A combined photocatalytic slurry reactor–immersed membrane module system for advanced wastewater treatment

Photocatalysis with titanium dioxide semiconductor catalyst can effectively degrade recalcitrant organic pollutants present in biologically treated sewage effluents. Focusing on process efficiency and sustainability within a broader program, this study presents results obtained with a bench-scale hybrid treatment system. The process train comprised of a slurry (suspension) type continuous photocatalytic (CP) system and an immersed hollow fibre membrane micro-ultrafilter (MF/UF) unit. The CP reactor charged with 1 g/L P-25 catalyst removed 63% dissolved organic carbon (DOC) from a synthetic wastewater (representing biologically treated sewage effluent). The addition of 0.05 g/L of powdered activated carbon (PAC) increased DOC removal up to 76%. The start-up times to achieve 60% DOC removal were 31 min and 15 min, respectively. These results show a 16 times improvement in volumetric load over a comparable batch reactor system used in previous studies by our group.Slurry type photocatalytic reactors need subsequent particle separation to retain the catalyst in the system and allow the discharge of treated effluent. The immersed membrane module accomplished this without prior slurry settling step. Membrane feed pre-treatment with pH adjustment and particle charge neutralisation with aluminium chloride coagulant led to improved critical membrane fluxes, 15.25 L/m² h and 19.05 L/m² h, respectively. In each experiment MF/UF produced near zero turbidity permeate, completely retained the photocatalyst, and flocculation also improved the efficiency of DOC removal. Membrane fouling was controlled by particle aggregation rather than feed DOC levels, but the latter had significant impact on coagulant demand. The complete treatment train achieved up to 92% DOC reduction with 12 mg/L AlCl₃ dosage using in-line coagulation conditions. The results show that in-line coagulation offers a simple yet effective means to improve the performance of slurry type photocatalytic–MF/UF hybrid systems for advanced water and wastewater treatment applications.     

In‐line Flocculation‐Submersed MF/UF Membrane Hybrid System in Tertiary Wastewater Treatment

Abstract

Coagulation/flocculation pre‐treatment of feeds can successfully mitigate the drawbacks of membrane micro‐ and ultra filtration processes: fouling and limited ability to remove organic pollutants. Laboratory experiments conducted with a synthetic wastewater (representing biologically treated secondary effluent) using 0.1 µm pore size hollow fiber membrane showed that simple in‐line flocculation pre‐treatment with inorganic coagulants dramatically reduced membrane fouling rates. The hybrid system also ensured over 70% organic matter removal in terms of dissolved organic carbon (DOC). In the experiments in in‐line flocculation outperformed clarification pre‐treatment at optimum coagulant dosages. Differences in floc characteristics and elevated suspended solids concentrations in the membrane tank may explain this finding, but the exact causes were not investigated in this study. The beneficial effects of in‐line flocculation pre‐treatment to MF/UF separation were also confirmed in the treatment of septic tank effluent in a membrane bioreactor (MBR). The fouling rate of the 0.4 µm pore size (flat‐sheet) membrane was substantially reduced with 10–100 mg L^?1 ferric chloride coagulant doses, and total dissolved chemical oxygen demand (DCOD) removal also increased from 66% up to 93%. These findings are consistent with the results of other experimental studies and show that pre‐treatment controls submersed MF/UF filtration performance.     

Optimizing the coagulant dose to control membrane fouling in combined coagulation/ultrafiltration systems for textile wastewater reclamation

Optimal coagulation conditions need to be re-examined when coagulation is coupled to membrane filtration for wastewater treatment. This work focused on the optimization of coagulant dosing in order to control membrane fouling in ultrafiltration (UF), following coagulation for the reclamation of textile wastewater. The effects of pore size and coagulant types and dosages on flux decline were investigated using a stirred-cell UF unit. The flux was greatly enhanced for the UF membrane when a coagulant was added, whereas for the microfiltration (MF) membrane the flux decreased. This could be attributed to changes in the size of coagulated particles and their interaction with membrane pores. At a low dosage (e.g., 0.0371 mM as Al), the polyaluminum chloride (PACl) coagulant was found to control the flux decline most effectively for low ionic-strength wastewater. The optimal dose minimized the fouling and cake layer resistances, although it was sharp and dependent on influent composition. The cake layer protected the membrane from fouling, but it provided additional resistance to permeation. Analyses of turbidity, particle size, and membrane surface exhibited the characteristics of coagulated particles and their cake structures that are closely associated with flux behavior.     

Flat-plate submerged membrane bioreactor for the treatment of higher-load graywater

Graywater treatment has been the focus when topics of decentralized treatment systems are discussed. In this paper, the treatment of higher-load graywater, a mixture of washing machine and kitchen sink wastewater, was investigated. A 10 L lab-scale submerged membrane bioreactor (subMBR) was operated with a flat-plate membrane for 87 days. Permeate was intermittently withdrawn at constant transmembrane pressure (TMP) induced by water level difference and without pump requirement. The pollutants' removal and membrane behavior were monitored. The COD removal was around 96% and a permeate COD of about 26 mg L^− 1 was obtained. The total linear alkylbenzene sulfonate (LAS) removal achieved was > 99%, indicative of its non-inhibited degradation even at influent concentration of 30.8 mg L^− 1. The subMBR was operated at almost stable and constant flux of 0.22 m³ m^− 2 d^− 1 at a mean HRT of 13.6 h.     

An integrated wastewater treatment and reuse concept for the Olympic Park 2008, Beijing

In a Sino-German research project, a joined developed sustainable water reclamation concept was developed for different applications of municipal water reuse at the Olympic Green 2008. The concept combines advanced technological processes like membrane bioreactors, specific phosphorus (P) adsorption columns and ultrafiltration (UF) with nature-based treatment processes like wetland and bank filtration mechanisms. The project’s approach is not only to comply with the reclamation requests of the Olympic Green 2008, but also to give an example for better, adapted and energy efficient reuse applications throughout China. The study shows that fixed-bed granular ferric hydroxide (GFH) adsorbers after a membrane bioreactor (MBR) can maintain a total phosphorus (TP) concentration of <0.03 mg L⁻¹. A low P concentration will be necessary to control eutrophication in the artificial Olympic Lake filled with treated wastewater. With an adsorption capacity of approx. 20 mg g⁻¹ d.m. at a corresponding equilibrium concentration of 1 mg L⁻¹ P, GFH reaches long operation times and can be repeatedly regenerated by caustic solutions with an efficiency of 50%. Apart from scenic impoundments, treated wastewater will be used for irrigation and toilet flushing. The latter requires a superior quality that will be delivered by low pressure UF treatment after lake (bank) filtration. A crucial reduction of fouling potential for dead-end UF is expected.     

强化混凝对超滤处理碎煤加压气化废水生化出水试验研究

研究了碎煤加压气化废水生化出水经不同药剂的强化混凝预处理后出水的超滤膜通量变化规律。结果表明,初始膜通量随着混凝药剂投加量的增大而增大,在PFC投加量为150 mg/L时,初始膜通量为纯水通量的80.4%,原水未经混凝预处理时初始通量仅为纯水通量62.5%,经过长期运行,强化混凝后水样超滤通量衰减趋势减缓。不同预处理条件下受污染的超滤膜经简单碱洗(NaOH,浓度10 mmol/L)-酸洗(HCl,浓度10 mmol/L)浸泡后,通量恢复效果不同,处理原水、PFC(150 mg/L)、PAC(150 mg/L)的超滤膜初始通量恢复率分别为79.4%、84.1%、85.1%。     

Effect of coagulation on palm oil mill effluent and subsequent treatment of coagulated sludge by anaerobic digestion

A new effluent treatment scheme is proposed for treating palm oil mill effluent based on coagulation and anaerobic digestion of coagulated sludge. The effectiveness of anionic (N9901) and cationic (N9907) polyelectrolytes manufactured by NALCO (Malaysia) was evaluated both as coagulant and coagulant aid. The results showed that the anionic and cationic polyelectrolytes were best suited as a coagulant aid, and the cationic polyelectrolyte showed better performance than the anionic polyelectrolyte. For an influent chemical oxygen demand (COD) concentration of 59 700 mg L^?1 at an alum dosage of 1700 mg L^?1, the residual COD, suspended solid removal, sludge volume and pH were found to be 39 665 mg L^?1, 87%, 260 mL L^?1 and 6.3, respectively. For the above influent COD and alum dosage with the addition of 2 mg L^?1 of cationic polyelectrolyte as coagulant aid, the results were 30 870 mg L^?1, 90%, 240 mL L^?1 and 6.2, respectively. The sludge resulting from the coagulation process using alum as coagulant and cationic polyelectrolyte as coagulant aid was tested for its digestibility in an anaerobic digester. The quantity of biogas generated per gram of volatile solids (VS) destroyed at a loading rate of 26.7 ± 0.5 and 35.2 ± 0.4 g VS L^?1 d^?1 was found to be 0.68 and 0.72 L g^?1 VS destroyed. The anaerobic biomass when subjected to varying alum dosage in the coagulated palm oil sludge did not exhibit inhibition as the digester performance was in conformity with the regular treatment process Copyright © 2006 Society of Chemical Industry     

Sequencing coagulation–photodegradation treatment of Malachite Green dye and textile wastewater through ZnO micro/nanoflowers

Sequencing coagulation–photodegradation over ZnO micro/nanoflowers was assessed for Malachite Green (MG) dye removal and followed by the MG-containing textile wastewater treatment. The ZnO micro/nanoflowers were prepared using a facile reflux route and analyzed by various characterization techniques. The flower-like morphological structures of ZnO were witnessed through microscopy analyses. X-ray diffraction findings showed that the prepared ZnO samples were highly crystalline with hexagonal wurtzite structure. The operational parameters including type of coagulant, coagulant dosage, solution pH, photocatalyst dosage and light power exerted their individual influences on the removal of MG dye. The CaCO₃ was the best coagulant among the three coagulants tested due to its high formation of precipitates and adsorption of cationic dye molecules. Using CaCO₃ as a coagulant, 88.3% MG removal was obtained at coagulant dosage of 160?mg and solution pH of 9.0. Complete removal of MG was found with 0.5?g?L^?1 ZnO micro/nanoflowers and 105?W light power. The kinetic analysis showed that a Langmuir?Hinshelwood model was in good agreement with dye removal data. Moreover, a complete removal of MG dye and 80.0% of chemical oxygen demand removal over sequencing coagulation–photodegradation were observed for MG-containing textile wastewater treatment. The sequencing coagulation–photodegradation process using ZnO micro/nanoflowers indicated much promise to be an attractive method for textile effluent treatment applications.     

Treatment of textile dye effluents using coagulation–flocculation coupled with membrane processes or adsorption on powdered activated carbon

This study describes the treatment of textile wastewater by various combinations of physicochemical and membrane processes. The basic physicochemical treatment consists in coagulation/flocculation (CF) with different coagulant and flocculant concentrations. The parameters analyzed prior and after treatment are turbidity, chemical oxygen demand (COD) and absorbance (Abs). The optimal process parameters for CF are 5 for pH, 100 mg/l for coagulant (Al₂(SO₄) ₃) of 100 mg/l and 4 mg/l for flocculant. This simple treatment by CF was inefficient concerning COD reduction and dyes deterioration. It was therefore combined with microfiltration (MF) or ultrafiltration (UF) on one hand and adsorption on powdered activated carbon (PAC) on the other. The CF/MF, CF/UF and CF/PAC combinations ensure a COD removal of 37%, 42% and more than 80% respectively and a color reduction of 65%, 74% and 50% respectively.     

On the performances of lead dioxide and boron-doped diamond electrodes in the anodic oxidation of simulated wastewater containing the Reactive Orange 16 dye

The performances of the Ti-Pt/β-PbO₂ and boron-doped diamond (BDD) electrodes in the electrooxidation of simulated wastewaters containing 85 mg L⁻¹ of the Reactive Orange 16 dye were investigated using a filter-press reactor. The electrolyses were carried out at the flow rate of 7 L min⁻¹, at different current densities (10-70 mA cm⁻²), and in the absence or presence of chloride ions (10-70 mM NaCl). In the absence of NaCl, total decolourisation of the simulated dye wastewater was attained independently of the electrode used. However, the performance of the BDD electrode was better than that of the Ti-Pt/β-PbO₂ electrode; the total decolourisations were achieved by applying only 1.0 A h L⁻¹ and 2.0 A h L⁻¹, respectively. In the presence of NaCl, with the electrogeneration of active chlorine, the times needed for total colour removal were markedly decreased; the addition of 50 mM Cl⁻ or 35 mM Cl⁻ (for Ti-Pt/β-PbO₂ or BDD, respectively) to the supporting electrolyte led to a 90% decrease of these times (at 50 mA cm⁻²). On the other hand, total mineralization of the dye in the presence of NaCl was attained only when using the BDD electrode (for 1.0 A h L⁻¹); for the Ti-Pt/β-PbO₂ electrode, a maximum mineralization of 85% was attained (for 2.0 A h L⁻¹). For total decolourisation of the simulated dye wastewater, the energy consumption per unit mass of dye oxidized was only 4.4 kWh kg⁻¹ or 1.9 kWh kg⁻¹ using the Ti-Pt/β-PbO₂ or BDD electrode, respectively. Clearly the BDD electrode proved to be the best anode for the electrooxidative degradation of the dye, either in the presence or absence of chloride ions.     

用活性炭吸附强化超滤过程脱除废水中染料的研究(英文)

In this study, orange G dye was efficiently removed from aqueous solution by ultrafiltration (UF) mem-brane separation enhanced with activated carbon adsorption. The powdered activated carbon (PAC) was deposited onto the UF membrane surface, forming an intact filter cake. The enhanced UF process simultaneously exploited the high water permeation flux of porous membrane and the high adsorption ability of PAC toward dye molecules. The influencing factors on the dye removal were investigated. The results indicated that with sufficient PAC incor-poration, the formation of intact PAC filtration cake led to nearly complete rejection for dye solution under opti-mized dye concentration and operation pressure, without large sacrificing the permeation flux of the filtration process. Typically, the dye rejection ratio increased from 43.6% for single UF without adsorption to nearly 100% for the en-hanced UF process, achieving long time continuous treatment with water permeation flux of 47 L·m 2·h 1. The pre-sent study demonstrated that adsorption enhanced UF may be a feasible method for the dye wastewater treatment.     

Effect of temperature on the performance of microbial fuel cells

Single and double chamber microbial fuel cells (MFCs) were tested in batch mode at different temperatures ranging from 4 to 35 °C; results were analysed in terms of efficiency in soluble organic matter removal and capability of energy generation. Brewery wastewater diluted in domestic wastewater (initial soluble chemical oxygen demand of 1200 and 492 mg L⁻¹ of volatile suspended solids) was the source of carbon and inoculum for the experiments. Control reactors (sealed container with support for biofilm formation) as well as baseline reactors (sealed container with no support) were run in parallel to the MFCs at each temperature to assess the differences between water treatment including electrochemical processes and conventional anaerobic digestion (in the presence of a biofilm, or by planktonic cells). MFCs showed improvements regarding rate and extent of COD removal in comparison to control and baseline reactors at low temperatures (4, 8 and 15 °C), whilst differences became negligible at higher temperatures (20, 25, 30 and 35 °C). Temperature was a crucial factor in the yield of MFCs both, for COD removal and electricity production, with results that ranged from 58% final COD removal and maximum power of 15.1 mW m⁻³ reactor (8.1 mW m⁻² cathode) during polarization at 4 °C, to 94% final COD removal and maximum power of 174.0 mW m⁻³ reactor (92.8 mW m⁻² cathode) at 35 °C for single chamber MFCs with carbon cloth-based cathodes. Bioelectrochemical processes in these MFCs were found to have a temperature coefficient, Q10 of 1.6.A membrane-based cathode configuration was tested and gave promising results at 4 °C, where a maximum power output of 294.6 mW m⁻³ reactor (98.1 mW m⁻² cathode) was obtained during polarization and a maximum Coulombic efficiency (Y_Q) of 25% was achieved. This exceeded the performance at 35 °C with cloth-based cathodes (174.0 mW m⁻³; Y_Q 1.76%).     

Removal of geosmin (trans-1,10-dimethyl-trans-9-decalol) from aqueous solution using an indirect electrochemical method

Geosmin was effectively removed using an electrochemical method at the Ti/RuO₂-Pt anode in the presence of NaCl as a reactant. At a current density of 40 mA cm⁻², the geosmin concentration decreased from 600 ng L⁻¹ to 6 ng L⁻¹ in 60 min in the presence of 3.0 g L⁻¹ NaCl. HOCl formed during electrolysis would likely play an important role in the geosmin oxidation. The electrochemical method exhibited good performance for geosmin removal under various conditions. The geosmin removal rate increased with increasing current density, while the geosmin removal rates were similar at different initial pH values. The Ti/RuO₂-Pt anode also performed well for electrochemical degradation of geosmin at both low and high concentrations. According to the present experimental results, the electrochemical method should be a promising alternative for the efficient and rapid removal of musty odor compounds in a water treatment process.     

Batch treatment of saline wastewater by Halanaerobium lacusrosei in an anaerobic packed bed reactor

BACKGROUND: This study considers batch treatment of saline wastewater in an upflow anaerobic packed bed reactor by salt tolerant anaerobic organisms Halanaerobium lacusrosei . RESULTS: The effects of initial chemical oxygen demand (COD) concentration (COD₀ = 1880–9570 mg L^?1), salt concentration ([NaCl] = 30–100 g L^?1) and liquid upflow velocity (V_up = 1.0–8.5 m h^?1) on COD removal from salt (NaCl)‐containing synthetic wastewater were investigated. The results indicated that initial COD concentration significantly affects the effluent COD concentration and removal efficiency. COD removal was around 87% at about COD₀ = 1880 mg L^?1, and efficiency decreased to 43% on increasing COD₀ to 9570 mg L^?1 at 20 g L^?1 salt concentration. COD removal was in the range 50–60% for [NaCl] = 30–60 g L^?1 at COD₀ = 5200 ± .100 mg L^?1. However, removal efficiency dropped to 10% when salt concentration was increased to 100 g L^?1. Increasing liquid upflow velocity from V_up = 1.0 m h^?1 to 8.5 m h^?1 provided a substantial improvement in COD removal. COD concentration decreased from 4343 mg L^?1 to 321 mg L^?1 at V_up = 8.5 m h^?1, resulting in over 92% COD removal at 30 g L^?1 salt‐containing synthetic wastewater. CONCLUSION: The experimental results showed that anaerobic treatment of saline wastewater is possible and could result in efficient COD removal by the utilization of halophilic anaerobic bacteria. Copyright © 2008 Society of Chemical Industry     

Effect of coagulant‐flocculant reagents on aerobic granular biomass

BACKGROUND: Technologies based on aerobic granular biomass are presented as a new alternative application to wastewater treatment due to its advantages in comparison with the conventional activated sludge processes. However, the properties of the aerobic granules can be influenced by the presence of residual amounts of coagulant‐flocculant reagents, frequently used as pre‐treatment before the biological process. In this work the effect of these compounds on aerobic granular biomass development was tested. RESULTS: The presence of coagulant‐flocculant reagents led to a worse biomass retention capacity with a lower VSS concentration compared with a control reactor (4.5 vs. 7.9 g VSS L^?1) and with a higher SVI (70 vs. 40 mL [g TSS]^?1) and diameter (5.0 vs. 2.3 mm). These reagents also caused a decrease in the maximum oxygen consumption rate, but the removal efficiencies of organic matter (90%) and nitrogen (60%) achieved were similar to those in the control reactor. CONCLUSION: The continuous presence of residual levels of coagulant‐flocculant reagents from the pre‐treatment unit negatively affected the formation process and the physical properties of the aerobic granules; however, the removal of organic matter and nitrogen were not affected. Copyright © 2012 Society of Chemical Industry     

Effect of limited artificial aeration on constructed wetland treatment of domestic wastewater

To study the effect of limited artificial aeration on domestic wastewater treatment in the constructed wetlands (CWs), four pilot-scale horizontal subsurface flow CWs were operated from October 2006 to September 2007. The types of the four units include aerated and planted CW (APCW), planted CW (PCW), aerated CW (ACW) and CW, and all the units have the identical dimensions of 3 m in length, 0.7 m in width and 1 m in depth. The automated aeration was activated when the oxygen concentrations in the units were lower than 0.2 mg/L and ceased when the oxygen concentrations in the CWs were higher than 0.6 mg/L. More stable alkaline pH values were found in aeration units than that in the non-aeration units. APCW, in which the removal efficiencies of BOD, NH₄⁺-N and TN were 94.4% (16.7 g BOD d^− 1 m^− 2), 89.1% (4.54 g NH₄⁺-N d^− 1 m^− 2), and 86.0%( 4.99 g TN d^− 1 m^− 2) respectively, was more effective at pollutant removal than the other three units. There were no significant differences in TP removal between the aeration units and non-aeration units. Less surface area is needed due to high removal efficiency in APCW and the additional cost of operation is quite little. The results from this experiment indicated that limited artificial aeration in constructed wetlands is a cost-effective method for treating domestic wastewater.     

电絮凝气浮法处理分散艳蓝E-4R废水的研究

采用电絮凝气浮法处理分散艳蓝E-4R染料废水,考察了电解时间、废水初始浓度、pH值及外加电解质氯化钠和絮凝剂等不同反应条件对废水处理效果的影响。结果表明,染料废水脱色率随着电解时间的加大而逐渐增大并随初始浓度的增大而慢慢降低;pH值在2.5~10范围内电解均可获得较高的脱色率。初始浓度为400 mg/L的染料废水,电解20 min后脱色率即达87.39%,但TOC去除率只有10.49%。投加50 mg/L氯化钠后,脱色率和TOC去除率分别达到93.61%和73.49%,TOC去除率提高60%以上。在电解的条件下投加不同絮凝剂能提高染料废水的处理效果,其处理效果从大到小依次为:硫酸铝>三氯化铝>硫酸亚铁,它们的适宜用量分别为50,100,100 mg/L。     

Ozone oxidation of β-lactam antibiotic molecules and toxicity decrease in aqueous solution and industrial wastewaters heavily contaminated

In this work, ozone oxidation of the antibiotics amoxicillin (AMX), cephalexin, and ceftriaxone was investigated in different samples: (i) aqueous solutions (100 mg L^?1), (ii) an industrial wastewater containing AMX at 125 mg L^?1 (chemical oxygen demand 6000 mg O₂ L^?1), and (iii) a heavily contaminated industrial wastewater containing the antibiotics at a total concentration of 320 mg L^?1. High performance liquid chromatography, molecular absorption spectrophotometry in the ultraviolet/visible region, and total organic carbon measurements showed that ozonation of antibiotics solutions led to removal higher than 95% with 10–20% mineralization. Industrial wastewater also showed very good efficiency for antibiotic removal (80–98%) after ozonation. Moreover, Microtox® test showed 86% toxicity reduction for the industrial wastewater.     

三种絮凝剂除藻效果的比较

以合肥市环城河为研究对象,采用聚合氯化铝（PAC）、聚合氯化铝铁（PAFC）、聚合硫酸铝铁（PAFS）三种絮凝剂对该含藻水体进行强化混凝除藻、除浊的试验研究,考察了絮凝剂种类及添加量、水样的pH、助凝剂的种类以添加量等因素对强化混凝效果的影响。结果表明：在相同添加量时,聚合氯化铝的除藻、除浊效果最好,当添加量为27 mg/L时,叶绿素a的去除率为87.46%,浊度的去除率为92.74%,添加高分子助凝剂PAM、HCA对原水的浊度、叶绿素a有一定的去除效果,助凝剂与絮凝剂的配合使用可改善絮凝剂的的混凝去除效果,助凝剂PAM的效果较好,当PAM的投加量为2 mg/L时,叶绿素a的去除率可提高5.91%,浊度的去除率可提高1.70%。     

Production of electricity from the treatment of continuous brewery wastewater using a microbial fuel cell

A single air-cathode microbial fuel cell (MFC) was constructed, carbon fiber was used as anode and continuous brewery wastewater as substrate. The MFC displayed a maximum power of 24.1 W m⁻³ (669 mW m⁻²) and an internal resistance of 23.3 Ω running on raw wastewater (chemical oxygen demand (COD) = 1501 mg L⁻¹). The effect of phosphate buffer solution (PBS) addition and substrate concentration of wastewater on the performance of MFC was demonstrated. Data showed that both PBS addition and increase of substrate concentration had a favorable effect on the electrochemical performance and substrate removal efficiency of the MFC. However, it can be concluded from the polarization curve that MFC operated under raw brewery wastewater had a relatively low internal resistance, which resulted in a favorable performance of the MFC compared with other MFCs using raw wastewater. Thus it is feasible and sustainable in nature because of the utilization of raw wastewater as substrate for in situ power generation apart from treatment.