Article

Aerobic digestion of starch wastewater in a fluidized bed bioreactor with low density biomass support

Department of Chemical Engineering, Annamalai University, Annamalai Nagar, 608002 Tamil Nadu, India.
Journal of Hazardous Materials (Impact Factor: 4.33). 06/2007; 143(1-2):82-6. DOI: 10.1016/j.jhazmat.2006.08.071
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ABSTRACT A solid-liquid-gas, multiphase, fluidized bed bioreactor with low density particles was used in this study to treat the high organic content starch industry wastewater. The characteristics of starch wastewater were studied. It shows high organic content and acidic nature. The performance of a three phase fluidized bed bioreactor with low density biomass support was studied under various average initial substrate concentrations, by varying COD values (2250, 4475, 6730 and 8910 mg/L) and for various hydraulic retention times (8, 16, 24, 32 and 40 h) based on COD removal efficiency. The optimum bed height for the maximum COD reduction was found to be 80 cm. Experiments were carried out in the bioreactor at an optimized bed height, after the formation of biofilm on the surface of low-density particles (density=870 kg/m(3)). Mixed culture obtained from the sludge, taken from starch industry effluent treatment plant, was used as the source for microorganisms. From the results it was observed that increase in initial substrate concentration leads to decrease in COD reduction and COD reduction increases with increase in hydraulic retention time. The optimum COD removal of 93.8% occurs at an initial substrate concentration of 2250 mg/L and for the hydraulic retention time of 24h.

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    • "The conventional treatment methods for recalcitrant effluents involve thin-film evaporation [11], filtration [12], sedimentation of suspended solids [13], fluid neutralization, coagulation [14], flocculation [15], and biological treatments (activated sludge process or anaerobic digestion). The biological approach is the most common for treating industrial wastewater including that from corn wet milling [16] [17]. However, there are several disadvantages such as the production of sludge, which has varying settling properties, the sensitivity to shock-loading, and a limited capacity to remove poorly biodegradable substances [16] [18]. "
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    ABSTRACT: An electrochemical system was developed to successively apply electrochemical oxidation (EO) and electrochemical adsorption (EA) treatments. This coupled EO–EA treatment system was used for remediating steepwater effluent samples obtained from a commercial corn wet milling plant. The effects of system operating parameters such as pH, supporting electrolyte, current density, treatment duration, repeating EO–EA cycle etc. were investigated based on the amount of chemical oxygen demand (COD) removed. The effluent was also characterized for 5-day biological oxygen demand (BOD5), reduced sugars (as dextrose), lactic acid, protein, and phosphorus at different stages during electrochemical remediation. The initial EO treatment improved the system effectiveness during the subsequent EA treatment by enhancing the oxidation process, partially decomposing and creating new functional groups on the pollutants. This increased the affinity of the pollutant adsorbates with activated carbon particles filled within the EA cell, which served as both bipolar microelectrodes and enhanced adsorbents. By operating at pH 12, using NaCl as supporting electrolyte, the COD was reduced by 93.5% after 4 h of EO followed by 16 h EA. Repeating the EO–EA treatment (4 h of EO followed by 4 h of EA) further reduced the total COD by 99.2%, though with higher energy consumption. However, the total energy consumption for our process is much lower than that for other electrochemical treatments reported. The results show that our coupled EO–EA treatment process is very effective for remediating highly recalcitrant effluents such as corn wet milling steepwater. Furthermore, the treated water is very clear and is suitable for industrial reuse.
    Journal of Environmental Chemical Engineering 03/2015;
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    • "The conventional treatment methods for recalcitrant effluents involve thin-film evaporation [11], filtration [12], sedimentation of suspended solids [13], fluid neutralization, coagulation [14], flocculation [15], and biological treatments (activated sludge process or anaerobic digestion). The biological approach is the most common for treating industrial wastewater including that from corn wet milling [16] [17]. However, there are several disadvantages such as the production of sludge, which has varying settling properties, the sensitivity to shock-loading, and a limited capacity to remove poorly biodegradable substances [16] [18]. "
    [Show abstract] [Hide abstract]
    ABSTRACT: An electrochemical system was developed to successively apply electrochemical oxidation (EO) and electrochemical adsorption (EA) treatments. This coupled EO–EA treatment system was used for remediating steepwater effluent samples obtained from a commercial corn wet milling plant. The effects of system operating parameters such as pH, supporting electrolyte, current density, treatment duration, repeating EO–EA cycle etc. were investigated based on the amount of chemical oxygen demand (COD) removed. The effluent was also characterized for 5-day biological oxygen demand (BOD5), reduced sugars (as dextrose), lactic acid, protein, and phosphorus at different stages during electrochemical remediation. The initial EO treatment improved the system effectiveness during the subsequent EA treatment by enhancing the oxidation process, partially decomposing and creating new functional groups on the pollutants. This increased the affinity of the pollutant adsorbates with activated carbon particles filled within the EA cell, which served as both bipolar microelectrodes and enhanced adsorbents. By operating at pH 12, using NaCl as supporting electrolyte, the COD was reduced by 93.5% after 4 h of EO followed by 16 h EA. Repeating the EO–EA treatment (4 h of EO followed by 4 h of EA) further reduced the total COD by 99.2%, though with higher energy consumption. However, the total energy consumption for our process is much lower than that for other electrochemical treatments reported. The results show that our coupled EO–EA treatment process is very effective for remediating highly recalcitrant effluents such as corn wet milling steepwater. Furthermore, the treated water is very clear and is suitable for industrial reuse.
    Journal of Environmental Chemical Engineering 03/2015; 3(2). DOI:10.1016/j.jece.2015.03.019
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    • "This process is eliminated in the aerobic system [18]. Three phase fluidized bed reactor has been successfully employed in treating wastewaters like starch, refinery, phenol, and high strength industrial wastewater and have been found efficient in treating the wastewater [15] [18] [19]. "
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    ABSTRACT: In this study, a biocarrier made up of low density polypropylene of surface area 524 mm2 per particle and of density 870 kg/m3 was used in the treatment of wastewater using fluidized bed reactor. Holdup studies are performed for bed heights (0.2 m to 0.8 m) to predict the operating conditions. The effect of Bed height (0.6 m to 1 m), Hydraulic retention time (6 hr to 40 hr), and superficial gas velocity (0.00106 m/s, 0.00159 m/s, 0.00212 m/s), Concentration (2 g/l – 7.5 g/l) on the percentage of COD reduction were studied. For bed height of 0.8m, optimum holdup and maximum COD reduction was obtained. From the results, it was observed that percentage of COD reduction increases as the superficial gas velocity increases and decreases as the initial concentration decreases. A COD reduction of 97.5% was achieved at an initial concentration of 2 g/l and for a superficial gas velocity of 0.00212 m/s at hydraulic retention time of 40 hr.
    Energy Procedia 07/2014; 50:214–221. DOI:10.1016/j.egypro.2014.06.026
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