A long term domestic wastewater treatment experiment was conducted using a recirculating ceramic ultra filtration membrane bioreactor (CUFMB) system. Three experiments were run with a hydraulic retention time of 5h, ...
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A long term domestic wastewater treatment experiment was conducted using a recirculating ceramic ultra filtration membrane bioreactor (CUFMB) system. Three experiments were run with a hydraulic retention time of 5h, sludge retention times of 5d, 15d, and 30d and a membrane surface flow rate of 4m/s. The experiment studied the membrane fouling mechanism and cleaning techniques. The results show that a CUFMB system can provide continuous good quality effluent which is completely acceptable for reuse. The system is also not affected by fluctuations of the inlet flow. The CUFMB sludge loading rate is similar to that of conventional biological treatment units. However, the volumetric loading rate of the CUFMB is 24 times that of conventional biological treatment units. Membrane fouling occurs due to channel clogging, which could be easily removed, and surface fouling, which can be effectively removed using the method described in this work which includes water rinsing, base cleaning, and acid washing.
In the present research, a submerged membrane bioreactor was tested to treat domestic wastewater. Three experimental runs were conducted all with a hydraulic retention time of 5h and sludge retention times (SRTs) of 5...
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In the present research, a submerged membrane bioreactor was tested to treat domestic wastewater. Three experimental runs were conducted all with a hydraulic retention time of 5h and sludge retention times (SRTs) of 5, 10, and 20 d. The pollutant removal performance of the membrane bioreactor, the membrane effluent quality, and a kinetic model for sludge growth in the bioreactor were investigated. The combined process was capable of removing over 90% of both COD (chemical oxygen demand) and NH 3 N on the average. The total removal for COD was almost independent of SRT, but that for NH 3 N improved with increasing SRT. Membrane effluent quality meets the water quality standard for reuse issued by the Ministry of Construction of China. Increasing SRT causes the concentrations of suspended solids (SS) and volatile suspended solids (VSS) in the bioreactor to increase. However, the ratio of VSS/SS did not change much. Kinetic analysis showed that the sludge yield coefficient (kg VSS·kg COD -1 ) and the endogenous coefficient of microorganisms were 0.25 and 0.04d -1 , which are similar to those of the conventional activated sludge process.
In this paper, the distribution, removal and binding forms of heavy metals in polluted seeds of rice were studied using the methods of histochemistry and biochemistry. The results indicate that the distribution of hea...
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In this paper, the distribution, removal and binding forms of heavy metals in polluted seeds of rice were studied using the methods of histochemistry and biochemistry. The results indicate that the distribution of heavy metals in rice grains was very uneven. The heavy metals in rice grains chiefly exist in association with the parts of high protein. Separation of proteins by Sephadex chromatography and subsequent analysis by atomic absorption spectroscopy revealed that Cd, Pb and As were mainly bound to protein of 54.5 and 5.50 kD molecular weights. During the rice processing, the concentrations of heavy metals in the edible rice decrease greatly, for some heavy metals in these parts of chaff, coarse rice bran and fine rice bran were removed.
The adsorption behaviour of 4 chlorophenol from aqueous solution to activated sludge was quantitatively characterized in this paper. The effects of the initial pH values, initial chlorophenol concentration and adsorb...
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The adsorption behaviour of 4 chlorophenol from aqueous solution to activated sludge was quantitatively characterized in this paper. The effects of the initial pH values, initial chlorophenol concentration and adsorbent dosage on bioadsorption were investigated. The maximum adsorption capacity was found to be 110.5 mg/g at 100 mg/L initial concentration. The Freundlich and Langmuir adsorption isotherms were applied to describe the biosorption processes and the isotherm constants were evaluated.
The formation of organic peroxides in the Cl\|atom\|initiated photooxidation of CH\-4 in O\-2\|N\-2 mixtures at 101 325 Pa and 298 K was studied with HPLC and FT\|IR methods. Four peroxidic products were detected, whi...
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The formation of organic peroxides in the Cl\|atom\|initiated photooxidation of CH\-4 in O\-2\|N\-2 mixtures at 101 325 Pa and 298 K was studied with HPLC and FT\|IR methods. Four peroxidic products were detected, which were H\-2O\-2, hydroxymethyl hydroperoxide (HOCH\-2OOH; HMHP), methyl peroxide (CH\-3OOH; MHP) and dimethyl peroxide (CH\-3OOCH\-3). A chromatogram peak at retention time of 8.08 min was assigned tentatively to peroxyformic acid (HC(O)OOH). The identification of HMHP in the reaction system showed that one of the reaction paths for the self\|reaction of CH\-3OO· led to producing Criegee intermediate ·CH\-2OO·. The formation mechanism of organic peroxide in the photooxidation of CH\-4 is more complicated than it was assumed before. Photooxidation of CH\-4 is probably an important source of organic peroxides in the troposphere.
Microorganisms capable of degrading di-n-butyl phthalate (DBP) were immobilized by polyvinyl alcohol (PVA) and used for DBP degradation. The characteristics of DBP degradation by immobilized and free cells were invest...
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Microorganisms capable of degrading di-n-butyl phthalate (DBP) were immobilized by polyvinyl alcohol (PVA) and used for DBP degradation. The characteristics of DBP degradation by immobilized and free cells were investigated. The experimental results showed that the degradation rate of immobilized cells was higher than that of free cells. The optimal pH and temperature for DBP degradation were determined to be 7.0 and 25 degrees C, respectively. The semi-continuous degradation test demonstrated that high-frequency feeding of low concentration (50 mg/L) was more favourable than low-frequency feeding of high concentration (150 mg/L) for DBP degradation. The main intermediates of DBP degradation by immobilized cells were identified using a gas chromatography/mass spectrometry method. The results revealed the presence of monobutyl phthalate, phthalic acid, and protocatechuate. A tentative pathway for DBP degradation was proposed, which demonstrated that the metabolic mechanism of immobilized cells remained the same as that of the free cells. (C) 1997 Elsevier Science Ltd.
Experiments were conducted during April-Oct. 1994 in a Beijing rice field. Four types of rice varieties have been tested. Large cultivar differences in methane emission flux have been found. Variety 93812 emitted abou...
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Experiments were conducted during April-Oct. 1994 in a Beijing rice field. Four types of rice varieties have been tested. Large cultivar differences in methane emission flux have been found. Variety 93812 emitted about fivefold more CH4 than did the Qiuguang variety. An organic amendment plus (NH4)(2)SO4 as the base fertilizer and (NH4)(2)SO4 as the topdressing applied in different amounts and growth stages, compared with no topdressing, reduced methane emission about 58% and increased rice yield about 31.7%. Emission peaks of CH4 in the tillering stage and reproductive stage were suppressed. A comprehensive strategy could meet both the goal for sustainable rice productivity and methane reduction. Such a strategy includes: 1. Selection of cultivars which have reduced root exudate and litter but increased root mass most of which growing in the oxidized soil layer, cultivars also need an effective number of tillers for optimum yield but with less CH4 transportation ability;2. Application of organic manure combined with chemical fertilizers, that reduce CH4 emissions. Fertilizers such as SO42- or other inhibitors can be maintained for a long period in soil;3. Adoption of scientific irrigation mode such as flooding-drainage-intermittent irrigation,that can both increase the rice yield and decrease the CH4 emission, etc..
The biodegradation of di-n-butyl phthalate (DBP) in soil microcosoms by indigenous microbial population and a DBP degrading inoculum as well as DBP adsorption by soil was investigated. The results demonstrated that th...
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The biodegradation of di-n-butyl phthalate (DBP) in soil microcosoms by indigenous microbial population and a DBP degrading inoculum as well as DBP adsorption by soil was investigated. The results demonstrated that the adsorption of DBP by soil conformed to Freundlich equation. The indigenous bacteria were capable of degrading phthalate in soil. The innoculation of the soil with DBP degrader enhanced the DBP degradation rate. The enumeration of microorganisms indicated a good correlation between phthalate degradation and microbial counts. (C) 1997 Elsevier Science Ltd.
Activated sludge obtained from a coke-plant wastewater treatment plant was acclimated and used as seeding microbes to investigate the kinetics of biodegradation of di-n-butyl phthalate (DBP), one of the most frequentl...
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Activated sludge obtained from a coke-plant wastewater treatment plant was acclimated and used as seeding microbes to investigate the kinetics of biodegradation of di-n-butyl phthalate (DBP), one of the most frequently identified phthalic acid esters in diverse environments and the most widely used plasticizer in China. DBP biodegradation conformed to the first-order model with respect to its concentration and the rate constant was independent of the initial concentration when the initial DBP concentration was less than 200 mg/litre. (C) 1997 Elsevier Science Ltd.
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