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UDC 628.35
Stepanov S. V., Stepanov A. S., Gabidullina L. A., Dubov O. V.
Biological treatment of oil refinery wastewater in a biosorption membrane reactor
Summary
The basic process and kinetic regularities of biomembrane and biosorption membrane treatment of fuel and lube refinery wastewater are presented. The enhancement of denitrification process is suggested by reducing the dissolved oxygen concentration in the circulating flow of activated sludge by vacuum treatment. Summarizing the results of operating a pilot vacuumizing unit the more efficient use of biosorption membrane technology compared to the biomembrane method is shown. Single dosing of 1 g of powdered activated carbon per 1 liter of mixed liquor provided for reducing the mean monthly concentration of pollutants in permeate: in COD – from 68 to 49 mg/l; in BODfull – from 6 to 3.5 mg/l; in oil products – from 0.65 to 0.21 mg/l. The kinetic constants of the processes of eliminating the basic pollutants in membrane and biosorption membrane reactors were determined. It was stated that the specific oxidation rate in biosorption membrane reactors exceeded the similar indicators of membrane bioreactors only for easily sorbed substances – oil products and organic pollutants evaluated in BODfull. Vacuum treatment of circulating activated sludge during 5 minutes at minus 90 kPa pressure in a membrane bioreactor provided for 2-fold reduction of the dissolved oxygen concentration, improvement of the sedimentation properties of activated sludge (compared to the flow scheme without vacuum treatment) and the dissolved oxygen concentration less than 0.5 mg/l in the anoxic zone of the membrane bioreactor.
Key words
wastewater , nitrification , activated sludge , membrane bioreactor , denitrification , oil refinery , kinetic constant , activated carbon , biosorption membrane reactor
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UDC 628.31:661.5
MOROZOVA K. M., Stepanov S. V., Stepanov A. S., Sokolova T. V., Solkina O. S., Zhukova M. A.
Biological treatment of dairy industry wastewater in a membrane bioreactor
(part 2)
Summary
The technology of biological treatment of dairy wastewater is described that provides for meeting the standard maximum permissible concentrations for fishery water bodies. The results of the experimental studies in a pilot membrane bioreactor with real wastewater of «Pestravskii» butter factory are presented. The main process and kinetic parameters of the biological wastewater treatment processes have been obtained that are needed for designing a membrane bioreactor with nitrification-denitrification that provides for meeting the standard maximum permissible concentrations for fishery water bodies or requirements to the effluents discharged into a public sewer. The maximum specific rate of diary wastewater pollutants oxidation Vmax at 7 g/l activated sludge concentration and 20 °С temperature is 40 mg/(g·h), Michaelis constant Km – 15 mg/l, inhibition coefficient of metabolism products – 0.54 l/g, temperature constant X for aerobic heterotrophic conversion – 0.079 deg–1. Compared to the traditional treatment facilities the use of biomembrane technology at the wastewater biological treatment stage provides for 1.4–1.5 reducing the treatment time, reactor volume and footprint owing to the increase of the oxidation capacity of the aeration units by increasing the activated sludge concentration to 10 g/l; and ensuring almost complete removal of suspended solids by eliminating the tertiary treatment stage. Possible elimination of chemical flotation stage before biological treatment is shown that provides for reducing the expenditures for expensive chemicals and streamlining the process flow scheme.
Ключевые слова
wastewater , biological treatment , activated sludge , membrane bioreactor , kinetic constant , dairy factory
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UDC 628.31:661.5
Stepanov S. V., Solkina O. S., MOROZOVA K. M., Stepanov A. S., Zhukova M. A.
The effect of membrane chemical washing on biological treatment processes
Summary
The results of research studies in the field of biomembrane treatment of dairy wastewater are presented. The experimental studies were carried out during four months. As a model effluent milk solution was used with addition of nutrients in the form of mineral salts – potassium monophosphate, ammonium chloride and sodium nitrate in ratios corresponding to the concentrations of these substances in original wastewater after physical and chemical treatment. The experiment was aiming at determining the process and kinetic characteristics of biological processes in a membrane bioreactor. The studies of the model wastewater in a pilot bioreactor showed that at 7–9 g/l sludge dosage and 0.36 m3/(m2·day) specific flow rate corresponding to the regular operation mode of flat-frame membranes the operation of the plant without chemical washing was possible for about two months. It was stated that membrane washing with citric acid at 1000 mg/l solution concentration (5–20 mg/l acid concentration in the membrane tank) provided for reducing the rate of biochemical processes with only mixed liquor acidification. The citric acid toxicity did not appear at mixed liquor pH in the range of 6.83–7.17. The study of membrane washing with sodium hypochlorite solution in concentration of 2000 mg/l as NaOCl showed the competitive inhibition of the organics oxidation rate with practically complete inhibition of biochemical processes at the active chlorine concentration in the reactor more than 26.1 mg/l. The time of restoring the original rate of organics oxidation at 6.6 mg/l active chlorine concentration in the reactor was 220 minutes after wastewater supply had been started and permeate had been removed.
Key words
biological treatment , membrane bioreactor , kinetic constant , dairy wastewater , membrane chemical washing , specific oxidation rate
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UDC 628.35:661.5
Strelkov A. K., Stepanov S. V., Blinkova L. A., MOROZOVA K. M., Belyakov A. V.
Investigating the processes of single-stage biological treatment
of oil refinery wastewater
Summary
The results of investigating the operation of the Novokuibyshevsk oil refinery waste biological treatment facilities are presented. It was found that denitrification process was not possible in two-stage process of wastewater treatment because of
high concentration of dissolved oxygen in the denitrification tank and low concentration of organics in raw wastewater. Full-scale experiment with single-stage mode of operation of the entire biological treatment facilities was carried out. After the first-stage aeration tanks de-commissioning the total activated sludge amount in the system increased almost 1.5-fold. Sludge concentration in the aeration tanks (of the second stage) increased from 0.5–1 to 2–2.5 mg/l; COD sludge load was reduced from 143 to 77 mg/(g·day). The improved nitrification efficiency and denitrification start were recorded. Kinetic constants were determined for the processes of organics and oil products oxidation, for nitrification and denitrification required for designing wastewater treatment facilities with nitrification-denitrification technology. Inhibition by substrate was found at the concentration of oil products in effluent higher than 4 mg/l. Nitrification inhibition was observed at ammonia nitrogen concentration in effluent higher than 1 mg/l. The full-scale experiment of conversion of the Novokuibyshevsk oil refinery waste biological treatment facilities to one-stage operation provided for testing on commercial scale the advanced nitrification-denitrification technology and recommending this process flow scheme for the introduction at other RF oil refineries.
Key words
wastewater , biological treatment , nitrification , denitrification , oil refinery , kinetic constant
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UDC 628.35:661.5
Stepanov S. V., SHVETSOV V. N., MOROZOVA K. M., Belyakov A. V., Blinkova L. A.
Investigating nitrification-denitrification technologies of oily wastewater treatment
Summary
The results of investigating biological treatment by nitrification-denitrification technology of oily wastes of the Novokuybyshevsky oil refinery are presented. Possible meeting the advanced requirements to the effluent quality in relation to nitrogen compounds, particularly, by industrial wastewater treatment without blending with municipal wastewater is shown. The kinetic constants of nitrification-denitrification processes and oxidation of oil products required for designing wastewater treatment facilities are determined.
key words
wastewater , biological treatment , nitrification , denitrification , oil refinery , kinetic constant
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UDC 628.35:665.6
Stepanov S. V., Strelkov A. K., Blinkova L. A., MOROZOVA K. M., Belyakov A. V.
Estimating kinetic constants for the process of biochemical treatment of oil refinery wastewater
Summary
The results of studies carried out under periodic conditions at the wastewater biological treatment facilities of the Novokouibyshevsky, Kouibyshevsky, Syzransky and Atchinsky oil refineries are presented. With reference to the measured oxygen consumption rate the values of the maximum oxidation rate, Michaelis constants and coefficient of inhibition by activated sludge degradation products were obtained. Kinetic constants depend on the raw wastewater composition and are subject to daily fluctuations. The obtained values can be used in designing aeration tanks for oil refinery wastewater treatment.
Key words
wastewater , biological treatment , activated sludge , oil refinery , kinetic constant
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UDC 628.35:661.5
Stepanov S. V.
Specific features of designing oil refinery wastewater biological treatment facilities
Summary
Oil refinery wastewater is characterized by the presence of organics resistant to oxidation and practically total absence of phosphorus. The procedure of designing oil-containing wastewater biological treatment with nitrification-denitrification is used both for aeration tanks and membrane bioreactors. Designing is carried out with the use of kinetic relationships for all the regulated pollutants. During the experiments kinetic constants and coefficients of nitrification and denitrification processes, oxidation of organic substances (as BOD and COD), oil products, phenols and synthetic surfactants for wastewater of a number of oil refineries were obtained. Calculations algorithm includes the following stages: determining initial data – pollutant concentrations and wastewater flow rates; choosing the process flow scheme of the treatment facilities; calculating specific rate of biological treatment process on the basis of kinetic constants and coefficients; calculating activated sludge growth, nitrogen and phosphorus losses in the process of assimilation; estimating the retention time for oxidation of separate ingredients of pollutants and denitrification; determining the maximum aerobic process time in respect to the limiting component and treatment level in respect to other ingredients; calculating the required air consumption; checking the necessity of dosing phosphorus compounds for nutrient makeup. To improve the denitrification efficiency the configuration of the facilities was enlarged with a mixed liquor deaerator. The process design of a membrane bioreactor differs from the design of aeration tanks with nitrification-denitrification by correction of specific oxidation rate with account of the obtained kinetic constants and coefficient of inhibition with metabolism products at higher concentrations of activated sludge in the bioreactor. The experimental results allowed supplementing the procedure of designing wastewater biological treatment facilities with nitrification-denitrification developed by NII VODGEO.
Key words
wastewater , biological treatment , nitrification , activated sludge , membrane bioreactor , denitrification , oil refinery , kinetic constant
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