Electrooxidation of industrial wastewater containing 1,4-dioxane in the presence of different salts

The treatment of 1,4-dioxane solution by electrochemical oxidation on boron-doped diamond was studied using a central composite design and the response surface methodology to investigate the use of SO₄ ^2? and HCO₃ ^? as supporting electrolytes considering the applied electric current, initial chemical oxygen demand (COD) value, and treatment time. Two industrial effluents containing bicarbonate alkalinity, one just carrying 1,4-dioxane (S1), and another one including 1,4-dioxane and 2-methyl-1,3-dioxolane (S2), were treated under optimized conditions and subsequently subjected to biodegradability assays with a Pseudomonas putida culture. Electrooxidation was compared with ozone oxidation (O₃) and its combination with hydrogen peroxide (O₃/H₂O₂). Regarding the experimental design, the optimal compromise for maximum COD removal at minimum energy consumption was shown at the maximum tested concentrations of SO₄ ^2? and HCO₃ ^? (41.6 and 32.8 mEq L^?1, respectively) and the maximum selected initial COD (750 mg L^?1), applying a current density of 11.9 mA cm^?2 for 3.8 h. Up to 98 % of the COD was removed in the electrooxidation treatment of S1 effluent using 114 kWh per kg of removed COD and about 91 % of the COD from S2 wastewater applying 49 kWh per kg of removed COD. The optimal biodegradability enhancement was achieved after 1 h of electrooxidation treatment. In comparison with O₃ and O₃/H₂O₂ alternatives, electrochemical oxidation achieved the fastest degradation rate per oxidant consumption unit, and it also resulted to be the most economical treatment in terms of energy consumption and price per unit of removed COD.     

A new bioseed for determination of wastewater biodegradability: analysis of the experimental procedure

A new bioassay proposed in the patent P201300029 was applied to a pre-treated wastewater containing a mixture of commercial pesticides to simulate a recalcitrant industrial wastewater in order to determine its biodegradability. The test uses a mixture of standardized inoculum of the lyophilized bacteria Pseudomonas putida with the proper proportion of salts and minerals. The results highlight that biodegradation efficiency can be calculated using a gross parameter (chemical oxygen demand (COD)) which facilitates the biodegradability determination for routine water biodegradability analysis. The same trend was observed throughout the assay with the dehydrated and fresh inoculums, and only a difference of 5 % in biodegradation efficiency (E _f) was observed. The obtained results showed that the P. putida biodegradability assay can be used as a commercial test with a lyophilized inoculum in order to monitor the ready biodegradability of an organic pollutant or a WWTP influent. Moreover, a combination of the BOD₅/COD ratio and the P. putida biodegradability test is an attractive alternative in order to evaluate the biodegradability enhancement in water pre-treated with advanced oxidation processes (AOPs).     

臭氧氧化6-APA制药厂生化处理出水的特性及动力学简

通过现场实验研究了6-APA制药厂生化处理出水的臭氧氧化特性及其动力学规律。结果表明,当臭氧浓度为27.5 mg/L,气水接触时间为80 min时,COD、UV₂₅₄、NH₃-N和色度的去除率分别可达72.95%、73.28%、72%和96.25%,达到《发酵类制药废水工业水污染物排放标准》（GB 21903-2008）排放控制要求。拟合结果表明,在0~10、10~30和30~90 min时段内,臭氧氧化过程遵循拟一级反应,但反应速率逐渐降低。当气水接触时间为30 min时,废水可生化性可由0.1提高至0.35,采用臭氧/生物处理的联合工艺也有望使出水达到相同的排放控制要求。     

Decolorization of textile wastewater by photo-fenton oxidation technology

This paper describes the use of photo-fenton process for color removal from textile wastewater stream. The wastewater sample to be treated was simulated by using colorless polyvinyl alcohol (PVA) and reactive dyestuff of R94H. As a result, the hydroxyl radical (HO*) oxidation can effectively remove color, but the chemical oxygen demand (COD) was removed in a slight degree. The color removal is markedly related with the amount of HO* formed. The optimum pH for both the OH* formation and color removal occurs at pH 3-5. Up to 96% of color can be removed within 30 min under the studied conditions. Due to the photoreduction of ferric ion into ferrous ion, color resurgence was observed after 30 min. The ferrous dosage and UV power affect the color removal in a positive way, however, the marginal benefit is less significant in the higher range of both. PVA as the major background COD of a textile wastewater stream inhibits the color removal insignificantly as its concentration increases.     

Integrated Bacillus sp. immobilized cell reactor and Synechocystis sp. algal reactor for the treatment of tannery wastewater

The wastewater discharged from leather industries lack biodegradability due to the presence of xenobiotic compounds. The primary clarification and aerobic treatment in Bacillus sp. immobilized Chemo Autotrophic Activated Carbon Oxidation (CAACO) reactor removed considerable amount of pollution parameters. The residual untreated organics in the wastewater was further treated in algal batch reactor inoculated with Synechocystis sp. Sodium nitrate, K₂HPO₄, MgSO₄.7H₂O, NH₄Cl, CaCl₂·2H₂O, FeCl₃ (anhydrous), and thiamine hydrochloride, rice husk based activated carbon (RHAC), immobilization of Bacillus sp. in mesoporous activated carbon, sand filter of dimensions diameter, 6 cm and height, 30 cm; and the CAACO reactor of dimensions diameter, 5.5 cm and height, 30 cm with total volume 720 ml, and working volume of 356 ml. In the present investigation, the CAACO treated tannery wastewater was applied to Synechocystis sp. inoculated algal batch reactor of hydraulic residence time 24 h. The BOD₅, COD, and TOC of treated wastewater from algal batch reactor were 20?±?7, 167?±?29, and 78?±?16 mg/l respectively. The integrated CAACO system and Algal batch reactor was operated for 30 days and they accomplished a cumulative removal of BOD₅,COD, TOC, VFA and sulphide as 98 %, 95 %, 93 %, 86 %, and 100 %, respectively. The biokinetic constants for the growth of algae in the batch reactor were specific growth rate, 0.095(day^?1) and yield coefficient, 3.15 mg of algal biomass/mg of COD destructed. The degradation of xenobiotic compounds in the algal batch reactor was confirmed through HPLC and FT-IR techniques. The integrated CAACO–Algal reactor system established a credible reduction in pollution parameters in the tannery wastewater. The removal mechanism is mainly due to co-metabolism between algae and bacterial species and the organics were completely metabolized rather than by adsorption.     

Treatability studies on wastewater from textile dyeing factories in Bursa, Turkey

The textile industry is one of the most rapidly developing industries in Turkey. It generates a large amount of wastewater, with corresponding concerns about pollution. The main sources of pollution in wastewater are the dyeing and finishing processes. The dyestuffs and polyvinyl alcohol (PVA) are the main refractory organics of concern in terms of meeting more stringent effluent standards of chemical oxygen demand (COD) and colour. In this study, wastewaters from textile dyeing factories in Bursa were characterised, and physical, chemical and biological treatability studies were carried out. In the physical and chemical studies, 60.80% COD, 80% suspended solids (SS) and 10.92% turbidity removal efficiencies were obtained. In the biological studies, 90% COD and 40% SS removal were obtained. The initial soluble inert COD of wastewater was determined by using comparison methods. The initial inert COD of wastewater and the microbial product concentration were determined as 37 mg/l and 13 mg/l, respectively.     

Improvement of biodegradability of PVA-containing wastewater by ionizing radiation pretreatment

Background

Polyvinyl alcohol (PVA) has been widely used as sizing agents in textile and manufacturing industry, and it is a refractory compound with low biodegradability.

Objective

The objective of this paper was to treat the PVA-containing wastewater using gamma irradiation as a pretreatment strategy to improve its biodegradability and to determine the roles of different kinds of radical species played during pretreatment.

Methods

Gamma radiation was carried out in a ⁶⁰Cobalt source station, PVA concentration was analyzed by using a visible spectrophotometer and specific oxygen uptake rate (SOUR, milligram of O₂ per gram of mixed liquor volatile suspended solids (MLVSS) per hour) was measured by a microrespirometer.

Results

The results showed that the biodegradability of PVA-containing wastewater with low initial concentration (e.g., 327.8?mg/l) could be improved greatly with increasing irradiation dose. However, PVA gel formation was observed at higher initial PVA concentration (e.g., 3,341.6?mg/l) and higher irradiation dose, which inhibited PVA degradation by aerobic microorganisms. However, the formed gel could be separated by microfiltration, which led to more than 90% total organic carbon (TOC) removal.

Conclusion

Ionizing radiation could be used as a pretreatment technology for PVA-containing wastewater, and its combination with biological process is feasible.     

多元微电解技术对高浓度化学清洗废水预处理的影响

以高浓度化学清洗废水为研究对象,分别考察了常规混凝沉淀、多元微电解2种工艺对有机物污染物的去除效率和改善废水可生化性的效果。结果表明:多元微电解工艺的最佳pH 3.0,填充比1∶3,微电解1 h,气水比1∶1的条件下,其对COD平均去除率可达到60%,而直接混凝沉淀仅为10.5%,多元微电解工艺能使BOD5/COD值由原来的0.12升高到0.32,提高了废水的可生化性,减轻了后续生化处理负荷,是对高浓度化学清洗废水的有效预方法。     

Rapid immobilization of viable Bacillus pseudomycoides in polyvinyl alcohol/glutaraldehyde hydrogel for biological treatment of municipal wastewater

A new approach for easy synthesis of Bacillus pseudomycoides immobilized polyvinyl alcohol (PVA)/glutaraldehyde (GA) hydrogel for application in a wastewater treatment system is reported. Optimization studies revealed that GA/PVA mass ratio of 0.03 and acidic pH of 2 were required for hydrogel synthesis and eventually for bacterial cell immobilization. The synthesized crosslinked matrix possessed a pore size suitable for microbial cell entrapment while maintaining cell accessibility to external environment for bioremediation. Possible crosslinking and bacterial cell immobilization in the hydrogel were evidenced by FTIR, XRD, and SEM studies, respectively. Further, the extent of crosslinking of GA with PVA was investigated and confirmed by transmittance and permeability experiments. The viability and proliferation of hydrogel embedded cells (after 25 days) was confirmed by confocal fluorescence microscopy which also indicated that acidic pH of polymer solution did not affect the immobilized live cells. B. pseudomycoides immobilized hydrogel were demonstrated to be effective for treatment of municipal wastewater and reduced biochemical oxygen demand (BOD), chemical oxygen demand (COD), and protein content below the recommended levels. Overall, the results from this bench-scale work show that employing bacteria-embedded PVA/GA hydrogel for the treatment of municipal wastewater yield promising results which should be further explored in pilot/field-scale studies.

     

Fenton氧化对制浆造纸废水分子量及可生化性变化的影响

以制浆造纸废水的初沉池出水为研究对象,对不同剂量的Fenton氧化试剂处理制浆造纸厂初沉废水的效果进行了研究,初沉废水中的分子量大于10 000的有机污染物含量占到83%,废水可生化性较差;在Fe2+与H2O2的摩尔比为1∶5,废水pH为3.5的条件下,H2O2(30%)投加量小于3.25 mL/L时,Fenton试剂的氧化效率更高;H2O2(30%)投加量为6.50 mL/L时,废水中污染物的去除率更高,其中废水COD的去除率为79.5%,AOX的去除率为75.3%,色度去除率为97.5%,同时处理后废水中分子量在500~3 000之间的有机物含量占到82.98%,废水的BOD5/COD值提高到0.56。Fenton氧化作为前置技术处理制浆造纸废水,可以降低废水中的有机物分子量,减少废水的生物毒性,增加废水生物降解性,有助于后续生物处理的正常运行。     

Bioelectrochemical anaerobic sewage treatment technology for Arctic communities

This study describes a novel wastewater treatment technology suitable for small remote northern communities. The technology is based on an enhanced biodegradation of organic carbon through a combination of anaerobic methanogenic and microbial electrochemical (bioelectrochemical) degradation processes leading to biomethane production. The microbial electrochemical degradation is achieved in a membraneless flow-through bioanode–biocathode setup operating at an applied voltage below the water electrolysis threshold. Laboratory wastewater treatment tests conducted through a broad range of mesophilic and psychrophilic temperatures (5–23 °C) using synthetic wastewater showed a biochemical oxygen demand (BOD₅) removal efficiency of 90–97% and an effluent BOD₅ concentration as low as 7 mg L^?1. An electricity consumption of 0.6 kWh kg^?1 of chemical oxygen demand (COD) removed was observed. Low energy consumption coupled with enhanced methane production led to a net positive energy balance in the bioelectrochemical treatment system.     

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.     

2种组合工艺处理靛蓝废水的中试实验研究

分别采用水解酸化/好氧MBBR/BAF和水解酸化/好氧MBBR/臭氧氧化/BAF 2种组合工艺对实际靛蓝废水进行处理规模为24 m3/d的中试研究。实验结果表明,当进水COD平均初始浓度为2 100 mg/L、平均色度为90倍、系统总水力停留时间为40 h时,前一种组合工艺对COD和色度的去除率分别达93.27%和89.87%;而后一种组合工艺对COD和色度的去除率分别达97.96%和100%,工艺中臭氧氧化单元可使处理后出水中有机物的数量大大降低。表明水解酸化/好氧MBBR/臭氧氧化/BAF组合工艺处理靛蓝废水更为有效,但增加臭氧氧化单元会使每吨废水处理成本增加0.55元。     

Pre-oxidation and coagulation of textile wastewater by the Fenton process

This paper evaluates the Fenton process, involving oxidation and coagulation, for the removal of color and chemical oxygen demand (COD) from synthetic textile wastewater containing polyvinyl alcohol and a reactive dyestuff, R94H. The experimental variables studied include dosages of iron salts and hydrogen peroxide, oxidation time, mixing speed and organic content. The results show that color was removed mainly by Fenton oxidation. The color removal reached a maximum of 90% at a reaction time of 5 min under low dosages of H2O2 and Fe2+. In contrast, the COD was removed primarily by Fenton coagulation, rather than by Fenton oxidation. The ratio of removal efficiency between Fenton process and ferric coagulation was 5.6 for color removal and 1.2 for COD removal. It is concluded that Fenton process for the treatment of textile wastewater favors the removal of color rather than COD.     

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 %     

Synthetic olive mill wastewater treatment by Fenton’s process in batch and continuous reactors operation

Degradation of total phenol (TPh) and organic matter, (expressed as total organic carbon TOC), of a simulated olive mill wastewater was evaluated by the Fenton oxidation process under batch and continuous mode conditions. A mixture of six phenolic acids usually found in these agro-industrial wastewaters was used for this purpose. The study focused on the optimization of key operational parameters of the Fenton process in a batch reactor, namely Fe²⁺ dosage, hydrogen peroxide concentration, pH, and reaction temperature. On the assessment of the process efficiency, > 99% of TPh and > 56% of TOC removal were attained when [Fe²⁺] = 100 ppm, [H₂O₂] = 2.0 g/L, T = 30 °C, and initial pH = 5.0, after 300 min of reaction. Under those operational conditions, experiments on a continuous stirred-tank reactor (CSTR) were performed for different space-time values (τ). TOC and TPh removals of 47.5 and 96.9%, respectively, were reached at steady-state (for τ = 120 min). High removal of COD (> 75%) and BOD₅ (> 70%) was achieved for both batch and CSTR optimum conditions; analysis of the BOD₅/COD ratio also revealed an increase in the effluent’s biodegradability. Despite the high removal of lumped parameters, the treated effluent did not met the Portuguese legal limits for direct discharge of wastewaters into water bodies, which indicates that coupled chemical-biological process may be the best solution for real olive mill wastewater treatment.     

添加乙醇碳源对驯化菌种降解油制气废水的影响

进行了添加乙醇作为碳源强化油制气废水生物降解的研究,并利用GC／MS分析对油制气废水中芳烃类化合物的降解进行了初步研究。研究表明,共代谢基质乙醇的加入,可使菌种S-2、Y-3、XH-3、M-3对COD、氨氮、可萃取有机物等指标的去除率分别提高17．6％～25．6％、34．9％～42．8％、10．4％～14．2％;但在所采用的时间范围内,酚类化合物的去除率降低;芳烃类化合物的去除率提高15．4％～21．2％。除了维持无共代谢条件下对芳环数≤3的芳烃类化合物的良好降解能力外,对芳环数为4～6的化合物降解能力也有所提高。     

UV/H_2O_2/TiO_2联合水解酸化+MBR工艺处理亚砜废水

二甲基亚砜(DMSO)废水因其COD高、可生化性差的特性而较难处理。本实验以采用硫酸二甲酯法生产DMSO的某化工厂废水为研究对象,设计并建立了组合式光催化氧化装置联合水解酸化+MBR工艺的中试系统,探讨了组合式光催化氧化装置、氧化剂投加量、pH、反应时间和水力停留时间对系统处理效果的影响。结果表明,组合式光催化氧化装置可有效提高DMSO废水的可生化性。最优工艺参数为:按H2O2与原水COD质量浓度比为2∶1投加H2O2,在pH值为4、反应时间为6 h、水力停留时间为4 h的条件下,该系统对原水COD(5 000 mg/L)去除率大于98%,出水COD达到《污水综合排放标准》(GB 8978-1996)一级要求。     

臭氧预氧化处理葡萄酒废水

葡萄酒废水的季节性波动常造成生化处理系统不稳定,使传统的生化处理工艺难以满足新的污水排放标准的要求。研究了臭氧预处理工艺对葡萄酒废水的处理效果及主要控制参数,结果表明,单独的臭氧预氧化对COD几乎无去除效果,但对色度的去除可达到90%;采用O3/H2O2组合工艺可使COD的去除率提高4倍。经臭氧预处理的出水再采用SBR进行好氧处理时,出水COD能降至80 mg/L以下,COD的降解速度及程度都高于未经臭氧处理的稀释原水。高效液相色谱(HPLC)分析显示,经臭氧处理后,除麦芽糖成分被完全去除外,其他各种成分的数量变化不大;GC/MS对废水中多酚类有机物的分析显示,臭氧预处理可将大量难降解的多酚类有机物分解,从而有助于后续生化处理的出水达到更高的污水排放标准。     

Insights into real cotton-textile dyeing wastewater treatment using solar advanced oxidation processes

Different advanced oxidation processes (AOPs) were applied to the treatment of a real cotton-textile dyeing wastewater as a pre-oxidation step to enhance the biodegradability of the recalcitrant compounds, which can be further oxidized using a biological process. Tests were conducted on a lab-scale prototype using artificial solar radiation and at pilot scale with compound parabolic collectors using natural solar radiation. The cotton-textile dyeing wastewater presents a lilac color, with a maximum absorbance peak at 641 nm, alkaline pH (pH?=?8.2), moderate organic content (DOC?=?152 mg C L^?1, COD?=?684 mg O₂ L^?1) and low-moderate biodegradability (40 % after 28 days in Zahn–Wellens test). All the tested processes contributed to an effective decolorization and mineralization, but the most efficient process was the solar-photo-Fenton with an optimum catalyst concentration of 60 mg Fe²⁺ L^?1, leading to 98.5 % decolorization and 85.5 % mineralization after less than 0.1 and 5.8 kJ_UV L^?1, respectively. In order to achieve a final wastewater with a COD below 250 mg O₂ L^?1 (discharge limit into water bodies imposed by the Portuguese Legislation-Portaria no. 423/97 of 25 June 1997), considering the combination of a solar-photo-Fenton reaction with a biological process, the phototreatment energy required is 0.5 kJ_UV L^?1, consuming 7.5 mM hydrogen peroxide, resulting in 58.4 % of mineralization $ \left({t}_{30\mathrm{W}}=3.2\ \min; \overline{T}=30.7\ {}^{\circ}\mathrm{C};\overline{\mathrm{pH}}=2.80;{\overline{\mathrm{UV}}}_{G,n}={13\ \mathrm{W}\ \mathrm{m}}^{-2}\right). $