Section Six
PROCESSES AND PRODUCT DEVELOPMENT
48    AMMONIA REMOVAL FROM WASTEWATER
BY STEAM STRIPPING:
A PROCESS EVALUATION
G. B. Wickramanayake, Principal Research Scientist
S. Khabiri, Researcher
E. A. Voudrias, Research Scientist
Environmental Science Department
Battelle Memorial Institute
Columbus, Ohio 43201
INTRODUCTION
The extraction of metal values from some ores requires the use of hydrometallurgical techniques
which employ ammoniacal lixiviants. The metal values are recovered from the pregnant liquors,
leaving an aqueous wastewater which is high in dissolved solids and ammonia. This wastewater
requires treatment for removal of the ammonia, as well as the dissolved solids to meet the discharge
standards required under the Effluent Guidelines for the Nonferrous Metals Industry.
The possible methods of removing ammonia from wastewaters include biological nitrification-
denitrification, break point chlorination, evaporation, reverse osmosis, ion exchange, air stripping,
and steam stripping. The present study is focused on steam stripping which has been reported to be
capable of removing over 99% of ammonia in high-strength industrial wastes.1 The EPA Draft
Development Document for Effluent Guidelines for the Miscellaneous Nonferrous Metals Industry2
also identified steam stripping as generally more suitable than air stripping in treating highly concentrated ammonia wastes generated by the metals smelting and refining industry.
OBJECTIVES
Low pH and high dissolved solids are characteristics of non-ferrous metal industry wastewaters that
contain high levels of ammonia. In practice, the wastewater pH is raised by adding lime (CaO) or
caustic (NaOH) to increase the concentration of free ammonia that can be removed during the
stripping process. One of the objectives of this paper is to compare the effects of these pretreatment
methods on different wastewaters.
The variability of wastewater composition has a significant effect on the overall treatment process.
It is believed that some anions, especially sulfate and fluoride ions which vary widely from one waste
stream to the other, are of importance in selecting an appropriate pretreatment method. The objectives of this paper include determination of the effects of change in anionic composition and concentration on the ammonia removal process.
Because of the variability of wastewater characteristics from one stream to another, establishment
of the effects of different ionic strengths and compositions and the pH adjustment methods on
ammonia removal process for different wastewaters by experimental studies does not seem to be
practical. One alternative is to analyze the effects of different waste characterisitics on ammonia
removal by employing a computer code that is capable of modeling the changes in physical and
chemical characteristics of these systems. The objectives of this study also included identification of a
suitable chemical speciation and reaction-path model and application of the model to a set of representative waste streams.
43rd Purdue Industrial Waste Conference Proceedings, © 1989 Lewis Publishers, Inc., Chelsea, Michigan 48118.
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