Dongfeng Zhao

Tertiary treatment of textile wastewater with combined media biological aerated filter (CMBAF) at different hydraulic loadings and dissolved oxygen concentrations.

An up-flow biological aerated filter packed with two layers media was employed for tertiary treatment of textile wastewater secondary effluent. Under steady state conditions, good performance of the reactor was achieved and the average COD, NH(4)(+)-N and total nitrogen (TN) in the effluent were 31, 2 and 8mg/L, respectively. For a fixed dissolved oxygen (DO) concentration, an increase of hydraulic loading resulted in a decrease in substrate removal. With the increase of hydraulic loadings from 0.13 to 0.78m(3)/(m(2)h), the removal efficiencies of COD, NH(4)(+)-N and TN all decreased, which dropped from 52 to 38%, from 90 to 68% and from 45 to 33%, respectively. In addition, the results also confirmed that the increase of COD and NH(4)(+)-N removal efficiencies resulted from the increase of DO concentrations, but this variation trend was not observed for TN removal. With the increase of DO concentrations from 2.4 to 6.1mg/L, the removal efficiencies of COD and NH(4)(+)-N were 39-53% and 64-88%, whenas TN removal efficiencies increased from 39 to 42% and then dropped to 35%.

Laboratory investigation of oil-suspended particulate matter aggregation under different mixing conditions.

Oil-suspended particulate matter aggregation (OSA) has been recognized by the oil spill remediation community to effectively enhance the cleansing of spilled oil in the marine environment. While studies have investigated the application of mineral fines as an effective method to facilitate oil dispersion, decision-makers still lack information on the role of mixing energy in OSA formation and its significance to oil dispersion in real spills. This work studied the effect of level and duration of mixing energy on OSA formation using the standard reference material 1,941 b and Arabian light crude oil. The results showed that dispersed small oil droplets increased with an increase of both the level and duration of mixing energy to form multi-droplet OSAs. The sizes of the dispersed droplets varied between 5 and 10 μm under different conditions studied. The maximum oil trapping efficiency increased from 23% to 33%, the oil to sediment ratio increased from 0.30 to 0.43 g oil/g sediment, and the required shaking time decreased from 2.3 to 1.1h as the shaking rate increased from 2.0 to 2.3 Hz. Based on the size measurement results, a breakage effect on the formed OSAs and sediment flocs was confirmed under high mixing energy level.

Nitrite accumulation in continuous-flow partial autotrophic denitrification reactor using sulfide as electron donor

The nitrite accumulation in handling nitrate and sulfide-laden wastewater in a continuous-flow upflow anaerobic sludge blanket reactor was studied. At sulfide/nitrate-nitrogen ratio of 1:0.76 and loading rates of 1.2kg-Sm-3d-1 and 0.4kg-Nm-3d-1, the elemental sulfur and nitrite accumulation rates peaked at 90% and 70%, respectively, with Acrobacter, Azoarcus and Thauera presenting the functional strains in the studied reactor. The accumulated nitrite was proposed a promising feedstock for anaerobic ammonia oxidation process. An integrated partial autotrophic denitrification-anaerobic ammonia oxidation-aeration process for handling the ammonia and sulfide-laden wastewaters is proposed for further studies.

Synthesis of three-dimensional ordered macroporous TiO2, Gd/TiO2 and their photocatalytic activity

In this paper, three-dimensional ordered macroporous (3DOM) TiO2 and Gd/TiO2 materials were synthesized by colloidal crystal templating process. The obtained samples were analyzed by field-emission scanning electron microscope, transmission electron microscopy, X-ray diffraction, diffuse reflectance spectra and Brunauer–Emmett–Teller method. The photocatalytic activity of various samples was evaluated by degradation of methyl orange in aqueous solution under UV and visible light irradiation. At the same time, Degussa P25 (a commercial Titania) powders were used for comparison. The results indicated that 3DOM Gd/TiO2 samples showed a significant shift in the onset absorption towards the longer wavelength compare to pure 3DOM TiO2, and displayed excellent photocatalytic activity under both UV and visible light irradiation.

Studies on preparation and characterization of 3DOM TiO2 and TiO2/SiO2 materials with high photocatalytic ability

In this paper, three-dimensional ordered macroporous (3DOM) TiO2 and TiO2/SiO2 materials were prepared by traditional colloidal-crystal-templating method. The microstructures of samples were analysed by scanning electron microscope, X-ray diffraction analysis, thermogravimetric-differential thermal analysis and nitrogen adsorption/desorption. The results indicated that the microstructures of samples, including three-dimensional ordered macroporous structure and crystalline form, could be adjusted by changing the calcination temperatures. Finally, the samples were used as photocatalysts to decompose methyl orange wastewater under UV-light. Both 3DOM TiO2 and 3DOM TiO2/SiO2 displayed good photocatalytic ability. Moreover, the introduction of Si could increase the transformation temperature of TiO2 from anatase to rutile, which made 3DOM TiO2/SiO2 had better photocatalytic ability than pure 3DOM TiO2.

Investigation of the kinetics of oil–suspended particulate matter aggregation

The process of oil-suspended particulate matter aggregation (OSA) has been recognized by the oil spill remediation community to enhance the natural cleansing of oiled shorelines. A laboratory study was conducted to investigate the kinetics of OSA formation under various mixing intensities using the standard reference material 1941b and Arabian heavy crude oil. The results showed that formation of OSAs increased exponentially with mixing time and reached a maximum within 5h. The maximum oil trapping efficiency increased from 24% to 47%, and the required shaking time decreased from 4.5 to 1.2h as the sediment concentration and mixing energy increased. The maximum oil-to-sediment ratio reached 0.24-0.68 g oil/g sediment within 5h. Most of the formed OSAs were solid OSAs and single droplet OSAs with low mixing energies, and multi-droplet OSAs with high mixing energies. The sizes of the dispersed oil droplets and OSAs were also investigated.

A lab-scale MED dealing with salinity wastewater: the study of optimal operation schemes and parameters

AbstractMulti-effect distillation (MED) system with a top brine temperature lower than 70°C, is one of the most successful desalination technologies. In this paper, a lab-scale vertical tube MED system was performed for salinity wastewater desalination of petrochemical enterprises, and five salinity wastewater treatment schemes including different combinations of evaporator types were investigated. As a result, the falling-falling-climbing (FFC) system was considered as the optimal scheme. Then, the operation parameters including the feedwater salinity, temperature, flow rate, and the fresh steam flow rate were further optimized. The results indicated that the CR and gained output ratio (GOR) would rise up by increasing effect numbers, fresh steam flow rate, and feedwater temperature. While CR and GOR would fall down with the increase of the feedwater salinity and flow rate. Therefore, the optimal operation parameters were experimentally determined as follows: the feedwater with salinity of 0.6%, flow rat...

Experimental Assessment of Water Sprays Utilization for Controlling Hydrogen Sulfide Releases in Confined Space

This paper reported the utilization of water spray for controlling H2S release in a confined space, which is especially important in industry. A typical spray tower was modified to simulate the confined space for peoples enterable routine operation (e.g., pump room), in which the dilution capacity of water sprays can also be evaluated. This work consists of two parts: the first part focuses on the influences of different operating conditions on chemical dilution capacities of water sprays in mechanisms; the second one is comparison between two nozzle configurations for evaluating their feasibilities of practical application. Water sprays express eligible performance for H2S release control even though their dilution capacity was weakened at high gaseous concentrations and rates of releases. The presence of Na2CO3 can significantly improve absorption effectiveness of H2S in water and the optimal Na2CO3 additive was found to be 1.0 g·L−1 in this test. Compared with Na2CO3, adjusting water flow rate may be an effective strategy in enhancing dilution capacity of water sprays due to the fact that larger flow rate led to both less dilution time (TD) and dilution concentration (CD). Furthermore, multinozzle configuration is more efficient than single-nozzle configuration under the same water consumption.

Screening of Bioflocculant-Producing Strains and Study on the Production and Oily Wastewater Flocculation Characteristics

A flocculant-producing bacterial strain, named KL3-5 was screened by means of the pyridine screening from 10 soil samples. The flocculating rate of bioflocculant produced by KL3-5 strain was 94.6%. The strain KL3-5 was identified as proteusbacillus vulgaris of Enterobacter family according to its morphological, physiological, biochemical, and 16S rDNA sequence characteristics. It was indicated that all of the content of bioflocculant was polysaccharides by the qualitative analysis of sugar and protein. When flocculant addition was 0.05mL, the removal rate of COD and oil could get to 32% and 67%, and the removal efficiencies were better than the PAC which was 61% and 30%, respectively. The flocculation sediment from KL3-5 was only 0.6g·L-1.

Screening of a thermophilic hydrocarbon-degrading bacterial group and bioremediation of petroleum polluted soil

A thermophilic oil-degrading bacterial group, named KL6–3 was screened by means of enrichment culture from soil contaminated by heavy oil from Karamay of Xinjiang Oilfield. Its oil degradation rate was up to 48.6% at 45 °C and oil concentration of 10g·L-1(data not reported). To evaluate biodegradation to petroleum polluted soil of the KL6–3, the soil samples collected from Karamay supplemented with the KL6–3 group were incubated for 90 days at 45 °C. The physicochemical quality, microorganism quantity and hydrocarbon component of the oil polluted soil were studied. The results showed that the presence of KL6–3 group could enhance the degradation of crude oil. The petroleum hydrocarbon was mainly degraded by microorganism. The saturates and aromatics were easy to be degraded and the resin and asphaltene were hard to be degraded. The microorganism quantity was increased significantly with manual composting.