The Biodegradability of Synthetic Size Material
Used in Textile Processing
WILLIAM H. HAHN, Project Manager
EDWIN L. BARNHART, President
RICHARD B. MEIGHAN, Project Manager
Hydroscience, Inc.
Westwood, New Jersey 07675
HISTORICAL BACKGROUND
Increasing public concern over water pollution and strict governmental discharge
requirements have made it necessary for many textile mills to investigate methods of
improving their waste treatment practices.
A significant portion of textile waste strength results from desizing operations.
Traditionally, the principal sizing material used was starch. In recent years, however, many
mills have changed to polyvinyl alcohol as a warp size for yarns of the synthetic and cotton-
synthetic blends.
The term "polyvinyl alcohol" is used to describe many grades of the polymer which
may vary widely in composition and properties. In this paper, polyvinyl alcohol refers
specifically to Elvanol® T-25 (PVA), manufactured by E.I. DuPont de Nemours and
Company.
From a waste treatment standpoint, the use of PVA represented a low-BOD substitute
for starch. PVA has been reported (1, 2) to have a five-day BOD of less than 3 percent of its
theoretical demand while starch is around 50%. It had, therefore, been assumed that PVA
either passed unchanged through the treatment system or was partially adsorbed on the
biomass (3). More recently, several workers (4, 5) have reported laboratory studies which
have shown that acclimated microorganisms are capable of biodegrading PVA. If discharge
regulations were based only on effluent BOD5 concentrations, this would be of little consequence. However, the recently promulgated guideline limitations for the textile industry
(6, 7) which contain specific COD discharge limitations, have made the question of PVA
biodegradation fundamentally important to the textile industry. Existing data is limited
and textile mills are not regularly monitoring PVA through their treatment plants.
Since a number of textile finishing mills discharge their wastes into municipal
treatment systems, a laboratory study examining the biodegradation of PVA in a domestic
waste environment has been reported separately (8). The study undertaken by
Hydroscience, Inc., was designed to better define the mechanisms of PVA removal in a
waste treatment system receiving only textile wastes.
Hydroscience undertook the research study to better define the mechanisms of PVA
removal in a textile waste treatment facility. The basic objectives of the study may be
530