Two-stage Filtration Research Articles

Hydrus-1D simulation of two-stage cross-flow pre-filtration of turbid river water

Abstract Simulation is a modus operandi often used for imitating real-world processes. It involves a system and set of assumptions used for computing a numerical model, from which the outcome is an estimate of the true characteristics of how the system behaves. The intention of this research was to investigate the efficiency of fabric in two-stage cross-flow filtration using linen, crepe-backed satin, burlap and cotton fabric filter media. The results from previous pilot-scale experiments performed showed that linen fabric was the most effective medium at retaining particles. In continuation of this research, the aim of this paper was to utilize Hydrus-1D simulation software to simulate cross-flow filtration with fabric filter medium. This was done to further confirm the efficiency of cross-flow filtration, in particular with linen fabric filter media. Simulation entailed investigating fabric water content versus pressure head; bottom pressure head versus time; fabric water storage versus time; and cumulative infiltration versus time with both single and four layers of fabric filter media. Hydrus-1D simulation was productive since it confirmed that cross-flow filtration with linen fabric filter media has the potential of becoming a pre-filtration step in surface water treatment, further adding to the results obtained from previous pilot-scale experiments.

Recovery of Water from Textile Dyeing Using Membrane Filtration Processes

The aim of the work was to purify model textile wastewater (MTW) using a two-stage membrane filtration process comprising nanofiltration (NF) and reverse osmosis (RO). For this purpose, a nanofiltration membrane TFC-SR3 (KOCH) and reverse osmosis membrane AG (GE Osmonics) were used. Each model wastewater contained a selected surfactant. The greatest decrease in flux in the initial phase of the process occurred for the detergents based on fatty-acid condensation products. An evident decrease in performance was observed with polysiloxane-based surfactants. No fouling effect and high flux values were observed for the wastewater containing a nonionic surfactant based on fatty alcohol ethoxylates. During RO, a significantly higher flux and lower resistance were observed for the feed that originally contained the anionic agent. For the MTW containing the nonionic surfactant, the conductivity reduction ranged from 84% to 92% depending on the concentrate ratio at the consecutive stages of RO. After treatment, the purified wastewater was reused in the process of dyeing cellulose fibers with reactive dyes. The research confirmed that textiles dyed with the use of RO filtrates did not differ in quality of dyeing from those dyed in pure deionized water.

Biophysical properties of tense quaternary state polymerized human hemoglobins bracketed between 500kDa and 0.2μm in size.

Polymerized hemoglobin (Hb)-based oxygen carriers (HBOCs) are a scalable and cost-effective red blood cell (RBC) substitute. However, previous generations of commercial polymerized HBOCs elicited oxidative tissue injury in vivo due to the presence of low molecular weight polymeric Hb species (<500 kDa) and cell-free Hb (64 kDa). Polymerized human Hb (PolyhHb) locked in the tense quaternary state (T-state) exhibits great promise to meet clinical needs where past polymerized HBOCs failed. This work shows that separation of T-state PolyhHb via a two-stage tangential flow filtration (TFF) purification train such that the Hb polymers are bracketed between 500 kDa and 0.2μm creates a uniform polymer size and largely eliminates the Hb species which elicit deleterious side effects in vivo. Biophysical characterization of these materials demonstrates their potential effectiveness as an RBC substitute and verifies the low percentage of low molecular weight Hb polymers and cell-free Hb. Size exclusion chromatography confirms that T-state PolyhHb can be consistently produced in a size range between 500 kDa and 0.2μm. Furthermore, the average molecular weight of all PolyhHb species produced is one or two orders of magnitude larger than that of the commercial polymerized HBOCs Hemolink and Oxyglobin, respectively. Haptoglobin binding kinetics confirms that two-stage TFF processing of PolyhHb reliably removes cell-free Hb and low molecular weight polymeric Hb species. T-state PolyhHbs demonstrate lower auto-oxidation rates compared to unmodified Hb and prior generations of commercial polymerized HBOCs. These results demonstrate T-state PolyhHb's feasibility as a next-generation polymerized HBOC for potential use in transfusion medicine.

Fouling and mitigation mechanisms during direct microfiltration and ultrafiltration of primary wastewater

Direct membrane filtration (DMF) has recently gained attention as an alternative secondary biological wastewater treatment process. This study evaluated direct microfiltration (MF) and ultrafiltration (UF) performance and cleaning protocols during crossflow DMF of primary municipal wastewater effluent. Several types of MF and UF membranes were examined by threshold flux determination, and two types of membranes (MF, 0.08 μm; UF, 100 kDa) were chosen for exploring membrane fouling mechanisms at different feed pressures via both fouling resistance analysis and optical coherence tomography (OCT) observation. The results revealed that both MF and UF displayed three-stage fouling behaviors, i.e., initial intermediate pore blocking followed by two-stage cake filtration. Increasing feed pressure from 8 kPa to 50 kPa could accelerate physically reversible fouling rate (consistent with simulated cake filtration constant). During physical flushing, the cake layer was more readily removed from the UF membrane; while residual porous cake layer was present on the MF membrane, regardless of the feed pressure. With extending filtration-cleaning cycle, shortening filtration duration and elevating cleaning solution temperature to from 25 °C to 50 °C benefited for irreversible fouling alleviation. At 50 °C, the geothermal water performed similar cleaning behaviors as clean water, facilitating lower reversible and irreversible fouling than the geothermal brine. This study shed light on the feasibility of using high temperature geothermal water for periodic physical cleaning during DMF of wastewater under Icelandic scenario.

Influence of suspended microcrystalline polymer system on characteristics of produced water from High Ca and Mg oilfields and corresponding oil removal methods

Suspended microcrystalline polymer flooding is a new promising EOR technology developed to improve oil recovery from high Ca and Mg reservoirs. However, as the technology is currently in the research and field experimental stage, the characteristics of its produced water and the corresponding water treatment methods are still not clear. In this study, the effects of polymer concentration on physical characteristics of the three simulated produced waters, namely, polymer flooding produced water (PFPW), high Ca and Mg PFPW (HPFPW) and suspended microcrystalline PFPW (SMPFPW), were investigated to understand the particularity of SMPFPW. Pattern of oil droplet diameters in SMPFPW exhibited a bimodal distribution with peak diameters at 4 and 150 μm. The viscosities of three waters are SMPFPW ≥ PFPW > HFPW in descending order. The absolute ζ potential of SMPFPW was 1.01 ∼ 2.42 times higher than that of HPFPW, but was substantially lower than that of PFPW due to high ionic strength. At same polymer concentrations (0 ∼ 300 mg/L), the oil content in SMPFPW is 1.78 ∼ 2.47 times that in HPFPW and 1.49 ∼ 1.87 times that in PFPW because of its unique spatial structure of polymers. From degreasing experiments, oil removal rate of SMPFPW by gravity sedimentation is higher than that of PFPW but slightly lower than that of HPFPW, polymer concentration play vital roles in oil-water separation. An inexpensive and practical routine, gravity sedimentation coupled with two-stage composite material filtration, for oil removal is proposed for SMPFPW on the basis of lab experiments.

Effect of main-stage filter media selection on the loading performance of a two-stage filtration system

This study experimentally evaluates the performance of a two-stage indoor air filtration system with the focus on main-stage filter media selection. The impact of the main-stage filter media properties on the effectiveness of adding a pre-stage filter media is compared among three main-stage filter media types commonly used in heating, ventilation, and air conditioning (HVAC) filtration system: cellulose, melt-blown, and expanded PTFE membrane. The pre-stage filter media effectiveness was found to be significantly affected by the incoming aerosol size distribution. Although counter-intuitive, having an additional pre-stage filter was found to cause a service lifetime drop for cellulose-type main-stage filters depending on incoming aerosol size distribution, while universally enhanced life spans were found for melt-blown and PTFE membrane-coated main-stage filters. The mechanism that causes a shortened service life of cellulose main-stage filter with the presence of a pre-stage filter was explored in detail and was found to be associated with the special particle loading behavior of conventional cellulose media. The rapid pressure drop increase of cellulose media in depth and transitional filtration regimes was strongly affected by the incoming aerosol size distribution, with a steeper slope (faster pressure drop increase) associated with finer particles penetrating more deeply into the inhomogeneous pores of cellulose media. The pre-stage filter alters the particle size distribution of the main-stage faces, with an increased fraction of fine particles that negatively impacts the main-stage filter loading behavior. This observation and mechanism analysis are the first time being reported, which suggests a careful selection of the combination of pre-stage and main-stage filter types with the consideration of incoming contaminant properties. It is essential for researchers and engineers in designing energy-efficient two-stage filtration systems.

Assessing Pretreatment Effectiveness for Particulate, Organic and Biological Fouling in a Full-Scale SWRO Desalination Plant.

In this study, the removal of particulate, organic and biological fouling potential was investigated in the two-stage dual media filtration (DMF) pretreatment of a full-scale seawater reverse osmosis (SWRO) desalination plant. Moreover, the removal of fouling potential in two-stage DMF (DMF pretreatment) was compared with the removal in two-stage DMF installed after dissolved air floatation (DAF) (DAF-DMF pretreatment). For this purpose, the silt density index (SDI), modified fouling index (MFI), bacterial growth potential (BGP), organic fractions and microbial adenosine triphosphate (ATP) were monitored in the pretreatment processes of two full-scale SWRO plants. Particulate fouling potential was well controlled through the two stages of DMF with significant removal of SDI15 (>80%), MFI0.45 (94%) and microbial ATP (>95%). However, lower removal of biological/organic fouling potential (24–41%) was observed due to frequent chlorination (weekly) of the pretreatment, resulting in low biological activity in the DMFs. Therefore, neutralizing chlorine before media filtration is advised, rather than after, as is the current practice in many full-scale SWRO plants. Comparing overall removal in the DAF-DMF pretreatment to that of the DMF pretreatment showed that DAF improved the removal of biological/organic fouling potential, in which the removal of BGP and biopolymers increased by 40% and 16%, respectively. Overall, monitoring ATP and BGP during the pretreatment processes, particularly in DMF, would be beneficial to enhance biological degradation and lower biofouling potential in SWRO feed water.

Treatment and recycling of acidic fracturing flowback fluid

ABSTRACT Acidic fracturing flowback fluid (AFFF) has the characteristics of low pH value, high chemical oxygen demand (COD), high corrosiveness and complex components. Surface discharge without treatment may contaminate the environment. However, wastewater treatment after centralized transportation has potential safety risks and requires high costs. In this study, we confirmed that calcium and magnesium could affect cross-linking property of fracturing fluid prepared by flowback fluid, and conducted a three-step process, two-stage filtration, chemical precipitation, and flocculation precipitation, on AFFF. After treatment, we made new hydraulic fracturing fluid using the treated acidic flowback fluid as base fluid and compared the quality of the new hydraulic fracturing fluid to the ones used freshwater as base fluid. The results showed when concentration of sodium carbonate, polyaluminium chloride (PAC), polyacrylamide (PAM) were 145, 1000, and 20 mg/L respectively, the treatment result was optimal. After treatment, the oil content of AFFF decreased from 7400 to 26.53 mg/L and suspended solids (SS) from 650 to 18.24 mg/L, and the removal rate of high-valence metal ions was more than 99%. The rheological properties and viscoelasticity of new fracturing fluid prepared by the treated AFFF were similar to the ones prepared by freshwater, which met the requirements of high temperature and shear resistance for ultra-deep wells.

A Point-of-Use (POU) Water Disinfection: Silver Nanowire Decorated Glass Fiber Filters

Investigation of a new, low-cost, safe and highly efficient water disinfection alternative to conventional methods has prime importance. This study aims to develop silver nanowire decorated glass fiber (AgNW-GF) filters for the removal of E. coli from water. This is the first study to fabricate a novel AgNW-GF filter and to investigate its use for point-of-use (POU) water disinfection. To this purpose, the effects of flow rate, AgNW loading and influent E. coli concentration on the removal efficiency of E. coli and Ag release from AgNW-GF filters were investigated. Effect of filtrate volume on Ag release was also analyzed. Disk diffusion tests revealed that AgNW-GF filters with different AgNW loadings had antibacterial effects against E. coli at a concentration range of 103 – 108 CFU/ml. Flow tests were conducted in order to investigate optimal conditions at which AgNW-GF filters achieved the highest E. coli removal efficiency. Optimal flow rate, AgNW loading and influent E. coli concentration were found out as 1 ml/min, 9.9 mg/g, and 103 CFU/ml, respectively. The highest removal efficiency was obtained as 2.12 log after two-stage serial filtration under optimal conditions. The released Ag amounts were all below the limit value of 100 ppb for potable water. Under determined optimal conditions, AgNW-GF filter was found as a promising alternative for POU water disinfection method to be used in contaminated natural water (<103 CFU/ml).

Physical Measures to Reduce Exposure to Tap Water-Associated Nontuberculous Mycobacteria.

Nontuberculous mycobacteria (NTM) that cause human disease can be isolated from household tap water. Easy-to-use physical methods to reduce NTM from this potential source of exposure are needed. Filters and UV disinfection have been evaluated for their ability to reduce numbers of waterborne non-NTM organisms from drinking water, but their efficacy in reducing NTM counts are not well-established. Thus, five commercially available disinfection methods were evaluated for their potential as practical, efficient, and low-cost methods to reduce NTM from tap water. First, suspensions of tap water–adapted Mycobacterium smegmatis were passed through either a point-of-use, disposable, 7-day or 14-day Pall-Aquasafe filter. The 7-day filter prevented passage of M. smegmatis in effluent water for 13 days, and the 14-day filter prevented the passage of M. smegmatis for 25 days. Second, a granular activated carbon filter system failed to significantly reduce Mycobacterium abscessus and Mycobacterium avium numbers. Third, suspensions of tap water–adapted M. abscessus, M. avium, and M. chimaera (“MycoCocktail”) were passed through the “LifeStraw GO” hollow-fiber, two-stage membrane filtration system. LifeStraw GO prevented passage of the MycoCocktail suspension for the entire 68-day evaluation period. Finally, two different water bottle UV sterilization systems, “Mountop” and “SteriPEN,” were evaluated for their capacity to reduce NTM numbers from tap water. Specifically, MycoCocktail suspensions were dispensed into Mountop and SteriPEN water bottles and UV treated as per the manufacturer instructions once daily for 7 days, followed by a once weekly treatment for up to 56 days. After 4 days of daily UV treatment, both systems achieved a >4 log reduction in MycoCocktail CFU. After the 56-day evaluation period, suspension and biofilm-associated CFU were measured, and a >4 log reduction in CFU was maintained in both systems. Taken together, physical disinfection methods significantly reduced NTM numbers from tap water and may be easy-to-use, accessible applications to reduce environmental NTM exposures from drinking water.

Analyzing filtration flow rate change of woven geotextiles for fine grained slurries

Many studies have been performed in recent years to investigate the dewatering phenomena of slurry using geotextile tubes. The laboratory test methods primarily used the pressure filtration test (PFT) and falling head test (FHT) to evaluate the dewatering nature of geotextiles using slurries with different fines contents. The objective of this paper is to examine and analyze the published test data obtained from various testing conditions, and to develop a general equation that can predict the change of flow rate over time. For the PFT, a power law showed a good fit with test data at different fines content ranges. Furthermore, the change of filtration rate with time decreased with the fines content, indicating that slurry with high fines content resulted in a faster drop in filtration rate than slurry with low fines content. For the FHT, a two-term power law was found to fit all of the test data, indicating a two-stage filtration behavior.

A modular variable-process treatment system for operation liquid waste: A case study

The components of petroleum wastewater are complex and variable, which makes it hard to meet the reinjection requirements based on a fixed treatment process. Therefore, an efficient wastewater treatment system adapting to variable water quality is necessary. In this study, the types and composition of wastewater from the Changqing oilfield were systematically analyzed. The characteristics of different types of wastewater were clustered by a water quality matrix. Based on the results, viscosity is an important limiting factor in wastewater treatment. Six types of wastewater could be divided into high contaminative wastewater (HCW), medium contaminative wastewater (MCW) and low contaminative wastewater (LCW). Thus, a modular and variable-process wastewater treatment system was developed. The system consists of five modular units including oil removal, viscosity reduction, DAF/DOF, two-stage filtration, and ultraviolet disinfection. Each module can be flexibly used for the wastewater treatment according to the variable water quality and characteristics of raw water. The system was stable and reliable during 160 days of field operation. The suspended solids (SS), petroleum concentration, and median particle size of treated wastewater were less than 2.0 mg/L, 6.0 mg/L and 1.5 μm, respectively, which meet the requirements of the reinjection standard. The treatment system can improve the wastewater treatment efficiency with variable water quality in the oilfields and protect regional environmental safety.

ANALYSIS OF PHYSICOCHEMICAL WASTEWATER TREATMENT IN ARCTIC ZONES

The large part of the Russian Federation locates in arctic and subarctic climatic zones, which determine the specificity of design, construction and operation of sewage systems of these regions. Nowadays, the most part of small Arctic towns has no wastewater treatment facilities, while the available biological treatment facilities do not work properly. An alternative way is physicochemical treatment, which is more resistant to severe climate and volley wastewater discharge than biological treatment. The paper presents the research results of total change the biological into physicochemical treatment. The main stages of such a treatment include coagulation, filtration, oxidation and two-stage filtration (mechanical and absorption). The experiments show a 90.8% decrease in the concentration of chemical oxygen and a 74% and 82.5% decrease in nitrates and ammonium.

Harvesting colonial Microcystis flos-aquae using two-stage filtration: Influence of pre-filtration on harvesting performance

The harvesting of bloom-forming colonial Microcystis flos-aquae using filtration helps with bloom control, the acquisition of a biomass resource and nutrient removal from eutrophic lakes. In this study, two-stage filtration of three combinations for M. flos-aquae harvesting was investigated, and the main factors affecting two-stage filtration performance were analysed. The results showed that compared with filtration with a 5 μm membrane alone, pre-filtration with a 20 μm screen improved biomass harvesting rate by 25.03% while 200 μm and 550 μm screens pre-filtrations resulted in decreases of 26.90% and 42.20%, respectively. The influences of colony size distribution and cellular concentration on filtration performance were predicted well using a multiple linear regression model (MLR). According to the model analysis, filtrate with larger colony size and narrower size distribution resulted higher harvesting performance. As the cellular concentration increased, the averaged flux decreased, while biomass harvesting rate increased initially, reached the highest value and then decreased. These results could be applied for the development of efficient filtration harvesting strategies for Microcystis bloom control.

Asymmetric Al2O3 and PES/Al2O3 hollow fiber membranes for green tea extract clarification

Green tea (Camellia sinensis) leaves are particularly rich in polyphenols. Here we propose the clarification of green tea extract by an innovative process consisting of a two-stage filtration through asymmetric alumina (Al2O3) hollow fibers, which we specially designed for this application by the phase inversion technique. The fibers presented outer sponge like-layers, mainly responsible for the membrane selectivity (turbidity of green tea extract was reduced by 90%) and mechanical strength (135 MPa), and an inner finger-like layer that reduced the resistance to flux permeation (water permeability of 2.56 × 10−9 m3 s−1 m−2 Pa−1). In order to increase the membrane retention coefficient, we deposited a polyethersulfone (PES) coating layer on the fiber outer surface. This polymeric layer further reduced the green tea extract turbidity by 97.8% in the permeate. As a consequence, no team cream formed even after 30 days of refrigerated storage. Thus, the membranes that we conceived enabled to obtain a product with superior clarity and stability. Additionally, a mathematical description of flux decay during the filtration processes showed that cake formation and internal pore blockage models better described flux decay through Al2O3 and PES/Al2O3 hollow fibers, respectively.

Energy consumption, indoor thermal comfort and air quality in a commercial office with retrofitted heat, ventilation and air conditioning (HVAC) system

Retrofit on existing buildings for better energy performance is widely desired due to large share of building energy consumption. Meanwhile, the importance of thermal comfort and air pollution exposure has attracted increasing attention for occupant health, productivity and sustainable development. Heat, ventilation and air conditioning (HVAC) systems are responsible for a substantial proportion of energy use in buildings and are closely related to indoor environment quality. This study examined the energy consumption and indoor environment in a commercial office building with a retrofitted HVAC system. The retrofitting measures included a sensor-based building management system, dehumidification of outdoor air, and a two-stage particle filtration system. Energy data were collected before and after the retrofit. Field measurements were conducted in both winter and summer to evaluate the thermal comfort and indoor exposure to air pollutants in the retrofitted area. An experiment was designed to assess the benefits of upgraded filters on exposure to ambient particles during summer. By combining all of these measures, the retrofitted HVAC system was able to reduce energy use by 50% while maintaining generally acceptable indoor thermal comfort. Most of the time, the indoor particle levels complied with the World Health Organization's guidelines. The upgraded filtration system with a pleated filter reduced outdoor PM ingress by 30% to 60% more than the aluminum filter used before the retrofit. Co-benefit assessment provides insights into sustainability in building development during a retrofit by holistically examining energy use and the environment.

Influence of pre-stage filter selection and face velocity on the loading characteristics of a two-stage filtration system

A two-stage filtration test system was successfully developed previously, and the objective of this study is to investigate the effect of pre-filter selection and face velocity of pre-stage and main-stage on the loading characteristics of a two-stage filtration system. Three different types of pre-stage filter media with different capture efficiency, i.e., G3, G4 and M5 pre-filters, were selected as filter type variables. Three different face velocities on pre-stage, i.e., 26.3, 45.0 and 65.2 cm·s−1, and three different face velocities on main-stage, i.e., 2.1, 3.6, 5.2 cm·s−1 were chosen as face velocity variables. Self-defined indexing parameters were used to analyze the effect of pre-filter in this study. The experimental results indicated that although M5 pre-filter with the highest capture efficiency presents the best protection to mitigate the pressure drop growth of main-filter, the pressure drop of M5 pre-filter itself increases the fastest, resulting in the shortest effective protecting time of M5 pre-filter in front of a main-stage filter, so the overall effectiveness of M5 pre-filter fades out due to the limited protection period. On the other hand, G4 pre-filter can run for a relative longer time while maintaining the pressure drop of the whole two-stage filtration system to increase relatively slowly. G4 pre-filter achieves highest T** value, outperforming the lowest efficient G3 pre-filter by its higher efficiency and the highest efficient M5 pre-filter by longer effective protection period. With the decrease of face velocity on either the pre-stage or the main-stage, the effectiveness of pre-filter on main-filter and the whole two-stage filtration system improves, by slowing down the pressure drop increasing rate of main-stage filter, which further contributes to extend the service lifetime of the main-filter and increase dust holding capacity of the whole filtration system. Besides, the specific resistance k2 of the dust cake formed on main-filter were found deeply affected by the main-stage face velocity. With the face velocity on the main-stage increased, the specific cake resistance k2 increased obviously, which implies that the dusts structure on the main-filter changed and became more compacted under higher main-stage filtration velocity. To better illustrate the relatively importance between pre-filter grade and filtration velocity selection, the analyzed performance indexing parameters were further arranged in a set of contour plots, which unveils the predominance of pre-filter grade over filtration velocity within the variation ranges tested in current study.

Improvement of 3D Power Line Extraction from Multiple Low-Cost UAV Imagery Using Wavelet Analysis.

Three-dimensional (3D) mapping of power lines is very important for power line inspection. Many remotely-sensed data products like light detection and ranging (LiDAR) have been already studied for power line surveys. More and more data are being obtained via photogrammetric measurements. This increases the need for the implementation of advanced processing techniques. In recent years, there have been several developments in visualisation techniques using UAV (unmanned aerial vehicle) platform photography. The most modern of such imaging systems have the ability to generate dense point clouds. However, image-based point cloud accuracy is very often various (unstable) and dependent on the radiometric quality of images and the efficiency of image processing algorithms. The main factor influencing the point cloud quality is noise. Such problems usually arise with data obtained via low-cost UAV platforms. Therefore, generated point clouds representing power lines are usually incomplete and noisy. To obtain a complete and accurate 3D model of power lines and towers, it is necessary to develop improved data processing algorithms. The experiment tested the algorithms on power lines with different voltages. This paper presents the wavelet-based method of processing data acquired with a low-cost UAV camera. The proposed, original method involves the application of algorithms for coarse filtration and precise filtering. In addition, a new way of calculating the recommended flight height was proposed. At the end, the accuracy assessment of this two-stage filtration process was examined. For this, point quality indices were proposed. The experimental results show that the proposed algorithm improves the quality of low-cost point clouds. The proposed methods improve the accuracy of determining the parameters of the lines by more than twice. About 10% of noise is reduced by using the wavelet-based approach.

Purifying agents for produced fluid from chemical flooding in conventional and heavy oil reservoirs

Compared with water flooding, the produced wastewater quality of polymer flooding and ASP flooding has changed significantly. The effect of chemical flooding agent on the stability and purification process of oil droplets and suspended solids in wastewater was analyzed. The two-stage sedimentation-pressure filtration process and the continuous batch sedimentation-two-stage filtration process used in the treatment of chemical flooding wastewater are introduced. The application of organic flocculants, inorganic flocculants, reverse demulsifiers, chemical desiliconizing agents and other purifying agents in the treatment of chemical flooding wastewater is summarized. The key research directions of wastewater treatment from chemical flooding in the future are put forward.

Continuous integrated antibody precipitation with two-stage tangential flow microfiltration enables constant mass flow.

Continuous precipitation is a new unit operation for the continuous capture of antibodies. The capture step is based on continuous precipitation with PEG6000 and Zn++ in a tubular reactor integrated with a two‐stage continuous tangential flow filtration unit. The precipitate cannot be separated with centrifugation, because a highly compressed sediment results in poor resolubilization. We developed a new two‐stage tangential flow microfiltration method, where part of the concentrated retentate of the first stage was directly fed to the second stage, together with the wash buffer. Thus, the precipitate was concentrated and washed in a continuous process. We obtained 97% antibody purity, a 95% process yield during continuous operation, and a fivefold reduction in pre‐existing high‐molecular‐weight impurities. For other unit operations, surge tanks are often required, due to interruptions in the product mass flow out of the unit operation (e.g., the bind/elute mode in periodic counter‐current chromatography). Our setup required no surge tanks; thus, it provided a truly continuous antibody capture operation with uninterrupted product mass flow. Continuous virus inactivation and other flow‐through unit operations can be readily integrated downstream of the capture step to create truly continuous, integrated, downstream antibody processing without the need for hold tanks.