filter cloth filter

Why choose a filter cloth filter? 　　1. Chinese-branded equipment developed independently by the company, with independent intellectual property rights, and whose performance and specifications surpass those of similar foreign equipment (in terms such as nanofiltration membranes and equipment specifications). 2. A team of hundreds of high-level experts and researchers specializing in engineering design, construction, operation, and project management. It possesses sustained and outstanding R&D capabilities, holding a leading position in China’s market for advanced wastewater filtration. 3. It provides wastewater filtration and reuse services to nearly 10 million residents in China, operating nearly 100 projects across the country. 4. A professional team develops cost-effective solutions tailored to the needs of various clients. 5. With customer satisfaction as its top priority, it offers real-time monitoring of operations, close communication with clients, immediate feedback, and comprehensive maintenance services after deployment. Those who are interested are encouraged to learn more – the advantages over conventional filters are quite significant.

The operating states of a microfiltration fabric filter include: the filtration process, the negative pressure backwashing process, and the sludge discharge process. (1) Filtration: The wastewater flows under gravity into the filter tank, which is equipped with baffle devices to dissipate energy. Wastewater is filtered through a filter cloth; the filtrate is collected through hollow tubes, while the flow under gravity is discharged from the filter tank via an overflow channel. The entire process is continuous. (2) Cleaning: Some of the sludge from the filtration process adheres to the outside of the filter fabric, gradually forming a sludge layer. As sludge accumulates on the filter cloth, the filtration resistance of the filter cloth increases, and the water level in the filter tank gradually rises. The water level difference between the filter tank and the effluent tank can be monitored using a pressure measuring device. When this water level difference reaches the cleaning set value (high water level), the PLC can activate the back-suction pump to start the cleaning process. During cleaning, the filter can continue to filter. During filtration, the filtration turntable remains stationary, which facilitates the deposition of sludge at the bottom of the tank. During cleaning, the filtration turntable rotates at a speed of 1 revolution per minute. The suction pump creates negative pressure to draw on the surface of the filter cloth, removing the sludge particles that have accumulated there. The water inside the filtration drum is also drawn away simultaneously; this water cleans the filter cloth from the inside out, and the cleaned water is then discharged. The flushing area accounts for only about 1% of the total area of the filtering turntable. The backwashing process is intermittent. During cleaning, on the pipeline connected to the suction pump, each automatic control valve controls two filter turntables as one group; during a complete cleaning cycle of the microfiltration fabric filter, the cleaning of these different groups takes place alternately, while the suction pump continues to operate continuously. (3) Sludge discharge: The filter disc of the microfiltration fabric filter is equipped with a hopper-shaped bottom, which facilitates the collection of sludge at the bottom of the tank. The sediment at the bottom of the sludge tank reduces the amount of sludge on the filter cloth, allowing for an extended filtration time and less water to be used for cleaning. After a set period of time, the PLC activates the sludge discharge pump, which returns the sludge to the sewage pretreatment facility through the sludge discharge pipe at the bottom of the tank. Among them, the sludge discharge interval and the duration of sludge discharge can be adjusted.

Thank the original poster for providing it; I’d like to learn from it*

This post was last edited by arenbang on 2009-11-18 at 16:04. Pilot study on the filter cloth filter system for advanced treatment of urban wastewater. The filter cloth filter process is an efficient water treatment method that enables filtration and sedimentation to be carried out simultaneously within the same filter. Applying this process to the advanced treatment of urban wastewater, the addition of flocculants enables simultaneous removal of TP and turbidity. The removal efficiency of this process on TP, turbidity, TN, and COD in the secondary treatment effluent from urban sewage treatment plants, as well as its operating patterns, were studied. Studies show that by using ferric chloride as a flocculant, and at an appropriate dosage of the chemical, the removal rate of TP from the secondary effluent of wastewater treatment plants exceeds 53%, while the removal rate of turbidity exceeds 32%. Compared with traditional sand filtration processes, this process offers advantages such as simple operation, compact structure, small footprint, and low head loss. It is a more economical and straightforward treatment unit suitable for advanced treatment in existing urban sewage treatment plants to further improve the quality of the treated water. With the increasing shortage of freshwater resources and rising water demand, the recycling and reuse of wastewater have become one of the effective measures to address water scarcity. The effluent from the secondary treatment stage of urban sewage treatment plants has a stable volume and quality, with low levels of pollutants; conventional advanced treatment processes are sufficient to meet the requirements for urban reuse water, and this amount of reused water can account for one-third of the city’s total water demand. The cloth-media filtration system is a newly developed surface filtration system. It falls under the category of granular filtration, just like sand filtration, with a filtration rating of 10μm. Compared with sand filters, the filter cloth filter system has many advantages in terms of technical and economic indicators. It features good treatment efficiency, stable water quality and volume, low energy consumption (with an elevation loss of only 0.3m), low head loss during filtration, short backwashing time, small floor space (only 1/2 of that of conventional processes), and easy maintenance and operation. This technology has begun to be adopted by some advanced wastewater treatment plants in Europe and the United States as a subsequent advanced treatment unit for urban wastewater, in order to further improve water quality. In China, there are few reports on the research and application of the filter cloth filter process. 1 Test Materials and Methods 1.1 Test Apparatus and Operating Parameters The filter cloth filter system is shown in Figure 1. The filtration components of a filter cloth filter include a central tube/filtering turntable, a backwashing system, a sludge removal system, a central drive system, and a support frame system. The secondary effluent from the wastewater treatment plant flows by gravity into the filter; after being filtered through the filter fabric, the filtered liquid is collected through hollow tubes and discharged from the filter via an overflow channel. During the filtration process, some of the lighter sludge adheres to the outside of the filter cloth, forming a sludge cake. During filtration, the filter disc remains stationary, and the filter cloth filter is equipped with a hopper-shaped bottom, which facilitates the precipitation of heavier sludge at the bottom of the tank. As sludge accumulates on the filter cloth, the filtration resistance of the filter cloth increases, and the water level in the filter tank gradually rises. Backwashing of the filter cloth is controlled by the liquid level height; generally, this level is set at 0.1~0.3 m. The head loss in this process is much lower than that in conventional filtration processes. When the filter fluid level difference reaches the set value, the PLC activates the backwash pump to start the backwashing process. The filter cloth used in the pilot-scale device for filter beds is of a nylon needle-like structure, supported by polyester. During filtration, these needle-like structures hang down to form a filtering layer. When the backwash pump is activated, the suction force generated by the pump causes these needle-like structures to unfold, and the sludge on the surface of the filter cloth as well as within the filtering layer is removed through the suction action of the backwash pump. During backwashing, the filter disc rotates at a speed of 1 r/min. The backwash pump uses the water in the filter tank to draw and flush the surface of the filter fabric, removing the sludge particles accumulated on it and discharging the backwash water; therefore, a separate backwash water tank is not required in a filter fabric filter system. The sludge that settles at the bottom of the tank is removed regularly by activating the sludge discharge pump, which expels it through the sludge discharge pipe at the bottom of the tank. Figure 2 shows the flow diagram of the experimental setup. The filter cloth filter unit uses two disc filter cloth filters, which are placed in stainless steel tanks; all equipment is made of corrosion-resistant materials. The effective flow area of a single filter disc is 1.12 m²; the average water treatment capacity per disc is 212 m³/d, with a maximum capacity of 424 m³/d. The backwash sludge discharge pump of the pilot-scale filter cloth filter equipment has a power of 1.5 kW, a flow rate of 14.76 m³/h, and a head of 6.7 m. The secondary effluent from the wastewater treatment plant passes through a flocculation tank; at the same time, the flocculant is also delivered to this reactor via a metering pump. Stirring ensures thorough mixing of the wastewater with the chemical, and the phosphates in the water undergo a process of micro-flocculation within the reactor under the action of the flocculant. The effluent from the flocculation tank flows by gravity into the filter cloth filter; the micro-flocculation reaction time is 20 seconds, and the flocculation stirring speed is 130 r/min. After filtration in the filter cloth filter, the effluent is measured using a rotameter before being discharged. The filtration level set for the filter cloth filter is 0.3 m, the backwashing time is 1 minute; the system automatically discharges sludge once after every 3 filter cloth washes, and the sludge discharge time is 1 minute. 1.2 Experimental water quality To examine the filtration characteristics of filter cloth filters, the secondary effluent from two sewage treatment plants in a city in the south was selected as the raw water; Plant 1 used an MUCT process with nitrogen and phosphorus removal functions, while Plant 2 employed a three-channel oxidation ditch treatment process. Pilot tests for advanced treatment were conducted at the outlet of the wastewater treatment plant; the effluent from urban wastewater treatment plants is shown in Table 1. It can be seen that the quality parameters of the effluent from Wastewater Plant 1, such as TP, ammonia nitrogen, and TN, are all better than those of Wastewater Plant 2. 1.3 Analysis Methods The analysis parameters in this study include: turbidity, TP, COD, and TN. Turbidity is measured using the HACH 2100P portable turbidimeter, while other water quality parameters are tested in accordance with the \"Methods for Monitoring and Analyzing Water and Wastewater\" compiled by the Environmental Protection Bureau. 1.4 Test Procedure Due to the different coagulation properties of various flocculants, this experiment first employed beaker tests to screen five types of agents: ferric chloride, polyaluminum chloride (PAC), polyaluminum ferric chloride (PAFC), ferrous sulfate, and polyferric sulfate. As a result, FeCl3 was selected as the flocculant to be used, both domestically and internationally, for investigating the filtration efficiency of micro-flocculation combined with filter cloth filters. For the secondary wastewater from sewage treatment plants, pilot tests were conducted on filter cloth filter systems using different dosages of chemicals, in order to study the patterns of pollutant removal. Operating parameters for three different filtration flow rates of 18, 23, and 28 m³/h were also studied. 2 Test Results and Analysis 2.1 Removal Efficiency of TP and Control of Dosage The precise control of dosage is crucial for the proper operation of the micro-flocculation filtration process; it directly affects the phosphorus removal rate as well as the operational cycle of the entire filtration process. Figure 3 shows the removal efficiency of TP by the filter cloth filter process at a flow rate of 28 m³/h, under different doses of ferric chloride (0, 3, 5, 7, and 9 mg/L respectively). It can be seen that the filter cloth filter system removes particulate TP from the secondary effluent mainly without the addition of chemicals, with a removal rate of approximately 10% for TP in this case. After the addition of chemicals, the removal rate of TP in the filter cloth filter system at Sewage Plant No. 1 ranged from 27% to 53%, while at Sewage Plant No. 2 it ranged from 18% to 56%. Moreover, the removal rate of TP increased as the amount of flocculant added increased. This is because the TP in the secondary effluent from wastewater treatment plants is mainly in the form of dissolved phosphates, and it can undergo a chemical reaction with iron-based flocculants to form precipitates. As can also be seen from Figure 3, for Wastewater Plant No. 1, the rate of increase in removal efficiency slows down when the dosage of ferric chloride is 5 mg/L; at this point, the average concentration of TP in the effluent is 0.25 mg/L, which is already a low value. The effluent from Plant 2 has a high TP level. When the dosage of ferric chloride was 5 mg/L, the insufficient amount of chemical used resulted in no significant increase in the system’s TP removal efficiency; however, when the dosage was increased to 9 mg/L, there was a significant improvement in TP removal efficiency. 2.2 Effect of dosing amount on turbidity removal The turbidity removal efficiency of the filter cloth filter system at different dosing amounts is shown in Figure 4. As can be seen from Figure 4, without the addition of chemicals, the filter cloth filter system shows little effect in removing turbidity. After the chemicals are added, the turbidity removal efficiency of the filter cloth filter increases significantly. For Wastewater Plant No. 1, when the dosage of ferric chloride is 5 mg/L, the filter cloth filter achieves the highest turbidity removal rate, at 32%. Increasing the dosage of this chemical further results in a slight decrease in the turbidity removal rate. This is because the TP level in the water fed into the filter cloth filter system is low, resulting in less consumption of iron salts; however, the color imparted by these iron salts causes an increase in turbidity. To ensure the removal of turbidity, the dosage of ferric chloride should be 3~5 mg/L. At the Second Wastewater Treatment Plant, due to the higher levels of TP and turbidity, the filter cloth filter achieves a higher removal rate of turbidity compared to the First Wastewater Treatment Plant; it also consumes more chemicals, with the optimal dosage point being at 7 mg/L. 2.3 Effect of dosage on TN and COD removal efficiency As can be seen from Figures 5 and 6, under the condition of adding chemicals, the filter cloth filter system achieves a COD removal rate of 6.5% to 18%, and a TN removal rate of 3% to 18%. This is because in the secondary effluent from wastewater treatment plants, soluble COD represents the main form of organic matter, and soluble COD cannot form precipitates with iron ions; therefore, the efficiency of COD removal by the system is less affected by the amount of flocculant used. Due to the very short hydraulic retention time in the filter cloth filter system (less than 5 minutes), processes such as nitrification and denitrification do not occur within it, resulting in a low removal rate of TN. 2.4 Effect of dosing amount on the operating cycle of the filter cloth filter: The impact of different dosing amounts on the backwashing frequency of the filter cloth filter system is shown in Figure 7. The backwash frequency increase curve in Figure 7 shows that as the dosage of ferric chloride increases, the filtration cycle shortens while the TP removal rate increases. This may be due to the fact that as the dosage of the chemical added increases, the ferric chloride coagulant undergoes hydrolytic polymerization to form iron hydroxide precipitates, which then remove particulate pollutants through flocculation. As the dosage of the chemical added increases, the particulate pollutants generated as a result also increase, which leads to a significantly faster rise in the head loss in filter cloth filters. For Wastewater Plant 1, once the dosage exceeds 7 mg/L, the increase in backwashing frequency slows down. When the dosage is too high (9 mg/L), it exceeds the amount of iron salts required for the reaction, thereby slowing down the increase in backwashing frequency. At a filtration elevation of 0.3 m, when the dosage of ferric chloride is 5 mg/L, a backwashing frequency of 56 times per day – approximately 26 minutes per backwash – is achieved, which holds good practical significance. If the dosage is increased further, the head rise will be too rapid and the cycle time will become too short, resulting in higher operating costs. Due to the high TP concentration in the effluent from the second wastewater treatment plant, as the dosage of chemicals increased, the backwashing frequency rose rapidly; when the chemical dosage reached 7 mg/L, the backwashing frequency was 130 times, or about 11 minutes per backwash. It explains that a filter cloth filter is, after all, a type of surface filtration technology; compared with the commonly used deep-bed media filtration technology, it has a lower capacity to handle pollutants and can sustain a lower solid load. 2.5 Effect of operating water volume on the operation cycle of the fabric filter: Under a filtration head of 0.3 m and a chemical dosage of 5 mg/L, the impact of different operating water volumes on the backwashing frequency of the fabric filter system is shown in Figure 8. It can be seen that as the flow rate increases, the head loss in the filter cloth filter also rises more rapidly; the filtration cycle is significantly shortened, and the backwashing frequency increases in a linear relationship with the flow rate. This is because the filtration in filter cloth filters belongs to gravity filtration, a type of surface filtration. The main principle of filtration here is the formation of a filter cake as particles are trapped by the filter cloth; increasing the flow rate of water leads to an accelerated formation of this filter cake on the surface of the filter cloth, resulting in a thicker filter cake layer and thus an increased frequency of backwashing. 3 Conclusions (1) The micro-flocculation-filter cloth filter process can effectively remove TP from water; the removal efficiency of TP increases as the amount of flocculant used increases, exceeding 50% for TP removal. It also provides good removal effects on turbidity, but its effectiveness in removing TN and COD is poor. (2) Controlling the appropriate dosage of chemicals and the water flow rate is key to the operation of the micro-flocculation-cloth filter process. The backwashing frequency increases as the dosage of chemicals rises, and it is linearly related to the water flow rate. (3) Utilizing it as a subsequent advanced treatment unit for phosphorus removal and further water quality improvement of the secondary effluent from urban sewage treatment plants offers advantages such as low head loss, high degree of automation, and reduced land use, making it an economically viable process.