Study on efficiency and mechanism of ultrasonic controlling membrane fouling in ceramic membrane bioreactors.

In recent years, ceramic membranes have been increasingly used in membrane bioreactors (MBRs). However, membrane fouling was still the core issue restricting the large-scale engineering application of ceramic MBRs. As a novel and alternative technology, ultrasonic could be used to control membrane fouling. This research focused on the efficiency and mechanism of ultrasonic controlling membrane fouling in ceramic MBRs. The results showed that ultrasonic reduced the sludge concentration in MBR, and the average particle size of sludge was always in a high range. The sludge activity of the system was stable at 6-9 (mg O2·(g MLSS·h)-1), indicating that ultrasonic did not destroy the activity of microorganisms in the system. The extracellular polymer substance (EPS) of the ultrasonic group was slightly higher than that of the control group, while the soluble microbial product (SMP) content was relatively stable. The ceramic membrane of the ultrasonic group has a partial retention effect on the organic components. The application of ultrasonic slowed down the decrease of the hydrophilicity of the ceramic membrane. The main pollutants on the membrane surface exist in the form of aromatic and heteroaromatic rings, alkynes, and so forth. Ultrasonic removes the amide substances from the membrane surface. Membrane fouling resistance is mainly due to membrane pore blockage, accounting for 75.53%. PRACTITIONER POINTS: Enrich the research on the mechanism of ultrasonic technology in membrane fouling control. The MBR can still operate normally with ultrasonic applied. The time for the ceramic membrane to reach the fouling end point is 2.4 times that without ultrasonic. The main cause of membrane fouling was pore blocking, accounting for 75.53%.

AnCMBR-AFB-integrated process for the treatment of high nitrogen and phosphorus wastewater.

Improving the nitrogen and phosphorus removal rates and efficiently controlling membrane fouling are the keys to fully exploiting the applicability of anaerobic membrane bioreactor (AnMBR) process in high-concentration wastewater treatment. To that purpose, an integrated reactor composed of an anaerobic ceramic membrane bioreactor and N anaerobic fluidized bed (AnCMBR-AFB) was built and pollutant removal efficiency, nitrogen and phosphorus recovery characteristics, and membrane pollution features of this integrated reactor were investigated. The results revealed that the integrated reactor had good pollutant removal efficiency, with turbidity, chromaticity, and UV254 average values of the effluent being 0.470 NTU, 0.011 A, and 0.057 cm-1, respectively, and the average CODCr removal rate was 80%. The nitrogen and phosphorus recoveries were significantly higher than the nitrogen and phosphorus removal rates of conventional AnMBR at 23.20 ± 1.17% and 43.34 ± 1.54%, respectively. Microscopic analysis revealed the formation of magnesium ammonium phosphate (MAP) crystals on the carrier's surface, and friction between the carrier and the membrane surface could delay membrane fouling while allowing the contaminated membrane surface to retain significant roughness. Membrane fouling was mostly brought on by amides and saturated hydrocarbons, and inorganic metal ions also played a role to some extent.

High-efficiency cleaning technology and lifespan prediction for the ceramic membrane treating secondary treated effluent.

Chemical cleaning is one of the key technical means to control membrane fouling, restore membrane flux and ensure the stable operation of membrane systems. In the experiment, the six most representative chemical cleaning agents for ceramic membranes, such as sulfuric acid (H2SO4), sodium hydroxide (NaOH), sodium hypochlorite (NaClO), ethylenediaminetetraacetic acid disodium salt (EDTA-Na2), sodium dodecyl sulfate (SDS) and nonylphenol polyoxyethylene ether (OP-10), were used as research objects. The cleaning effect of the two-step combined cleaning of chemical cleaning agents on the fouled membrane was systematically investigated. Results showed that the order of the chemical cleaning agent had a significant effect on the cleaning effect. The best chemical cleaning program was determined to be NaClO first and then SDS: the fouled ceramic membrane was soaked in NaClO solution at 0.15% for 2.5 h and further soaked in SDS solution at five times its own critical micelle concentration for 2.5 h. The predicted long-term lifespan of the ceramic membranes was 4.91 years. Scanning electron microscopy-energy spectrum analysis showed that the surface roughness of the cleaned ceramic membrane was slightly higher than that of the new membrane. The contact angle was slightly lower than that of the new membrane.

Microfluidics-Assisted Fabrication of Dual Stopband Photonic Microcapsules and Their Applications for Anticounterfeiting.

The assembly of two different kinds of colloidal particle-based photonic structures into an individual micro-object can achieve multifunctionality. In this study, core-shell photonic microcapsules with dual structural colors and photonic stop bands were prepared through a standard microfluidic technique. Photocurable resin suspension of silica nanoparticles and an aqueous suspension of nanogels were used as shell and core parts of microcapsules, respectively. The structural colors of shells and cores can be tuned by adjusting the concentrations of silica nanoparticles and soft nanogels in their corresponding suspensions. The individual microcapsules possess two distinct stop bands when the two suspensions are combined appropriately. Remarkably, the color information of the core part cannot be directly viewed at a macroscopic level (such as visual inspection) but can be detected at a microscopic scale (such as optical microscopy observation). The color information hidden enables the capability for information encryption and has potentially critical applications in anti-counterfeiting, display, and other fields.

Study on pickling technology to control fouling of ceramic membrane treating secondary treated effluent.

The application of membrane technology in the field of water treatment was increasingly widespread, but membrane fouling still restricted its development, and the membrane needed to be chemically cleaned. This research focused on the high-efficiency pickling technology of ceramic membrane, and developed the cleaning technology of ceramic membrane in cooperation with surfactant. In the experiment, the municipal secondary effluent was used as the raw water, and the single-step, mixed and step-by-step cleaning effects of three strong acids, three weak acids and surfactants on ceramic membranes and polyvinylidene difluoride (PVDF) membranes were investigated. For ceramic membrane, the optimal cleaning combination was H2SO4 first and then DTAC, and the flux recovery rate could reach 96.94%; for PVDF membrane, the optimal cleaning combination was HNO3 first and then H2SO4, and the flux recovery rate could reach 93.72%. In addition, the surface of initial, polluted, and cleaned membranes were analyzed by scanning electron microscope and contact angle, and the fouling mechanism of the ceramic membrane was analyzed. The results showed that through physical cleaning and chemical cleaning, most of the pollutants on the membrane surface and pores were removed. The cleaning method can effectively control the membrane pollution.

Study on interface thermodynamic mechanism of membrane fouling in flat sheet ceramic membrane treating oilfield produced water.

In this study, a flat sheet ceramic membrane experimental device was constructed, and the thermodynamics of membrane fouling interface was studied for oilfield produced water. The flux of ceramic membrane in three kinds of model solutions were measured with time, as well as the surface tension, contact Angle and Zeta potential of solid. The thermodynamic mechanism of membrane fouling interface combined with XDLVO theory were explored for three kinds of model solutions. The thermodynamic study of the interface of ceramic plate membrane shows that the total interaction energy between membrane and oil droplets decreases with the increase of the distance between two interfaces at initial stage of membrane fouling, and finally transforms from the mutual attraction to the mutual repulsion. The total interaction energy between reservoir and oil droplet is shown as mutual attraction, and the total interaction energy decreases with the increase of the distance between reservoir and oil droplet interface. The zeta potential of crude oil was affected by salinity to some extent. The electrostatic shielding effect of the salt ions leads to a decrease in the ζ-potential of the three solutions. They are in the order: model solution A > model solution B > model solution C. This leads to a decrease in the electrostatic interaction (EL). And since the oil layer has the same composition as the oil droplets, the EL interactions in the three solutions can behave as mutual repulsion.

Establishment of nitrous oxide (N2O) dynamics model based on ASM3 model during biological nitrogen removal via nitrification.

Nitrous oxide (N2O), as one of the six greenhouse gases, is mainly produced in the biological nitrogen removal process of wastewater treatment plants (WWTPs). Establishing the N2O kinetic model can provide insight into the N2O generation mechanism and regulate its production. This work uses Activated Sludge Model NO.3 (ASM3) as the basic framework, combines organic storage with endogenous respiration theory, and couples ammonia-oxidizing bacteria (AOB) denitrification pathway and the NH2OH/NOH model to establish a kinetic model. Meanwhile, the Sequencing Batch Reactor (SBR) process with artificial simulated urban domestic sewage was used as the carrier; MATLAB and EXCEL software were used as tools to establish a model calculation programme. The simulated values obtained by substituting the operating conditions of the SBR process into the model and the measured values of the SBR process were analysed. The correlation coefficient (R2) between the experimental values and simulated values obtained for the 5 components of COD, ammonia, nitrite, nitrate and total N2O is 0.952, 0.996, 0.902, 0.991 and 0.956, respectively, which indicates that the N2O kinetic model has great consistency, this further shows that the established model modelling mechanism is clear and accurate, and provides a new method for the N2O dynamic model.

Removal of phosphorus from wastewater by Diutina rugosa BL3: Efficiency and pathway.

A novel phosphorus removal yeast BL3 was isolated from an alternating anaerobic/aerobic biofilter and identified as Diutina rugosa by 26S rDNA gene sequence analysis. Yeast BL3 could effectively remove phosphorus from synthetic wastewater containing 2-20 mg/L phosphorus under optimal environmental conditions. The highest phosphorus removal efficiency was above 70% under the conditions of DO 6.86 mg/L, C/P ratios of 60, N/P ratios of 3.3, pH 6.0-9.0, and at 25.0-35.0 °C. The phosphorus distribution in the aqueous solution and different components of yeast BL3 analysis indicated that around 55%-70% and 20%-40% of removed phosphorus were transferred into extracellular polymeric substances (EPS) and yeast cells, respectively. The plausible phosphorus transfer pathway was proposed based on the phosphorus distribution and species analysis, suggesting the important role of EPS as a phosphorus reservoir. These results indicate that yeast BL3 can efficiently remove phosphorus under aerobic conditions without alternating anaerobic/aerobic cycling, and thus has significant potential for practical application in wastewater phosphorus removal.

Production of an electro-biological particle electrode (EBPE) from lithium slag and its removal performance to salicylic acid in a three-dimensional electrocatalytic biological coupling reactor (3D-EBCR).

Electro-biological particle electrode (EBPE) prepared by lithium slag was used to remove salicylic acid in a three-dimensional electrocatalytic biological coupling reactor (3D-EBCR). The physical and chemical properties of the EBPE, the removal performance of salicylic acid and the degradation mechanism were studied. Results revealed as follows: (1) the EBPE prepared by lithium slag contained effective catalytic components including Fe2O3, SnO2, ZnO, MnO, Rb2O and TiO2, with stable structure and good adsorption performance; (2) the 3D-EBCR with EBPE had strong adaptability to the current intensity in the range of 0.25-0.40 A, and the removal rates of COD and salicylic acid were maintained above 87.1% and 85.2% respectively; (3) salicylic acid was removed through the synergistic action of adsorption, electrochemical oxidation and biological action.

Electrocatalysis degradation of tetracycline in a three-dimensional aeration electrocatalysis reactor (3D-AER) with a flotation-tailings particle electrode (FPE): Physicochemical properties, influencing factors and the degradation mechanism.

Novel particle electrodes, i.e. flotation tailings particle electrode (FPE), were prepared using flotation tailings, garden soil, and soluble starch with a mass ratio of 16:3:1, and then used in tetracycline wastewater treatment. The physicochemical properties of FPE were systematically characterized using SEM, XRD, FT-IR and XRF. Tetracycline adsorption and its adsorption mechanism onto FPE was explored for the first time. Parameters affecting FPE's degradation efficiency and energy consumption such as current density, electrolysis time, initial concentration, initial pH and aeration rate were examined. The electrocatalytic degradation of tetracycline shows that the degradation of tetracycline meets the pseudo-first-order kinetics. Moreover, the numbers of •OH produced on the surfaces of the cathode, anode and particle electrode were compared. Results showed that the adsorption-saturated FPE can be regenerated by electrochemical action to induce further absorption and form in-situ electrocatalysis. In order to find out the transformation products in water and degradation pathways of Tetracycline, UHPLC method was used to obtain the degradation pathways for Tetracycline. So, this work could provide a fabrication of high-efficiency and low-cost electrocatalytic for removal of pharmaceuticals pollutants from waste water as well as deeper insight into electrocatalytic mechanism, transformation products, and degradation pathways of Tetracycline in water.

Performance and bacterial community composition of volcanic scoria particles (VSP) in a biological aerated filter (BAF) for micro-polluted source water treatment.

A laboratory-scale biological aerated filter (BAF), using volcanic scoria particles (VSP), was used for treating micro-polluted source water. The system reached a steady-state stage and performed better at removing pollutants. In steady-state stage, the effluent ammonia ( NH 4 + - N ) and chemical oxygen demand (COD) were consistently maintained below 0.3 and 3 mg/L, respectively. Both the NH 4 + - N and COD removal efficiencies decreased with shorter hydraulic retention time (HRT). The effluent NH 4 + - N and COD exceeded health standards at 15 min of HRT. Although performance was relatively poor for VSP-BAF at low temperature, the NH 4 + - N removal still achieved the drinking water quality standard. The influences of influent NH 4 + - N and COD concentration changes were similar to that of temperature. A better performance was observed in NH 4 + - N removal under higher influent NH 4 + - N concentrations. In contrast, the effluent COD was more than 3 mg/L when the influent COD concentrations increased to about 9 mg/L. The phylogenetic and cluster analyses indicated that the effect of HRT on bacteria community structure was higher than that of temperature, while the ammonia-oxidizing bacteria (AOB) are sensitive to temperature. The main phyla identified in total bacteria communities were Proteobacteria, Bacteroidetes, Firmicutes, and Nitrospirae. The main AOB were Nitrosomonadales and an uncultured ammonia-oxidizing bacterium. PRACTITIONER POINTS: The BAF using VSP obtained a good performance for treating micro-polluted source water. The influence of HRT on the system was more significant than that of temperature. The system is resistant to NH 4 + - N concentration shocks while is unable to withstand the COD increasing. The effect of HRT on bacteria community structure was significantly higher than that of temperature.

Effect of power ultrasound on crystallization characteristics of magnesium ammonium phosphate.

Magnesium ammonium phosphate (MAP) crystallization could be utilized for the recovery of phosphorus from wastewater. However, the effectiveness of the recovery is largely determined by the crystallization process, which is very hard to be directly observed. As a result, a specific ultrasonic device was designed to investigate the crystallization characteristics of MAP under various ultrasonic conditions. The results demonstrated that the metastable zone width (MZW) narrowed along with the rising of the ultrasonic power. Similarly, for the 6mM MAP solution, with the ultrasonic power gradually enhanced from 0W to 400W, the induction time was shortened from 340s to 38s. Meanwhile, the crystallization rate was accelerated till the power reached 350W, and then remained a constant value. It can be observed from the scanning electron microscopy (SEM), the MAP crystal became bigger in size as well as the crystal size distribution (CSD) became broad and uneven, with the increase of ultrasonic power. The results indicate that the crystallization process enhanced by power ultrasound could be used as an effective method to eliminate and recover the phosphorus from wastewater.

An approach for phosphate removal with quartz sand, ceramsite, blast furnace slag and steel slag as seed crystal.

The phosphate removal abilities and crystallization performance of quartz sand, ceramsite, blast furnace slag and steel slag were investigated. The residual phosphate concentrations in the reaction solutions were not changed by addition of the ceramsite, quartz sand and blast furnace slag. The steel slag could provide alkalinity and Ca(2+) to the reaction solution due to its hydration activity, and performed a better phosphate removal performance than the other three. Under the conditions of Ca/P 2.0, pH 8.5 and 10 mg P/L, the phosphate crystallization occurred during 12 h. The quartz sand and ceramsite did not improve the phosphate crystallization, but steel slag was an effective seed crystal. The phosphate concentration decreased drastically after 12 h after addition of steel slag, and near complete removal was achieved after 48 h. The XRD analysis showed that the main crystallization products were hydroxyapatite (HAP) and the crystallinity increased with the reaction time. Phosphate was successfully recovered from low phosphate concentration wastewater using steel slag as seed material.

Performances and nitrification properties of biological aerated filters with zeolite, ceramic particle and carbonate media.

The performance and nitrification properties of three BAFs, with ceramic, zeolite and carbonate media, respectively, were investigated to evaluate the feasibility of employing these materials as biological aerated filter media. All three BAFs shown a promising COD and SS removal performance, while influent pH was 6.5-8.1, air-liquid ratio was 5:1 and HRT was 1.25-2.5 h, respectively. Ammonia removal in BAFs was inhibited when organic and ammonia nitrogen loading were increased, but promoted effectively with the increase pH value. Zeolite and carbonate were more suitable for nitrification than ceramic particle when influent pH below 6.5. It is feasible to employ these media in BAF and adequate bed volume has to be supplied to satisfy the requirement of removal COD, SS and ammonia nitrogen simultaneously in a biofilter. The carbonate with a strong buffer capacity is more suitable to treat the wastewater with variable or lower pH.

[Serum types of enterovirus and clinical characteristics of 237 children with hand, foot and mouth disease in Shenzhen].

OBJECTIVE: To study the clinical and epidemiologic characteristics and the serum types of enterovirus of hand, foot and mouth disease (HFMD) in children. METHODS: The RT-nPCR method was established with universal primers within 5' untranslated region of enterovirus and VP1 region of Coxsackievirus A16 (CAV16) and enterovirus 71 (EV 71). Enteroviruses were detected with RT-nPCR in 237 children with HFMD. Clinical and epidemiologic characteristics and serum types of enterovirus of the patients with HFMD were studied. RESULTS: The patients'age ranged from 7 months to 11 years (mean 4.2 +/- 0.5 years). The majority (94.5%) were less than 6 years old. HFMD was mostly seen in spring and winter (67.9%). Oral mucosal pox or ulcer as well as hand and foot rashes were observed in all 237 patients. Fever occurred in 141 patients (59.5%). Of the 237 patients, 133 (56.1%) were RT-nPCR positive. Of the 133 cases, 38 were positive for EV71, 64 were positive for CAV16, and 31 were negative for both EV71 and CAV16. The patients infected by different types of enteroviruses had similar clinical characteristics. Gene colon and sequence analysis for 12 strains of enteroviruses PCR positive products presented as EV71 (n=5), CAV16 (n=5), ECHO13 (n=1), and CAV5 (n=1). CONCLUSIONS: HFMD tends to occur in younger children less than 6 years old. The majority are affected in spring and winter. EV71 and CAV16 are common pathogens of HFMD. There is no relationship between clinical characteristics and serum types of enteroviruses in HFMD patients.