Environmental Fate of NTA
BRUCE C. FERGUSON, Microbiologist
RUSSELL L. TODD, Microbiologist
HARVEY W. HOLM, Microbiologist
JOHN D. POPE, JR., Microbiologist
Water Quality Office, EPA
Southeast Water Laboratory
National Pollutants Fate Research Program
Athens, Georgia
HENRY J. KAMA, Research Assistant
University of Georgia
Savannah River Ecology Laboratory
Aiken, South Carolina
INTRODUCTION
The increased rate of eutrophication in our streams and lakes has caused
increased concern for more control of water pollution. Experts are seeking ways to
reduce pollution loads and types of pollutants which contribute most to eutrophication. One of the most widely-discussed pollutants is phosphate. Along with industrial
effluents, agricultural runoff and human wastes, phosphates in detergents constitute
a major source of phosphates in our nation's surface waters. The amount of
phosphate in municipal sewage contributed by detergents is estimated as high as 70
percent. Obviously, something must be done to reduce or eliminate these high
concentrations. Substitutes for detergent phosphates with other compounds have
been proposed as a means of deterring eutrophication. Nitrilotriacetic acid (NTA),
one of the proposed compounds, has become a source of considerable controversy.
Epstein (1) stated that oxygen, acclimated organisms, warm temperatures, low
hydraulic loads, and low concentrations are necessary for biodegradation of NTA.
Bouveng (2) concluded that the organisms responsible for degrading NTA at 5
C and 20 C were different types, and changes in temperature would result in a new
acclimation period being needed.
Pfiel and Lee (3) demonstrated that the acclimation of organisms to NTA was
not permanent and organisms which initially acclimated to NTA in one week
required varying periods of time to reacclimate with varied removal times of and
re-exposure to NTA.
Thompson and Duthie (4) found NTA to be metabolized to CO2, H2O, and
inorganic nitrogen by both wastewater and river water microorganisms at rates
comparable to those of glucose and citric acid. These rates of NTA removal from the
sludge systems were found to be 100 percent after 23 hours of aeration, and 90
percent after six hours of aeration. Swisher, et al, (5), using a fill-and-draw (24 hour)
cycle and continuous-flow activated sludge units, found that both NTA and NTA-Fe
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