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Hitachi

Hitachi Infrastructure Systems (Asia) Pte. Ltd.

Overview

This compact system uses membranes to treat drinking water with high efficiency and provide clean water.

Features

  1. High-quality, safe treated water
    Combining back pressure washing and air scrubbing/washing makes physical washing possible, and the system can be stably operated for a long period of time.
  2. Clean treated water
    The system of course removes E. coli and bacteria, but also removes cryptosporidium and viruses.
  3. Conserves space
    There is no need for floc formation tanks, sedimentation tanks, or sand filtration tanks that are necessary for drinking water treatment equipment that uses the coagulation sedimentation method, so this system conserves space.
  4. Easy pre-treatment
    Using an external pressure-type module creates a large gap between the casing, so pre-treatment is easy and the system can handle raw water with high turbidity.
  5. Reduced operating cost
    This is a full filtration system, so no power is needed for circulation, which reduces the power cost.
  6. Operation is easy to manage
    Fully automatic operation is possible, so operation is easy to manage.
  7. Construction time can be shortened
    Unitizing the equipment reduces the on-site work and shortens construction time.

(in-house comparison)

System & device summary

Image: Membrane-type drinking water treatment device

Our membrane system is different from other systems in these respects:

Our membrane system

Water pass-through system

Image: Water pass-through system

External pressure system
Water flow: Flows from the outside of the membrane to the inside
Suspended matter: Adheres to the outside of the membrane
  • There is a large gap between the casing and the membrane, so pre-treatment is easy and the system can handle raw water with high turbidity.
  • There is a large membrane area per membrane module unit of volume.

Operating system

Full filtration (dead-end) type
The full amount of water is filtered, without circulating membrane supply water.

Image: Operating system

Washing system

Image: Back pressure washing system

Back pressure washing system
Reversing the treated water from the inside of the membrane to the outside knocks out the contaminants clogging the fine holes of the membrane and the contaminants on the surface of the membrane.

Image: Air washing system

Air washing method (air scrambling)
Sending air from the bottom of the membrane module causes the sides of the membrane (configured in a U-shape) to rub together, which knocks off the contaminants from the surface of the membrane.
  • Combining the two methods thoroughly washes the membrane.

Membrane material

Polyacrylonitrile
We use polyacrylonitrile (PAN) because it can be used in a wide pH range and doesn't degrade due to hydrolysis or bacterial attacks.

Competitors' membrane systems

Water pass-through system

Image: Water pass-through system

Internal pressure type
Water flow: From the inside of the membrane to the outside
Suspended matter: Adheres to the inside of the membrane
  • Sufficient pre-treatment is required to prevent clogging.
  • Sufficient care needs to be taken when using this on raw water with high turbidity.
  • There is a large membrane area per membrane module unit of volume.

Operating system

Circulation filtration (cross-blow) type
In this system, a flow is created parallel to the membrane surface, and filtration is performed while controlling the build-up of suspended solids from the membrane supply water along the membrane surface.

Image: Operating system

Washing system

Raw water is flushed along the outside of the membrane, which knocks off contaminants adhering to the membrane surface.

Image: Back pressure washing system

  • Back pressure washing system

Membrane material

Cellulose acetate
This is an organic membrane, so the membrane may become degraded by hydrolysis or bacterial attacks.

Applications

  • Drinking water treatment plant