Decolorization and COD reduction of disperse and reactive dyes wastewater using chemical-coagulation followed by sequential batch reactor (SBR) process

This paper summarizes the results of disperse and reactive dyes wastewater treatment processes aiming at the destruction of the wastewater's color and chemical oxygen demand (COD) reduction by means of coagulation/flocculation (CF) followed by sequential batch reactor (SBR) process. The color removal efficiency of magnesium chloride aided with lime [MgCl₂/CaO] was compared with that of alum [Al₂ (SO₄)₃] and lime [Cao]. The experimental results showed that treatment with lime alone (600 mg/l) at pH value of 11.7 proved to be very effective. Color removal reached 100% and COD was reduced by 50%. Treatment with magnesium chloride aided with lime at pH value of 11 removed color completely and reduced the COD value by 40%. However, lime or lime in combination with magnesium chloride produced high amounts of sludge (1.84 kg/m³ for lime & 1.71 kg/m³ for MgCl₂ aided with lime). Also, the pH of the treated effluent was around 11 and needs correction prior to discharge into sewer network. The use of 200 mg/l alum without pH adjustment removed 78.9% of the color. To improve the effectiveness of alum, the cationic polymer namely cytec was used as a coagulant aid. This significantly increased color removal from 78.9 up to 94% and COD reduction was around 44%. Moreover, sludge production was only 0.36 kg/m³. Chemically pre-treated effluent was subjected to SBR process at an HRT of 5.0 h. Residual COD_total, total biochemical oxygen demand (BOD_{5 total}) and total suspended solids (TSS) in the final effluent were 78 ± 7.7; 28 ± 4.2 and 17 ± 4.2 mg/l, corresponding to the removal efficiency of 68.2; 76.3 and 61.4% respectively. Furthermore, almost complete removal of COD_particulate and BOD_5particulate has been achieved.     

Decolourization and COD removal from reactive dye‐containing wastewater using sonophotocatalytic technology

Decolourization and COD removal from synthetic wastewater containing Reactive Brilliant Orange K‐R (RBOKR) dye using sonophotocatalytic technology was investigated. Experimental results showed that this hybrid technology could efficiently remove the colour and reduce COD from the synthetic dye‐containing wastewater, and that both processes followed pseudo first‐order kinetics. At the condition of 0.1 m³ h^?1 airflow, 0.75 g dm^?3 titanium dioxide and 0.5 mmol dm^?3 RBOKR solution, the rate constants of decolourization and COD removal were 0.0750 and 0.0143 min^?1 respectively for the sonophotocatalytic process; 0.0197 and 0.0046 min^?1 respectively for the photocatalytic process and 0.0005 and 0.0001 min^?1 respectively for the sonochemical process. The rate constants of sonophotocatalysis were greater than that of both the photocatalytic and sonochemical processes either in isolation or as a sum of the individual process, indicating an apparent synergetic effect between the photo‐ and sono‐processes. Copyright © 2003 Society of Chemical Industry     

Comparison study of dyestuff wastewater treatment by the coupled photocatalytic oxidation and biofilm process

Degradation of Rhodamine B (RhB) and COD by means of the coupled photocatalytic oxidation (PCO) and biofilm systems has been studied. The coupled PCO-biofilm systems were divided into two operation systems. The one (R1) consisted of a pre-PCO and a post-biofilm reactor system and the other (R2) was a pre-biofilm and a post-PCO reactor system. In a batch experiment, the order of initial decolorization rate was photocatalytic oxidation > adsorption > photolysis. The color removal rate of RhB was decreased with an increase of the initial COD concentration. In a continuous experimental study, almost all color was removed in the PCO reactor. During 180 days, the color and COD removal efficiencies in the R2 (pre-biofilm + post-PCO) system were higher than those in the R1 (pre-PCO + post-biofilm) system. In our experimental ranges, the PCO process was superior to Fenton oxidation in the color and COD removal.     

Preliminary bench and pilot plant experiences for On-board wastewater treatment by ozone

This paper presents results obtained during a series of bench and pilot plant experiences on the utilization of ozone technology to treat sanitary wastewater coming from boats. Data on ozone solubility in soft water and sea water in a bench reactor were obtained. The analysis of the abatement of BOD, Total Coliforms, UV-absorbance and other parameters were performed on simulated saline and soft on-board wastewater considering increasing batch reactor retention time. The results indicated that the best abatement was obtained in saline wastewater with about 70% BOD and a 95% Total Coliform reduction in 30 minutes; further UV spectra have shown a sensible abatement of the absorbance readings. Pilot plant experiences on a saline wastewater confirm the potential possibility to treat hygienic on-board wastewater with ozone technology.     

射流式SBR工艺处理染料废水的研究

对COD浓度为1 500~2000 mg/L,挥发酚≤800 mg/L,pH为6~8的染料生产废水,经射流式SBR工艺生化处理,COD可降至154 mg/L,挥发酚去除率几乎达100%,出水水质达到国家污水综合排放二级标准。     

Removal of COD from coking-plant wastewater in the moving-bed biofilm sequencing batch reactor

The objective of this paper is to investigate COD removal efficiency of the coking-plant wastewater by applying the moving-bed biofilm sequencing batch reactor (MBBSBR). The operation is simple and 30% WD-F10-4 BioM™ were packed as carrier materials. It was found that the coking-plant wastewater could be effectively treated with 92.9% of COD removal efficiency at a low organic loading rate (OLR) of 0.449 kgCOD·m⁻³·d⁻¹ The removal efficiency decreased gradually down to 70.9% when OLR increased to 2.628 kgCOD·m⁻³·d⁻¹. The system has strong tolerance to organic shock loading in this experiment. The COD removal results in the blank experiments of biofilm and sludge showed that the attached biofilm has higher activity than suspended sludge and contributes about 60% to the COD removal. This work was presented at the 7 ^th China-Korea Workshop on Clean Energy Technology held at Taiyuan, Shanxi, China, June 26–28, 2008.     

微波-Fenton试剂法去除焦化废水中COD和色度的研究

对微波-Fenton试剂法处理焦化废水生化出水进行了研究,通过试验确定最优处理工艺条件:H2O2投加量为800mg/L,Fe2+投加量为100mg/L,溶液初始pH值为3,微波辐射功率为100W,微波辐射时间为120s。在该试验条件下,处理后的水质COD的质量浓度为30～60mg/L,去除率为80%～85%;色度为30～50度,去除率为87.5%～90%。     

污水回用时pH、COD对细菌生长及杀菌性能的影响

研究了污水回用水循环冷却水时pH、COD对细菌生长及杀菌性能的影响。结果表明，pH值在酸性范围内有利于铁细菌生长，对异养菌生长没有影响；pH值变化对优氯净的杀菌性能没有影响，而异噻唑啉酮不适于牛口峪污水回用时的杀菌。高COD有利于细菌的生长，但对杀菌剂的杀攻性能没有影响，相反与一些杀菌剂有一定的协同效应。     

A New Approach to Determine the Practical Ozone Dose for Color Removal from Textile Wastewater

In this study, the effect of applied ozone dose and pH on color removal from textile wastewater was studied. A lab-scale ozonation system was used in the experiments. When the applied ozone dose increased, the color removal efficiency and the rate constants increased, whereas ozone utilization ratio decreased. On the other hand, increasing the pH increased color removal efficiency and ozone consumption but decreased specific ozone dose. By using the experimental results, a new model has been developed to determine the required ozone dose for the removal of color. By means of this method, it was possible to determine the required ozone dose for reducing the amount of color up to desired levels. Experimental results and the model predictions were in good agreement not only for textile wastewater but also for different industrial effluents. Some parameters affecting ozone utilization such as pH, could also be incorporated into the model.     

山梨酸生产废水预处理的研究

介绍了山梨酸生产废水的水质。采用混凝-汽提-臭氧氧化方法对山梨酸生产废水进行预处理。实验结果表明:经该工艺处理后,山梨酸废水中化学需氧量(COD)的去除率达到了99.3%。该预处理工艺在有效治理废水的同时,实现了资源回收,具有很好的工业应用前景。     

Impact of chemical oxidation on biological treatment of a primary municipal wastewater. 1. Effects on cod and biodegradability

Municipal wastewaters taken from a primary sedimentation tank were subjected to different chemical oxidation processes (ozonation or UV radiation alone or combined with hydrogen peroxide) to observe the evolution of COD and BOD/COD ratios. Ozonation of wastewater led to different increases of COD level reduction depending on pH and carbonate‐bicarbonate ion concentrations. Direct photolysis or hydrogen peroxide alone were found to be inappropriate technologies. On the other hand, advanced chemical oxidation, that is, oxidation with ozone or UV radiation combined with hydrogen peroxide, increased COD level reduction only when wastewater was previously decarbonated. Thus, elimination of carbonate‐bicarbonate ions, increase of pH and addition of hydrogen peroxide (10^‐3 M) yield increases COD level reduction rates. Finally, preozonation also allows improvement of wastewater biodegradability.     

烘箱快速消解-分光光度法测定制浆废水中的COD

介绍了用烘箱消解测定废水COD,烘箱消解分光光度法测定COD代替玻璃仪器回流消解测定COD,通过对两种消解分析样品测定的COD数据比较,结果表明烘箱消解法测定COD较国准法操作简便,速度快,并且检测数据同样准确可靠,完全能够用于实际检测工作中。     

Kinetics of the Decolorization by Fenton's Reagent

Fenton's reagent was employed in the decolorization of aqueous solutions of one of three dyestuffs (Acid Red 27, Reactive Blue 81, Acid Blue 62). The decolorization with Fenton's reagent was found to be simple and fast. In order to determine the reaction kinetics of the decolorization the stopped-flow technique under pseudo-first order conditions was used. Experiments were carried out at pH=2, at the excess of ferrous salts (FeCl₂·4H₂O or FeSO₄·7H₂O). The rate constants of the decolorization determined by us are in the same order of magnitude: 90 to 100 dm³/(mol-s) for FeSO₄·7H₂O/H₂O₂, and 40 to 50 dm³/(mol-s) for FeCl₂·4H₂O/H₂O₂ systems. The difference between the rate constants for both ferrous salts indicates that the Fenton's reaction may proceed via different mechanisms.     

Ozonation of Exhausted Reactive Dye-Bath Analogues: the Use of Atrazine as an OH* Probe Compound

Ozonation and O₃/H₂O₂ treatment of a spent reactive dye–bath analogue containing aminofluorotriazine type reactive dyestuffs were examined in semi–batch experiments at different pH (2, 7 and 12), bicarbonate (0.18 M at pH7) and carbonate (0.19 M at pHl2) alkalinity. Atrazine (23.2 µM) was added as an OH* – sensitive probe compound to the reactive dye–bath analogue to evaluate the individual contributions of both direct molecular (O₃) and indirect radical (OH*) type reaction pathways for the treatment of spent dye–bath ingredients. From the obtained results it was evident that particularly de–aromatization (expressed in terms of UV₂₅₄ and UV₂₇₀ removal) kinetics were significantly retarded in the presence of HCO₃, CO₃ ^2‐ and particularly H₂O₂. O₃ decomposition and consumption increased appreciably when H₂O₂ (0.125 mM at pH7) was added as compared in the presence of carbonate/bicarbonate alkalinity when H₂O₂ was added indicating that H₂O₂ and alkalinity could act as radical chain reaction promoters (carriers) and inhibitors, respectively. Atrazine degradation and UV₂₇₀ abatement rates paralleled each other revealing that particularly de–aromatization of the spent dye–bath constituents mainly involves the action of OH*. Nitrate formation was distinctly higher at pH7 than at pH 12 as a consequence of the stronger OH* scavenging effect of carbonate alkalinity at pH12.     

不同浓度范围废水COD检测条件探讨

针对一些废水在处理过程中COD范围差异大,COD测定准确度、精密度低的问题,考察了不同浓度范围影响COD测定的关键性因素,结果显示:在440、600 nm处,Cr(Ⅵ)浓度不适会引起COD测定准确度、精密度降低.采用c( 1/6 K2Cr2O7)为0.02、0.05、0.5 mol/L的重铬酸钾溶液,分别对COD为0～...     

紫外分光光度法测COD影响因素研究

以沈阳建筑大学校园人工湖水为水样,考察浊度和pH值对紫外分光光度法测试COD所产生的影响。结果表明：当水样无机浊度或有机浊度含量较低时,不会对COD的测定产生影响,但含量较高则要考虑对相关方程进行修正。水样的pH值=1.8～9.0时,COD基本没有变化,当pH〉9.5时,影响COD的测定结果。     

Color and COD retention by nanofiltration membranes

In the present study the application of the nanofiltration process was investigated mainly in the retention ofcolor and chemical oxygen demand (COD) present in textile industry wastewater. Nanofiltration experiments were carried out in a pilot unit, operating in crossflow. Three different types of spiral wound membranes, DK 1073, NF 45 and MPS 31 were used simultaneously in the same unit. The results of the tests showed that for color retention, the values were around 99% for the DK 1073 and NF 45 membranes and the 87% for COD retention for the DK 1073. The permeate flux for the different wastewaters varied from 30.5 to 70 L/h.m². Fouling was observed in all membranes due to the accumulation of molecular species close to the filtering surface. The process was efficient and promising for the reuse of wastewater from this type of industry.     

Application of ozone on the decolorization of reactive dyes — Orange-13 and Blue-19

This study investigated the feasibility of applying ozone (O₃) to reduce the color content of wastewater caused by two commercial reactive dyes (Blue-19 and Orange-13). In the bench-scale experiment, experimental parameters including pH, ozone dosage, and reaction time were evaluated in a 14-L reactor to obtain the optimal operating conditions. Results show that ozone dosage and pH dominated the effectiveness of the decolorization process. The color content could be reduced from 2000 to 200 ADMI (American Dye Manufacture Institute) values within a reaction time of 30 min with the ozone input rate of 2.66 g/h. The pH values of 3 and 10 favored decolorization of Blue-19 and Orange-13, respectively. This was due to the effects that reactive and oxidizing species of molecular ozone and hydroxyl radicals were predominant at low and high pH, respectively. Moreover, molecular ozone was more selective to certain dye structures during the oxidation process. Kinetic analyses show that decolorization of Orange-13 and Blue-19 followed first-order kinetics. The degree of decolorization was primarily proportional to the ozone dosage. Results from this study provide insights into the characteristics and mechanisms of decolorization by the O₃ technique. Results will also aid in designing a system for practical application.     

Ozonation and Precipitation for Treatment of Bleachery Effluents from Pulp Mills

Results from precipitation of an oxygen/peroxide-bleachery effluent from pulp mills with and without preozonation are presented. Reductions in DOC levels by about 60% were achieved at the pH optimum of 5.5 at an AI/D0C ratio of 0.25 g/g. Increasing alum dosages did not improve the elimination. Ozonation at pH 2 reduced COD, DOC, UV and color levels, while under alkaline conditions an increase of color could be obtained. This effect, based on a polymerization of organics, could be improved at low ozone dosages, by reducing the ozone dosage rate, elevating the pH up to 11 and diluting the wastewater. However, the shift towards high and low molecular weight fractions indicated competing degradation reactions, which counteract a suggested improvement of precipitation by preozonation.