66    SODIUM SULFIDE/FERROUS SULFATE METALS
TREATMENT FOR HAZARDOUS WASTE
MINIMIZATION
Charles Carpenter, Environmental Research Engineer
Air Force Engineering and Services Center
Tyndall Air Force Base, Florida 32403
Dan Suciu, Research Specialist
Penny Wikoff, Research Specialist
EG&G Idaho
Idaho Falls, Idaho 83415
INTRODUCTION
Electroplating facilities for the Air Force range from small operations with one or two baths
(500-1500 gallons) to shops with over 40,000 square feet of tank space.1 The principal contaminants
in the wastewater from these processes are chromium, nickel, copper, cadmium, lead and zinc.
Complexing and chelating agents are added to metal finishing solution for brightening, cleaning, and
to inhibit or prevent precipitation of the metals. These agents include tartrates, phosphates, ethylene-
diaminetetraacetic acid (EDTA), and ammonia.2
These metals and other chemicals are carried into the rinse water, which must be treated at the
Industrial Waste Treatment Plant (IWTP) at the Air Logistic Centers (ALC) on five Air Force Bases
(AFB). The 1988 and 1989 discharge limits for the IWTP at Tinker AFB for the metals of concern are
listed in Table I. The effluent from the IWTP must meet these limits to comply with the National
Pollutant Discharge Elimination (NPDES) Permit.3 As seen from Table I, discharge limits are becoming more stringent, making them harder to meet.
Conventional treatment methods for these wastewaters result in the generation of large quantities
of sludge. The sludges require special handling and costly disposal at approved hazardous waste
disposal facilities. These costs are rising continuously. Tinker AFB was paying $168 per ton one year
ago. They now pay $220 per ton. This is an increase of over $110,000 per year for that facility. Costs
are expected to continue to rise as more stringent regulations are promulgated. Sludge reduction can
decrease these costs to manageable levels. Methods of reducing the sludge include reduction amount
of wastewater, treatment optimization, plating chemical conservation, and sludge dewatering.
A program was initiated by the Air Force Engineering and Services Center under contract to EG&G
Idaho to determine the feasibility of the use of sodium sulfide and ferrous sulfate to reduce the
hexavalent chromium, precipitate the metals, and decrease sludge production and chemical usage.
Table I.   Tinker AFB NPDES Permit Requirements
Constituent
Cadmium, total
Chromium, total
Chromium, hexavalent
Copper, total
Lead, total
Nickel, total
Zinc, total
44th Purdue Industrial Waste Conference Proceedings, © 1990 Lewis Publishers, Inc., Chelsea, Michigan 48118.
Printed in U.S.A.
617
Concentration
(mg/L)
1988
1989
0.03
0.02
1.0
0.1
0.1
0.01
0.1
0.05
0.1
0.1
1.0
0.5
1.0
0.6