Treatment of dye wastewater containing acid orange II using a cell with three-phase three-dimensional electrode.

The removal of color and chemical oxygen demand (COD) from simulated dye wastewater containing Acid Orange II was experimentally investigated using coagulation-electrooxidation. Two kinds of coagulation methods, ferrous-mediated coagulation and electrocoagulation were tested as pretreatment. The electrooxidation was carried out in a cell with a three-phase three-dimensional electrode using granular activated carbon as particle electrodes. Particular attention was paid to probe the effect of cell voltage, airflow rate, solution conductivity and treatment time on the electrochemical treatment efficiency. The experimental results showed that the coagulation-electrooxidation process could efficiently remove the color and the COD from the simulated dye wastewater. The overall COD and color removal efficiencies reached as high as 99% and 87%, respectively, by ferrous coagulation (molar rate of Fe(II)/ dye: 0.5) and 30-min electrolysis (cell voltage: 20.0 V and airflow: 0.1 m3 h(-1)).     

Cloud point extraction of toxic eosin dye using Triton X-100 as nonionic surfactant

An attempt has been made to remove color from wastewater containing toxic eosin dye (anionic dye) by cloud point extraction (CPE) in batch mode using a nonionic surfactant, Triton X-100 (TX-100). Most of the dye molecules get solubilized in the coacervate phase leaving a color free dilute phase. The effects of the concentration of feed mixture, temperature and salt concentration on the concentration of both dye and surfactant in the coacervate phase and dilute phase have been studied after the complete separation of two phases. Experimental investigations have also been carried out for the recovery of surfactant from dilute phase applying solvent extraction (SE) in batch condition. It has been observed that 87.5-100 percent eosin removal is possible for the feed dye concentration of up to 200 ppm using 0.1(M) of TX-100 and 0.2(M) of salt (NaCl) at 80 °C. About 88 percent of TX-100 can be recovered from dilute phase using solvent extraction method. It is concluded that the cloud point extraction techniques for the dye removal may be an alternative to the present dye removal processes.     

Textile Wastewater Treatment With Activated Sludge And Powdered Activated Carbon

The objective of the study is to determine the effectiveness of batch activated sludge process and powdered activated carbon adsorption for organic and color removal from textile wastewaters. Factors affecting treatment performance investigated in the study included raw wastewater strength, various combinations of dye to starch in the wastewater, aeration time. Synthetic wastewaters using starch solution and disperse-red-60 dye were used in the adsorption study. The 3 wastewater strengths used included low, medium and high strength. The 5 different dye to starch combinations used included 0% dye+100% starch, 25% dye+75% starch, 50% dye+50% starch, 75% dye+25% starch, and 100% dye+0% starch. The batch bio-oxidation was conducted for a period of 24 hours. The COD removal efficiency, color removal, bio-oxidation rate constant, F/M ratio, SVI, pH and temperature were determined. The results indicated that starch was much easier to remove by the batch activated sludge process compared to disperse-red-60 dye, which was virtually non-biodegradable. Wastewaters containing 100% starch had the highest COD removal efficiency. Increase in dye concentration in wastewater resulted in decrease in the COD removal efficiency. The COD removal efficiency ranged from 6 to 45% for low strength wastewater of 100mg/L COD, 27 to 80% for medium strength wastewater of 500mg/L COD, and 23 to 65% for high strength wastewater of 1000mg/L COD. The low strength wastewaters had the best settling characteristics, while the medium strength wastewaters had the worst. For high PAC dosage of 15g/L, high COD removal efficiencies of 88 to 98% removal and E * ab of 36 to 47 were obtained. It is recommended that activated sludge be used to remove high COD organic pollutants first, followed by PAC adsorption to remove dye waste in the treatment of textile wastewaters.     

Colour removal from a simulated dye wastewater using a two-phase anaerobic packed bed reactor

In recent years, rapid technological advances in the textile and dyeing industry have yielded benefits to society but have also generated new and significant environmental problems. The treatment alternatives applicable for the removal of colour vary, depending upon the type of dye wastewater. A synthetic, simulated mixed dye waste (Basic Yellow 28, Basic Yellow 21, Basic Red 18.1, Basic Violet Red 16, Basic Red 46, Basic Blue 16, Basic Blue 41) representing a known waste from a fibre production factory, was investigated. The biological process of anaerobic digestion has been recognised as a simple and energy-efficient means of treating and stabilising a wide range of organic industrial wastewaters. This study sets out to demonstrate the effect of different loading rates, dye concentrations and hydraulic retention times (HRTs) on colour removal efficiency under mesophilic anaerobic conditions. The reactor was operated under mesophilic conditions at different organic loading rates (OLRs) and HRTs for nine months. The results of this study show that a 2-stage mesophilic anaerobic up-flow packed bed reactor can remove up to 90% of the colour from a mixed cationic dye containing 1000 mg/l of dye. Colour removal efficiency falls as the influent dye concentration increases, but rises with increased hydraulic retention time and increased organic loading. The primary colour removal mechanism was one of biosorption with subsequent biodegradation. Acetoclastic methanogens were moderately inhibited at low organic loading rates of 0.25 kg COD/m3 d, at which level, acidogenesis and acetogenesis appeared to be unaffected. Inhibition of acidogenesis became marked at higher OLRs (1 kg COD/m3 d) and when the HRT was reduced from 5 to 3 days.     

Inhibition kinetics of salt-affected wetland for municipal wastewater treatment

A mathematical model was developed in order to describe the system behavior and performance of a constructed wetland (CW) treatment under salt-affected conditions. The rate of biodegradation of organic wastes was modeled using the first-order kinetics while the effect of salt concentrations was accounted by growth inhibition. Experimental data were used to determine model constants of the mathematical model. The experimental units were planted with cattail (Typha angustifolia) and fed with spiked municipal wastewater. The hydraulic retention time varied from 12 to 120 h and wastewater conductivity was in the range of 4-32 mS/cm. At specified conditions the model was found to well describe the trend of the experimental data in terms of BOD removal with the Pearson correlation of 0.872. The model also permits construction of a nomograph which can be used to aid the design and prediction of CW treatment under salt-affected conditions.     

Dye removal from textile dye wastewater using recycled alum sludge

The removal of dyes from textile dying wastewater by recycled alum sludge (RAS) generated by the coagulation process itself was studied and optimized. One hydrophobic and one hydrophilic dye were used as probes to examine the performance of this process. It was found that RAS is a good way of removing hydrophobic dye in wastewater, while simultaneously reducing the fresh alum dosage, of which one third of the fresh alum can be saved. The back-diffusion of residued dye from the recycling sludge is detected but is easily controlled as long as a small amount of fresh alum is added to the system. The use of RAS is not recommended for the removal of hydrophilic dyes, since the high solubility characteristics of such dyes can cause deterioration in the water quality during recycling.     

Optimisation of process parameters for bioreduction of azo dyes using Bacillus firmus under batch anaerobic condition

A new dye decolourising bacterial strain was isolated from textile wastewater and identified as Bacillus firmus. The study indicated that the bacterium could efficiently decolourise different azo dyes under static culture conditions. Characterisation of the efficiency of azo dye reduction by this isolate using both spectral and HPLC analysis was found to be a function of process parameters which include dye concentration, culture broth pH, incubation temperature, aeration as well as nitrogen source. For decolourisation, the optimal pH and temperature were 7–8 and 20–35°C respectively, while remarkable dye degradation was obtained within 18 h for dye concentrations below 100 mg L^?1. With the addition of yeast extract and under optimal conditions, dye reduction was enhanced and complete colour removal was achieved within 12 h. Colour removal was shown to be due to biodegradation rather than adsorption of dyes on bacterial cells. This study confirms the ability of the new dye‐degrading strain, Bacillus firmus, to decolourise and degrade different azo dyes and highlights its high biotechnology potential for the eco‐friendly treatment of textile wastewater when optimal conditions are applied.     

The effect of heavy metals on nitrogen and oxygen demand removal in constructed wetlands

The objective of this study is to investigate the respective effects of Zn, Pb and Cd as well as the combined effect of Zn, Pb, Cd and Cu on the removal of nitrogen and oxygen demand in constructed wetlands. Four laboratory-scale gravel-filled subsurface-flow constructed wetland units planted with cattails (Typha latifolia) were operated outdoors and fed with primary-treated domestic wastewater at a constant flow rate of 25 ml/min. After 6 months, three of the wetland units were fed with the same type of wastewater spiked with Zn(II), Pb(II) and Cd(II), respectively, at 20, 5 and 1 mg/l for a further 9 months. The remaining unit was fed with the same type of wastewater spiked with a combination of Zn(II), Pb(II), Cd(II) and Cu(II) at concentrations of 10, 2.5, 0.5 and 5 mg/l, respectively, over the same period. The chemical oxygen demand (COD) and ammoniacal nitrogen (AN) concentrations were monitored at the inlet, outlet and three additional locations along the length of the wetland units to assess the performance of the wetland units at various metal loadings. At the end of the study, all cattail plants were harvested for the determination of total Kjeldahl nitrogen and metal concentrations. The results showed that the COD removal efficiency was practically independent of increasing metal loading or a combination of metal loadings during the duration of the study. In contrast, the AN removal efficiency deteriorated progressively with increasing metal loading. The relative effect of the heavy metals was found to increase in the order: Zn相似文献   

Removal of Congo Red dye by adsorption onto phyrophyllite

Synthetic dye‐containing wastewaters from textile, paper, plastic and leather‐tanning industries are a most common organic pollutant. Such dyes may be toxic not only to aquatic life, but also to human beings. Consequently, dye removal from wastewater significantly benefits the environment. The aim of this study was to investigate the effectiveness of phyrophyllite as an adsorbent for Congo Red dye from wastewater. Dye sorption rates were investigated in bench‐scale studies. Evaluation of adsorption performance of phyrophyllite on Congo Red necessitated the determination of Langmuir and Freundlich isotherms. Adsorption of Congo Red on phyrophyllite was found to be in conformity with both isotherms. The adsorption capacity for phyrophyllite was found to increase with decrease in particle size and with increase in temperature and intensity of agitation. The results indicated that phyrophyllite was a good adsorbent for Congo Red from wastewaters.     

An approach to textile dye removal using sawdust from Aspidosperma polyneuron

The textile industry is responsible for discarding wastewater contaminated with dyes. The timber industry generates waste in the form of sawdust. The aim of the present study was to evaluate the adsorptive potential of sawdust obtained from the Aspidosperma polyneuron tree for the removal of the textile dye from wastewater. Sawdust was subjected to different pre-treatments (acid, alkaline and polyethyleneimine) in order to increase its adsorption capacity. Based on the results from the isotherms, treatment with polyethyleneimine (PEI) led to the greatest adsorption capacity and fits the Freundlich model, indicating cooperative adsorption. Other treatments with sawdust best fit the Langmuir model, but the untreated sawdust presented better results than the treated sawdust. These results were only surpassed by sawdust treated with PEI. A. polyneuron revealed good potential for use as an adsorbent to remove dyes, which is a novel result, since to date there is no study on its use as a sorbent material.     

Bioaugmented membrane bioreactor (MBR) with a GAC-packed zone for high rate textile wastewater treatment

The long-term performance of a bioaugmented membrane bioreactor (MBR) containing a GAC-packed anaerobic zone for treatment of textile wastewater containing structurally different azo dyes was observed. A unique feeding strategy, consistent with the mode of evolution of separate waste streams in textile plants, was adopted to make the best use of the GAC-zone for dye removal. Dye was introduced through the GAC-zone while the rest of the colorless media was simultaneously fed through the aerobic zone. Preliminary experiments confirmed the importance of coupling the GAC-amended anaerobic zone to the aerobic MBR and also evidenced the efficacy of the adopted feeding strategy. Following this, the robustness of the process under gradually increasing dye-loading was tested. The respective average dye concentrations (mg/L) in the sample from GAC-zone and the membrane-permeate under dye-loadings of 0.1 and 1 g/L.d were as follows: GAC-zone (3, 105), permeate (0, 5). TOC concentration in membrane-permeate for the aforementioned loadings were 3 and 54 mg/L, respectively. Stable decoloration along with significant TOC removal during a period of over 7 months under extremely high dye-loadings demonstrated the superiority of the proposed hybrid process.     

Anaerobic treatment of real textile wastewater with a fluidized bed reactor

Anaerobic treatability of a real cotton textile wastewater was investigated in a fluidized bed reactor (FBR) with pumice as the support material. The immobilized biomass or attached volatile solids level on the support material was 0.073 g VSS/g support material at the end of the 128-d start-up period. During the operation period, real cotton textile wastewater was fed to the anaerobic FBR both unsupplemented (in Stages 1 and 2) and supplemented (with synthetic municipal wastewater in Stage 3 and glucose in Stages 4-6). The effect of operational conditions such as organic loading rate (OLR), hydraulic retention time (HRT), influent glucose concentration as the co-substrate, etc. was investigated to achieve the maximum color removal efficiency in the reactor. Results indicated that anaerobic treatment of textile wastewater studied was possible with the supplementation of an external carbon source in the form of glucose (about 2g/l). The corresponding maximum COD, BOD(5) and color removals were found to be around 82%, 94% and 59%, respectively, for HRT of around 24h and OLR of 3 kg COD/m(3)/d. Further increase in external carbon source added to real textile wastewater did not improve the color removal efficiency of the anaerobic FBR reactor.     

光催化协同臭氧降解蒽醌染料废水

采用光催化协同臭氧技术降解蒽醌染料分散艳蓝E-4R,研究了光催化／臭氧法处理染料的主要影响参数,结果表明：增加臭氧的流量有利于提高脱色率,溶液初始pH值则对降解的影响较小,在光催似臭氧体系中,对降解起到主要作用的是·OH的氧化作用。     

Anaerobic/aerobic treatment of coloured textile effluents using sequencing batch reactors

Conventional biological wastewater treatment plants do not easily degrade the dyes and polyvinyl alcohols (PVOH) in textile effluents. Results are reported on the possible advantages of anaerobic/aerobic cometabolism in sequenced redox reactors. A six phase anaerobic/aerobic sequencing laboratory scale batch reactor was developed to treat a synthetic textile effluent. The wastewater included PVOH from desizing and an azo dye (Remazol Black). The reactor removed 66% of the applied total organic carbon (load F: M 0.15) compared to 76% from a control reactor without dye. Colour removal was 94% but dye metabolites caused reactor instability. Aromatic amines from the anaerobic breakdown of the azo dyes were not completely mineralised by the aerobic phase. Breakdown of PVOH by the reactor (20-30%) was not as good as previous reports with entirely aerobic cultures. The anaerobic cultures were able to tolerate the oxygen and methane continued to be produced but there was a deterioration in settlement.     

Comparative treatment of dye-rich wastewater in engineered wetland systems (EWSs) vegetated with different plants

In Dar es Salaam City there are more than a thousand tie-and-dye (TAD) small-scale industries (SSIs) that discharge dye-rich wastewater indiscriminately with resultant water pollution. Due to the decentralised nature of the TAD SSIs, coupled with financial constraints facing their operators, control of their pollution needs a simple cost-effective waste treatment technology. Engineered wetland systems (EWSs) constitute such a technology. A pilot scale EWS was evaluated with respect to its effectiveness in treating dye-rich wastewater. The role of wetland plants was assessed through comparing treatment performance efficiencies between an unplanted and vegetated EWS beds. On the whole, it has been demonstrated that the EWS has the potential to effectively treat dye-rich wastewater. Colour, which is the most apparent problem issue with textile wastewater, was reduced by 72-77%. COD was reduced by 68-73%, while sulphate was reduced by 53-59%. The proportionately high COD removal suggests the reduction in colour was accompanied by almost complete degradation of dyes and daughter products. The overall treatment efficiency of the vegetated units was more than twice as high as that of the unplanted bed. On average, the bed vegetated with coco yam plants performed better (7.6%) than the one planted with cattail plants.     

Decolorization of an azo dye by unacclimated activated sludge under anaerobic conditions

Studies on the reductive decolorization of a complex azo dye, Reactive Red 3.1, were made as part of the development of a practical approach to better exploit the metabolic potential of biomass in wastewater treatment. Decolorization was achieved at low and variable rates by mixed microbial cultures under various environmental conditions, including low pH and high salt concentration. It was caused by reductive cleavage of the azo bond to yield two aromatic amines. More reliable and effective decolorization rates, of up to 20–30 mg l⁻¹ h⁻¹, were given by unadapted activated sludge, (6 g l⁻¹) incubated with 400 mg l⁻¹ of Reactive Red 3.1 under anaerobic conditions. Decolorization also occurred best in static conditions.     

The evaluation of low‐cost biosorbents for removal of an azo dye from aqueous solution

There is a need to develop innovative and alternative technologies that can remove dyes from wastewater. In this study, low‐cost and locally available two renewable biosorbents (cotton stalk and apricot seed) were investigated to remove of Astrazone Black from aqueous solution. The effects of various experimental parameters such as dye concentration, adsorbent amount, adsorbent particle size and initial pH were tested, and optimal experimental conditions were examined. The results showed that as the amount of adsorbent was increased, the percentage of dye removal increased accordingly. The ratios of dye sorbed increased as the adsorbent particle size decreased. In addition, antibacterial effect of untreated and treated (decolourized) dye on a soil bacterium, Pseudomonas aeruginosa, was determined. The removal of this dye with agricultural wastes reduced the toxic effect on P. aeruginosa. This reduction in toxic effect is important both in respect of environmental biotechnology and waste detoxification.     

Bacterial growth on aniline: implications for the biotreatment of industrial wastewater

The degradation of aniline by bacterial consortia was investigated under aerobic, fermentative, nitrate-reducing and sulphate-reducing conditions and a variety of salt concentrations (0.2, 4 and 7% NaCl w/v) and pH values (5 and 7). A variety of degradation conditions were studied to provide information and recommendations for large-scale biological treatment of aniline-containing wastewater. Under aerobic conditions, degradation of aniline (2 mM) was achieved under all combinations of salinity and pH tested. The rate of bacterial growth decreased with increasing salinity. The bacterial consortium of each batch culture generally maintained its ability to degrade aniline when salt concentrations and pHs were changed although often the lag-phase prior to growth was extended. Microbial populations in fixed film continuous reactors were also able to resist changes in NaCl concentration. Increasing aniline concentration (0.25–1 g l⁻¹) under 0.2% NaCl (pH 5 and 7) conditions, resulted in aniline removal without affecting growth rates. At the lower pH, cell yield was not adversely affected by an increase in aniline concentration. However, at neutral pH, cell yield decreased with increasing aniline concentration. Cultures capable of degrading aniline under fermentative, nitrate-reducing and sulphate-reducing conditions were not obtained.     

膜生物反应器处理造纸废水研究

为了确定针对造纸废水处理的外置式膜生物反应器的最佳运行条件,采用中试膜生物反应器系统处理实际造纸废水,试验对COD和色度的平均去除率分别为93.7%和79.2%,并确定膜组件清洗周期为150 d。     

水解酸化/接触氧化/亚滤技术处理染整废水

采用水解酸化／生物接触氧化／亚滤技术处理纺织染整废水，运行结果表明，该工艺对COD、色度、SS的平均去除率分别为91％、92．5％、90．9％以上，废水经处理后满足染整工艺对水质的要求，可以考虑回用。该工艺具有剩余污泥少、耐冲击负荷能力强、难降解有机物去除率高等优点，在纺织印染废水处理中具有工程实用性。