COD fractionation of tannery wastewaters--particle size distribution, biodegradability and modeling

This study aims to establish the scientific link between particle size distribution (PSD) and biodegradability of different COD fractions of tannery wastewater, by means of sequential filtration/ultrafiltration, respirometric analysis and model evaluation. PSD profiles were determined in physical segregation experiments, using eight membrane discs, each with different pore sizes between 2 and 1600 nm. Biodegradability-related COD fractionation was determined at each size interval by model simulation and calibration of the corresponding oxygen uptake rate (OUR) profiles. Activated Sludge Model No. 3 (ASM3), modified for direct growth on hydrolysis products, was adopted for evaluation. PSD analyses defined a COD fingerprint with two significant portions at the two ends of size distribution, with 60% of the total COD at the particulate range, 25% at the soluble range and the remaining 15% well distributed among the colloidal range. Comparative evaluation of the sequence of OUR profiles yielded values of applicable model coefficients. It also enabled the assessment of size distribution for each major COD fraction, as an original tool for better interpretation of specific biodegradation characteristics of the selected tannery wastewater. Results also revealed a very slowly biodegradable/residual particulate COD component with a significant inhibitory effect. Model-based evaluation of the OUR profiles enabled quantifying the impact of inhibition in terms of changes in rate coefficients for growth, hydrolysis of soluble COD and endogenous decay.     

Effect of Fenton's oxidation on the particle size distribution of organic carbon in olive mill wastewater

The study evaluated the effect of Fenton's oxidation on the particle size distribution (PSD) of significant parameters reflecting the organic carbon content of olive oil mill wastewater (OMW). The organic carbon content of the studied OMW was characterized by a COD level of around 40,000 mg/L, with 13,500 mg/L of TOC and 1670 mg/L of total phenols. The corresponding antioxidant activity (AOA) was determined as 33,400 mg/L. PSD of the selected organic carbon parameters was investigated using a sequential filtration/ultrafiltration procedure. COD fractionation based on PSD revealed two major components, a soluble fraction below 2 nm and a particulate fraction above 1600 nm representing 49% and 20% of the total COD, respectively. The remaining COD was distributed in the colloidal and supracolloidal zones. The PSD of TOC, total phenols and AOA exhibited similar profiles with peaks at the two ends of the studied size range. Overall COD removals achieved via Fenton's oxidation both at pH = 3.0 and pH = 4.6 (the original pH of the OMW) remained in the range of 40-50%. As anticipated, the effect of Fenton's treatment was more pronounced in the soluble size range. Fenton's oxidation at pH = 3.0 resulted in 46% and 63% removals for total phenols and AOA, respectively. The results obtained indicated that Fenton's process could only be useful as an alternative preliminary treatment option of the required full treatment scheme that could involve a sequence of filtration, oxidation and/or biological treatment steps.     

Pilot scale treatment of textile wastewater by combined process (fluidized biofilm process-chemical coagulation-electrochemical oxidation)

The performance of pilot scale combined process of fluidized biofilm process, chemical coagulation and electrochemical oxidation for textile wastewater treatment was studied. In order to enhance biological treatment efficiency, two species of microbes, which can degrade textile wastewater pollutants efficiently, were isolated and applied to the system with supporting media. FeCl3 x 6H2O, pH 6 and 3.25 x 10(-3) mol/l were determined as optimal chemical coagulation condition and 25 mM NaCl of electrolyte concentration, 2.1 mA/cm2 of current density and 0.71/min of flow rate were chosen for the most efficient electrochemical oxidation at pilot scale treatment. The fluidized biofilm process showed 68.8% of chemical oxygen demand (COD) and 54.5% of color removal efficiency, even though using relatively low MLSS concentration and short sludge retention time. COD and color removals of 95.4% and 98.5% were achieved by overall combined process. The contribution of fluidized biofilm process to the overall combined process was increased over 25.7% of COD reduction and 20.5% of color reduction by adopting support media in biological treatment. It can be thought that the fluidized biofilm process was effective, and pollutant loading on post-treatment was pretty much decreased by this system. This combined process was highly competitive in comparison to the other similar combined systems. It was concluded that this combined process was successfully employed and much effectively decreased pollutant loading on post-treatment for textile wastewater treatment at pilot scale.     

Aerobic Biological Treatment of a Pharmaceutical Wastewater: : Effect of Temperature on COD Removal and Bacterial Community Development

The effect of temperature was studied on the efficiency of soluble COD removal and bacterial community development during the aerobic biological treatment of a pharmaceutical wastewater. Using wastewater and bacterial inoculum obtained from the full-scale facility treating this wastewater, batch laboratory cultures were operated at 5°C intervals from 30°C to 70°C. Following four culture transfers to allow for bacterial acclimation, residual soluble COD levels were measured and bacterial community fingerprints were obtained by denaturing gradient gel electrophoresis (DGGE) of polymerase chain reaction (PCR)-amplified 16S rRNA gene fragments. Soluble COD removal efficiency declined as temperature increased from 30°C (62%) to 60°C (38%). Biological treatment of this wastewater failed to occur at temperatures higher than 60°C. Gradual shifts in bacterial community structure were detected as temperature increased, including a concomitant reduction in the number of different bacterial populations. The impact of temperature on a two-stage biological treatment process was also compared. Better soluble COD removal was achieved when both reactors were operated at 30°C compared to a system where the two stages were consecutively operated at 55°C and 30°C. These results indicate that operation of aerobic biological wastewater treatment reactors at elevated temperatures can have adverse effects on process performance.     

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.     

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。     

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.     

Color removal from cotton textile industry wastewater in an activated sludge system with various additives

The low biodegradability of many dyes and textile chemicals indicates that biological treatment is not always successful in the treatment of cotton textile wastewater, in terms of color removal. In this study, a specific organic flocculant (Marwichem DEC), powdered activated carbon (PAC), bentonite, activated clay and commercial synthetic inorganic clay (Macrosorb) were directly added into the activated sludge laboratory pilot plant model. Before dosage, the optimum sludge retention time and hydraulic retention time were determined as 30 days and 1.6 days, respectively. The Monod kinetic constants were determined as Y = 0.76 kg MLSS/kg COD, Kd = 0.026 l/day, K(S) = 113.3 mg/L, k = 0.42 l/day and mu(max) = 0.32 kg MLSS/kg COD day. Under these conditions the average COD removal was 94% and color removal was 36%. The addition of these materials did not change COD removal significantly. The most effective materials were found to be DEC and PAC for color removal. While the color removal efficiency for 120 mg/L DEC addition was 78%, it was 65% for 100 mg/L, 77% for 200 mg/L and 86% for 400 mg/L PAC addition. The advantage of DEC compared to PAC was the lower sludge production. Statistical analyses using multiple linear regression indicate that there is no relationship between the effluent color with the influent color and total suspended solids (TSS) for DEC and PAC addition. On the other hand, when only bentonite, activated clay and Macrosorb were added, the effluent color was primarily dependent on the influent color and the TSS concentration had little effect. When the data is examined by using Kruskal-Wallis H and Mann-Whitney U tests and it was found that there was a significant difference between the color data groups.     

Treatment of cotton textile wastewater using lime and ferrous sulfate

This technical note summarizes the results of a textile wastewater treatment process aiming at the destruction of the wastewater's color by means of coagulation/flocculation techniques using ferrous sulfate and/or lime. All the experiments were run in a pilot plant that simulated an actual industrial wastewater treatment plant. Treatment with lime alone proved to be very effective in removing the color (70-90%) and part of the COD (50-60%) from the textile wastewater. Moreover, the treatment with ferrous sulfate regulating the pH in the range 9.0+/-0.5 using lime was equally effective. Finally, the treatment with lime in the presence of increasing doses of ferrous sulfate was tested successfully, however; it proved to be very costly mainly due to the massive production of solids that precipitated.     

Treatment capability of a physical—Chemical package plant

A short-term study of a commercially-available physical—chemical waste treatment plant is reported. Results indicate that an excellent quality of effluent can be consistently obtained despite wide fluctuations of influent wastewater characteristics. Physical, chemical, and biological parameters were monitored. The short-term data obtained offer some evidence of superior treatment efficiency in terms of COD, color, turbidity, and phosphorus removals when compared to more conventional treatment methods.     

Biological treatability of dairy wastewaters

Biological treatability of an integrated dairy plant wastewater containing a small fraction of whey-washwaters mixture has been experimentally investigated. Emphasis has been placed on the assessment of the initially inert fraction, S₁ and soluble residual microbial products, S_p. Parallel batch experiments have been conducted to determine the kinetic and stoichiometric coefficients of the degradable COD. The results have shown that the wastewater tested had practically no initially inert fraction, but generated residual microbial products amounting to 6–7% of the initial degradable COD. The results obtained have been fed into a set of equations describing the steady state operation of an activated sludge system with sludge recycle and a relationship indicating the variation of the total effluent COD with the sludge age has been defined for the wastewater tested. It is noted that effluent COD cannot be biologically reduced below 85 mg l⁻¹, regardless of the sludge age, due to generation of residual fractions.     

ABR水解/生物接触氧化处理印染废水

采用厌氧折流板反应器（ABR）水解／生物接触氧化法处理印染废水，在ABR的HRT为12h的条件下测定了ABR各格室及生物接触氧化池出水的色度、COD。结果表明，ABR出水色度达到了纺织染整行业一级排放标准，最终出水COD达到了行业二级排放标准。     

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)).     

内电解—UASB—BAF工艺处理草浆造纸中段废水的研究

采用铁炭内电解-UASB-BAF组合工艺对草浆造纸中段废水进行处理.结果表明,组合工艺对草浆造纸中段废水的COD、色度、SS具有较好的去除效果,在5种试验工况条件下,COD、色度和SS的去除率分别可达83%～90%,75%～85%和88%～93%;UASB工艺可以提高造纸中段废水的可生化性,试验过程中,经UASB处理后B/C最大可提高到0.5左右.综上所述,铁炭内电解-UASB-BAF组合工艺可以有效去除草浆造纸中段废水中的污染物质,可望在草浆造纸中段废水处理领域得到广泛应用.     

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。     

Cork industry wastewater partition by ultra/nanofiltration: a biodegradation and valorisation study

Wastewater from cork processing industry present high levels of organic and phenolic compounds, such as tannins, with a low biodegradability and a significant toxicity. These compounds are not readily removed by conventional municipal wastewater treatment, which is largely based on primary sedimentation followed by biological treatment. The purpose of this work is to study the biodegradability of different cork wastewater fractions, obtained through membrane separation, in order to assess its potential for biological treatment and having in view its valorisation through tannins recovery, which could be applied in other industries. Various ultrafiltration and nanofiltration membranes where used, with molecular weight cut-offs (MWCO) ranging from 0.125 to 91 kDa. The wastewater and the different permeated fractions were analyzed in terms of Total Organic Carbon (TOC), Chemical Oxygen Demand (COD), Biochemical Oxygen Demand (BOD), Total Phenols (TP), Tannins, Color, pH and Conductivity. Results for the wastewater shown that it is characterized by a high organic content (670.5-1056.8 mg TOC/L, 2285-2604 mg COD/L, 1000-1225 mg BOD/L), a relatively low biodegradability (0.35-0.38 for BOD₅/COD and 0.44-0.47 for BOD₂₀/COD) and a high content of phenols (360-410 mg tannic acid/L) and tannins (250-270 mg tannic acid/L). The results for the wastewater fractions shown a general decrease on the pollutant content of permeates, and an increase of its biodegradability, with the decrease of the membrane MWCO applied. Particularly, the permeated fraction from the membrane MWCO of 3.8 kDa, presented a favourable index of biodegradability (0.8) and a minimized phenols toxicity that enables it to undergo a biological treatment and so, to be treated in a municipal wastewater treatment plant. Also, within the perspective of valorisation, the rejected fraction obtained through this membrane MWCO may have a significant potential for tannins recovery. Permeated fractions from membranes with MWCO lower than 3.8 kDa, presented a particularly significant decline of organic matter and phenols, enabling this permeates to be reused in the cork processing and so, representing an interesting perspective of zero discharge for the cork industry, with evident environmental and economic advantages.     

微波-生物接触氧化法处理制药废水的研究

为探讨微波与生物接触氧化法用于处理制药废水的可行性,进行了相关试验研究.考察了微波处理对制药废水中COD的去除效果,结果表明：在微波辐射时间为2、8、10 min的条件下,对COD的去除率随着微波功率的增加呈相同的变化趋势;微波功率为382.5、434、459、510 W的条件下,对COD的去除率均随微波辐射时间的延长而有不同程度的提高;降低pH值有利于提高微波处理对COD的去除率.应用微波与生物接触氧化的组合工艺处理制药废水的试验结果表明：生物接触氧化的最佳处理时间为760 min;微波处理对COD的去除率为10%～15%,生物接触氧化法直接处理时,对原水COD的去除率较低,出水COD＞300mg/L;经过微波处理后（459 W、8min）再进行生物接触氧化处理（760 min）,则对COD的总去除率＞95%,最终出水的COD＜300mg/L,表明该组合工艺用于处理制药废水是可行的.     

Application of ferrous hydrogen peroxide for treatment of DSD-acid manufacturing process wastewater

A pretreatment method for the biological treatment of wastewater from 4,4'-diaminostilbene-2,2'-disulfonic acid (DSD-acid) manufacturing processes, a refractory dye intermediate wastewater, based on combined ferrous hydrogen peroxide oxidation and coagulation-flocculation, was developed. When the wastewater was treated with ferrous hydrogen peroxide oxidation ([Fe2+] = 2.7 mmol/L, [H2O2] = 0.21 mol/L) after a flocculation using an organic flocculant TS-1 at a dosage of 3 g/L, the overall COD and color removals were 64 and 62%, respectively. BOD5/COD value of the effluent was 0.3. Ferrous hydrogen peroxide oxidation treatment can reduce the solubility of organic molecules with sulfonic group and increase the efficiency of coagulation treatment. The COD and color removals were both more than 90% when FeCl3 was used as the coagulation (dosages of two-step coagulation were 0.031 and 0.012 mol/L respectively) after a ferrous hydrogen peroxide oxidation pretreatment at a H2O2 dosage of 0.06 mol/L.     

曝气生物滤池处理高档卷烟纸生产废水

采用混凝沉淀/曝气生物滤池(BAF)组合工艺对卷烟纸生产废水进行处理,处理水量为2 000～3 400 m3/d,混凝沉淀出水COD为120～400 mg/L,色度为2～4倍。经BAF工艺处理后的出水COD<100 mg/L,去除率稳定在50%～80%,色度<4倍。工程运行实践表明,采用混凝沉淀/BAF组合工艺处理高档卷烟纸生产废水稳定可行,具有良好的经济效益和环境效益。     

高效产酸发酵反应器处理医药原料废水

以高效产酸发酵反应器作为高浓度医药原料废水的二段厌氧生物处理的产酸装置,通过中试研究获得了反应器运行过程的COD容积负荷,水力停留时间、进水COD浓度,搅拌速度等参数及与COD去除率的关系,为实际工程设计及运行提供了依据。