Membrane fouling reduction through electrochemically regulating flocs aggregation in an electro-coagulation membrane reactor

Coupling coagulation and applied electric field is an efficient method to regulate cake layer porosity and hydrophilicity for alleviating ultrafiltration membrane (UF) fouling. However, the Al/Fe flocs aggregation behavior are induced from electric field and determine the cake layer structure, which has not been studied comparatively yet. Herein, the anti-fouling performance in an efficient electro-coagulation membrane reactor (ECMR, in which UF membrane modules are placed between electrodes) was investigated with Al/Fe anode and various electrochemical parameters from the viewpoint of regulating flocs aggregation. Both the cake layers formed from Al and Fe flocs under an electric field were more porous and hydrophilic in comparison with that formed without electric fields, resulting in an enhanced water flux under higher electric field strength. Comparing with Fe flocs, Al flocs had a faster growth rate and larger size, facilitating membrane pore block resistant, which was more pronounced in a higher current density. Furthermore, the cake layer formed from Al flocs was more porous than that formed from Fe flocs. Therefore, the anti-fouling performance of ECMR with Al anode was superior to that of ECMR with Fe anode. When the electric field strength increased from 0 to 10?V/cm, the normalized specific flux was improved from 71.2% to 89.4% for ECMR (Al) and from 48.1% to 70.1% for ECMR (Fe) at 30?min.     

Nano CuO/g-C3N4 sheets-based ultrafiltration membrane with enhanced interfacial affinity, antifouling and protein separation performances for water treatment application

To improve the interfacial affinity and antifouling properties of polyphenylsulfone(PPSU)membrane, nano CuO/g-C3 N4(g-CN) sheets were synthesized via facile calcination route as one pot synthesis method. The uniformly assembled nanohybrid fillers, CuO on g-CN sheets were confirmed by using XRD, TEM, EDX and FTIR analysis. The non-solvent induced phase inversion technique was used to fabricate the nanohybrid ultrafiltration(UF)membranes by doping different concentration(0.5–1 wt.%) of nano CuO/g-C_3 N_4(g-CN)sheets within the PPSU matrix. The results of contact angle, atomic force microscopy,energy-dispersive X-ray spectroscopy reveal that surface structure and physico-chemical properties of nanohybrid membrane plays lead role in solute interaction and rejection compared to bare membrane, M0. Furthermore, the interfacial affinity of membrane was explored in detail via surface free energy, spreading coefficient, wetting tension and reversible work of adhesion analysis. Nanohybrid UF membrane, with 0.5% of the filler(M1)displayed remarkable permeation flux of 202, 131 L/m2/hr for pure water and protein solution, respectively while maintaining a high protein rejection(96%). Moreover, the exceptional dispersion of the nanosheets in the polymer matrix enhanced FRR(79%) and decreased the overall resistance of M1 compared to the pristine membrane(M0). Overall results suggest that the incorporation of nano sheets is a facile modification technique which improves the comprehensive membrane performance and holds a great potential to be further explored for water treatment.     

味精废水的超滤前处理工艺研究

针对高氨氮、高CODcr的味精工艺废水处理工程,进行了超滤膜工艺相关试验。在超滤运行工艺参数分析基础上,重点分析了叠片过滤及纤维过滤两类不同超滤前处理的运行工况,从而得出特定水源条件下超滤的前处理工艺及参数。     

超滤膜技术在环境工程水处理中的应用

随着我国经济水平的不断提高,也给我国环境带来了巨大的影响。与此同时,科技水平的不断发展,也使我国水处理技术日臻完善。目前,在环境工程水处理的过程中不仅可以通过物理、化学方法,还可以通过超滤膜技术来对环境工程水处理的质量进行监控,其是以传统水处理工艺为基础,通过全面的改革及调整,形成的一种新型的处理技术,能够确保水环境具备理想的可行性和适宜性,从而提升水处理效果。     

Co-application of energy uncoupling and ultrafiltration in sludge treatment: Evaluations of sludge reduction,supernatant recovery and membrane fouling control

• Effects of metabolic uncouplers addition on sludge reduction were carried out. • TCS addition effectively inhibited ATP synthesis and reduced sludge yield. • The effluent quality such as TOC and ammonia deteriorated but not significantly. • Suitable dosage retarded biofouling during sludge water recovery by UF membrane. Energy uncoupling is often used for sludge reduction because it is easy to operate and does not require a significant amount of extra equipments (i.e. no additional tank required). However, over time the supernatant extracted using this method can deteriorate, ultimately requiring further treatment. The purpose of this study was to determine the effect of using a low-pressure ultrafiltration membrane process for sludge water recovery after the sludge had undergone an energy uncoupling treatment (using 3,3′,4′,5-tetrachlorosalicylanilide (TCS)). Energy uncoupling was found to break apart sludge floc by reducing extracellular polymeric substances (EPS) and adenosine triphosphate (ATP) content. Analysis of supernatant indicated that when energy uncoupling and membrane filtration were co-applied and the TCS dosage was below 30 mg/L, there was no significant deterioration in organic component removal. However, ammonia and phosphate concentrations were found to increase as the concentration of TCS added increased. Additionally, due to low sludge concentrations and EPS contents, addition of 30–60 mg/L TCS during sludge reduction increased the permeate flux (two times higher than the control) and decreased the hydraulic reversible and cake layer resistances. In contrast, high dosage of TCS aggravated membrane fouling by forming compact fouling layers. In general, this study found that the co-application of energy uncoupling and membrane filtration processes represents an effective alternative method for simultaneous sludge reduction and sludge supernatant recovery.     

Cross-stacked super-aligned carbon nanotube/activated carbon composite electrodes for efficient water purification via capacitive deionization enhanced ultrafiltration

• A high-performance electrode was prepared with super-aligned carbon nanotubes. • SACNT/AC electrode achieved a ~100% increase in desalination capacity and rate. • SACNT/AC electrode achieved a ~26% increase in charge efficiency. • CUF process with SACNT/AC achieved an up to 2.43-fold fouling reduction. • SACNT/AC imparts overall improved water purification efficiency. The practical application of the capacitive deionization (CDI) enhanced ultrafiltration (CUF) technology is hampered due to low performance of electrodes. The current study demonstrated a novel super-aligned carbon nanotube (SACNT)/activated carbon (AC) composite electrode, which was prepared through coating AC on a cross-stacked SACNT film. The desalination capability and water purification performance of the prepared electrode were systematically investigated at different applied voltages (0.8–1.2 V) with a CDI system and a CUF system, respectively. In the CDI tests, as compared with the control AC electrode, the SACNT/AC electrode achieved an approximately 100% increase in both maximum salt adsorption capacity and average salt adsorption rate under all the applied voltage conditions, demonstrating a superior desalination capability. Meanwhile, a conspicuous increase by an average of ~26% in charge efficiency was also achieved at all the voltages. In the CUF tests, as compared with the control run at 0 V, the treatment runs at 0.8, 1.0, and 1.2 V achieved a 2.40-fold, 2.08-fold, and 2.43-fold reduction in membrane fouling (calculated according to the final transmembrane pressure (TMP) data at the end of every purification stage), respectively. The average TMP increasing rates at 0.8, 1.0, and 1.2 V were also roughly two times smaller than that at 0 V, indicating a dramatical reduction of membrane fouling. The SACNT/AC electrode also maintained its superior desalination capability in the CUF process, resulting in an overall improved water purification efficiency.     

Two-stage biodegradation coupled with ultrafiltration for treatment of municipal landfill leachate

The municipal landfill leachate was treated in a hydrolysis–acidification reactor (HAR)/aerobic bio-contact oxidation reactor (ABOR) following a pretreatment with ultrafiltration (UF) membrane. Experiments were conducted continuously for 44 days at a constant flow rate of 20 l d⁻¹ and organic loading rates (OLRs) from 0.75 to 1.5 kgCOD m⁻³ per day. The results showed that COD of the leachate steadily decreased from 20,015 mg l⁻¹ to less than 3000 mg l⁻¹, and NH₄-N decreased from 368.6 mg l⁻¹ to 259.3 mg l⁻¹ in the UF process. The COD and NH₄-N removal efficiency of HAR was 56.7% and 27.7%, and that of ABOR was 94.6% and 86.7%, respectively. The total COD and NH₄-N removal efficiency reached 99.6% and 93.2%, respectively. UF and HAR played a critical role in raising the biodegradability of the landfill leachate, while ABOR had an important function on removing the dissolved NH₄-N in leachate.     

Effect of pre-ozonation on optimized coagulation of a typical North-China source water

Although ozone is widely used as a pre-oxidant before coagulation in water treatment, the effect of pre-ozonation on optimized coagulation for removal of particle and natural organic matter (NOM) is still not fully understood. In this paper, pilot-scale investigation was conducted to examine the impact of pre-ozonation on coagulation for particle and NOM removal. Changes in the particle and NOM distributions were characterized by various methods, including laser light granularity system, particle counter, ultrafiltration, and resin absorbent fractionation. A novel composite flocculant–HPAC was compared with the traditional ferric chloride coagulant in terms of coagulation efficiency under the influence of pre-ozonation. Typical micro-polluted North China surface water was used for pilot coagulation tests. The results show that the effect of pre-ozonation on coagulation is associated with the dosage of ozone, coagulant type, and water contamination characteristics. For FeCl₃, pre-ozonation acts as a coagulation aid at low dosage (1.0 mg L⁻¹ O₃) for turbidity and UV₂₅₄ removal; while at higher dosage (2.0 mg L⁻¹ O₃), pre-ozonation is detrimental to UV₂₅₄ removal although it is still beneficial for turbidity removal. In the case of composite flocculant–HPAC, pre-ozonation demonstrates negligible influence on both turbidity and UV₂₅₄ removal. Ozone can simultaneously aggregate fine particles and break down large ones, making them more mineralized and easier to remove. NOM with intermediate molecular weight and hydrophobic neutral property increases at lower ozone dosage, favoring removal by coagulation. At higher ozone dosages, NOM becomes more hydrophilic and its molecular weight becomes smaller, decreasing NOM removal.     

超滤膜在新疆污水处理中的应用研究

超滤膜能有效去除大肠杆菌、细菌、SS等污染物质,并对COD和BOD也有一定的去除效果。由于新疆特殊的气候原因,导致新疆的污水水质与内地差异较大,因此采用超滤膜对新疆疾病控制中心生活污水处理站二级生化处理达标外排水进行深度处理,分别进行了管路流体力学特性实验、超滤膜截留特性实验、膜污染实验、膜的清洗实验等,掌握了膜污染变化规律和污染防治方法．为日后的此类工程设计提供了参考数据．     

The role of extracellular organic matter on the cyanobacteria ultrafiltration process

The membrane fouling caused by extracellular organic matter (EOM) and algal cells and organic matter removal of two typical cyanobacteria (M. aeruginosa and Pseudoanabaena sp.) during ultrafiltration (UF) process were studied in this work. The results showed that EOM had a broad molecular weight (Mw) distribution and the irreversible membrane fouling was basically caused by EOM. Moreover, humic acid and microbial metabolites were major components of EOM of two typical cyanobacteria. Since EOM could fill the voids of cake layers formed by the algal cells, EOM and algal cells played synergistic roles in membrane fouling. Fourier transform infrared spectroscopy analysis indicated that the CH₂ and CH₃ chemical bonds may play an important role in membrane fouling caused by EOM. Interestingly, the cake layer formed by the algal cells could trap the organic matter produced by algae and alleviate some irreversible membrane fouling. The results also showed that although the cake layer formed by the algal cells cause severe permeate flux decline, it could play a double interception role with UF membrane and increase organic matter removal efficiency. Therefore, when using UF to treat algae-laden water, the balance of membrane fouling and organic matter removal should be considered to meet the needs of practical applications.