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1.
Textile wastewater containing a high level of color and refractory chemical oxidation demand (COD) is difficult to treat using traditional wastewater treatment processes. Typically, a chemical process was suggested as a pretreatment to remove color and increase biodegradability of refractory organic materials. A biological process was then used to remove organic materials and reduce chemical costs for textile wastewater treatment. Fenton oxidation is one of the most effective chemical processes for removing color and COD for textile wastewater. In Fenton processes, oxidations by generated hydroxyl radical are the key factor for color removal in textile wastewaters; thus, monitoring oxidation reduction potential (ORP) should have high potential in Fenton dosage control for color removal in textile wastewater treatment. The main object of this study is to build a Fenton dosage control strategy that uses ORP monitoring and artificial neural network (ANN) models for removing color from textile wastewaters. Two wastewaters, synthetic and real textile, were used in this study. Experimental results have shown that the ANN models precisely represent the correlation between monitoring ORP, Fenton doses, color removal efficiency, and effluent color value, and therefore can be used to control Fenton doses for removing color from textile wastewater. Finally, another series of Fenton dose-control experiments for different color removal control targets were conducted to evaluate this proposed Fenton dose control strategy. Experimental results indicate that the proposed control strategy precisely controls the required Fenton doses for different control targets for both synthetic and real textile wastewaters, and result in reduced chemical costs.  相似文献   

2.
Synthetic organic colorants, the majority of which are recalcitrant in nature, are used universally in many different manufacturing processes. The dyes are released into the environment in industrial effluents and are highly visible even at low concentrations (<1 mg∕L). Added to this, certain dyes, dye precursors, and aromatic amines have been shown to be carcinogenic. Thus, appropriate treatment of dye wastewaters to remove color and the dye compounds is clearly an important issue. Methanogenic toxicity tests on several food dyes provided a range of toxicity results, from noninhibitory (IC50 >20 g∕L) to inhibitory (IC50 0.2 mg∕L). Batch biodegradability assays indicated that the dyes were not readily utilized by the anaerobic microorganisms as a sole substrate. Decolorization of the dye tartrazine was investigated in a laboratory-scale anaerobic baffled reactor at a concentration of 250 mg∕L. Reduction in COD of 50–60% and color reduction of about 95% was achieved. Initially the tartrazine was not readily decolorized; however, decolorization improved with acclimation of the biomass. An industrial wastewater from a food dye manufacturer was fed to a second laboratory-scale anaerobic baffled reactor at a concentration of 5% (volume-to-volume ratio) and then increased to 10% (volume-to-volume ratio). Anaerobic degradation of the wastewater was efficient. Methanogenic activity was high; the organic content of the influent was reduced by about 70%, and color was reduced by almost 90%  相似文献   

3.
Three dye solutions, namely, C.I. Acid Yellow 17, C.I. Basic Blue 3, and C.I. Basic Red 2, were treated in an upflow anaerobic sludge blanket (UASB) reactor followed by a semi-continuous aerobic activated sludge tank. When hydraulic retention time was about 12 hours, no significant color removal was observed in the aerobic stage. In the anaerobic stage, Acid Yellow 17, Basic Blue 3, and Basic Red 2 were removed by 20%, 72%, and 78%, respectively. To treat wastewater from a dye manufacturing factor with COD concentration of 1200 mg/l and Color of 500 degrees (dilution factor), an UASB reactor (4.5 liters) and an activated sludge tank (5 liters, adjustable), COD and color were removed by more than 83% and 90% at a COD loading rate of 5.3 kg COD/m3-day in the anaerobic stage, and at the hydraulic retention time of 6-10 hours for the anaerobic stage and 6.5 for the aerobic stage. The anaerobic stage of the A/O system removes both color and COD. In addition, it also improves biodegradability of dyes for further aeroic treatment.  相似文献   

4.
A single unit anaerobic granular bed baffled reactor (GRABBR) is proposed as an alternative to a separately operated two-phase anaerobic digestion system. This overcomes the problems related to wastewater treatment at high loading rates which usually results in accumulation of intermediate acid products, and consequently inhibits methanogenesis. This study was carried out to evaluate the stability of a five compartment GRABBR system when treating synthetic glucose wastewater at various operational conditions. The reactor was started with volumetric organic loading rate (OLR) of 1 kg chemical oxygen demand (COD)/m3?day, equivalent to 120 h hydraulic retention time (HRT), and loading rates were gradually increased at suitable intervals to up to 20 kg COD/m3?day (6 h HRT). At steady state, the overall soluble COD (SCOD) removal was over 95% under all applied loading conditions. At lower loadings, the reactor operated as a completely mixed system, and most of the treatment was achieved in the first compartment. At higher loadings, the entire system transformed into different phases, acidogenesis being dominant near the influent point, whilst methanogenesis was the main activity in the compartments near the effluent point. Granule breaking and flotation was observed in the acidogenic zone, whilst the methanogenic zone retained its original granular form. High assimilation rate of influent nitrogen was observed in the first compartment with the formation of nongranular biomass, identified as Klebsiella pneumoniae. The success of GRABBR as a single unit two-phase anaerobic digestion system could save the cost of an extra unit traditionally employed to achieve similar goals in treatment of high strength wastewaters.  相似文献   

5.
A continuous flow flat sheet hybrid membrane aerated biofilm reactor (MABR) was used to treat a synthetic wastewater containing perchloroethylene (PCE); 1.25–2.5?g chemical oxygen demand (COD)/L of glucose was also added to the synthetic wastewater as a source of COD representative of a real wastewater. The reactor was able to biodegrade 70?mg?L?1 of PCE in 9?h without the accumulation of any intermediate compounds, resulting in a removal rate of 247?mmol of PCE?h?1?m?3 in a reactor with a specific membrane area of 4.048?m2?m?3. MABRs have never been used before for PCE degradation, and this rate is one of the highest volumetric PCE degradation rates reported in the literature. COD removal was also good and varied from 85 to 92%. Since very few volatile fatty acids accumulated in the system, most of the residual COD was attributed to soluble microbial products as reported by previous researchers. A mass balance on chloride during this study showed that only 72–81% of it could be accounted for. It is probable that some of the chlorinated ethenes were adsorbed onto the biofilm or that aerobic intermediates of low-chlorinated compounds such as trichloroethanol, dichloroacetyl, and chloroacetaldehyde were produced in the system. Nevertheless the chloride mass balance in this work compares well with the literature. Due to their high PCE and COD removal rates, hybrid MABRs have the potential to be used for a number of refractory organics which require combined anaerobic/aerobic biological treatment for degradation.  相似文献   

6.
Three 3?L laboratory scale submerged anaerobic membrane bioreactors (SAMBRs) with in situ membrane cleaning due to the bubbling of recycled biogas underneath them were studied for their ability to treat dilute wastewaters. Both Mitsubishi Rayon hollow-fiber and Kubota flat sheet membranes made of polyethylene with a pore size of 0.4?μm were used in this study, and the effect of different substrates (460?mg/L of glucose or synthetic) on chemical oxygen demand (COD) performance in the SAMBR was investigated. It was found that both membranes resulted in similar COD removals (>90% soluble COD at a hydraulic retention time of 3?h), but that the transmembrane pressure across the hollow fiber membranes was higher under similar conditions. Molecular weight analysis of the feed, reactor contents, effluent, and extracellular polymers using high pressure liquid chromatography showed that the membrane filtered out most of the high MW soluble organics, resulting in high COD removals. The experimental results from the SAMBR show the potential benefits of using this novel reactor design in a biological wastewater treatment process to minimize energy use and sludge production.  相似文献   

7.
Evaluation of Water Reuse Technologies for the Textile Industry   总被引:1,自引:0,他引:1  
Treatment technologies were evaluated for application in water reuse for the textile industry. Technologies tested included electrochemical oxidation, hypochlorite oxidation, ozonation, granular activated carbon (GAC) adsorption, bisulfite catalyzed sodium borohydride reduction, Fenton’s reagent, coagulation, and anaerobic biodegradation. Bench-scale side-by-side tests were conducted using a spent dyebath wastewater from a jigg dyeing operation. The dyebath contained three reactive dyes and auxiliary chemicals (e.g., common salt, soda ash, acetic acid, and caustic). Each technology was evaluated for its effectiveness at removing color and chemical oxygen demand (COD) and anticipated operating costs. Ozone, GAC, and electrochemical oxidation produced high-quality effluent, suitable for reuse. Although hypochlorite oxidation and sodium borohydride reduction resulted in significant color removal, it was not sufficient to meet reuse criteria. Results were either insignificant or inconclusive for coagulation, Fenton’s reagent, and anaerobic biodegradation. Auxiliary chemicals had great impact on the performance of many of the alternatives evaluated.  相似文献   

8.
A rotating-perforated-tubes biofilm reactor was used for treatment of synthetic wastewater at different operating conditions. The biofilm reactor consisted of two sections each having 25 perforated tubes mounted on three perforated discs. The battery of the tubes was rotated with the aid of a shaft and a motor. Effects of major process variables such as feed wastewater flow rate and COD concentration on the system performance were investigated. Kinetics of COD removal was investigated and kinetic constants determined by using the experimental data. An empirical design equation was developed to quantify the system's performance as a function of major process variables.  相似文献   

9.
The performance of a sequencing batch biofilter integrating anaerobic/aerobic conditions in one tank to treat a pharmaceutical wastewater effluent was studied. A pilot reactor, packed with a porous volcanic stone (puzzolane) was used in the study. The reactor operated as a sequencing batch biofilter, SBB, with reaction times varying for the anaerobic stage from 8 to 24 h and for the aerobic one from 4 to 12 h. The volume of exchange was from 16 to 88%. The pharmaceutical wastewater contained organic chemicals including phenols and o-nitroaniline, a concentration of organic matter that varied from 28,400 to 72,200 mg/L (as total COD), 280 to 605 mg N-NH4/L. and 430 to 650 mg SST/L. In order to acclimatize the microorganisms to the industrial wastewater, the organic load was increased stepwise from 1 to 7.7 kg COD/m3/d. The adequate time was obtained when the removal efficiency of COD reached 80%, or more. Maximal removal loads, associated to high removal efficiencies (95-97% as COD), varied from 4.6 to 5.7 kg COD/m3/d. Under these conditions color removal was 80% as Pt-Co units. Microtox analysis was performed to the wastewater and to the anaerobic and aerobic stages. It was observed that the aerobic stage was the responsible for wastewater detoxification. Results showed that the anaerobic/aerobic SBB was able to treat efficiently initial concentrations of the raw effluent up to 28,400 mg COD/L.  相似文献   

10.
Color removal from cotton textile processing wastewater by addition of powdered activated carbon (PAC) into a lab-scale activated sludge system was examined. The activated sludge system was continuously operated in different sludge ages (SRTs) and hydraulic retention times (HRTs). SRT = 30?d and HRT = 1.6?d operation resulted in up to 36% color removal and 94% COD removal. PAC was added 100, 200, and 400 mg/L into the activated sludge system under these operating conditions. The results indicated that 100 mg/L PAC was sufficient to remove the maximum color measured (up to 50 m?1) from the wastewater. The addition of PAC did not affect chemical oxygen demand (COD) removal significantly. Oxygen uptake rate (OUR) tests were also performed to investigate the microbial activities controlling the system performance. The average OUR was 74.1 mg/L/h without PAC addition while it was 70 mg/L/h with PAC addition. Adsorbable organic halogens of the effluent wastewater decreased from 400 to 50 μg/L with the addition of PAC. Toxicity dilution factor decreased from 2 to 1.5 with the PAC addition into the activated sludge system.  相似文献   

11.
A conceptual neural-fuzzy model based on adaptive-network-based fuzzy inference system (ANFIS) was proposed to estimate effluent chemical oxygen demand (COD) of a full-scale anaerobic wastewater treatment plant for a sugar factory operating at unsteady state. The fitness of simulated results was improved by adding two new input variables into the model; phase vectors of operational period and effluent COD values of last five days (history). In modeling studies, individual contribution of each input variable to the resulting model was evaluated. The addition of phase vectors and history of five days into the input variable matrix in ANFIS modeling for anaerobic wastewater treatment was applied for the first time in literature to increase the prediction power of the model. By this way, the correlation coefficient between estimated and measured values of output variable (COD) could be increased to the value of 0.8940, which is considered a good fit.  相似文献   

12.
The static granular bed reactor (SGBR) is a unique high-rate anaerobic reactor designed to operate in a simple downflow manner, offering high chemical oxygen demand (COD) removal efficiencies (greater than 90%) resulting from high biomass retention in the system. A study was performed to evaluate the SGBR versus a control system, the upflow anaerobic sludge blanket (UASB) reactor, and to evaluate performance idiosyncrasies of the SGBR and the control. The two reactors were operated at three different hydraulic retention times (HRTs): 8, 16, and 24 h. The reactors treated synthetic wastewater, intended to simulate food industry waste, composed of sucrose and nonfat dry milk. Overall, COD removal was higher for the SGBR than for the UASB reactor. In particular, at a HRT of 8 h, the SGBR achieved a COD removal of 90.7% and the UASB reactor reduced the COD concentration by 77.5%. The UASB reactor’s specific COD loading factor proved rate limiting with values ranging from 0.19 to 0.94?gCOD/(gVS?d) versus 0.11 to 0.34?gCOD/(gVS?d) for the SGBR. A tracer study idealized hydraulics within the two systems, and the results showed minimal dead volume and 4–6% short circuiting for both reactors.  相似文献   

13.
Anaerobic and aerobic treatment of high-strength pharmaceutical wastewater was evaluated in this study. A batch test was performed to study the biodegradability of the wastewater, and the result indicated that a combination anaerobic-aerobic treatment system was effective in removing organic matter from the high-strength pharmaceutical wastewater. Based on the batch test, a pilot-scale system composed of an anaerobic baffled reactor followed by a biofilm airlift suspension reactor was designed. At a stable operational period, effluent chemical oxygen demand (COD) from the anaerobic baffled reactor ranged from 1,432 to 2,397?mg/L at a hydraulic retention time (HRT) of 1.25 day, and 979 to 1,749?mg/L at an HRT of 2.5 day, respectively, when influent COD ranged from 9,736 to 19,862?mg/L. As a result, effluent COD of the biofilm airlift suspension reactor varied between 256 and 355?mg/L at HRTs of from 5.0 to 12.5 h. The antibiotics ampicillin and aureomycin, with influent concentrations of 3.2 and 1.0?mg/L, respectively, could be partially degraded in the anaerobic baffled reactor: ampicillin and aureomycin removal efficiencies were 16.4 and 25.9% with an HRT of 1.25 day, and 42.1 and 31.3% with HRT of 2.5 day, respectively. Although effective in COD removal, the biofilm airlift suspension reactor did not display significant antibiotic removal, and the removal efficiencies of the two antibiotics were less than 10%.  相似文献   

14.
Feasibility of the upflow anaerobic sludge blanket (UASB) process was investigated for the treatment of tapioca starch industry wastewater. After removal of suspended solids by simple gravity settling, starch wastewater was used as a feed. Start-up of a 21.5-L reactor with diluted feed of approximately 3,000 mg∕L chemical oxygen demand (COD) was accomplished in about 6 weeks using seed sludge from an anaerobic pond treating tapioca starch wastewater. By the end of the start-up period, gas productivity of 4–5 m3/m3r?day was obtained. Undiluted supernatant wastewater with a COD concentration of 12,000–24,000 mg∕L was fed during steady-state reactor operation at an organic loading rate of 10–16 kg COD/m3r?day. The upflow velocity was maintained at 0.5 m∕h with a recirculation ratio of 4:1. COD conversion efficiencies >95% and gas productivity of 5–8 m3/m3r?day were obtained. These results indicated that removal of starch solids from wastewater by simple gravity settling was sufficient to obtain satisfactory performance of the UASB process.  相似文献   

15.
An innovative anaerobic–aerobic integrated bioreactor system consisting of an upflow anaerobic sludge blanket (UASB) and a jet loop reactor was developed to investigate the feasibility of combined removal of carbon and nitrogen for a low-strength wastewater at different hydraulic retention times (HRTs) and recycle ratios. Total chemical oxygen demand (COD) removal of the integrated system increased from 87 to 92%, at a combined system HRT of 44?h, when the recycle ratio was increased from 100 to 400%, respectively. Denitrification efficiency of the integrated system increased from 49 to 86%, at all HRTs, when the recycle ratio was increased from 100 to 400%. The integrated system, on average, achieved more than 78% of total nitrogen at all HRTs. Nitrogen content of the biogas produced from the UASB reactor increased with increase in recycle ratios while the methane content exhibited a reverse trend, irrespective of the HRTs. Sludge volume index of the UASB reactor increased from 15?to?42?mL/g total suspended solids at the end of the study. Specific methanogenic activity of the granular sludge decreased from 1.3 to 0.8 g CH4–COD/g volatile suspended solids per day at the end of the study. Nitrogen and COD mass balance of the integrated system indicated that a substantial amount of influent nitrogen and COD was lost in the effluent as dissolved form.  相似文献   

16.
Conventional anaerobic mesophilic (AnM) digestion coupled with anaerobic thermophilic (AnT) pretreatment (AnTAnM system) and anaerobic thermophilic posttreatment (AnMAnT system) of mixed sludge (thickened waste activated sludge and primary sludge) was investigated. The main objectives were to investigate the ability of AnTAnM and AnMAnT systems to produce a product sludge that can meet Class A sludge requirements and to enhance sludge treatment in terms of volatile solids (VS) destruction, gas production, sludge supernatant chemical oxygen demand (COD) reduction, and sludge dewaterability. Lab-scale AnTAnM and AnMAnT systems were operated at a system sludge residence time of 15 days and temperature of 62°C in AnTAnM and AnMAnT thermophilic reactors. A lab-scale control anaerobic digester was operated at a system sludge residence time of 15 days and temperature of 37°C. The AnTAnM and AnMAnT systems and control achieved VS reductions of >38% (Class A sludge vector attraction reduction requirement). Average VS reductions by the AnTAnM (61%) and AnMAnT (63%) systems were significantly higher than VS reduction by the control (50%). The fecal coliform densities in the AnTAnM and AnMAnT system product sludges were below 1,000 most probable number (MPN) per gram total solids (TS) (Class A sludge fecal coliform density limit) compared to 106 MPN∕g TS in the control product sludge. The product sludge from the AnTAnM and AnMAnT systems and the control anaerobic digester met the Class A sludge Salmonella density limit (<3 MPN∕4 g TS) when fed with feed sludge containing 2–12 MPN∕g TS. Average methane production by the AnTAnM mesophilic digester (0.66 ± 0.10 m3∕kg VS destroyed) was higher than those of the AnMAnT (0.51 ± 0.06 m3∕kg VS destroyed) and the control anaerobic mesophilic digesters (0.52 ± 0.03 m3∕kg VS destroyed). The average supernatant CODs in the AnTAnM system product sludge (10,500 ± 200 mg∕L) and AnMAnT system product sludge (10,200 ± 150 mg∕L) were approximately the same and were significantly lower than the supernatant COD in the control anaerobic digester (14,100 ± 350 mg∕L). All three systems were fed with feed sludge containing an average supernatant COD of 22,500 mg∕L. Dewaterability of the product sludges, measured as time to filter, was 244 and 207 s for AnTAnM and AnMAnT systems, respectively, whereas it was 364 s for the control anaerobic digester product sludge.  相似文献   

17.
A steady-state laboratory-scale sequencing batch reactor process for biological phosphorus removal (BPR) was developed, and the influence of wastewater biodegradability on BPR was studied in batch tests. Biodegradability was expressed in this work as the readily biodegradable fraction of wastewater COD (rbCOD) present in the mixed liquor after the anaerobic stage of the anaerobic/oxic cycle of the BPR process. The rbCOD fraction was changed by varying the organic composition of synthetic wastewater (different carbohydrates were used: saccharose, cellobiose, starch, and cellulose) or varying the anaerobic retention time (1.25, 4, 9, and 24 h) when only one kind of low biodegradable synthetic wastewater (starch composed) was used. A clear positive trend was observed between rbCOD and anaerobic P release, but such a clear relationship was not observed with BOD5 measurements. Soluble carbohydrates allowed a BPR mechanism, but particulate carbohydrates seemed to cause nonbiological P removal. An increase in anaerobic retention time improved rbCOD concentrations up to 50%, approximately, and P removal, but excessive retention times, >9 h, should be used to reach good BPR results.  相似文献   

18.
The use of a combined anaerobic fluidized bed and zeolite fixed bed system in sanitary landfill leachate treatment was investigated. Anaerobic treatability studies were successfully performed in the anaerobic fluidized bed reactor. The chemical oxygen demand (COD) removal was attained up to 90% with increasing organic loading rates as high as 18?g?COD/L?day after 80?days of operation. Good biogas production yield (Ygas) of 0.53?L biogas per gram removed COD with methane (CH4) content of 75% was obtained. The attached biomass concentration increased along the column height from bottom to top, and its mean value was found 6,065?mg/L after 100?days of operation. The anaerobically treated landfill leachate was further treated by a zeolite fixed bed reactor. While excellent ammonia removal (>90%) was obtained with the untreated zeolite, the regenerated zeolites showed higher performance. Consequently, this combined anaerobic and adsorption system is an effective tool to remove high COD and high ammonia in landfill leachate.  相似文献   

19.
In this study, oxidation-reduction potential (ORP) was employed to regulate oxygen dosing for online sulfide toxicity control during anaerobic treatment of high sulfate wastewater. The experiment was conducted in an upflow anaerobic filter, which was operated at a constant influent total organic carbon of 6,740 mg/L [equivalent to a chemical oxygen demand (COD) of 18,000 mg/L], but with different influent sulfates of 1,000, 3,000, and 6,000 mg/L. The reactor was initially run at natural ORP (the system’s ORP without oxygenation) of about ?290 to ?300?mV and then was followed by oxygenation to raise ORP by +25?mV above the natural level for each influent sulfate level. At 6,000 mg/L sulfate under the natural ORP, methanogenesis was severely inhibited due to sulfide toxicity, and the anaerobic process was almost totally upset. Upon oxygenation by raising ORP to ?265?mV, the dissolved sulfide was quickly reduced to 12.2 mg S/L with a concomitant improvement in methane yield by 45.9%. If oxygen was not totally used up by sulfide oxidation, the excess oxygen was consumed by facultative bacteria which had been found to stabilize about 13.5% of the influent COD. Both sulfide oxidation and facultative activity acted as a shield to protect the anaerobes from an excessive oxygen exposure. This study showed that direct oxygenation of the recirculated biogas was effective to oxidize sulfide, and the use of ORP to regulate the oxygen dosing was practical and reliable during anaerobic treatment of high sulfate wastewater.  相似文献   

20.
Carbon tetrachloride (CT) in a synthetic wastewater was effectively degraded in a 2?l upflow anaerobic sludge blanket reactor during the granulation process by increasing the chemical oxygen demand (COD) and CT loadings. The effect of operational parameters such as influent CT concentrations, COD, CT loading, food to mass (F/M) ratio, and specific methanogenic activity (SMA) were also detected during granulation. Over 97% of CT was removed at 37°C, at a COD loading rate of 10?g/L?day. Chemical oxygen demand and CT removal efficiencies of 92 and 88% were achieved when the reactor was operating at CT and COD loading rates of 17.5?mg/L?day and 12.5?g/L?day, respectively. This corresponds to an hydraulic retention time of 0.28?day and an F/M ratio of 0.57?g?COD/g?volatile?suspended?solids?(VSS)?day. In 4?weeks, the seed sludge developed the CT degrading capability that was not very sensitive to shocks. The granular sludge cultivated had a maximum diameter of 2.5?mm and SMA of 1.64?g?COD/g?VSS?day. Glucose biodegradation by CT acclimated anaerobic granules was expressed with competitive inhibition. However the competitive inhibition was not significant since the competitive inhibition coefficient (Ki) was as high as 18.72?mg/L. Kinetic coefficients of k (maximum specific substrate utilization rate), Ks (half velocity coefficient), Y (growth yield coefficient), and b (decay coefficient) were determined as 0.6/day, 1.1?mg/L, 0.23?g?VSS/g glucose-COD, and 0.01/day, respectively, based on growth substrate glucose–COD during CT biotransformation. The CT was treated via biodegradation and this contributed to 89% of the total removal. The removal contributions from biomass adsorption, abiotic transformation, and volatilization were negligible. Adsorption and volatilization accounted for only 0.8 and 0.5% of the total removal, respectively.  相似文献   

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