PRAB > News & Knowledge > Application Reviews > Battery Recycler Achieves Zero Liquid Discharge (ZLD) and Recovers Over 80% of Concentrate for Resale

Battery Recycler Achieves Zero Liquid Discharge (ZLD) and Recovers Over 80% of Concentrate for Resale

Challenge:

Recover water and Sodium Sulfate from spent sulphuric acid from recycled batteries


Solution:

PRAB EVALED® Vacuum Evaporator (RV F 60 FF)


Results:

Zero Liquid Discharge and recovery of 80% sodium suplhate for resale

Introduction

A company who recycles over 3,000,000 automotive battery units a year, and produced over 40,000 tons of lead every year needed to recover the water and Sodium Sulfate (Na2SO4) coming from the spent sulphuric acid in the batteries, in order to cut costs.

This would cut costs by allowing the company to reuse the wastewater back into the process and it would generate revenue by converting the sodium sulphate into a useful material that could be sold as part of a product for society.

Sodium sulfate is used in many products including home laundry detergents, carpet fresheners, cement, starch, cattle feed additives, and more. About half of the world’s sodium sulfate comes from natural sources, while the other half is a byproduct of other processes, such as battery recycling.

The Solution

Because no two wastewater streams are exactly alike, in order to find the best solution to meet the recycler’s goals, a careful review of their process was completed, along with a thorough testing and analysis of the wastewater. It was then determined that the PRAB EVALED® Vacuum Evaporator would be the best solution.

New Wastewater Treatment Process Implemented

Diagram - Spent Sulphuric acid from batteries is sent to storage basin which is sent to a wastewater inlet (63.7 ton/day or 12 gpm) which is sent to a PRAB Evaled Vacuum Evaporator which creates concentrate (24.2 ton/day) and distillate (39.5 ton/day). The Distillate is recycled and the concentrate is sent to concentrate tanks. From the Concentrate tanks, saturated liquid (28% TS) is sent back to the storage basin while the remaining sodium sulphate salt is sold as a by-product

 

PRAB Evaled Vacuum Evaporator used to treat pickling bath
PRAB EVALED Vacuum Evaporator (RV F 60 FF) installed at recycling facility (226 sq/ft footprint).
PRAB Evaled Vacuum Evaporator used to treat pickling bath
Recovered sodium sulfate. Over 80% of concentrate is now recovered for sale.

 
New Treatment Process Results:

Parameters u.m. Waste In Distilled Out Concentrate Out
pH 6.5 6
TS at 105˚C % 12 <.01 >80
Conductivity µS/cm >100,00 <80
Sulphates ppm >70,000 <50
COD ppm 95 <60
Chlorides ppm 48 13
Lead ppm 1.3 <1.0

 

Results Achieved

  • Zero Liquid Discharge (100% water reuse)
  • Over 80% of Na2SO4 is recovered
  • Na2SO4 is sold to cement factory
  • Dramatic cost reduction

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