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Solutions for Industrial Water Treatment
Zero Liquid Discharge (ZLD)
– with HERO™(*1)

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Overview

Water scarcity and water pollution are the serious issues being faced by many countries across the world. Recycle & reuse of wastewater is the most prudent solution to this problem. Therefore, some environmental authorities all over the world have instructed industries to introduce Zero Liquid Discharge (ZLD) system.

Toshiba group has a state of the art ZLD system based on HERO™ (*1) technology which provides superior degree of treatment with high efficiency and reduces life cycle cost to conventional systems.

(*1) HERO: High Efficiency Reverse Osmosis

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ZLD: Zero Liquid Discharge

ZLD system may be introduced in cases where water resources are limited, or where environmental sustainability is the priority.

Recycling system by RO (Reverse Osmosis) membrane generates reject water, which is highly concentrated effluent with TDS (Total Dissolved Solid). In most cases such reject water may not be allowed to be discharged. Therefore, industries install evaporators after RO, which evaporate reject water & concentrate salts to dryness. Also, since evaporators being an expensive system, it is a prerequisite to incorporate a high efficiency RO in the ZLD process so as to minimize RO-reject volume and have most optimized size of evaporator installed. This can be achieved by increasing the recovery across RO System in ZLD system based on HERO™ technology.

case study of operational cost

Four Issues in ZLD System with Conventional RO

The ZLD system with conventional RO has scaling & fouling issues which results in increase of feed pressure, decrease in permeate flow, lower permeate quality, frequent RO cleaning, longer downtime and eventually frequent replacement of RO membranes.

1 Hardness Scaling
Precipitation of saturated salts of calcium, magnesium & heavy metals of sulfates, phosphates, carbonates etc. onto the surface of the membrane.
2 Silica Scaling
Precipitation of reactive silica on exceeding its solubility limit on the surface of the RO membrane as conventional RO is operated at neutral or slightly acidic pH.
3 Organic Fouling
Result of deposition of organics, on the surface of the membrane, typically on the feed/concentrate side.
4 Biofouling
Growth of microbes on the surface of the RO membrane causing permanent irreversible damage to the surface of the RO membrane.

Conventionally, to prevent scaling, the RO-feed pH is lowered and antiscalant is dosed. This approach works for preventing hard scaling, but if the recovery rate goes higher, this will not work anymore. Further, lower pH decreases silica solubility and causes silica scaling. For many industrial effluent, some COD (Chemical Oxygen Demand) still remains after biological treatment. In many cases, conventional RO fails to sustainably operate at 80%+ recovery, due to silica and residual COD in the feed water.

Our Solution for ZLD: HERO™ - High Efficiency Reverse Osmosis

HERO™(*3) is the technology which prevents all the scaling/fouling factors (hardness, alkalinity, silica precipitation, organic fouling and bio-fouling) by resins, de-gasser and high pH operation and in turn maximizes recovery across RO System.

(*3) : HERO™ is a registered trademark and is a proven technology with 150+ reference installations worldwide.

In HERO™ system, all the scaling/fouling are eliminated; therefore, the system can maximize the RO water recovery rate up to significantly higher levels.

< Process Description >

Composition of Equipment
composition of equipment image
Lime/Caustic Clarifier and/or Ion Exchange System Degasser Tower or Degassing Membrane High pH RO Operation
Purpose
Hardness Removal (Softening) Alkalinity Removal More than pH 8.5
(Preferably 10 to 11)
To remove Ca, Mg and other heavy metals, which potentially cause scaling in RO To remove carbonic acid which is a cause of carbonate salt scaling in RO To improve silica solubility, to prevent adsorption of organics on RO, to inactivate bacteria, to enhance the zeta potential between membrane and particles
Solve
1. Hardness Scaling
Solve
1. Hardness Scaling
Solve
2. Silica Scaling
3. organic Fouling
4. Bio-fouling
Composition of Equipment composition of equipment image
Lime/Caustic Clarifier and/or Ion Exchange System Degasser Tower or Degassing Membrane High pH RO Operation
Purpose Hardness Removal (Softening) Alkalinity Removal More than pH 8.5
(Preferably 10 to 11)
To remove Ca, Mg and other heavy metals, which potentially cause scaling in RO To remove carbonic acid which is a cause of carbonate salt scaling in RO To improve silica solubility, to prevent adsorption of organics on RO, to inactivate bacteria, to enhance the zeta potential between membrane and particles
Solve
1. Hardness Scaling
Solve
1. Hardness Scaling
Solve
2. Silica Scaling
3. Organic Fouling
4. Biofouling

Comparison between ZLD with Conventional RO System and
ZLD with HERO™ System

HERO™ system lowers the operational cost due to high efficiency, low reject generation and smaller size of evaporator system installed as compared to conventional RO system.

  ZLD with Conventional RO ZLD with HERO™
Recovery Rate

LOW

Normally water recovery rate will be 70 to 80%.

HIGH

More than 90% recovery rate will be achieved. It depends on water condition.
Initial Cost

MODERATE

The larger evaporator size leads to a higher initial cost.

MODERATE

Increased cost by the additional pretreatment system (ion exchange, degasser) and the high pressure RO system, but decreased cost by smaller evaporator and smaller boiler.
Running Cost

HIGH

High steam consumption leads to a very high running cost.

MUCH LOWER

Running cost will be significantly lower than a normal RO system. The initial investment will be recovered in a short period of time.
Daily Inspection

GOOD

MODERATE

Compared to conventional RO, more equipment needs to be checked in daily inspection, but there is no special equipment which requires greater care.
Periodical Maintenance

MODERATE

Scaling/fouling trouble requires frequent RO CIP(Clean In Place). Hardness rich RO reject causes frequent cleaning of the evaporator.

GOOD

Scaling/fouling is prevented in HERO™, resulting in less frequent RO CIP and longer membrane life. Low hardness reject assures stable operation of the evaporator.

Available Area

HERO is enabled in the area where Toshiba group is available for sale except the following field.

  • Microelectronics industry in the whole world
  • Power industry in USA, Mexico, Canada, India
  • Oil refining, petrochemistry facilities owned by Reliance Industries Limited
  • Chinese coal-based chemical, gas and liquids production facilities
  • All Korean cases except the specific non-microelectronics instance
  • All cases of microelectronics in Japan

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Advantages of HERO™

Recovery of More Than 95 % water

Recovery rate of conventional RO system is limited to 70% - 80% depending on the inlet water quality.

We offer HERO™ system for ZLD application which can operate at more than 95%(*2) recovery rate in most cases.

RO system based on HERO™ can reduce reject water to one-fourth (1/4) in volume compared to conventional RO system and thus provide huge operational savings to the end user.

case study of operational cost

Improvement of Reverse Osmosis Membrane Life

Preventing the scaling/fouling factors increases life of RO membrane and decreases system shut down time. It also leads to huge reduction in life cycle cost of the system.

case study of operational cost

*The name of products, services and companies mentioned herein may be trademarks or registered trademarks of respective companies.

*The information contained herein is presented only as a guide for the applications of our products. No responsibility is assumed by Toshiba for any infringements of patents or other rights of third parties which may result from the use of our products. No license is granted or otherwise implied under any patent or patent rights of Toshiba or others.

*Toshiba products should not be embedded in other products for which the production or sale is prohibited by law.

*Toshiba does not assume any responsibility for incidental damage (including business interruption, loss of business information, and other pecuniary damage) arising out of the use or disability to use Toshiba products.

*All information herein is subject to change without notice, including product specifications.

*The products described in this document include products subject to foreign exchange and foreign trade laws.

*The products described in this document contain components made in the United States and subject to export control of the U.S. authorities. Diversion contrary to U.S. law is prohibited.

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Downloads

Zero Liquid Discharge(ZLD) with HERO System Leaflet

Please download Zero Liquid Discharge(ZLD) with HERO System Leaflet of Toshiba.

Zero Liquid Discharge(ZLD) with HERO(TM) System Leafle

SUMMARY

  • 1) Overview
  • 2) ZLD: Zero Liquid Discharge
  • 3) Advantages of HERO

Please download Zero Liquid Discharge(ZLD) with HERO System(PDF:504KB)
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