcus opacus grown on biomass gasification wastewater

This study examined the valorization of biomass gasification wastewater (BGWW) for lipids accumulation by Rhodococcus opacus and potential biodiesel application. Using synthetic mineral media based BGWW, the bacterium accumulated a maximum 65.8% (w/w) of lipids. 10% (v/v) inoculum size showed a more positive effect than 5% (v/v) inoculum size on both the chemical oxygen demand (COD) removal and lipid accumulation by R. opacus. Using the raw wastewater (untreated), the bacterium accumulated 54.3% (w/w) lipid with a wastewater COD removal efficiency of 64%. However, these values were further enhanced to 62.8% (w/w) and 74%, respectively, following supplementation of the wastewater with mineral salt media in the ratio 4:1. 1H and 13C nuclear magnetic resonance (NMR) spectroscopy analyses of the accumulated lipids revealed the presence of more saturated fatty acids than unsaturated fatty acids. Thermogravimetric analysis (TGA) of the accumulated lipids showed four thermal decomposition regions each with a good stability. Transesterification of the bacterial lipids to biodiesel and its properties revealed a very good potential of the strain for the production of biodiesel from PAH containing wastewater.

Modeling and optimization of oil refinery wastewater chemical oxygen demand removal in dissolved air flotation system by response surface methodology

In this present study the dissolved air flotation (DAF) system was investigated for the treatment of Kermanshah Oil Refinery wastewater. The effect of three parameters on flotation efficiency including of flow rate (outflow from the flotation tank), saturation pressure and coagulant dosage on chemical oxygen demand (COD) removal was examined experimentally. All the experiments were done under a certain time (in this case 3 min). After final testing maximum COD removal efficiency was obtained 67.86%. In the next step of study, response surface method (RSM) was applied to model oil refinery wastewater COD removal as a function of flow rate, saturation pressure and coagulant dosage. Coefficient of determination, R2, showed that the RSM model can explain the variation with the accuracy of 0.996, indicating there was strong correlation. Moreover, process optimization were performed to predict the best operating conditions using RSM method, which resulted in the maximum COD removal of the oil refinery wastewater. The maximum COD removal of oil refinery wastewater was estimated by RSM to be 67.87% under the operational conditions of flow rate (3.76 – 3.86 L/min), saturation pressure (4.99 - 5bar) and coagulant dosage (24.16 – 24.79 mg/L).

A novel PSB-EDI system for high ammonia wastewater treatment, biomass production and nitrogen resource recovery: PSB system

A novel process coupling photosynthetic bacteria (PSB) with electrodeionization (EDI) treatment was proposed to treat high ammonia wastewater and recover bio-resources and nitrogen. The first stage (PSB treatment) was used to degrade organic pollutants and accumulate biomass, while the second stage (EDI) was for nitrogen removal and recovery. The first stage was the focus in this study. The results showed that using PSB to transform organic pollutants in wastewater into biomass was practical. PSB could acclimatize to wastewater with a chemical oxygen demand (COD) of 2,300 mg/L and an ammonia nitrogen (NH4(+)-N) concentration of 288-4,600 mg/L. The suitable pH was 6.0-9.0, the average COD removal reached 80%, and the biomass increased by an average of 9.16 times. The wastewater COD removal was independent of the NH4(+)-N concentration. Moreover, the PSB functioned effectively when the inoculum size was only 10 mg/L. The PSB-treated wastewater was then further handled in an EDI system. More than 90% of the NH4(+)-N was removed from the wastewater and condensed in the concentrate, which could be used to produce nitrogen fertilizer. In the whole system, the average NH4(+)-N removal was 94%, and the average NH4(+)-N condensing ratio was 10.0.

Improve bio-activity of anaerobic sludge by low energy ultrasound.

This research focused on ultrasound-enhanced bio-activity of anaerobic sludge. Low energy ultrasound irradiation can increase the bio-activity of anaerobic sludge. Ultrasonic parameter, characteristics of anaerobic sludge and experimental conditions are important parameters which affect the enhancement effect on anaerobic sludge. In order to assess the effects of characteristics of anaerobic sludge and experimental conditions on ultrasonic irradiation of anaerobic sludge, experiments with different characteristics of anaerobic sludge were carried out and analyzed with the content of coenzyme F420 and dehydrogenase activity (DHA). The results showed that anaerobic sludge bio-activity was impacted by the initial temperature, initial chemical oxygen demand (COD), sludge concentration, and stirring during the ultrasonic process. Optimal performance was achieved when sound frequency, power density, and ultrasonic irradiation period was 20 kHz, 0.1 W/mL, and 10 min, respectively, under which the wastewater COD removal efficiency was increased by 12.9 percentage points. The results indicated that low temperature could affect the anaerobic sludge irradiation effect, while intermittent stirring could enhance the bio-activity of anaerobic sludge irradiation effect and low substrate concentration improved anaerobic sludge activity by ultrasound.

Simultaneous lipid production and dairy wastewater treatment using Rhodococcus opacus in a batch bioreactor for potential biodiesel application

This study examined the valorization of dairy wastewater in the production of lipids by Rhodococcus opacus for biodiesel application. Using synthetic media based on dextrose and ammonium nitrate as the carbon and nitrogen source, respectively, the bacterium accumulated 71% (w/w) of lipids. Using only the raw dairy wastewater, the bacterium accumulated 14.28% w/w lipid and reduced the initial wastewater chemical oxygen demand (COD) by 30%. These values were, however, enhanced to 30–33% w/w and 62%, respectively, by supplementing the dairy wastewater with mineral salt media in the ratio 1:3. Bioreactor experiments were further performed using raw dairy wastewater and mineral salt medium in 1:3 ratio under both uncontrolled and controlled temperature and pH conditions. Interestingly biomass growth, lipid accumulation in the bioreactor experiments were found to be lower as compared to those in the shake flask experiments, whereas the wastewater COD removal was much higher in the bioreactor study. 1H nuclear magnetic resonance (NMR) spectroscopy of the fatty acids accumulated by the bacteria using dairy wastewater based media revealed that it contained more saturated fatty acids than unsaturated fatty acids. Gas chromatography (GC) analysis of the biodiesel produced by either ex-situ or in-situ transesterification of the bacterial lipids further revealed the presence of methyl palmitate (34.90%), methyl stearate (35.48%) methyl myristate (29.79%), methyl linoleate (27.87%), and methyl palmitate (25.85) as the main esters. The estimated properties of the transesterified product indicated its potential for biodiesel applications.

Simultaneous enzymatic hydrolysis and anaerobic biodegradation of lipid-rich wastewater from poultry industry

Simultaneous enzymatic hydrolysis and anaerobic biodegradation of lipid-rich wastewater from poultry industry with porcine pancreatic lipase at different concentrations (from 1.0 to 3.0 g L−1) were performed. The efficiency of the enzymatic pretreatment was measured by the Chemical Oxygen Demand (COD) removal and formation of methane. All samples pretreated with lipase showed a positive effect on the COD removal and formation of methane. After 30 days of anaerobic biodegradation the methane production varied from 569 ± 95 to 1,101 ± 10 mL for crude wastewater and pretreated at 3.0 g L−1 enzyme, respectively. COD removal of wastewater supplemented at different enzyme concentrations was found to be threefold higher than crude wastewater. The use of lipases seems to be a promising alternative for treating lipid-rich wastewaters such as those from the poultry industry.

Treatment of Pharmaceutical Wastewater by Micro-Electrolysis and Fenton Oxidation Process

Pharmaceutical wastewater was treated by micro-electrolysis and Fenton process.The aim of this research was to optimize operating parameters in micro-electrolysis and Fenton process. Effectiveness of important process parameters such as mass ratio of iron to carbon, the initial pH, reaction time and H2O2 dosage on the performance of micro-electrolysis and Fenton process were investigated. The results show that the removal efficiency of pharmaceutical wastewater chemical oxygen demand (COD) could reach 37.3% at the optimal pH of 4 with the iron to carbon ratio of 1:1 after 80 min treatment. The operating conditions of Fenton process are 0.5% of H2O2 dosage, the pH value of 4 and the reaction time of 180 min. The pharmaceutical wastewater COD removal could reach 79.4%.

Kinetics of domestic wastewater COD removal by subsurface flow constructed wetlands using different plant species in temperate period

The objective of this work has been to study the kinetics of domestic wastewater chemical oxygen demand (COD) removal when using constructed wetlands (CWs) with different plant species and at different water depths. Kinetic rate constants were obtained by using several kinetic models, and also combined with different hydraulic models. Synthetic wastewater was fed to five identical pilot-scale CWs, planted with different species (CW1: unplanted; CW2: Phragmites australis; CW3: Lythrum salicaria; CW4: Cladium mariscus; CW5: Iris pseudacorus). Wastewater was treated under continuous operation during 5 months. Water samples were taken along intermediate points at the wetland, and also at three different depths (top, medium depth and bottom). The COD experimental data were fitted to different kinetic models previously and extensively reported in the literature: the K-C and K-C* equations, and also the ‘retardation’ model. Also, the effect of the hydraulics characteristics was considered. Apart from the ideal plug flow assumption, two different flow models were used when integrating the mass balance equations: the plug flow with dispersion model and a detention time gamma distribution (DTGD) model. The more developed plants (CW3 and CW5) were the ones that caused an increase in COD removal rate compared with the unplanted wetland. Differences in COD removal rates were observed at different depths in the unplanted wetland, and the higher rate constant values were obtained near the wetlands top. On the contrary, the higher plants development in CW3 and CW5 eliminated the influence of water depth. The retardation model offered the best mathematical fitting to the experimental data. By using non ideal flow models, an increase in the rate constant values was always obtained, especially in the wetlands whose hydraulic behaviour was very far from the ideal plug flow. The rate constants values obtained using the DTGD model were higher (25–54%), compared to the values obtained if ideal flow was considered. These results could aid the design of CW, particularly in temperate periods.