SECONDARY USE OF ACIDS AND ALKALIS FOR WASTEWATER TREATMENT

Revision Date: 10/01
Process Code: Navy/Marines: SR-15-99; Air Force: FA09; Army: N/A
Usage: Navy: Medium; Marines: Low;
Army: Medium; Air Force: Medium
Compliance Impact: Medium
Alternative for: Use of Virgin Chemicals for Neutralization
Applicable EPCRA Targeted Constituents: Sulfuric Acid (CAS: 7664-93-9), Sodium Hydroxide (Solution) (CAS: 1310-73-2)
Overview: The secondary use of acids and alkalis as treatment chemicals in an Industrial Wastewater Treatment Plant (IWTP) is a method to reduce the disposal of used or excess acids and alkalis as hazardous waste. The secondary use of acids and alkalis can reduce problems associated with disposal of acid and alkali waste streams, such as the high cost and the liability of normal waste disposal.

Activities that generate appropriate secondary use acids and alkalis include pickling baths, rinsewaters, metal plating operations, battery shop effluents, and boiler cleaning operations. In addition, expired shelf life materials may also be used as treatment chemicals in an IWTP. These secondary use acids and alkalis can replace treatment chemicals such as sulfuric acid and sodium hydroxide in chromic reduction, cyanide oxidation, metal precipitation, and neutralization processes in an IWTP.

Prior to implementing an acid and alkali secondary use program, tests must be conducted to establish the viability of each wastestream. In addition, the IWTP processes must be evaluated to ensure that the addition of the secondary use material to the wastewater will not interfere with the present design and operation of the treatment plant. Similarly, the program must operate without disrupting normal shop operations.

If use of the material is feasible, the lab should establish mixture ratios for the plant operators. The plant operator then uses the secondary use acids and alkalis in the batch processing of wastewater.


Compliance Benefit: The use of excess and expired acids and alkalis for wastewater treatment will decrease the amounts of these chemicals going out as waste. The decrease in hazardous waste helps facilities meet the requirements of waste reduction under RCRA, 40 CFR 262, Appendix, and may also help facilities reduce their generator status and lessen the amount of regulations (i.e., recordkeeping, reporting, inspections, transportation, accumulation time, emergency prevention and preparedness, emergency response) they are required to comply with under RCRA, 40 CFR 262. In addition, since excess and expired acids and alkalis are used instead of purchasing new product, the possibility a facility will meet any of the reporting thresholds of SARA Title III for those chemicals (40 CFR 355, 370, and 372; and EO 12856) is decreased.

The compliance benefits listed here are only meant to be used as a general guideline and are not meant to be strictly interpreted. Actual compliance benefits will vary depending on the factors involved, e.g. the amount of workload involved.


Materials Compatibility:
The IWTP should not use secondary use acids and alkalis for the final pH adjustment prior to discharge due to the amount of metals found in many of the waste streams. The IWTP should stock sufficient commercial process chemicals for use during waste shortages and for final neutralization.


Safety and Health: The safety and health concerns vary with the type of acids/alkalis chemicals being used. Proper personal protective equipment is recommended. Consult your local Industrial Health specialist, your local health and safety personnel, and the appropriate MSDS prior to implementing any of these technologies.


Benefits:
  • Secondary use of acids and alkalis in the IWTP eliminates the need to dispose of these materials as hazardous waste.
  • Reduces the amount of commercial chemicals kept on hand and the problems associated with the purchase and storage of these chemicals.


Disadvantages:
  • The IWTP should not use secondary use acids and alkalis for the final pH adjustment prior to discharge due to the amount of metals found in many of the wastestreams.
  • The use of secondary use acids and alkalis may decrease the amount of wastewater that can be treated in one batch since secondary use acids and alkalis may be dilute and add to the volume in a treatment tank.
  • To be cost effective, the facility must have a constant supply of secondary use acids and alkalis in a substantial volume.


Economic Analysis: Savings may result from the secondary use of acids and alkalis. The purchase of commercial chemicals will drop, as will the amount of used/excess material requiring disposal. As demonstrated in the example below, the majority of the savings would be the result of less waste being disposed of as hazardous and therefore, the economic benefit is a cost avoidance. Unfortunately, the actual cost savings can be significantly affected by several factors such as those discussed in the "Disadvantages" section above. The following cost comparison is based on information provided by the Navy Public Works Center in Norfolk, Virginia:

Assumptions:

  • Ten 50,000-gallon batches of wastewater are treated annually
  • 20 gallons of sulfuric acid are required per batch
  • 50 gallons of sodium hydroxide are required per batch
  • Sulfuric acid costs $0.70 per gallon
  • Sodium Hydroxide costs $0.70 per gallon
  • 10 man-hours are required per batch to maintain IWTP using virgin chemicals
  • 10 man-hours are required per batch to maintain IWTP using secondary use chemicals
  • $45 average hourly rate for plant operator
  • 90% of acid and alkali can be replaced with secondary use chemicals and the processes that produce these chemicals can provide a constant supply of acids and alkali that are not so dilute as to change the volume of wastewater that can be treated at one time
  • $6,000 is required for start up costs (SOPs and testing)
  • $2.85 per gallon to dispose of acid and alkali as a hazardous waste

Annual Cost Comparison for Use of Acids and Alkalis in an IWTP vs. Commercial Chemicals

 

Secondary Use Chemicals

Commercial Chemicals

Capital and Installation Costs $0 $6,000
Operational Costs:    
Labor: $4,500 $4,500
Chemical Cost: $50 $490
Hazardous Waste Disposal: $0 $2,000
Total Operational Costs: $4,550 $6,990
Total Income: $0 $0
Annual Benefit: -$4,550 -$6,990

Economic Analysis Summary

    Annual Savings for Secondary Use: $2,440
    Capital Cost for Diversion Equipment/Process: $6,000
    Payback Period for Investment in Equipment/Process: <1 year

Click Here to view an Active Spreadsheet for this Economic Analysis and Enter Your Own Values. To return from the Active Spreadsheet, click the reverse arrow in the Tool Bar.


Approving Authority: Approval is controlled locally and should be implemented only after engineering approval has been granted. Major claimant approval is not required.


NSN/MSDS:
Product NSN Unit Size Cost MSDS*
None Identified     $  


*There are multiple MSDSs for most NSNs.
The MSDS (if shown above) is only meant to serve as an example.


Points of
Contact:		 Navy:
Mr. Eddie Corl
Plant Chemist
Naval Operations Base
Norfolk Naval Shipyard
9742 Maryland Avenue, Building C-140
Norfolk, VA 23511-3095
Phone: (757) 445-8850
FAX: (757) 396-1242


Vendors: This is not meant to be a complete list, as there are other manufacturers of this type of equipment.

National Concrete Products
P.O. Box F
Greenwood,  DE   19950
Phone: (302) 349-5528 
FAX: (302) 349-9435
Contact: Mr. Mac McCombs


Sources: Mr. John Bunn, Navy Public Works Center, Norfolk, Virginia, March 1999.
Mr. Otis Carter, Naval Depot, Norfolk, IWTP, June 1997.
Mr. Joe Olson, Navy Public Works Center, Naval Air Station North Island, June 1997.
Mr. John Vanname, Naval Amphibious Base Little Creek, June 1997.


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