PRESSURE BAG FILTERS

Pressure bag filters are compact, replaceable filter systems used to retain particles or suspended solids in water and chemical solutions.
Overview

Pressure bag filters are compact, replaceable filter systems used to retain particles or suspended solids in water and chemical solutions. However, our company offers this equipment not only for liquid filtration but also as a practical and economical sludge dewatering solution for facilities with low sludge production. Bag filters, which eliminate the high investment and maintenance costs of classical filter press systems, enable easy dewatering of low-flow and low-solids-content sludges. Thus, they can be used as a simplified version of filter presses in small-scale treatment plants, maintenance stations, or pilot systems.

WORKING PRINCIPLE

Pressure bag filter typically consists of a cylindrical pressure vessel and a micron-level porous filter bag (bag filter) placed inside this vessel. Wastewater or sludge is pumped into the vessel. As the flow passes from inside the bag to outside, solid particles inside are retained on the bag surface; the cleaned liquid exits.
IN WATER FILTRATION APPLICATIONS

The bag retains particles in the range of 1–200 microns.

IN SLUDGE DEWATERING APPLICATIONS

The bag is selected to be highly porous and mechanically resistant; while water is discharged, the solid part remains inside the bag and forms a cake.

When the fill rate is reached, the bag can be easily removed, disposed of, or cleaned and reused. Thus, the system operates without needing complex hydraulic equipment or press plates.

DESIGN FEATURES

1. VESSEL AND MECHANICAL STRUCTURE
  • Material Options:

    • AISI 304 / 316 stainless steel

    • Carbon steel (epoxy coated)

    • FRP (fiberglass reinforced polyester)

    • HDPE (high density polyethylene) – corrosion-resistant and lightweight solution

  • Pressure Resistance:

    6 – 10 bar

  • Connection:

    Flanged, clamped, or quick-opening lid (clamp ring)

  • Sealing:

    EPDM, NBR or PTFE gasketed lid system

  • Filter Bag Capacity:

    5 – 200 liters (1 bag, 3 bag or multi-system)

2. FILTER BAG
  • Pilsan
    Material:

    Polypropylene (PP), polyester (PE), nylon or PTFE

  • Pilsan
    Micron Values:

    In the range of 1 – 1000 µm

  • Pilsan
    Structure:

    Sewn or welded, internally supported (metal mesh support)

  • Pilsan
    Durability:

    Up to 90 °C temperature; 3–5 bar operating pressure

  • Pilsan
    Bag Properties Used in Sludge Applications:

    • High-strength "dewatering bag" type is used.

    • Disposable or washable types are available.

    • The bag can be easily removed and squeezed – disposal process can be performed.

3. FILTRATION MODES
  • Pilsan
    Continuous Mode:

    Flow is constant, operates with pressure control (for water filtration).

  • Pilsan
    Batch Mode:

    Operates in specific volumes, stops with fill sensor (ideal for sludge).

USE IN SLUDGE DEWATERING

In small and medium-scale facilities (for example, in systems with 10–100 m³/day flow), classical filter press installation is often not economical. In this case, the bag filter system can operate as a compact dewatering unit.
1
Sludge Preparation

  • Sludge is stabilized with chemical coagulant or polymer.

  • Mixed in the mixing tank for a few minutes.

2
Filtration

  • Prepared sludge is pumped into the bag filter.

  • Water is filtered through bag pores, solid part remains inside the bag.

3
Cake Removal

  • When the fill rate is reached, the bag is removed.

  • Semi-dry sludge in the bag (20–30% dry matter) is disposed of.

4
Reuse

  • The bag can be cleaned or disposed of as single-use.

This method offers a practical solution with much lower investment costs compared to filter press, centrifuge or screw press systems in places such as laboratories, hospitals, small industrial facilities, pilot treatment systems.

ADVANTAGES

  • Multi-Purpose Use:

    Suitable for both water filtration and sludge dewatering.

  • Low Investment and Operating Cost:

    Ideal as an alternative to filter press.

  • Simple Operation:

    Easy control with automatic valves and sensors.

  • Modular Structure:

    Multiple bag vessels can be connected in parallel if desired.

  • Compact Design:

    Can operate in small spaces.

  • Corrosion Resistance:

    Long service life with stainless steel, HDPE or FRP material options.

  • Quick Maintenance:

    Bag replacement can be done in minutes.

  • Low Energy Consumption:

    Only the feed pump uses energy.

  • Quiet Operation:

    No mechanical moving parts.

APPLICATION AREAS

  • Small-scale wastewater treatment plants (10–100 m³/day)

  • Laboratory and hospital treatment systems

  • Industrial pilot or temporary facilities

  • Sludge dewatering after oil separator, grit chamber and chemical treatment

  • Small production lines (food, textile, metal, paint, etc.)

  • Water filtration and process water preparation systems

  • Pre-dewatering line before filter press

CONCLUSION

Pressure bag filters have been developed as a compact, portable and multi-purpose alternative to classical filtration systems. Our company offers these equipment not only for water filtration but also as a low-cost sludge dewatering solution for facilities with low sludge production. Bag filters produced with stainless steel, HDPE, FRP and carbon steel vessel options combine durability, ease of use and economical operation advantages. Thanks to this system, sludge disposal in small facilities has become as simple as a bag change, without needing complex equipment. Pressure bag filters are a modern, efficient and sustainable dewatering solution for small-scale facilities with their compact structure, low cost and high practicality.