Sulfuric Acid Neutralization and Concurrent
Sulfate Removal by Precipitation with Barium
PAUL H. KING, Professor of Sanitary Engineering
Virginia Polytechnic Institute and State University
Blacksburg, Virginia 24061
LOWELL R. NORRIS, III, Lieutenant
Civil Engineering Corp., United States Navy
Norfolk, Virginia 23711
CLIFFORD W. RANDALL, Professor of Sanitary Engineering
Virginia Polytechnic Institute and State University
Blacksburg, Virginia 24061
INTRODUCTION
Stringent enforcement of water quality standards has frequently forced industry to
seek new technology for reducing the concentrations in wastewater effluents of substances
heretofore considered capable of exerting relatively minor degradational influences on the
quality of surface waters. One such constituent which has historically received little attention is the sulfate ion. Sulfates are frequently discharged in high concentrations from a
variety of industrial operations which use sulfuric acid in large quantities. Examples of such
industries are steel mills, texile processing and finishing plants, and munitions
manufacturing operations. In most situations of this type, sulfuric acid wastewater is
neutralized and discharged without attention being given to the sulfate concentration of the
effluent. The work described herein was aimed at developing a process that would
accomplish sulfate removal concurrent with neutralization and would at the same time
result in a sludge having satisfactory dewatering properties.
Some precipitation of sulfate ions in solution can be accomplished using a variety of
cation agents, but from a practical standpoint the precipitation of barium sulfate is
advantageous since this material has a significantly lower solubility than any of the other
common sulfate salts. Two methods of removing sulfates from sulfuric acid wastewater
were investigated. Each one involved eventual addition of barium carbonate and
subsequent precipitation of barium sulfate. Among the process parameters evaluated were
required barium carbonate dosage, mixing conditions, solids separation, and dewatering
properties of the resulting sludge.
PREVIOUS STUDIES
Although concern over sulfates as pollutants has been moderate, it has been recognized
that the introduction of sulfates into the aquatic environment disrupts the biotape and
creates difficulty for other water users. Turbidity, taste, odor, toxicity problems, and
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