Many users frequently encounter issues such as loose, friable sludge cakes and high moisture content when using filter press.
The failure of a filter press to form a proper sludge cake is generally not due to the equipment itself; in most cases, it is most often caused by issues related to feed concentration, chemical,pressure, filtration time, or filter cloth.
1.Feed sludge concentration is too low.
Reason: The sludge contains excessive moisture and insufficient solids; the slurry is too dilute. Therefore, after entering the filter chamber, there is an inadequate volume of solid material to accumulate and compact effectively, resulting in a sludge cake that is soft and lacks structural integrity after filtration.
Performance: The discharged sludge cake is thin, exhibits high moisture content, crumbles easily when squeezed, and feels excessively soft.
Solution: Before entering into the filter press, concentrate the raw liquid to reduce its water content and increase the sludge feed concentration, thereby bringing it within a reasonable range of solids content. Additionally, extend the feeding duration to ensure the filter chamber is thoroughly filled with sludge.
2.Flocculant mismatch
Reasons:
1. The PAM dosage is too low, the sludge flocculation is poor, resulting in small and loose flocs.
2. The PAM dosage is too much, the sludge becomes viscous and the flocs become excessively large, resulting in reduced permeability.
3. A mismatch in PAM dissolution concentration or uneven agitation,resulting in incomplete dissolution.
4. The selection of PAM is incorrect; the cationic or anionic type does not match the specific characteristics of the sludge.
Performance:Solid-liquid separation is poor, and the sludge cake is loose and lacks firmness.
Solutions:
1. Select the appropriate type of flocculant based on the specific characteristics of the sludge.
2. Maintain the chemical solution concentration within the range of 0.1% to 0.3%, ensuring thorough mixing.
3. Conduct on-site testing to adjust the dosage—using the formation of compact flocs and clear effluent as key criteria—thereby ensuring a complete reaction between the PAM and the sludge.
3.Insufficient filtration pressure; inadequate squeezing force
Reasons:
1. The pressure in the hydraulic system has been lowered, preventing it from reaching the rated pressing pressure.
2. Insufficient hydraulic oil, impurities in the hydraulic oil, aging of the oil pump and piping, or pressure leakage in the hydraulic cylinder are causing insufficient pressure.
3. The secondary pressing mode of the diaphragm filter press has not been activated.
Performance:The surface of the sludge cake is dry, yet its interior remains wet and loose; its compactness is extremely poor.
Solutions:
1. Adjust the working pressure of the filter press to within its standard operating range.
2. Inspect the hydraulic circuit, seals, and hydraulic fluid to identify and troubleshoot any issues related to pressure loss or oil leakage.
3. Activate the secondary pressing mode on the diaphragm filter press to ensure thorough dewatering.
4.Pressing time is too short
Reason:In order to meet the schedule, the sludge was discharged before the rated pressing time had elapsed; consequently, the dewatering and consolidation process remained incomplete, and the internal moisture had not been fully expelled.
Performance:The moisture content of the sludge cake fails to meet standards; it is soft and cannot detach as a single, intact piece.
Solution:Set an appropriate pressing duration based on the characteristics of the sludge. In the case of highly viscous sludge, the pressing time must be extended accordingly; premature discharge is strictly allowed.
5.Filter cloth clogged; filter cloth model mismatched
Reasons:
1. Prolonged use of the filter cloth can result in its pores becoming clogged by sludge.
2. The mesh count of the filter cloth is too fine, resulting in poor water permeability and preventing the water from draining.
3. After discharging, the filter cloth was not cleaned promptly, and residual sludge clogged the cloth.
Performance:Slow feeding, low water discharge, and the sludge cake is dry on both sides but wet in the middle.
Solutions:
1. Regularly flush the filter cloth from both sides using a high-pressure water gun.
2. Regularly inspect the filter cloth; if severely clogged, replace it immediately.
3. For sludge containing a high proportion of fine particles, a filter cloth with good permeability should be selected.
6.Filter plate deformation and poor sealing
Reasons:
1. Prolonged use in a high-temperature, high-pressure environment will result in the deformation of the filter plates.
2. Foreign matter is lodged between the filter plates, resulting in improper sealing; consequently, the compression stroke fails to reach its full extent, and the filter chambers do not close tightly.
Performance:Sludge leakage from the sides, filter media loss, failure to fill the filter chambers, and incomplete, loose sludge cakes.
Solutions:Clear debris from the contact surfaces of the filter plates and replace any deformed plates to ensure the filter press is fully compressed and closed.
7.The filter media contains excessive oil and organic matter
Reason:Oily sludge and biochemical sludge—generated by industries such as kitchens, and petrochemicals—are characterized by high organic content.
Because grease encapsulates the solid particles, it is difficult for moisture to separate out; Therefore, these sludge is highly prone to failing to form a cohesive sludge cake.
Solutions:
1. Add lime, fly ash, and other materials to condition the sludge.
2. Using demulsifying flocculants to break down oil and colloids, reduce the feed rate, and extend the pressing and holding time.
8.Excessive feed rate
Reason:If the feed pump flow rate is excessive and the pressure is too high, the feed will surge directly into the filter chamber; this disrupts and scatters the already formed sludge cake, resulting in a loose structure that fails to consolidate properly.
Solution:Initially, feeding is conducted at low speed and low pressure; once the filter chamber is filled, the pressure is gradually increased and stabilized to complete the dewatering process safely and smoothly.
9.Effects of ambient temperature and sludge PH
Reasons:
1. In low-temperature environments, sludge activity is relatively poor, and flocculation performance is also compromised.
2. Sludge containing strong acids or alkalis disrupts the structure of flocs, resulting in a loose sludge cake.
Solutions:
1. In low-temperature environments, ensure that appropriate thermal insulation measures are implemented for the stock solution.
2. For acidic or alkaline wastewater, PH adjustment procedures must be carried out before entering the filter press.
In actual operation, do not be concerned if you encounter a situation where the filter press sludge cake fails to form properly.
1. First, troubleshoot the four primary issues: sludge concentration, flocculant, pressing pressure, and filtration time.
2. Second, inspect the filter cloth and the filter press’s hydraulic system.
3. Finally, perform conditioning treatment based on the specific properties of the sludge.
If adjustments are made in accordance with these corresponding procedures, the issue can generally be resolved.
