Section 11.    CHEMICAL WASTES
BIODEGRADATION OF CHEMICAL PLANT WASTEWATER
CONTAINING DIMETHYLFORMAMIDE
John L. Carter, Process Engineer
Black and Veatch, Engineers-Architects
Kansas City, Missouri 64114
David A. Young, Staff Engineer
Bendix Corporation
Kansas City, Missouri 64131
INTRODUCTION
Facilities for polyimide synthesis are being constructed in The Bendix Corporation, Kansas City
Division Chemical Polymer Plant. It will soon be possible to manufacture polyamino bismaleimide
and improved polyimides such as APO-BMI and sulfone BMI. In addition to polyimide resin,
however, the process produced a by-product wastewater containing dimethylformamide (DMF),
acetic acid, and other organics [1]. Initial plans were to dispose of this wastewater first to existing
Bendix lagoons, and subsequently to the Kansas City wastewater treatment plant. However, information obtained from DuPont in June 1980 concerning the "embryotoxicity" and hepatotoxicity [2] of
DMF indicated this disposal method was inadvisable. Therefore, methods to permit economical
disposal of the wastewater by recovery or chemical deactivation of DMF were investigated.
This investigation was concerned with the safe disposal of the wastewater from one reactor batch
(250 kg) of polyimide resin per month. Each batch produced 18,030 kg of wastewater per month. This
amount is equivalent to 25 1/hr. Physical, chemical, and biological removal methods were evaluated.
Investigations of nonbiological treatment of the polyimide wastewater eliminated most of the
available treatment alternatives. Consultation with the activated carbon technical departments of
Calgon and Westvaco indicated that DMF would not be adsorbed very well, if at all. Applications
engineers from DuPont and Envirogenics Systems Company reported that DMF was used as a solvent
in the manufacture of reverse osmosis membranes, causing the membranes to swell or dissolve.
Therefore, neither activated carbon nor reverse osmosis is suitable for treatment of DMF. Rhom and
Haas investigated the possibility of removing DMF with polymeric resins and found that DMF also
would dissolve resins. Biological treatment of DMF appeared to be the most promising. Design of the
treatment system is the subject of this paper.
LITERATURE REVIEW
Analytical Aspects of DMF
Gas chromatography is the most sensitive detection method for DMF and similar compounds.
Carbowax 20M, Tween 80, and LAC-778 columns also were successful in analyzing DMF [3]. Typical
column length was 4 feet, with 25 to 30% of the stationary phase coated on 60/80 mesh acid-washed
Chromosorb W or 60/70 mesh Anakrom ABS support media by Analab. The oven was operated at
130 to 150 F and a 5 /il sample was used. With an LAC-778 column, the practical detection limit for
DMF was 25 mg/1. The minimum detection limit using 20 /il sample volumes was 5 mg/1; however,
column life was very short.
Using the proper column filling, DMA and DMF could be measured [4]. In this study, flame
ionization (FID) and mass spectrometer detectors achieved low detection limits with minimum error.
The maximum error at 50 mg/1 for DMA or DMF did not exceed 15%. The mg/1 level of DMF was
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