DYE WASTEWATERS
ALTERNATIVES FOR BIOLOGICAL WASTE TREATMENT
Dennis W. Weeter, Associate Professor
Department of Civil Engineering
The University of Tennessee
Knoxville, Tennessee 37916
A. Gale Hodgson, Chemist
Tennessee Department of Public Health
Knoxville, Tennessee 37920
INTRODUCTION
Textile mills are usually located in or near small- to medium-size communities in the
southeastern states.   There are three such textile mills located in a small community in
Tennessee, and between them they make up the major portion of wastewater flow to
their activated sludge wastewater treatment plant (WWTP).   The WWTP is unable to reduce
the suspended solids and color to an acceptable discharge level.
One textile mill is interested in what action can be pursued to achieve an acceptable
discharge level.   This textile mill uses  6 dyes in their dyeing operation, the concentration
of each dye being varied within the operation according to the intensity of color required.
The dye wastewater is diluted to a 1:7 ratio within the mill and again diluted to a 1:3
ratio with the other textile mills and domestic wastewater at the WWTP.
Because the available treatment is biological in nature and for economic reasons, the
initial investigation will be by biological applications.   The objective of this study is to
evaluate the 6 dyes using biological applications.   The dye will be investigated at concentrations above and below the ratios within the textile mill and at the treatment plant.
The main concern of the study will be the removal of color and the organic loading
associated with the dyes.
The initial study was to evaluate the degradability of each dye by determining the
amount of oxygen uptake by long-term biological oxidation processes.   Each dye was
analyzed for metal concentrations and the possible introduction of toxic or inhibitory
ions.   Bioadsorption of the dyes and color reduction was investigated by using both an
acclimated and a nonacclimated sludge.
LITERATURE REVIEW
Treatment of wastewaters from textile dyeing operations are characteristically high in
color and organic content.   Most textile wastewater treatment plants employ an aeration-
type wastewater treatment, which uses extended aeration periods to combat waste variability, hard-to-biodegrade compounds, high pH values and alkalinity, high chlorides,
bleaches or oxidants, colloidal color, trace metals, and possible toxicants.   Earlier work
emphasized the removal of biochemical oxygen demand (BOD), but recently the major
concern has shifted to the removal of chemical oxygen demand (COD), suspended solids
(SS), color, and colloid size particles.