BIOLOGICAL TREATABILITY STUDY OF WASTEWATER
FROM A NYLON FIBERS AND PLASTICS FACILITY
Gregory A. Anderson, Laboratory Director
Rivanna Water and Sewer Authority
Charlottesville, Virginia 22903
Gregory D. Boardman, Assistant Professor
Department of Civil Engineering
David A. Wallis, Assistant Professor
Department of Chemical Engineering
Virginia Polytechnic Institute and State University
Blacksburg, Virginia 24061
INTRODUCTION
Allied Corporation's fiber plant at Chesterfield, Virginia, is one of the world's largest producers
of Nylon-6. Nylon-6 refers to a polymeric material, that is manufactured from caprolactam, a cyclic
amide of six carbon atoms, nine hydrogen atoms, and one nitrogen atom. The wastewater generated
at the plant contains rather high levels of organic nitrogen due to the presence of caprolactam, and is
presently handled in a treatment train consisting of three holding ponds and a land application
system. The objective of the work described in this paper was to investigate the feasibility of reducing
nitrogen levels in the wastewater by using aerobic, biological treatment, thereby increasing the life of
the land application system.
There is information in the literature which indicates that caprolactam can inhibit the growth of
microorganisms [1-6]. Also, it has been reported that nitrification is repressed at caprolactam levels
in the area of 100 to 1000 mg/l [6]. At the lower end of the range the process is slightly inhibited, while
at the higher caprolactam levels, virtually no nitrate and little nitrite form. These concepts were
important to consider because if caprolactam levels in the influent streams to the biological reactors of
this study were too high, the treatment processes could be inhibited. In addition, to accomplish the
goals of this study it was necessary to minimize nitrification so that the release of nitrogen from the
wastewater in the form of ammonia volatilized could be maximized.
Others who have studied the biodegradation of caprolactam in aerobic environments have
reported that the compound was most rapidly degraded at pH levels in the aera of 6 to 8.6, and at
temperatures in the area of 33 to 42 C [4,7-10]. Pitter [11] and Livke et al [12] reported that greater
than 90% of the chemical oxygen demand and biochemical oxygen demand could be removed from
caprolactam-containing wastewaters under aerobic conditions. Therefore, some information in the
literature indicates wastewaters containing caprolactam can be treated effectively by means of aerobic
biological processes. This information is rather limited in its usefulness because many of the experiments described were conducted with pure or stream populations of bacteria, and at levels of
caprolactam much lower than those used in this study. The wastewater considered herein probably
contained about 10,000 mg/l of caprolactam.
METHODS AND MATERIALS
This study was conducted in two phases. In the first phase a series of aerobic batch experiments
were performed. In the second phase of the work, aerobic continuous-flow reactors were studied. The
wastewater used in all of the studies was obtained from the storage ponds at the Allied facility and
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