Decolorization and biodegradability of photocatalytic treated azo dyes and wool textile wastewater

The photodegradation and biodegradability have been investigated for four non-biodegradable commercial azo dyes, Reactive YellowKD-3G, Reactive Red 15, Reactive Red 24, Cationic Blue X-GRL, an indicator. Methyl Orange, and one industrial wool textile wastewater, using TiO2 suspensions irradiated with a medium pressure mercury lamp. The color removal of dyes solution and dyeing wastewater reached to above 90% within 20-30 min. of photocatalytic treatment. Biochemical oxygen demand (BOD) was found to increase, while chemical oxygen demand (COD), total organic carbon (TOC) decreased, so that the ratio of BOD5/COD of the wastewater increased from original zero up to 0.75. The result implies that photocatalytic oxidation enhanced the biodegradability of the dye-containing wastewater and therefore relationship between decolorization and biodegradability exists. When the color disappeared completely, the wastewater biodegraded normally and could be discharged for further treatment. The experimental results demonstrate that it is possible to combine photocatalysis with conventional biological treatment for the remedy of wastewater containing generally non-biodegradable azo dyes.     

Hydraulic residence time effects on performance of an activated sludge unit treating wastewater containing dichlorophenol.

Wastewaters containing chlorophenol compounds are difficult to treat by biological means because of the toxic effects of those compounds on microorganisms. To investigate the adverse effects of chlorophenols on microorganisms, synthetic wastewater containing 2,4 dichlorophenol (DCP) was biologically treated in an activated sludge unit at different hydraulic residence times (HRTs) between 5 and 40 hours, whereas the feed chemical oxygen demand (COD), DCP concentrations, and sludge age were kept constant at 2500 +/- 50 mg/L, 150 mg/L, and 20 days, respectively. The resazurin method based on dehydrogenase activity was used for assessment of the feed and effluent wastewater toxicity. Percent COD, DCP, and toxicity removals increased, and the effluent COD, DCP, and toxicity levels decreased with increasing HRT. Biomass concentration in the aeration tank increased with increasing HRT because of low levels of DCP at high HRT levels, resulting in high COD, DCP, and toxicity removals. The sludge volume index decreased with increasing HRT, yielding well-settling organisms as a result of low levels of toxicity and high concentrations of active cells. Percent DCP and COD removals decreased with increasing specific DCP loading rate. The rates of DCP and COD removals showed a maximum at a low DCP concentration of 6 mg/L in the aeration tank, corresponding to a 25-hour HRT.     

Treatment of pharmaceutical wastewater containing antibiotics by O3 and O3/H2O2 processes

Ozonation of three different synthetic pharmaceutical formulation wastewater containing two human antibiotics and a veterinary antibiotic has been studied to enhance the their biodegradability. The effects of pH and initial chemical oxygen demand (COD) value as well as addition of hydrogen peroxide on ozonation process were investigated. Total organic carbon (TOC), COD, biochemical oxygen demand (BOD), and aromatic content (UV254) were the parameters followed to evaluate the performance of ozonation process. Comparison of the biodegradability of selected wastewaters containing different antibiotics confirmed that the variation of biodegradability was associated with the target compound. While BOD5/COD ratio of veterinary antibiotic formulation wastewater was increased from 0.077 to 0.38 with an applied ozone dosage of 2.96 g/l, this ratio for human antibiotic I and human antibiotic II was increased from 0 to 0.1 and 0.27 respectively. Moreover the results of this investigation showed that the ozonation process is capable of achieving high levels of COD and aromaticity removals at about their natural pH values.     

Elucidation of the behavior of tannery wastewater under advanced oxidation conditions

Diverse advanced oxidation process (AOP) techniques applying UV, TiO2/UV, O3 and O3/UV were used to degrade pollutants contained in tannery wastewater. The total mineralization of these pollutants is desirable, but it is quite energy consuming and sometimes impossible. Therefore the objective was to achieve an enhancement of biodegradability, preferentially with a decrease in toxicity in parallel. This work demonstrates that the dominant pollutants were chemically degraded by oxidation, while changes in carbon content were only marginal. These results were obtained monitoring the total organic carbon content (TOC), chemical and biochemical oxygen demand (COD and BOD), and substance-specific pollutant content by application of gas chromatography/mass spectrometry (GC-MS) and liquid chromatography/mass spectrometry (LC-MS). Daphnia magna toxicity testing performed in parallel proved a decrease in toxicity after AOP treatment of the tannery wastewater.     

Advanced oxidation of a pulp mill bleaching wastewater.

The degradation, by several advanced oxidation reactions, of a pulp mill ECF bleaching effluent, was studied. The initial biodegradability of the organic matter present in the effluent, estimated as the BOD5/COD, was low (0.3). When the effluent was submitted to ozonation and to five different advanced oxidation systems (O3/UV, O3/UV/ZnO, O3/UV/TiO2, O2/UV/ZnO, O2/UV/TiO2), the biodegradability increase significantly. After five minutes of reaction, the O3/UV system appears as the most efficient in to transform the organic matter to more biodegradable forms. A similar effect was observed when the effluent was submitted to an activated sludge treatment. The COD, TOC and toxicity reduction correlated well with the biodegradability enhancement after AOPs treatments.     

Ozonation of an azo dye C.I. Remazol Black 5 and toxicological assessment of its oxidation products

The effect of ozonation (20.5 mgl(-1)) on the degradation processes of an azo dye, Remazol Black 5 (RB5; CI) was studied. Conventional parameters such as chemical oxygen demand (COD), total organic carbon (TOC), pH, conductivity, colour removal, biodegradability (BOD(5/28)), and toxic potential of the dye and its degradation products were monitored during the process. The results obtained indicated that ozonation is a highly effective way to remove the colour of a corresponding dye solution. However, a considerable organic load still remained as indicated by high COD and TOC residues. The COD, TOC reductions were about 40% and 25% for 6 h ozonation of 2 gl(-1) RB5 aqueous solution. During the ozonation process the rapid decrease of pH and the sharp increase of conductivity indicated the formation of acidic by-products and small fragments and ions which were identified by high performance ion chromatography. The BOD28 data revealed that first by-products after partial ozonation (10-150 min) of RB5 were more biodegradable than the parent compound and ozonation can enhance the biodegradability of azo dyes. During the first 150 min of total 360 min of oxidation, the formation of first by-products with high toxic potential took place as it could be confirmed by two acute toxicity-screening tests, the bioluminescence test (Vibrio fischerii) and the neutral red cytotoxicity assay (rat hepatoma cells). The significant enhancement of microbial biodegradability after long-term ozonation could also be seen as a decrease of toxic intermediates in correlation with the ozonation time as indicated in BOD28 biological degradation test results.     

十三碳二元酸发酵有机废水处理研究

运用物化预处理和ＳＢＲ生化工艺对十三碳二元酸发酵废水中高浓度有机物的降解特征及高２硫酸钠对微生物的有害抑制作用进行处理试验,研究结果表明。采用物化预处理与ＳＢＲ生化法相结合的工艺可有效地处理该类废水。经驯化的耐盐微菌胶力和裂口虫为主,废水的ＣＯＤｃｒ去除率可达９２％以上,ＢＯＤ５去除率可达９５％以上。     

微电解与Fenton试剂预处理农药废水的试验研究

农药废水是一种典型的高浓度有机工业废水 ,有机污染物浓度高 (CODCr>10 0 0 0mg L) ,可生化性差 (氯苯农药废水BOD5 CODCr=0 .0 3 ,对邻硝基氯苯农药废水BOD5 CODCr=0 .0 5 )。采用微电解和Fenton试剂氧化两种物化手段对菊酯、氯苯和对邻硝氯苯 3种废水按比例配制而成的综合农药废水进行预处理 ,结果表明 :在废水pH为 2— 2 .5时 ,经微电解处理后 ,BOD5 CODCr比值在 0 .45以上 ,可生化性提高 ;Fenton试剂对综合农药废水CODCr去除率为 60 %左右 ,色度去除率接近 10 0 %     

Adverse effects of erythromycin on the structure and chemistry of activated sludge

This study examines the effects of erythromycin on activated sludge from two French urban wastewater treatment plants (WWTPs). Wastewater spiked with 10 mg/L erythromycin inhibited the specific evolution rate of chemical oxygen demand (COD) by 79% (standard deviation 34%) and the specific N-NH₄⁺ evolution rate by 41% (standard deviation 25%). A temporary increase in COD and tryptophan-like fluorescence, as well as a decrease in suspended solids, were observed in reactors with wastewater containing erythromycin. The destruction of activated sludge flocs was monitored by automated image analysis. The effect of erythromycin on nitrification was variable depending on the sludge origin. Erythromycin inhibited the specific nitrification rate in sludge from one WWTP, but increased the nitrification rate at the other facility.     

Preparation of biofilm electrode with Xanthomonas sp. and carbon nanotubes and the application to rapid biochemical oxygen demand analysis in high-salt condition

A Xanthomonas sp. was isolated from the sludge on the drain outlet of a pharmaceutical factory. Then, the bacterium and carbon nanotubes (CNTs) were co-attached to an oxygen electrode for rapid analysis of biochemical oxygen demand (BOD). The response current was linear with BOD values in the range 10 to 300 mg/L for standard BOD solution with a response time of 35 seconds (R = 0.9994) and 20 to 580 mg/L for pharmaceutical wastewater with a response time < or =200 seconds (R = 0.9985), which means that this modified electrode might be used for online BOD analysis of pharmaceutical wastewater. Further studies revealed that the modified electrode can be used for BOD measurement in a high-salt condition. Also, the bacterium/CNTs biofilm can maintain its activity and good performance, even after being sealed and stored at 4 degrees C for 50 days.     

Effects of nano-copper(II) oxide and nanomagnesium oxide particles on activated sludge

Effects of nano-copper(II) oxide (nano-CuO) and nanomagnesium oxide (nano-MgO) particles on activated sludge endogenous respiration (aerobic digestion), biochemical oxygen demand (BOD) biodegradation, and nitrification were investigated through respiration rate measurement. For comparison, the effects of Cu(II) and Mg(II) ions on activated sludge were also studied. Results indicated that soluble Cu(II) has half maximum inhibitory concentration (IC50) values of 19, 5.5, 53, and 117 mg Cu/L for endogenous respiration, BOD biodegradation, ammonium oxidation, and nitrite oxidation, respectively. However, nano-CuO only inhibited BOD biodegradation at 240 mg Cu/L or more, and its associated toxicity was primarily caused by soluble Cu(II). In contrast, soluble Mg(II) was not toxic to activated sludge in the experimental concentration range, but nano-MgO inhibited BOD biodegradation and nitrification with IC50 values of 70 and 143 mg Mg/L, respectively. Further study indicated that the toxicity of nano-MgO resulted primarily from increased pH following MgO hydrolysis.     

Fenton氧化-生化组合工艺处理染料中间体废水

针对染料中间体废水具有COD高、BOD5/COD低和具有生物毒性的特性,采用Fenton氧化-水解酸化-好氧组合工艺进行染料中间体生产废水的处理试验,试验结果表明:废水经Fenton氧化及水解酸化工序后,废水的BOD5/COD值由0.03升高至0.48,经好氧生化工序处理后的出水COD和BOD5浓度分别达122.6 mg/L和54.6 mg/L,符合《污水综合排放标准》(GB8978-1996)二级标准,该组合工艺COD总去除率达94%.     

Oxidation-reduction potential changes in aeration tanks and microprofiles of activated sludge floc in medium- and low-strength wastewaters.

Real-time control of aeration tank operation is key to high-efficiency pollutant removal and energy savings. One of the aims of this study was to examine the potential for using redox potential (oxidation-reduction potential [ORP]) to indicate wastewater quality online in aeration tanks treating medium (chemical oxygen demand [COD] of 70 to 150 mg/L) and low (COD of 15 to 30 mg/L) pollutant-concentration wastewaters. The field-scale data provide a good relationship between ORP values and nutrient removal along the length of the aeration tanks. The ORP values increased dramatically as organic matter was removed along the aeration tanks, indicating the improvement of the bulk liquor redox status. Dissolved oxygen higher than 1.0 mg/L was necessary for good biodegradation and improvement of the liquid redox status. Nitrification occurred at higher ORP values (380 to 420 mV) than was the case for organic substrate oxidation (250 to 300 mV). The microprofiles obtained from microelectrode measurements substantiate the heterogeneity of the microbial processes inside activated sludge flocs. Because of microbial oxygen utilization, the aerobic region in the activated sludge floc was limited to the top layer (0.1 to 0.2 mm) of the activated sludge aggregate present in medium-strength wastewater, with an anoxic zone dominating inside the flocs. When dissolved oxygen in the bulk water was higher than 4.0 mg/L, the anoxic zone inside the floc disappeared. At low wastewater pollutant concentrations, the ORP and dissolved oxygen inside the activated sludge aggregates were higher than those from medium-strength wastewater. The prospect of using ORP as an online control approach for aeration tank operation and the potential reasons for activated sludge floc size varying with pollutant strengths are also discussed.     

外循环式UASB反应器处理槟榔废水

在中温（35±2℃）条件下,利用外循环式UASB反应器处理中高有机浓度的槟榔加工废水,并着重探讨了水力停留时间（HRT）对厌氧消化的影响。研究表明,当反应器稳定运行,水力停留时间为1 d,进水COD浓度5 000 mg/L左右,容积负荷在2.53-5.25 kg COD/（m3·d）时,COD去除率在38%以上,出水COD〈3 000 mg/L,平均产气率为0.41 m3/kg COD;若水力停留时间延长至4 d,容积负荷为1.26-1.30 kg COD/（m3·d）,COD去除率可以达到79%,出水COD〈1 200 mg/L,出水可生化性下降,BOD5/COD平均为0.28,实验取得了良好的处理效果,为利用厌氧技术处理槟榔加工废水提供了设计依据。     

Treatment of high-strength pet food wastewater using two-stage membrane bioreactors.

A two-stage membrane bioreactor was used to treat dissolved-air-flotation pretreated, high-strength pet food wastewater characterized by oil and grease concentrations of 50 000 to 82 000 mg/L and total chemical oxygen demand (COD) and five-day biochemical oxygen demand (BOD5) concentrations of 100 000 and 80 000 mg/L, respectively, to meet stringent surface discharge criteria (i.e., BOD5, total suspended solids [TSS], and ammonium-nitrogen [NH4(+)-N] of < 10 mg/L at an overall hydraulic retention time of 6.3 days). Organic contaminants were removed primarily in the first stage, followed by almost complete removal of ammonia in the second stage. Despite a rise in poorly biodegradable COD in the second stage, overall removal of TSS, BOD5, COD, and ammonia was 100, 99.9, 95.2, and 99.7%, respectively, thus readily achieving the required criteria. Consistent nitrite accumulation over a period of more than 100 days, even at dissolved oxygen concentrations of more than 2.5 mg/L, was remarkable. A residual alkalinity requirement for nitrification was quantified. Membrane performance was extensively studied in this work.     

厌氧滤池处理纺织印染废水的中试研究

对厌氧滤池反应器处理难降解印染废水进行中试研究。结果表明,厌氧滤池反应器水力停留时间(HRT)在8.1～14.6 h之间,进水COD浓度波动较大(500～1 000 mg/L)时,对COD平均去除率为20%。印染废水的BOD5/COD由0.23提高到0.35,废水可生化性明显改善。印染废水中硫酸根浓度略有下降,去除浓度为70 mg/L左右。厌氧滤池进出水颜色明显变化,由紫红色变为蓝黑色,紫外可见光谱分析表明废水中的有机物结构发生变化。     

铁炭微电解深度处理焦化废水的研究

采用曝气铁炭微电解工艺对焦化废水进行了深度处理.结果表明,在活性炭、铁屑和NaCl投加量分别为10 g/L、30 g/L和200 mg/L的条件下反应240 min,出水COD去除率在30%～40%;酸性条件可以进一步提高COD去除率;微电解可以去除原生化出水中的难降解有机物,出水物质的分子量主要集中于2000 Da以下,以脂类和烃类化合物为主;出水的可生化性有了大幅度提高,BOD5/COD由0.08增加到0.53.实验结果表明,铁炭微电解是深度处理焦化废水的一种有效工艺.     

市政污泥水热炭化废水组成成分特征

污泥水热炭化处理被认为是极具潜力的污泥安全处置与资源化利用的技术措施之一。为了解废水中碳、氮、磷、钾和重金属含量随水热炭化反应温度和反应时间的变化规律,对市政污泥190℃和260℃水热炭化不同时间（1、6、12、18和24 h）后的废水组成成分进行了研究。结果表明,水热炭化处理后,废水颜色由黑色变成浅黄色;pH由6.40提高到9.14;TOC、COD和BOD5最高分别增加了13 175 mg/L、55 998 O2mg/L和31 723 O2mg/L;氮和钾含量显著提高,但磷含量降低;Cd、Cr含量由未检测到分别增加到0.060 mg/L和2.326 mg/L,As、Pb含量均由0.032 mg/L分别增加到1.408 mg/L和0.590 mg/L,但Cu、Mn及Zn含量降低。比起反应时间,反应温度对废水组成成分的影响更大。     

Enhancement of chemical-oxygen demand and color removal of distillery spent-wash by ozonation.

Distillery spent-wash has very high organic content (75,000 to 125,000 mg/L chemical-oxygen demand [COD]), color, and contains difficult-to-biodegrade organic compounds. For example, anaerobic treatment of the distillery spent-wash used in this study resulted in 60% COD reduction and low color removal. Subsequent aerobic treatment of the anaerobic effluent resulted in enhancement of COD removal to 66%. In this paper, the effect of ozonation on various properties of the anaerobically treated distillery effluent, including the effect on its subsequent aerobic biodegradation, was investigated. Ozonation of the anaerobically treated distillery effluent at various ozone doses resulted in the reduction of total-organic carbon (TOC), COD, COD/TOC ratio, absorbance, color, and increase in the biochemical-oxygen demand (BOD)/COD ratio of the effluent. Further, ozonation of the anaerobically treated distillery effluent at an ozone dose of 2.08 mg/mg initial TOC and subsequent aerobic biodegradation resulted in 87.4% COD removal, as compared to 66% removal when ozonation was not used.     

Swine wastewater treatment using attached-growth and suspended-growth two stage sequencing batch reactors with real-time control.

Two two-stage sequencing batch reactors (TSSBR), one attached-growth and one suspended-growth, were operated under three levels of wastewater concentration (approximately 4,000, 2,000 and 500 TOC mg/L), respectively, to compare the pH and ORP (oxidation-reduction potential) patterns and system performance. In both TSSBR systems, the pH and ORP profiles varied with organic loading yet exhibited consistent patterns with distinctive features suitable for real-time control. For all runs at the three levels of influent, both systems achieved similar levels of treatment for BOD5, TOC and TSS of over 97.5, 93.4, and 97.3%, respectively. The attached-growth system out performed the suspended-growth system in achieving the same levels of treatment at much shorter aeration cycle times. The treatment efficiency for NO3(-)-N and PO4(-3) was greatly affected by the carbon content in the wastewater, and the best treatment was achieved during the TOC approximately 4,000 mg/L runs with final effluent at 4.0 and 21.3 mg/L, respectively.