Backwashing Process Research Articles

Activation of periodate by iron-containing sludge from groundwater treatment plants for degradation of methylene blue in wastewater

Currently, there are well-operated iron removal water plants in the northeast region of China. Among them, the backwash process produces a large amount of iron-containing sludge (IS) year by year, which can cause some harm to the environment if not treated. The main form of existence for IS is amorphous γ-FeOOH, and this work demonstrates that IS is a natural and highly active catalyst for periodate(PI). Moreover, IS showed strong stability in environmental factor effects and reproducibility experiments. EPR with quenching experiments proved that IS could activate PI to produce •OH, O2•−, 1O2, and IO3•. In the degradation experiments where methylene blue was chosen as the model pollutant, IO3•, and 1O2 were the substances that served the prominent role in degradation. This work provides an inexpensive and feasible way to dispose of waste iron-containing sludge from water plants and provides fundamental insights into the degradation mechanism of organic pollutants through the activation of PI by IS.

Effects of coagulant bath temperature toward separation performance and antifouling properties of PVDF/CA membranes for filtration of dyes

Phase inversion is used to prepare poly(vinylidene fluoride) (PVDF) microfiltration membranes by combining it with the hydrophilic polymer additive cellulose acetate (CA). For the filtration of methylene blue (MB) and acid yellow 17 (AY17), the effects of coagulant bath temperature (CBT) on the separation performance and antifouling properties are thoroughly investigated. SEM analysis shows that the membrane at higher CBT has a larger pore diameter than at lower CBT, resulting in differences in membrane surface hydrophilicity. It is found that the increase in surface hydrophilicity causes the permeability of PVDF/CA membranes to be higher at higher CBT than at lower CBT. Rejection values above 90% indicate that the membranes are more effective for MB separation at both lower and higher CBT. Otherwise, lower CBT provides better AC rejection than higher CBT. The Flux Recovery Ratio, which is higher at higher CBT, remains in the 75–95% range at lower CBT. As a result, lower CBT is better for membrane fouling resistance than higher CBT. In addition, the fouling observed at lower CBT is similar to the fouling observed at higher CBT, but lower CBT has a higher percentage of reversible fouling than higher CBT. The membranes with more reversible fouling are therefore easier to clean using the backwashing process. As a result, PVDF/CA membranes manufactured at lower CBT have better separation performance and antifouling characteristics than those manufactured at higher CBT.

Analyzing sediment transport in dam-break-driven swash processes: Insights from laboratory experiments using a high-speed camera

Dam-break-driven experimental tests are conducted to explore the intricate dynamics of water and sediment movement during a swash process. Utilizing a combined approach of a high-speed camera and an acoustic doppler velocity profiler, detailed records of flow velocity and sediment movements are captured. This study offers novel insights regarding flow shear stress, layer thickness and velocity of sediment transport in the backwash process, as well as behaviors of individual sand particles. Linear relationships serve to depict alterations in bed shear stress over time. The changing rate of bed shear stress can be influenced by the factors such as the beach slope, sediment grain size, and location on the beach. Increasing layer thickness of sediment transport corresponds with increasing outer layer velocity, exhibiting a linear-exponential relationship. A tentative interpretation of the inflection point (of linear and exponential relationship) designates it as a division between sheet load and a conjunction of sheet load and suspended load. With the onset of a bore and under the influence of turbulence and bubbles, sediment predominantly moves upwards, leading to sediment pickup. However, during both the late uprush phase and the backwash phase, the primary direction of sediment movement reverses downwards, favoring sediment settling. Empirical equations are formulated to estimate the parameters on the bed shear stress and the sediment transport layer. This study enhances understanding of water and sediment movement in swash processes, supplying validation data for numerical models.

Proteomic analysis of host cell protein fouling during bioreactor harvesting.

Chinese hamster ovary (CHO) cells are among the most common cell lines used for therapeutic protein production. Membrane fouling during bioreactor harvesting is a major limitation for the downstream purification of therapeutic proteins. Host cell proteins (HCP) are the most challenging impurities during downstream purification processes. The present work focuses on identification of HCP foulants during CHO bioreactor harvesting using reverse asymmetrical commercial membrane BioOptimal™ MF-SL. In order to investigate foulants and fouling behavior during cell clarification, for the first time a novel backwash process was developed to effectively elute almost all the HCP and DNA from the fouled membrane filter. The isoelectric points (pIs) and molecular weights (MWs) of major HCP in the bioreactor harvest and fouled on the membrane were successfully characterized using two-dimensional gel electrophoresis (2D SDS-PAGE). In addition, a total of 8 HCP were identified using matrix-assisted laser desorption/ionization-mass spectroscopy (MALDI-MS). The majority of these HCP are enzymes or associated with exosomes, both of which can form submicron-sized particles which could lead to the plugging of the filters.

A First Attempt to Describe the Real-Time Behavior and Fate of Marine Litter Items in the Nearshore and Foreshore under Low Energetic Marine Conditions

A field assessment was carried out in May 2023 in a natural protected area in South Italy to investigate the real-time behavior and fate of common marine litter items at different depths at the nearshore and foreshore under low energetic conditions. The field data were also compared with theoretical values calculated using theoretical formulations considering the Stokes drift current, wind-induced current, and current at breaking position. The wind approached from N to W, with values ranging from 2.4 to 3.8 m/s. The propagated significant wave height ranged from 14 to 21 cm, with an associated period of 3 s. Items with a positive buoyancy recorded different velocities. Very protruding (above water surface) items were greatly affected by windage and recorded velocities from 0.23 to 0.33 m/s; higher than the theoretical values that do not take into account windage. Theoretical values correctly predicted the velocity of other less-protruding items but slightly underestimated the velocity of neutral buoyancy items, evidencing in both cases the low relevance of the Stokes drift current. Items with a negative buoyancy moved (or not) in the bottom with different velocities. Different behaviors were observed at the breaking point, where items surfed (or not) spilling breaking waves, and at the foreshore, where items moved along the plunge step or in a “zig–zag” movement due to a swash–backwash process.

A new mathematical model to describe the trans-membrane pressure in the coupled cleaning process (rinsing + backwash)

Coupled cleaning (rinsing + backwash) during the constant flow rate process is an effective method for alleviating the membrane fouling. However, there is a lack of in-depth studies on the coupled cleaning process, especially for accurate descriptions of the variation of the trans-membrane pressure (pclean(t)). In this paper, a model based on the composite mechanism (open pores, loosen the cake and remove the cake) was first developed to describe the variation in pclean(t) during the coupled cleaning process for a 0.1 μm polyacrylonitrile (PAN) membrane fouled with activated sludge. Moreover, the model was validated by using different foulants (yeast, bovine serum protein, sodium alginate and humic acid), membranes (0.1 μm polyethersulfone (PES) and 0.1 μm polyvinylidene (PVDF) membranes). The results showed that the variation in pclean(t) could be accurately described during the coupled cleaning process under different backwash strengths (0.5, 1, 1.5 and 2) (R2 ≥ 0.997) or cross-flow velocities (0.05, 0.11, 0.17 and 0.22 m/s) (R2 ≥ 0.994). Moreover, the coupled cleaning process was divided into three stages: (1) pclean(t) decreased rapidly (open pores, loosen the cake and remove the cake). (2) pclean(t) decreased slowly (remove the cake) and (3) pclean(t) was almost unvaried (without open pores, loosen the cake and remove the cake). In addition, the model could also be applied to the single rinsing or backwash process. This model provided a theoretical basis for the membrane high-efficiency and energy-saving cleaning processes in MBRs.

Study of Flow Rate Effect on Horizontal Flow Concrete Sand Filter Filtration Performance

The need for clean water during the pandemic is significantly increasing due to high public awareness of adopting a clean and healthy lifestyle (PHBS), necessitating more water treatment. Conventional methods are used for water treatment, including coagulation-flocculation system, rapid sand filter, and disinfection. However, these methods have limitations such as reduced capacity and sand filter efficiency, leading to increased backwash costs due to the need for sand replacement caused by particle stratification. In response to these challenges, an innovative method to water treatment is the use of concrete sand filter (CSF). Previous studies predominantly focused on downflow filtration, but there has been limited analysis of horizontal flow. Therefore, this study aimed to assess filtration and backwash effectiveness of CSF with horizontal flow, specifically focusing on the capacity performance in treating water with varying levels of turbidity. Filtration experiment was carried out using simulated water at turbidity of 125 NTU based on the Mataram Channel Turbidity with variations of 0.2, 0.5, 1.0, 5.0, and 10.0 m hour-1, as well as backwash at flow rate of 40.91 m hour-1 for 3 minutes. The variables measured during filtration process included head losses and turbidity at the inlet and outlet of CSF. The results showed that the capacity performance during filtration process was directly proportional to flow rate. Meanwhile, the effectiveness of concrete filter was inversely proportional to flow rate. At initial turbidity <617 NTU, the 3 minutes backwash process obtained lower final turbidity compared to the raw water used, which was 5.19 NTU. Meanwhile, at turbidity 617 NTU, the final turbidity was still high, reaching approximately 14.6–26.4 NTU.

MONITORING THE QUALITY OF CLEAN WATER TREATMENT IN THE WATER TREATMENT PLANT FILTRATION UNIT USING THE BACKWASH METHOD

Water for an industry is a supporting material for both direct and indirect activities to support several systems. Requirements for the quality of water used in industry vary depending on its intended use. Water that comes from nature generally does not meet the necessary requirements so it must undergo a processing process first. Raw water sources play a very important role in the clean water industry. Raw water is the beginning of a process in the supply and treatment of clean water. Water Treatment Plant (WTP) or Water Treatment Plant (IPA) is a system/facility that functions to treat water from contaminated raw (influent) water to obtain the desired water quality treatment according to quality standards. The purpose of this study was to determine the effect of treated water quality and backwash effectiveness by comparing the values of chemical and physical parameters before and after the backwash process in the filtration process unit of a clean water treatment plant. After conducting the tests, it was concluded that the backwash process is very effective in maximizing the performance of a filtration process unit. The effective value of acidity (pH) is (0-5)%, hardness and turbidity is (40-50)%, total dissolved solid (TDS) is (5-10)% and conductivity is (10-20)%. This also shows that the quality of the water tested has met the quality standards in accordance with Permenkes No. 492 of 2010.

Theoretical model and numerical simulation of high-gravity backwashing process for deep bed filter in oilfield

With the large-scale application of polymer flooding technology, the polymer concentration in produced water is increasing, which leads to incomplete regeneration of filter media by gravity field hydraulic backwashing technology only. In this study, the high-gravity backwashing technology is constructed by coupling gravity field and swirl field, which promotes the development of the oilfield. Based on the cascade theory, this paper establishes a mathematical expression of radial collision force in the high-gravity backwashing process in the vortex tube and solves a mathematical equation of high-gravity backwashing velocity gradient G based on the efficient zone of collision force action. Meanwhile, based on the discrete element method and computational fluid dynamics theory, the inter-particle collision regulation of the high-gravity backwashing process is simulated by the coupled FLUENT-EDEM method, and the high-efficiency zone of the backwashing process is verified. In this high-efficiency zone, the theoretical and simulated values of velocity gradient G for different high-gravity values match well, with differences ranging from –5.8 % to +7.1 %, indicating that the theoretical model of high-gravity backwashing is correct. When the high-gravity value is 210–240 g, the total impulse of the filter bed per unit time reaches a great value, and the backwashing velocity gradient G is 3047.1 s−1, which is much larger than the G value of combined air-water backwashing. The high-gravity backwashing technology breaks through the technical bottleneck of low efficiency in the action of the gravity field. It enriches and develops the gravity field hydraulic backwashing technology of the filter bed.

Evaluation of Backwash Time Effect on Mesh Self-Washing Filter Parameters

Purpose: The study aims to determine the effect of the backwash time on the parameters of the mesh self-washing filter. Theoretical framework: The duration of the backwash process can significantly affect the operation parameters of the mesh self-washing filter Method: During the study, experiments were carried out using a laboratory stand on which a mesh self-cleaning filter was installed. In the experiments, the filter operation parameters were measured at different values of the backwash time. Mathematical modelling methods were also used to determine the filtration efficiency. Results and conclusion: The results of the study showed that the backwash time significantly impacts the operation of the mesh self-washing filter. The optimal backwash time is from 20 to 30 seconds, while the percentage of filter clogging due to removing impurities during backwash is reduced by 20-25% compared to a shorter or longer backwash time. Research implications: These filters work on the principle of direct filtration when water passes through a sieve to remove suspended solids. The filter material is periodically cleaned by backwashing, which involves changing the direction of water flow through a sieve to remove accumulated solid particles. Originality/value: Water purification by suspended solids with a size of more than 100 microns is carried out by an amount of more than 99.5%. The filter provides reproducible cleaning quality, and the cleaning efficiency does not decrease from cycle to cycle.

A chemically enhanced backwash model for predicting the instantaneous transmembrane pressure of flat sheet membranes in constant flow rate mode

In this study, a new model was proposed based on the cascade process of the chemical reaction and the physical removal mechanism to predict the instantaneous transmembrane pressure (p(t)) of yeast-fouled 0.1 μm polyacrylonitrile (PAN) membranes in the chemically enhanced backwash (CEB) process. The results indicated that the model predictions were in good agreement with the experimental data. Additionally, the transition point of the CEB mechanism, which changed from a combined cleaning (pore cleaning and cake cleaning) mechanism to an individual cake cleaning mechanism, appeared earlier at higher NaOCl concentrations or CEB fluxes. The corresponding available membrane area ratio also tended to stabilise earlier. In addition, the model predictions for different suspensions or solutions, membranes (0.1 μm polyethersulfone (PES) and polyvinylidene fluoride (PVDF) membranes), and chemical reagents were also in good agreement with the experimental data. Moreover, the integral of p(t) was used to correct Masse's energy consumption equation. The results show that the calculation method for the corrected equation is theoretically more accurate. Lower total energy consumption was obtained at a higher NaOCl concentration or lower CEB flux.

A step-by-step assessment of the backwashing process impact on the fouling mitigation of blended PVC/PC and nanocomposite PVC/PC/MAg membranes in a membrane bioreactor (MBR) treating pharmaceutical wastewater

Membrane bioreactors are widely used for industrial wastewater treatment. However, membrane fouling is one of the critical problems in applying these systems. fouling mitigation is an essential issue since membrane fouling results in decreased permeability, increased energy consumption, and reduced membrane lifespan which should be addressed in industrial designs. In this study, our objective was to evaluate the filtration performance and fouling behavior of the blended polyvinyl chloride/polycarbonate (PVC/PC) and nanocomposite PVC/PC/modified silver nanoparticles (PVC/PC/MAg) hollow fiber membranes in continuous and intermittent (filtration with backwashing) filtration experiments at constant pressure. Additionally, an experimental module was designed for the backwashing process so that the fouling phenomenon could be investigated step-by-step for both membranes. The performance of the nanocomposite membrane was compared with that of the blended membrane after each backwashing step in terms of flux recovery and fouling resistances. Permeate flux of the blended and nanocomposite membranes at the end of the continuous filtration experiments compared with the initial flux declined by 61% and 48%, respectively. During the intermittent filtration experiments, the average flux of the blended and nanocomposite membranes in the last step decreased by about 16% and 7% in comparison with the first step, respectively. Flux recovery for the nanocomposite membrane at the end of each backwashing step in the intermittent filtration experiment was over 95% resulting in lower permeability decline over the filtration process. Moreover, the present study reveals that incorporating silver nanoparticles into the structure of the PVC/PC membrane results in an increase in permeability and enhancement of antifouling properties, as well as it increases the flux recovery during the backwashing process in MAg-filled nanocomposite membranes.

Experimental study of the solitary wave induced groundwater hydrodynamics

Coastal groundwater hydrodynamics are affected by the swash uprush and backwash processes. In this study, laboratory experiments were carried out to investigate the solitary wave induced groundwater hydrodynamics over a coarse-grained sand beach. Pore water pressures at 27 cross-shore positions (covering both the subaqueous and subaerial areas) along 3 different beach depths were measured, and the synchronized shoreline position as well as the local water surface elevations (WSE) were also recorded. Temporal variation of the total water head (TWH) was found almost hydrostatically controlled by the instantaneous WSE in the subaqueous area. In the capillary truncated zone, the capillary effect contributes to the non-hysteresis phenomenon between the TWH and WSE. In other subaerial area, time-varying features of the TWH and WSE show clear differences in terms of their magnitudes and phases. Regarding the experimental observations, four representative regions could be identified along the cross-shore direction, i.e., Region I corresponding to the initially subaqueous area, Region II in between the still water shoreline and the top of capillary fringe (saturated beach), Region III in between the upper boundary of Region II and the maximum swash run-up, and Region IV landward beyond the Region III. With respect to the cross-shore distribution characteristics of the maximum TWH and the maximum WSE, as well as the time instants when the maximum TWH and the maximum WSE occur, different groundwater hydrodynamics were observed during the swash event in these four regions. In addition, spatiotemporal characteristics of the TWH were scrutinized and discussed. Both the vertical and horizontal TWH gradients in different regions were considered to reveal the sophisticated groundwater hydrodynamics. Finally, the groundwater movement pattern and its percolation circulation under the solitary wave swash were also specified. • Solitary wave induced groundwater hydrodynamics are investigated through detailed laboratory experiments. • Four regions are identified regarding the spatial characteristics of the maximum total water head and its occurrence time. • Hydrostatic effect, capillary effect and the wetting front are significant for the swash groundwater hydrodynamics. • Horizontal groundwater seepage flow is evident, even larger than the vertical one, during the entire swash process. • Two groundwater circulations are observed in the subaqueous and subaerial areas during the swash cycle.

Exploring the influence of air resistance on the hollow fiber membrane process in water treatment based on ultrasonic phased array technology

In water treatment with membrane filtration process, a lot of factors such as process design, operation, and fouling affect membrane flux. But it is often neglected the flux decline which attribute to air resistance. In this study, it has been observed that air resistance caused by air trapped initially at startup as well as the release of air from the permeating liquid has an adverse effect on the membrane filtration and backwash process in water treatment. In the study, a new in-situ monitoring method, ultrasonic phased array (UPA), was used to investigate the distribution of released air in the hollow fiber membrane module. The operation parameters such as backwash interval, duration and strength were investigated. A strategy was also proposed to mitigate the adverse effects of air resistance. The results showed that UPA can successfully monitor the distribution of released air, which has a good positive correlation with air sound pressure reflection R¯air. The released air is mainly distributed far away from the outlet, while as the backwash interval and strength increase, the range of released air distribution gradually expands. We also found the optimal operating parameters for the minimum released air volume that the backwash interval is 90 min and the backwash duration is 60 s. Besides, the air resistance has a good positive correlation with released air. Moreover, the released air migration results show that air dispersion and redissolution are beneficial to reduce the air resistance in the backwash process. In summary, the optimal operation can mitigate the air resistance in the variable membrane filtration mode in water treatment.

Membrane Backwash Performance Improvement-A Review

To date, different models and parameters have been used to design membrane backwash system for different applications and in most cases this has led to improved performance of membrane system. However, some of these developed backwashing system are inefficient, due to poor modelling of relevant physical parameters and variables that affect backwash system. An efficient cleaning design of a membrane backwash system has proven to be a promising approach or technique in improving membrane performance for different applications. As such, it is important to study all the relevant models and parameters that can be used in designing a membrane backwash system to improve the overall performance of the membrane system for oil-water separation application. In this review study, a series of models are identified and their potential application to establish critical operating process during backwash. This report has three section, namely: Identification of critical backwash operating conditions that could potentially optimize backwash system, flux recovery models and lastly, fouling-based models. The purpose of this review is to identify relevant parameters and relevant models during backwash process. More consideration is based on demonstrating the effectiveness of high intensity of critical operating condition during backwash, which canforce the oil droplet blockage to be dislodged out of the membrane pores with ease. As result, reduction in backwash duration and improve the overall performance. This study concludes as follows; the identification of critical parameter, majority of the models are based on conservation principle which is a (collective of conservation mass, momentum and energy) governed by Navier-Stokes laws. Also, modelling the oil droplet dislodging phenomenon, much consideration should be based on the driving back-pressure and interfacial tension forces, to deform and push the oil droplet blockage out of the pores. Furthermore, developed critical pressure models on filtration phase do not directly consider the different fouling formation between oil and solid particles.

A model describing the pressure drops across the membrane and cake layers for constant flux cross-flow microfiltration process

A combined model (pore-blocking/shrinking-cake filtration) was established based on the Darcy’s law, Hagen-Poiseuille equation and classic blocking law to study the fouling behavior of a 0.1 µm PAN membrane fouled with the extracellular polymer substance model solution (bovine serum albumin (BSA), sodium alginate (SA) and humic acid (HA)) under different operating conditions in the constant flux cross-flow filtration process. Results showed that the model predictions had good agreements with experimental data not only for single component solution (BSA, SA and HA), but also for the binary mixtures (BSA+SA, BSA+HA and SA+HA), ternary mixtures (BSA+SA+HA) and other membranes (0.1 µm PES and PVDF) (R2 ≥ 0.874). The dominant fouling mechanism is pore-blocking/shrinking at lower concentration, lower flux, or higher velocity in the whole stage. In contrast, the dominant fouling mechanism is pore-blocking/shrinking-cake formation in the first stage while it is cake formation in the second stage at a higher concentration, higher flux, or lower velocity. Meanwhile, the trans-membrane pressure (P) increased rapidly in the first stage for both situations while P kept constant for the first situation and P increased slowly for the second situation in the second stage. Furthermore, transition point and time from combined mechanism to individual mechanism were determined. This model can provide guides for industrial backwashing processes.

Evaluation of Membrane Fouling by Microplastic Particles in Tertiary Wastewater Treatment Processes

Microplastic (MP) pollution in aquatic environments poses substantial ecological, human, and economic threats. A common route of entry for MPs into the aquatic environment is through the effluent from wastewater treatment plants (WWTPs). Although membrane technologies as a tertiary treatment step have shown promise in mitigating the efflux of MPs, little is known about how MPs suspended in wastewater effluent affect membrane performance. One reason is that it is challenging to source MPs for filtration experiments which are representative of those found in WWTPs. As such, this study employed a milling and sieving process to create irregularly shaped polyethylene MPs approximately 10 μm in size which were then suspended in effluent wastewater (taken directly from a secondary clarifier tank). Membrane fouling caused by wastewater/MP interactions was investigated via constant pressure filtration experiments using commercial ultrafiltration and microfiltration membranes. It was found that even low concentrations of MPs in the wastewater increased the extent of membrane fouling. Furthermore, a backwashing process was found to significantly mitigate the effect of MP fouling on the membrane surfaces. The results from this study provide important insights into the governing factors for membrane fouling by MPs in water chemistries representative of WWTP effluents.

Renewable energy powered membrane technology: Impact of osmotic backwash on organic fouling during solar irradiance fluctuation

Organic fouling is a major issue of nanofiltration/reverse osmosis (NF/RO) membranes because it causes severe and usually irreversible flux decline. Consequently, NF/RO requires frequent chemical cleaning and/or replacement. In directly coupled photovoltaic (PV) powered NF/RO systems for brackish water desalination, solar energy fluctuations can induce a spontaneous osmotic backwash (OB) process, which may mitigate organic fouling. In this study, the feasibility of spontaneous OB as a self-cleaning method for organic fouling (humic acid with calcium) control under fluctuating conditions was evaluated with an online total organic carbon (TOC) analyser. The OB cleaning mechanisms with different solar energy fluctuating conditions, relevant feedwater chemistry (salinity, pH, and hardness) and membrane type (NF270 and BW30) were investigated. The visualisation of fouling layers by a helium ion microscope (HIM), a cryo scanning electron microscope equipped with a focused ion beam (FIB-SEM) and energy dispersive X-Ray spectroscopy (EDS) showed that partial foulants were removed by spontaneous OB, and the remaining layer was not uniform. Periodic solar irradiance step-response experiments’ results showed that spontaneous OB cleaning restored 46%–98% flux, depending on solar irradiance fluctuating conditions, feedwater chemistry, and membrane type. Specifically, low-level solar irradiance (i.e., more cloud coverage) and short operating time (i.e., high cleaning frequency) showed high OB cleaning efficiency. High salinity was found to enhance the OB performance but it was still ineffective for the enhanced organic fouling layer. Extremely pH (e.g. pH 2 or pH 12) weakened OB efficiency via a compact fouling layer/mixed fouling layer structures (calcite participation) in presence of calcium. Although spontaneous OB cleaning is promising to mitigate organic fouling, it is ineffective for severe organic fouling (e.g. 12.5 mM humic acid with 2.5 mM CaCl2). This work provides the contribution of process and water quality variables that make spontaneous OB effective for fouling control, which facilitates the further development and application of the OB technique in decentralised PV-NF/RO systems.

Optimization of Condenser Backwash Method to Maintain Condenser Performance During the Backwash Process in PLTGU Grati

The condenser is a device used to change the water vapor phase that has been used to rotate the turbine blade into a liquid phase by condensing it. When the condenser tube is dirty, it can disrupt the steam condensation process which affects the efficiency of the condenser. To overcome this problem a condenser backwash is carried out.  Condenser backwash has a good influence on unit efficiency but backwash activities also reduce production by decreasing vacuum condensers and steam turbine loads. When the vacuum condenser backwash process decreases + - 24 mmHg and the steam turbine load decreases + - 8 MW.The condenser backwash process is carried out from the control room with the observation of parameters from the local area or equipment. Backwash condensers are done one by one as needed. The condenser type in PLTGU Grati Block I is a type of crossflow with two sides, namely, side A and side B. Each side of the condenser has a different sequence backwash condition. This study will be carried out a backwash method that is different from the sequence of automatic sequences.In the normal condenser backwash activity of data table 3 we can know there is a decrease in steam turbine load ± 8MW and a decrease in vacuum ± 24 mmHg. This is because at a certain period the condenser performance is reduced because at the time of switching valve one side of the condenser is not irrigated by seawater so that the heat transfer in the condenser is reduced which has an impact on a load of steam turbine and vacuum condenser. After the research was obtained that the greater the opening of the valve inlet when the condenser backwash then the decrease in vacuum and steam turbine load decreased even no decrease in load.The backwash method that can be done to keep the vacuum condenser and steam turbine load stable is by maneuvering the valve inlet, outlet, and condenser backwash valve. The results of the analysis obtained were a more stable decrease in steam turbine production in 0 MW and a decrease in the vacuum of 14 mmHg.

Self-cleaning filtration with magnetically controlled particles

In this work, a new concept of dynamic granular bed was proposed based on magnetically controlled particles. Compared with conventional moving granular bed, a rotating granular layer was formed on dynamic granular bed, which can capture solid particulates. The dust cake can be kept at a certain amount of thickness even after long-term operation. Self-cleaning function of dynamic granular bed installation provides a long-term operation. Hence, the backwash process is not required in self-cleaning installation. Rotating magnetic field was used for granular bed formation with a predetermined porosity in this work. Mechanism of a dynamic granular bed formation described using experimental and visual surface layer data. Periodic working moving granular bed is then changed to continuous and steady working dynamic granular bed. Numerical data of the main filtration process showed a good agreement with experiment. The experimental results show that there exist optimal parameters of filtration superficial velocity and mass flow rate of filter granules for dynamic granular bed. Best efficiency obtained at a filtration superficial velocity of 0.03 m/s and a mass flow rate of 10 l/h for dynamic granular bed in the experiments.