Fe(II)EDTA/H_2O_2电催化降解甲基橙模拟废水的研究

在无隔膜电解槽中,采用SPR(Ru-Ir-TiO_2)为阳极,石墨为阴极,考察了Fe(II)EDTA/H_2O_2电催化降解甲基橙(methyl orange)模拟废水的影响,发现EDTA很大程度上促进了类电Fenton试剂对甲基橙模拟废水的降解.实验研究表明,在外加电压为5.0v,EDTA:Fe~(2+) =2:1(摩尔比,Fe~(2+) =40 mmol/L),H_2O_2=48 mmol/L,电解质Na_2SO_4=40 mmol/L,废水pH值为(6.5±0.1)的条件下,降解260 mg/L的甲基橙模拟废水90 min,EDTA的加入可以使甲基橙模拟废水的脱色率由29.5%上升到78.4%,COD由571.429 mg/L降至80 mg/L,COD的降解率为86%,EDTA在此过程中既是催化剂又是反应物,可有效避免EDTA带来二次环境污染的可能性.     

Fe（Ⅱ）EDTA／H2O2电催化降解甲基橙模拟废水的研究

在无隔膜电解槽中,采用SPR（Ru—Ir—TiO2）为阳极,石墨为阴极,考察了Fe（Ⅱ）EDTA／H2O2电催化降解甲基橙（methylorange）模拟废水的影响,发现EDTA很大程度上促进了类电Fenton试剂对甲基橙模拟废水的降解。实验研究表明,在外加电压为5．0V,EDTA：Fe2＋=2：1（摩尔比,Fe2＋=40mmol／L）,H202=48mmot／L,电解质Na2SO4=40mmol／L,废水pH值为（6．5±0．1）的条件下,降解260mg／L的甲基橙模拟废水90min,EDTA的加入可以使甲基橙模拟废水的脱色率由29．5％上升到78．4％,COD由571．429mg／L降至80mg／L,COD的降解率为86％,EDTA在此过程中既是催化剂又是反应物,可有效避免EDTA带来二次环境污染的可能性。     

Process performance evaluation of the contact stabilisation system at Birzeit University

The purification capacity of the contact stabilisation system at Birzeit University campus has been studied for two years. The oxidation capacity of organic matter, ammonium oxidation, and denitrification potential were determined. The reduction of chemical oxygen demand (COD) was 85%, and the effluent COD concentration was less than 110 mg/l (the average value was 88 mg/l). Suspended solids were removed with equal efficiency. The aerobic stabilization of organic solids was efficient, and no excess biosolids (sludge) had to be removed. High nitrification (70% of the influent nitrogen were nitrified) could be maintained at 15°C, and 42% of the oxidised nitrogen was denitrified. The specific oxygenation capacity of the treatment system is relatively high and reached about 5 kwh/kg COD. The specific wastewater treatment cost is about 0.52 US$/m3 or about 58 US$ per population equivalent per year. Based on the results obtained, batch operation and intermittent aeration of the biological process are suggested to achieve high effluent quality and to reduce power consumption.     

Load maximization of a liquid-solid circulating fluidized bed bioreactor for nitrogen removal from synthetic municipal wastewater

A novel liquid-solid circulating fluidized bed bioreactor (LSCFB) configured with anoxic and aerobic columns and lava rock as the biofilm carrier was used to treat synthetic municipal wastewater. Four different empty bed contact times (EBCTs) of 0.82, 0.65, 0.55, and 0.44 h were examined to optimize nutrient removal capability of the system. The LSCFB demonstrated tertiary effluent quality organic and nitrogen removal efficiencies. Effluent characteristics of the LSCFB were soluble biological oxygen demand (SBOD)10 mg l(-1) and total nitrogen (TN)<10 mg l(-1) at organic loading rate (OLR) of 5.3 kg m(-3)d(-1) and nitrogen loading rate of 0.54 kg Nm(-3)d(-1). Remarkably low yields of 0.14, 0.17, 0.19, and 0.21 g VSS g(-1)COD were observed at OLR of 2.6, 3.2, 4.1 and 5.3 kg COD m(-3)d(-1), where increment of biomass growth and detachment rate were also experienced with increasing OLR. However the system demonstrated only 30% phosphorus removal, and mass balances along the anoxic and aerobic columns showed biological phosphorus removal in the system. Organic mass balance showed that approximately 40% of the influent COD was utilized in the anoxic column and the remaining COD was oxidized in the aerobic column. The system is very efficient in nitrification-denitrification, with more than 90% nitrification of ammonium and overall nitrogen removal in the LSCFB was 70+/-11% even at an EBCT of 0.44 h.     

Scale-up of electrochemical oxidation system for treatment of produced water generated by Brazilian petrochemical industry

Scale-up of anodic oxidation system is critical to the practical application of electrochemical treatment in bio-refractory organic wastewater treatment. In this study, the scale-up of electrochemical flow system was investigated by treating petrochemical wastewater using platinized titanium (Ti/Pt) and boron-doped diamond (BDD) anodes. It was demonstrated that flow cell was successfully scaled-up because when it was compared with batch mode (Rocha et al. 2012b), higher performances on organic matter removal were achieved. Under the suitable operating conditions and better anode material, the chemical oxygen demand (COD) of petrochemical wastewater was reduced from 2,746 to 200 mg L^?1 within 5 h with an energy consumption of only 56.2 kWh m^?3 in the scaled-up BDD anode system. These results demonstrate that anode flow system is very promising in practical bio-refractory organic wastewater treatment.     

A cascade of anoxic and oxic fluidized bed biofilm reactors for treatment of synthetic municipal wastewater

In this study, a cascade of anoxic and oxic fluidized bed biofilm reactors system was carried out to treat synthetic municipal wastewater. The parameters of the influent flow rates and C/N ratios were discussed. System performance was acceptable for chemical oxygen demand (COD), ammonia, and total nitrogen removal. A decrease of ammonia and total nitrogen removal efficiencies, however, was observed when the influent flow rates increased to 5.04 and 6.12 1 h(-1). Total nitrogen removal decreased at the influent C/N ratio of 3:1. The measured ratios of COD reduction in the anoxic column to nitrogen removal through nitrification-denitrification were 3.7, 3.5, 3.3, and 3.1 g COD/g(-1) N on average when the influent C/N ratios changed from 6:1 to 3:1. The observed sludge yield (Yobs) was 0.169 g VSS g COD(-1) because of perfect denitrification in the anoxic column and the relatively long solids retention time.     

Investigation of Cr(VI) reduction in continuous-flow activated sludge systems

The aim of this research was to investigate hexavalent chromium, Cr(VI), reduction by activated sludge and to evaluate the use of continuous-flow activated sludge systems for the treatment of Cr(VI)-containing wastewater. Three series of experiments were conducted using two parallel lab-scale activated sludge systems. During the first experiment, one system was used as a control, while the other received Cr(VI) concentrations equal to 0.5, 1, 3 and 5mg l(-1). For all concentrations added, approximately 40% of the added Cr(VI) was removed during the activated sludge process. Determination of chromium species in the dissolved and particulate phase revealed that the removed Cr(VI) was sorbed by the activated sludge flocs mainly as trivalent chromium, Cr(III), while the residual chromium in the dissolved phase was mainly detected as Cr(VI). Activated sludge ability to reduce Cr(VI) was independent of the acclimatization of biomass to Cr(VI) and it was not affected by the toxic effect of Cr(VI) on autotrophic and heterotrophic microorganisms. During the second experiment, both systems were operated under two different hydraulic residence time (theta equal to 20 and 28h) and three different initial organic substrate concentration (COD equal to 300, 150 and 0mg l(-1)). Cr(VI) reduction was favored by an increase of theta, while it was limited by influent COD concentration. Finally, at the last experiment the effect of anoxic and anaerobic reactors on Cr(VI) reduction was investigated. It was observed that the use of an anoxic zone or an anaerobic-anoxic zone ahead of the aerobic reactor favored Cr(VI) reduction, increasing mean percentage Cr(VI) reduction to almost 80%.     

Sequential treatment via Trametes versicolor and UV/TiO2/Ru(x)Se(y) to reduce contaminants in waste water resulting from the bleaching process during paper production

An efficient sequential, biological and photocatalytic treatment to reduce the pollutant levels in wastewater due to the bleaching process during paper production is reported. For a biological pre-treatment, 800 ml of non-sterilized effluent was inoculated with Trametes versicolor immobilized in polyurethane foam, with 25 g l(-1) glucose, 6.75 mM CuSO(4), and 0.22 mM MnSO(4) added, and cultured at 25 degrees C with an air flow of 800 ml min(-1) for 8d. The fungus did not inhibit growth of the heterotropic populations of the effluent. After 4d of culture, the chemical oxygen demand (COD) reduction and colour removal (CR) were 82% and 80%, respectively, with laccase (LAC) and manganese peroxidase (MnP) activities of 345 U l(-1) and 78 U l(-1), respectively. The COD reduction and CR correlated positively (p<0.0001) with LAC and MnP activities. Chlorophenol removal was 99% of pentachlorophenol, 99% of 2,3,4,6-tetrachlorophenol (2,3,4,6-TCP), 98% of 3,4-dichlorophenol (3,4-DCP) and 77% of 4-chlorophenol (4-CP), while 2,4,5-trichlorophenol (2,4,5-TCP) increased to 0.2 mg l(-1). The pre-treated effluent was then exposed to a photocatalytic treatment. The treatment with photolysis resulted in 9% CR and 46% COD reduction, 42% CR and 60% COD reduction by photocatalysis, and 62% CR and 85% COD reduction by heterogeneous photocatalysis with the system TiO(2)/Ru(x)Se(y) (Fig. 4). With this treatment the bacterial and fungal populations also decreased by 5 logarithmic units with respect to the biological treatment alone (Fig. 5). The total sequential treatment resulted in a 92% CR (from 5800 UC), 97% COD reduction (from 59 g l(-1)) and 99% chlorophenol removal at 96 h and 20 min.     

水胺硫磷工业废水的酸性水解处理研究

水胺硫磷工业废水中 ,有机磷和硫化物含量均 >10 0 0 0mg/L ,COD高达 5 5 0 0 0mg/L左右 ,NH3 N在 4 0 0 0 0mg/L左右 ,BOD/COD仅为 0 .0 5 ,属典型难生物降解废水。本文采用常压酸性水解和脱氨除磷工艺处理该废水 ,有机磷、硫化物、NH3 N和总磷等去除率均 >90 % ,COD去除率达到 5 0 %以上 ,废水可生化性提高 ;同时 ,可回收得到硫氢化钠、氨水等物质 ,使废水资源得到了综合利用     

Screening of physical-chemical methods for removal of organic material, nitrogen and toxicity from low strength landfill leachates

Physical-chemical methods have been suggested for the treatment of low strength municipal landfill leachates. Therefore, applicability of nanofiltration and air stripping were screened in laboratory-scale for the removal of organic matter, ammonia, and toxicity from low strength leachates (NH4-N 74-220 mg/l, chemical oxygen demand (COD) 190-920 mg O2/l, EC50 = 2-17% for Raphidocelis subcapitata). Ozonation was studied as well, but with the emphasis on enhancing biodegradability of leachates. Nanofiltration (25 degrees C) removed 52-66% of COD and 27-50% of ammonia, the latter indicating that ammonia may in part have been present as ammonium salt complexes. Biological pretreatment enhanced the overall COD removal. Air stripping (24 h at pH 11) resulted in 89% and 64% ammonia removal at 20 and 6 degrees C, respectively, the stripping rate remaining below 10 mg N/l h. COD removals of 4-21% were obtained in stripping. Ozonation (20 degrees C) increased the concentration of rapidly biodegradable COD (RBCOD), but the proportion of RBCOD of total COD was still below 20% indicating poor biological treatability. The effect of the different treatments on leachate toxicity was assessed with the Daphnia acute toxicity test (Daphnia magna) and algal growth inhibition test (Raphidcocelis subcapitata). None of the methods was effective in toxicity removal. By way of comparison, treatment in a full-scale biological plant decreased leachate toxicity to half of the initial value. Although leachate toxicity significantly correlated with COD and ammonia in untreated and treated leachate, in some stripping and ozonation experiments toxicity was increased in spite of COD and ammonia removals.     

Degradation of 2,4-dichlorophenol by combining photo-assisted Fenton reaction and biological treatment.

The photo-Fenton reaction effect on the biodegradability improvement of 100 mg/L solution of 2,4-dichlorophenol (DCP) has been investigated. Biochemical oxygen demand (BOD) at 5 and 21 days, BODn/ chemical oxygen demand (COD) and BODn/total organic carbon (TOC) ratios, average oxidation state, and inhibition on activated sludge were monitored. For 50 mg/L hydrogen peroxide and 10 mg/L iron(II) initial concentrations and 40 minutes of reaction time in the photo-Fenton process, the biodegradability of the pretreated solution, measured as BOD5/COD ratio, was improved from 0 for the original DCP solution up to 0.18 (BOD21/COD = 0.24). At that point, all DCP was eliminated from the solution. To study the effect of the pretreatment step, the biological oxidation of pretreated solutions was tested in two semicontinuous stirred tank reactors, one operated with activated sludge and one with biomass acclimated to phenol. Results showed that more than 80% TOC removal could be obtained by codigestion of the pretreated solution with municipal wastewater. Total organic carbon removals of approximately 60% were also obtained when the sole carbon source for the aerobic reactors was the pretreated solution. The hydraulic retention times used in the bioreactors were of the same order of magnitude as those used at domestic wastewater treatment plants (i.e., between 12 and 24 hours). Kinetic studies based on pseudo-first-order kinetics have also been carried out. Constants were found to be in range 0.67 to 1.7 L x g total volatiles suspended solids(-1) x h(-1).     

Electrocoagulation-integrated hybrid membrane processes for the treatment of tannery wastewater

Three different combinations of treatment techniques, i.e. electrocoagulation combined with microfiltration (EMR), membrane bioreactor (MBR) and electrocoagulation integrated with membrane bioreactor (hybrid MBR, (HMBR)), were analysed and compared for the treatment of tannery wastewater operated for 7 days under the constant trans-membrane pressure of 5 kPa. HMBR was found to be most suitable in performance as well as fouling reduction, with 94 % of chemical oxygen demand (COD) removal, 100 % chromium removal and 8 % improvement in percentage reduction in permeate flux compared to MBR with only 90 % COD removal and 67 % chromium removal. The effect of mixed liquor suspended solids on fouling was also investigated and was found to be insignificant. EMR was capable of elevating the flux but was not as efficient as HMBR and MBR in COD removal. Fouling reduction by HMBR was further confirmed by SEM-EDX and particle size analysis.     

Electrochemical treatment of domestic wastewater using boron-doped diamond and nanostructured amorphous carbon electrodes

The performance of the electrochemical oxidation process for efficient treatment of domestic wastewater loaded with organic matter was studied. The process was firstly evaluated in terms of its capability of producing an oxidant agent (H₂O₂) using amorphous carbon (or carbon felt) as cathode, whereas Ti/BDD electrode was used as anode. Relatively high concentrations of H₂O₂ (0.064 mM) was produced after 90 min of electrolysis time, at 4.0 A of current intensity and using amorphous carbon at the cathode. Factorial design and central composite design methodologies were successively used to define the optimal operating conditions to reach maximum removal of chemical oxygen demand (COD) and color. Current intensity and electrolysis time were found to influence the removal of COD and color. The contribution of current intensity on the removal of COD and color was around 59.1 and 58.8 %, respectively, whereas the contribution of treatment time on the removal of COD and color was around 23.2 and 22.9 %, respectively. The electrochemical treatment applied under 3.0 A of current intensity, during 120 min of electrolysis time and using Ti/BDD as anode, was found to be the optimal operating condition in terms of cost/effectiveness. Under these optimal conditions, the average removal rates of COD and color were 78.9?±?2 and 85.5?±?2 %, whereas 70 % of total organic carbon removal was achieved.     

电絮凝处理牛仔布印染废水

用铁分别作为电絮凝反应系统的阴极和阳极,研究电絮凝法对牛仔布印染废水的处理效果。考察了电极电压、反应时间和pH等因素对电絮凝法去除实验所用废水中COD和色度效果的影响。结果表明,电极电压和反应时间是主要的影响因素,pH次之。电极电压24 V,反应时间35 min,pH为7.4时,脱色率可达99%,COD去除率在70%左右,处理效果最佳。因此,电絮凝法可以作为印染废水的预处理工艺,有效降低废水COD和色度。     

Isolation and characterization of Bacillus cereus IST105 from electroplating effluent for detoxification of hexavalent chromium

Purpose

Electroplating industries are the main sources of heavy metals, chromium, nickel, lead, zinc, cadmium and copper. The highest concentrations of chromium (VI) in the effluent cause a direct hazards to human and animals. Therefore, there is a need of an effective and affordable biotechnological solution for removal of chromium from electroplating effluent.

Methods

Bacterial strains were isolated from electroplating effluent to find out higher tolerant isolate against chromate. The isolate was identified by 16S rDNA sequence analysis. Absorbed chromium level of bacterium was determined by inductively coupled plasma-atomic emission spectrometer (ICP-AES), atomic absorption spectrophotometer (AAS), scanning electron microscope (SEM), transmission electron microscope (TEM) and energy dispersive X-ray analysis (EDX). Removal of metals by bacterium from the electroplating effluent eventually led to the detoxification of effluent confirmed by MTT assay. Conformational changes of functional groups of bacterial cell surface were studied through Fourier transform infrared spectroscopy.

Results

The chromate tolerant isolate was identified as Bacillus cereus. Bacterium has potency to remove more than 75% of chromium as measured by ICP-AES and AAS. The study indicated the accumulation of chromium (VI) on bacterial cell surface which was confirmed by the SEM-EDX and TEM analysis. The biosorption of metals from the electroplating effluent eventually led to the detoxification of effluent. The increased survivability of Huh7 cells cultured with treated effluent also confirmed the detoxification as examined by MTT assay.

Conclusion

Isolated strain B. cereus was able to remove and detoxify chromium (VI). It would be an efficient tool of the biotechnological approach in mitigating the heavy metal pollutants.     

Removal of hexavalent chromium of contaminated soil by coupling electrokinetic remediation and permeable reactive biobarriers

Purpose

In this study, a novel and ecological alternative have been developed to treat soils contaminated with hexavalent chromium coupling two well-known systems: electrokinetic remediation and permeable reactive biobarriers. The electric field promotes the electromigration of the hexavalent chromium oxyanions towards the anode. The biobarriers were placed before the anode electrode, in order to promote the reduction and retention of the chromium migrating in its direction. Thus, this technology provided a global treatment to soil removal without subsequent treatments of the contaminated effluents.

Methods

The electrokinetic system was coupled with two different permeable reactive biobarriers composed by Arthrobacter viscosus bacteria, supported either in activated carbon or zeolite. An electric field of 10?V was applied and two different treatment times of 9 and 18?days were tested.

Results

Removal values of 60% and 79% were obtained when electrokinetic treatment was coupled with zeolite and activated carbon biobarriers, respectively, for a test period of 18?day. The reduction of hexavalent chromium to trivalent chromium was around 45% for both systems.

Conclusions

In this work, two types of biobarriers were efficiently coupled to electrokinetic treatment to decontaminate soil with Cr(VI). Furthermore, the viability of the new coupling technology developed (electrokinetic?+?biobarriers) to treat low-permeability polluted soils was demonstrated.     

Effect of alkalinity on the performance of a simulated landfill bioreactor digesting organic solid wastes

This study investigated the effects of alkalinity on the anaerobic treatment of the organic solid wastes collected from the kitchen of Engineering Faculty in Dokuz Eylul University, Izmir, Turkey and the leachate characteristics treated in three simulated landfill anaerobic bioreactors. All of the reactors were operated with leachate recirculation. One reactor was operated without alkalinity addition. The second reactor was operated by the addition of 3 g l-1 d-1 of NaHCO3 alkalinity to the leachate and the third reactor was operated by the addition of 6 g l-1 d-1 NaHCO3 alkalinity to the leachate. After 65 d of anaerobic incubation, it was observed that the chemical oxygen demand (COD), volatile fatty acids (VFA) concentrations, and biochemical oxygen demand to chemical oxygen demand (BOD5/COD) ratios in the leachate samples produced from the alkalinity added reactors were lower than the control reactor while the pH values were higher than the control reactor. The COD values were measured as 18900, 3800 and 2900 mg l-1 while the VFA concentrations were 6900, 1400 and 1290 mg l-1, respectively, in the leachate samples of the control, and reactors containing 3 g l-1 NaHCO3 and 6 g l-1 NaHCO3 after 65 d of anaerobic incubation. The total nitrogen (TN), total phosphorus (TP) and ammonium nitrogen (NH4-N) concentrations in organic solid waste (OSW) significantly reduced in the reactor containing 6 g l-1 NaHCO3 by d 65. The values of pH were 6.54, 7.19 and 7.31, after 65 d of anaerobic incubation, respectively, in the aforementioned reactors results in neutral environmental conditions in alkalinity added reactors. Methane percentage of the control, reactors containing 3 g l-1 NaHCO3 and 6 g l-1 NaHCO3 were 37%, 64% and 65%, respectively, after 65 d of incubation. BOD5/COD ratios of 0.27 and 0.25 were achieved in the 3 and 6 g l-1 NaHCO3 containing reactors, indicating a better OSW stabilization. Alkalinity addition reduced the waste quantity, the organic content of the solid waste and the biodegradation time.     

Electrochemical oxidation of two organophosphoric obsolete pesticide stocks

Organophosphoric pesticides are widely used for crop and fruit tree treatment, but their disposal causes serious environmental problems. Two commercial organophosphoric pesticides (Monocrotophos and Phosphamidon) were treated by an electrolysis system using Ti/Pt as anode and stainless steel 304 as cathode. A number of experiments were run in a laboratory scale pilot plant and the results are presented. For Monocrotophos, the achieved reduction was over 28%, while for Phosphamidon it was nearly 26%. Phosphamidon had a higher energy demand than Monocrotophos. The COD/BOD5 ratio was improved considerably after electrolysis for both pesticides examined. Therefore, electrochemical oxidation could be used as a pretreatment method for their detoxification.     

基于Ti/SnO2阳极氧化法的典型染料废水电化学氧化规律

采用Ti／SnO2电极间接阳极氧化法处理直接深棕M和活性艳蓝KNR模拟染料废水,研究电解质种类、pH、电压、NaCl投加量及电解时间对其降解效果的影响;在最佳组合条件下,通过分析uV—Vis光谱以及降解过程中氮元素的存在形式,研究上述2种染料的降解规律。结果表明,在pH为3,电压20V,NaCl投加量为2．5g／L的条件下,电解30min后,直接深棕M和活性艳蓝KNR的脱色率分别达到80％和95％,60min后直接深棕M的COD去除率可达75％,活性艳蓝KNR的COD去除率达到90％;电解60min后,直接深棕M的偶氮双键完全破坏,萘环和苯环结构被逐步降解,活性艳蓝KNR溶液电解2min,其分子结构中的蒽醌共轭体系被破坏,随反应的进行,蒽醌结构逐渐被破坏,染料逐步降解。     

An improved UV/Fe3+ process by combination with electrocatalysis for p-nitrophenol degradation

p-nitrophenol (PNP) was investigated as a model pollutant under the improved UV/Fe3+ process by combination with electrocatalysis. In the individual UV/Fe3+ process, PNP degradation rate was dependent on Fe(III) concentration and decreased during degradation due to the depletion of ferric ion and thus it was very difficult to reach the quick mineralization of organics. These drawbacks could be significantly overcome in the modified UV/Fe3+ process, and synergetic effects for PNP and COD removal were observed at two investigated Fe(III) concentrations. The enhancements on the degree of conversion for PNP and COD in presence of 0.5 mM Fe(III) were 184% and 242%, respectively, and PNP of initial concentration of 1.0 mM could be completely removed within 1 h. Thus such a process would be very attractive to the rapid mineralization of the biorefractory compounds for wastewater treatment. The possible reasons for the synergetic effects were the electrochemical regeneration of ferric ion and the role of the oxygen that formed on the anode. Based on degradation intermediates identification and synergetic effect probe, a general reaction pathway for PNP degradation in the improved process was proposed.