Contact Oxidation Research Articles

Hydrolytic Acidification of Jujube Processing Wastewater + Contact Oxidation Treatment Test

In this paper, it uses the technology of coagulation sedimentation – hydrolytic acidification – contact oxidation in treating the jujube processing wastewater, which makes membrane forming on the combined filler in reactor successfully by adopting domestic wastewater, and then dilutes jujube processing wastewater with domestic wastewater according to certain proportion to realize acclimatization of the biological membrane and complete starting of the reactor, and finally completes the biochemical treatment test of the jujube processing wastewater diluted by the feed water via backflow of the yielding water. The yielding water is stable during the test operation, and it has greater removal efficiency as to CODcr and ammonia nitrogen. Jujube is full of nutriments, has wide varieties, and possesses edible value, healthy-keeping value and medical value. Jujube processing has a long history in our country, there are numerous jujube processing enterprises, and the jujube is mainly processed to dried jujube, preserved fruit, jujube vinegar, jujube chips, jujube milk and jujube wine, etc. However, it has a greater difficulty to treat the wastewater generated in the jujube processing process, and the wastewater is one of the wastewaters with serious pollution in the food industry (Xu et al., 2014; Bi et al., 2010; Chen and Li, 2008; Wang et al., 2013). This test uses the technology of coagulation sedimentation – hydrolytic acidification – contact oxidation in treating the jujube processing wastewater, and achieves certain effects.

Low Temperature Start-up of Coating Wastewater Treatment Works

The purpose of this paper was to realize rapid start-up of coating wastewater treatment works under low temperature. Thermal insulation treatment was carried out to the pool wall and pool top of the reactor, heating equipment was arranged to ensure that the reactor can provide appropriate temperature conditions for the inoculated sludge, the amount of influent water was reasonably controlled to ensure that microorganisms have appropriate proportion of nutrient elements, and the effluent water of the reactor was continuously detected and the biophase of the sludge was continuously observed. The practice results showed that the reactor ran stably, and the effluent water met the requirements on quality of washing water and boiler make-up water in Urban Wastewater Reclamation and Reuse Industrial Water Quality (GB/T 19923-2005). The coating wastewater has a complex composition, a high COD content and poor biodegradability (Sun et al., 2009; Zhang and Li, 2009; Dong et al., 2013) as it contains a large amount of residual acrylic resin, amino resin, nitrocellulose film-forming agent, water-soluble dye colorants, brighteners, surfactants and other additives. The present works processed the coating wastewater by adopting a process of coagulation-hydrolytic acidification-contact oxidation-sand filtration-activated carbon adsorption. When the project started, the local maximum temperature was about 0 ˚C and the average temperature was -5 ˚C, which was not suitable for the growth of microorganisms. The present works adopted rock wool covered insulation, electric heating system configuration and other measures to ensure successful start-up of the hydrolytic acidification pond and contact oxidation pond.

Multi-Level Contact Oxidation Process Performance When Treating Automobile Painting Wastewater: Pollutant Removal Efficiency and Microbial Community Structures

This study applied a multi-level contact oxidation process system in a pilot-scale experiment to treat automobile painting wastewater. The experimental wastewater had been pre-treated through a series of physicochemical methods, but the water still contained a high concentration of chemical oxygen demand (COD) and had poor biodegradability. After the biological treatment, the COD concentration of effluent could stay below 300 mg/L. The study analyzed the effects of hydraulic residence time (HRT) on COD, ammonia nitrogen (NH4+-N), and total nitrogen (TN). The optimal HRT was 8 h; at that time, removal efficiencies of COD, ammonia nitrogen, and total nitrogen were 83.8%, 86.3%, and 65%, respectively. The system also greatly reduced excess sludge production; the removal efficiency was 82.8% with a HRT of 8 h. The study applied high-throughput pyrosequencing technology to evaluate the microbial diversity and community structures in distinct stages of the biological reactor. The relevance between process performance and microbial community structure was analyzed at the phylum and class level. The abundant Firmicutes made a large contribution to improving the biodegradability of painting wastewater through hydrolysis acidification and reducing sludge production through fermentation in the biological reactor.

Bacterial community analysis of anoxic/aeration (A/O) system in a combined process for gibberellin wastewater treatment.

Gibberellin wastewater cannot be directly discharged without treatment due to its high concentrations of sulfate and organic compounds and strong acidity. Therefore, multi-stage anaerobic bioreactor + micro-aerobic+ anoxic/aeration (A/O) + biological contact oxidation combined processes are used to treat gibberellin wastewater. However, knowledge of the treatment effects of the A/O process and bacterial community structure in the aeration tank reactors of such systems is sparse. Therefore, this study was conducted to investigate the treatment effects and operation of the A/O process on gibberellin wastewater, as well as changes in the bacterial community structure of activated sludge in the aeration tank during treatment. Moreover, removal was examined based on evaluation of effluent after A/O treatment. Although influent chemical oxygen demand (COD), NH3-N and total phosphorus (TP) fluctuated, effluent COD, NH3-N and TP remained stable. Moreover, average COD, NH3-N and TP removal efficiency were 68.41%, 93.67% and 45.82%, respectively, during the A/O process. At the phylum level, Proteobacteria was the dominant phylum in all samples, followed by Chloroflexi, Bacteroidetes and Actinobacteria. Proteobacteria played an important role in the removal of organic matter. Chloroflexi was found to be responsible for the degradation of carbohydrates and Bacteroidetes also had been found to be responsible for the degradation of complex organic matters. Actinobacteria are able to degrade a variety of environmental chemicals. Additionally, Anaerolineaceae_uncultured was the major genus in samples collected on May 25, 2015, while Novosphingobium and Nitrospira were dominant in most samples. Nitrosomonas are regarded as the dominant ammonia-oxidizing bacteria, while Nitrospira are the main nitrite-oxidizing bacteria. Bacterial community structure varied considerably with time, and a partial Mantel test showed a highly significant positive correlation between bacterial community structure and DO. The bacterial community structure was also positively correlated with temperature and SO42-.

Multistage biological contact oxidation for landfill leachate treatment: Optimization and bacteria community analysis

Landfill leachate is a wastewater contained solid waste and is hard to treat due to its complex composition. The most effective treatment is biological method among leachate transfer, biological treatment, and physical and chemical methods, however, the chemical oxygen demand (COD) removal efficiency of present biological treatment has not been more than 90% at influent COD concentration of 2000 mg/L to 5000 mg/L. In this study, the multistage biological contact oxidation (MBCO) is performed for treating landfill leachate. The optimized parameters as followed achieve 91.28% COD removal efficiency: influent COD landfill leachate concentration of 4000 mg/L; 0.1 L/min·L (reactor volume) aeration rate; temperature (T) of 35 °C and hydraulic retention time (HRT) of 24 h and also obtained 318.64 mg/L ammonium nitrogen (NH3-N) effluent concentration, Besides, biofilm community structure show that Proteobacteria, Bacteroidetes and Firmicutes are identified as the dominant in phylum. All the results indicate that the MBCO is an effective technology for landfill leachate treatment.

A novel bio-electrochemical system with sand/activated carbon separator, Al anode and bio-anode integrated micro-electrolysis/electro-flocculation cost effectively treated high load wastewater with energy recovery

A novel bio-electrochemical system (BES) was developed by integrating micro-electrolysis/electro-flocculation from attaching a sacrificing Al anode to the bio-anode, it effectively treated high load wastewater with energy recovery (maximum power density of 365.1 mW/m3 and a maximum cell voltage of 0.97 V), and achieving high removals of COD (>99.4%), NH4+-N (>98.7%) and TP (>98.6%). The anode chamber contains microbes, activated carbon (AC)/graphite granules and Al anode. It was separated from the cathode chamber containing bifunctional catalytic and filtration membrane cathode (loaded with Fe/Mn/C/F/O catalyst) by a multi-medium chamber (MMC) filled with manganese sand and activated carbon granules, which replaced expensive PEM and reduced cost. An air contact oxidation bed for aeration was still adopted before liquid entering the cathode chamber. micro-electrolysis/electro-flocculation helps in achieving high removal efficiencies and contributes to membrane fouling migration. The increase of activated carbon in the separator MMC increased power generation and reduced system electric resistance.

Application of the Multi-stage Contact Oxidation Method in Automobile Painting Wastewater Treatment

Application of the Multi-stage Contact Oxidation Method in Automobile Painting Wastewater Treatment

Treatment of slaughter wastewater by coagulation sedimentation-anaerobic biological filter and biological contact oxidation process

The optimal process parameters and conditions for the treatment of slaughterhouse wastewater by coagulation sedimentation-AF - biological contact oxidation process were studied to solve the problem of high concentration organic wastewater treatment in the production of small and medium sized slaughter plants. The suitable water temperature and the optimum reaction time are determined by the experiment of precipitation to study the effect of filtration rate and reflux ratio on COD and SS in anaerobic biological filter and the effect of biofilm thickness and gas water ratio on NH3-N and COD in biological contact oxidation tank, and results show that the optimum temperature is 16-24°C, reaction time is 20 min in coagulating sedimentation, the optimum filtration rate is 0.6 m/h, and the optimum reflux ratio is 300% in anaerobic biological filter reactor. The most suitable biological film thickness range of 1.8-2.2 mm and the most suitable gas water ratio is 12:1-14:1 in biological contact oxidation pool. In the coupling process of continuous operation for 80 days, the average effluent’s mass concentrations of COD, TP and TN were 15.57 mg/L, 40 mg/L and 0.63 mg/L, the average removal rates were 98.93%, 86.10%, 88.95%, respectively. The coupling process has stable operation effect and good effluent quality, and is suitable for the industrial application.

Analyzing Loose Contact Oxidation of Diesel Engine Soot and Ag/CeO2 Catalyst Using Nonlinear Regression Analysis

Loose contact (LC) oxidation kinetics of carbon black (CB) model soot and Ag/CeO2 catalyst was deduced from thermogravimetric analysis (TG) experiments. In the LC mode at ≧750 K, CB particles were likely to be combusted also by non-catalyzed oxidation, especially those particles located far from the catalyst surface, as well as Ag/CeO2-catalyed oxidation. Since the non-catalyzed oxidation is not due to catalytic activity, in order to deduce the catalytic activity from TG data, a nonlinear regression analysis method was proposed in this study to extract only the catalyzed oxidation part of the TG data. It was verified that this was successfully done with the equations used by the very good curve fits to the experimental TG data, and the catalytic activity was correctly obtained from LC samples with various degrees of physical contact between the CB and catalyst.

Development of a novel proton exchange membrane-free integrated MFC system with electric membrane bioreactor and air contact oxidation bed for efficient and energy-saving wastewater treatment

A novel combined system integrating MFC and electric membrane bioreactor (EMBR) was developed, in which a quartz sand chamber (QSC) was used, replacing expensive proton exchange membrane (PEM). An air contact oxidation bed (ACOB) and embedded trickling filter (TF) with filled volcano rock, was designed to increase dissolved oxygen (DO) in cathodic EMBR to save aeration cost. Membrane fouling in EMBR was successful inhibited/reduced by the generated bioelectricity of the system. The combined system demonstrated superior effluent quality in removing chemical oxygen demand (>97%) and ammonia nitrogen (>93%) during the stable operation, and the phosphorus removal was about 50%. Dominant bacteria (Nitrosomonas sp.; Comamonas sp.; Candidatus Kuenenia) played important roles in the removal of organic matter and ammonia nitrogen. The system has good application prospects in the efficient use of water and the development of sustainable wastewater recycling technology.

Efficiency and Mechanism of Purifying High Iron-Manganese from Ground Water in the Cold Villages and Towns Based on The Coupling of Rice Husk and Iron-Manganese Oxidizing Bacteria

Aiming at the special geo-climatic conditions and typical problems constraining the development of villages and towns, making villages and towns have the following characteristics:green and low-carbon, energy saving and environmental friendly, the coupling process of adsorption by carbonized rice husk particles and biological oxidation using Bacillus megaterium bacteria was developed for purifying high iron-manganese from groundwater in the cold villages and towns. The quick start-up method of biological filter at low temperature was studied. Based on the contact oxidation and biological method, iron removal efficiency and reaction rate in different filtration layers under different filtration conditions were comparatively analyzed, and iron removal mechanism of biological filter was determined. Filter materials and the solid samples in backwash water at different stages were characterized and the manganese removal mechanism of biological filter was analyzed through SEM, FTIR, XPS, Raman spectra and EPR. The results showed that the active biological membrane reached mature and stable only after 15 d with the operation mode of bacteria liquid cycle and low filtration rate in the filter column. The effluent concentration met the requirements of drinking water quality (GB 5749-2006) in the stable operation process. Fe, Mn and bacteria were lower than 0.3 mg·L-1, 0.1 mg·L-1, 100 CFU·mL-1, respectively. Iron removal mechanism relied mainly on the physical and chemical effects, supplemented by biological function. During the biofilm culturing stage and initial stable operation stage of filter column, manganese removal relied mainly on the biological effect. The physical chemistry was preferred at later stable operation stage. The study provides technical support for the applications of treating collectively Fe2+ and Mn2+ in groundwater.

Microbial community composition and function in a pilot-scale anaerobic-anoxic-aerobic combined process for the treatment of traditional Chinese medicine wastewater

Biodegradation of traditional Chinese medicine (TCM) wastewater was investigated in a pilot-scale anaerobic-anoxic-aerobic combined process, which was composed of an expanded granular sludge blanket (EGSB) reactor, a hydrolysis acidification (HA) reactor and a biological contact oxidation (BCO) reactor. In stable stage, the average values of COD and color in the combined process effluent were 45.7mgL−1 and 13 times, respectively. Excellent linear relations (R2>0.915) were achieved between color and UV254 at three color levels. Comprehensive community structures of the combined process were analysed by Illumina MiSeq Sequencing, which revealed that microbial community in the aerobic reactor had the greatest diversity and richness. Bacteroidetes, Firmicutes and Proteobacteria were dominant phyla in the three reactors, and Bacteroidales, Geobacter, ZB2 were the predominant functional microorganisms in the anaerobic, anoxic and aerobic reactors, respectively. Good removal efficiencies and presence of core microorganisms confirmed that the combined process was feasible for treating TCM wastewater.

河道排污口原位净化槽中试研究

对暂时无法截污纳口的排污口水质进行原位处理，是保护水资源，改善水环境的关键。为了提升河道排污口水质，对排污口原位净化槽去除污染物的性能进行中试试验。原位净化槽主要由吸附过滤部分和好氧接触氧化部分组成，吸附过滤部分填料由提篮盛装，接触氧化部分挂膜材料采用生物填料。本次试验对原位净化槽对于河道排污口CODCr、 NH+4-N、TP的去除效果进行研究。结果表明：当水体CODCr含量平均值为170.0 mg/L时，去除率达到53.7%；水体 NH+4-N平均值为10.5 mg/L时，平均去除率为52.2%；当水体排污口水体TP含量为2.43 mg/L时，净化槽平均去除率达到72.9%。 It is the key to protect the water resources and improve the water environment by carrying out the in-situ treatment of the water quality of the sewage outfall which cannot be cut off. In order to improve the quality of sewage outfall, pilot test was carried out on the removal of pollutants in the sewage purification tank. In-situ purification tank mainly consists of adsorption and aerobic contact oxidation filter parts, the filler for adsorbing filtration holding by the basket, and the biofilm material of contact oxidation fraction using biological filler. In this experiment, the removal effect of CODCr, NH+4-N and TP on the sewage outfall of the river in-situ purification tank was studied. The results show that when the water content of CODCr average value is 170.0 mg/L, the removal rate reached 53.7%; the average NH+4-N value of water is 10.5 mg/L, the average removal rate was 52.2%; when the water content of TP sewage water purification tank is 2.43 mg/L, the average removal rate reached 72.9%.

Design and electronic transport properties of organic thiophene molecular rectifier with the graphene electrodes

Molecular electronics offers new possibilities for continually miniaturizing the electronic devices beyond the limits of standard silicon-based technologies. There have been significant experimental and theoretical efforts to build thiophene molecular junctions and study their quantum transport properties. However, in most of these studies Au is used as lead material. It is well known that the fabrication of the traditional molecular device is now hindered by technological difficulties such as the oxidation of metallic contacts, and the interface instability between the organic molecule and the inorganic metallic electrodes. In this paper, we use the graphene electrodes to construct a series of thiophene-based devices. The graphene electrodes proposed in this paper are able to avoid such problems. Moreover, the stability of graphene electrodes at room temperature paves the way to studying the electron transport through a single molecule under the ambient conditions. Firstly, we design a series of molecular rectifying devices based on thiophene dimer and its derivatives, in which the hydrogen atom on the thiophene monomer is substituted with a representative electron-donating group (NH2) and electron-withdrawing group (NO2). Secondly, we investigate systematically the electronic transport properties through these molecular junctions by performing the first principles calculations based on density functional theory and nonequilibrium Green's function. The calculated results show that these thiophene molecular devices substituted with NH2 and NO2 possess the rectifying behavior and negative differential resistance properties. Furthermore, we also find that the position of substituent group NH2 or NO2 has a major influence on the electronic transport properties. In order to explore the physical mechanism behind these transport properties, the electronic structures of the molecules, the transmission spectrum, and the molecular projected eigenstates are analyzed. The results reveal that the position of NH2 can adjust the intensity of the negative differential resistance. When the NH2 group is close to the molecular end, the negative differential resistance behavior in this molecular device is more prominent than in other molecules. In addition, the position of NO2 can change the direction of the rectification. When the NO2 group is close to the molecular end, the current in negative bias is larger than in positive bias, resulting in a negative rectification. In contrast, when the NO2 group is close to the molecular centre, a positive rectification occurs. Our results can provide a worthy complement to thiophene molecular experiment, and also has a guiding significance for designing other molecular electronic devices.

Effect of initial roughness and oxidation on the running-in wear of machined surfaces under dry sliding

It is usually considered that initial roughness of a surface affects running-in wear. Oxidation of the surface is bound to occur during machining operation. The present investigation aims at understanding the influence of initial roughness and surface oxidation on the wear rate. Studies were conducted with a ball-on-flat geometry in a reciprocating tester at room temperature and at 100°C. Flat surfaces with initial roughness values of 0.42, 0.96 and 1.81 µm were used for dry tests of 120 minutes duration. It was observed that running-in wear rates were low and were inversely related to roughness. This phenomenon was explained on the basis of contact temperature rise and oxide thickness. After running-in, all the balls showed wear rates within a range of about 10% from 20 to 60 minutes. The roughness of the flats stabilised in the range of 0.04 µm to 0.06 µm at the end of the test.

Performance of Multilevel Contact Oxidation in the Treatment of Wastewater from Automobile Painting Industry

A multilevel contact oxidation system was applied in a pilot-scale experiment to treat the automobile painting wastewater, which had poor biodegradability and contained high concentration of Chemical Oxygen Demand (COD). The wastewater used for this experiment study was the actual painting wastewater which had been pre-treated by the physic-chemical process, and its Biological Oxygen Demand (BOD5)/COD was less than 0.1,COD concentration was 800∼1500mg/L. The results showed that the multilevel contact oxidation system could efficiently degrade the COD of the painting wastewater. When the experimental system kept stable operation, the total removal rate of COD and suspended solid (SS) were 84% and 82.5% respectively with the Hydraulic Retention Time (HRT) of 8 hours. Meanwhile, this system had a strong ability to resist the impact of COD concentration change. The COD concentration of final treated wastewater was less than 500 mg/L, which could reach the factory discharge requirement for the paint shop. Besides, this system with simple structure was able to reduce the excess sludge production greatly, which would reduce much cost for the treatment of painting wastewater.

Study on Treatment of Campus Domestic Wastewater for Landscape Water Treatment by Hydrolytic Acidification - Biological Contact Oxidation Process

In this paper, the issue of supplementing water source for landscape water is discussed. The quality of domestic sewage after treatment by hydrolytic acidification-biological contact oxidation method is analysed from the three aspects of effluent ammonia concentration, BOD concentration and turbidity in a certain period of time. It is proved that it is feasible the campus sewage as a water feature to supplement water. This will provide the reasonable suggestion for the domestic sewage as the supplementary water source for landscape water.

Impact of thermal processes on multi-crystalline silicon

Fabrication of modern multi-crystalline silicon solar cells involves multiple processes that are thermally intensive. These include emitter diffusion, thermal oxidation and firing of the metal contacts. This paper illustrates the variation and potential effects upon recombination in the wafers due to these thermal processes. The use of light emitter diffusions more compatible with selective emitter designs had a more detrimental effect on the bulk lifetime of the silicon than that of heavier diffusions compatible with a homogenous emitter design and screen-printed contacts. This was primarily due to a reduced effectiveness of gettering for the light emitter. This reduction in lifetime could be mitigated through the use of a dedicated gettering process applied before emitter diffusion. Thermal oxidations could greatly improve surface passivation in the intragrain regions, with the higher temperatures yielding the highest quality surface passivation. However, the higher temperatures also led to an increase in bulk recombination either due to a reduced effectiveness of gettering, or due to the presence of a thicker oxide layer, which may interrupt hydrogen passivation. The effects of fast firing were separated into thermal effects and hydrogenation effects. While hydrogen can passivate defects hence improving the performance, thermal effects during fast firing can dissolve precipitating impurities such as iron or de-getter impurities hence lower the performance, leading to a poisoning of the intra-grain regions.

Ammonium removal from coking wastewater in a pilot‐scale two‐stage aerobic biofilm system: Biokinetic analysis

AbstractA novel four‐stage pilot‐scale anaerobic/anoxic/oxic/oxic (A2/O2) biofilm process was successfully developed to treat coking wastewater with high ammonium loading. In this study, three different dynamical models including the first‐order substrate removal model, the Monod‐biological contact oxidation (Monod‐BCO) model, and the modified Stover‐Kincannon model were particularly applied to analyze kinetics of ammonium removal in a two‐step aerobic stage. For the O1 reactor, all models were appropriate for describing ammonium removal and the correlation coefficients of first‐order substrate removal model, BCO model, and modified Stover‐Kincannon model were 0.8974, 0.9210, and 0.9726, respectively. The model verification indicated that the modified Stover‐Kincannon model was slightly more applicable to predict ammonium removal in the O1 reactor. It was demonstrated that the maximum removal rate of ammonium was 0.208 kg/(m3 · d) by the Stover‐Kincannon model. For the O2 reactor, the modified Stover‐Kincannon model turned out to be the best fitting kinetic model for ammonium removal compared to the first‐order substrate removal model (R2 = 0.1556) and Monod‐BCO model (R2 = 0.5022). The maximum ammonium conversion rate (Um2‐O2) by the modified Stover‐Kincannon model was 1.180 kg/(m3 · d), while saturation rate constant k3‐O2 was 1.221 kg/(m3 · d). Furthermore, the determination coefficient between measured and predicted values obtained by the modified Stover‐Kincannon model was quite high (R2 = 0.9788) in the O2 process and a lower average residual square (6.60 × 10−6) was also obtained. The results of kinetic studies by the Stover‐Kincannon model can predict ammonia removal efficiency well in two‐step aerobic biofilm reactors of a coking wastewater treatment combined system.

Achieving Successful River Restoration in Dense Urban Areas: Lessons from Taiwan

A paradigm shift in river management practice is underway, from a hard engineering-dominated emphasis that endeavours to control water, to a multi-functionality-framed approach that strives to restore a river’s ecology, scenery and ecosystem services. In Taiwan, the Laojie River in Taoyuan City, where a channelized and piped urban river was recently transformed into an accessible, linear green infrastructure feature, is widely regarded as the first extensive and successful river restoration project in Taiwan’s densely-urbanized, flood-prone areas, yet its actual performance is rarely examined in any depth. Through in-depth interviews, fieldwork and a review of government documents, this paper presents findings on the practical factors involved in the practice of river restoration and their implications for urban river management. First, local people support river restoration with de-culverting, but potential flooding is a concern that results from different flood-risk perceptions and ineffective flood-risk communication between the government and public. Second, a mix of hard and soft edges to the watercourse improves the riverside landscapes in a densely-urban, flood-prone area. Third, due to a lack of basin-wide supporting sanitary sewer systems, a combination of on-site gravel contact oxidation treatment systems and riverside sewage-intercepting facilities still fails to improve the river water quality. Fourth, people’s positive attitudes towards river restoration are largely associated with landscape aesthetics and recreational value, rather than water quality and biodiversity. It is revealed that using the Cheonggyecheon Stream in South Korea as a frame for river restoration seems effective in providing local people with an example of successful river restoration, based mainly on flood prevention and recreational and aesthetic improvement. Moreover, the effective flood-risk communication is mainly reliant on an intelligible presentation of related information to the general public. Practical, continuous and extensive public participation, with various types of involvement and resources along with a solid system of social objectives by which to assess the outcome, is central to the social aspect of river restoration.