Textile dyeing in Mali : possibilities for small scale effluent treatment
Water treatment is an important issue in Mali, an arid country where the Niger River is the main recipient for a large part of the effluents from industrial and small scale activities. Clothes dyed with synthetic dyestuffs are an important part of the culture in Mali. Dyeing of textiles is to a larg...
| Autor principal: | |
|---|---|
| Formato: | H2 |
| Lenguaje: | Inglés francés |
| Publicado: |
SLU/Dept. of Soil and Environment
2009
|
| Materias: |
| Sumario: | Water treatment is an important issue in Mali, an arid country where the Niger River is the main
recipient for a large part of the effluents from industrial and small scale activities. Clothes dyed with
synthetic dyestuffs are an important part of the culture in Mali. Dyeing of textiles is to a large extent
an informal activity, mainly performed by women.
The objective for this thesis work was to investigate potential capacity of cheap, locally accessible
materials in treatment of effluents from textile dyeing. Effluents studied were sampled at three sites
with small scale textile dyeing in Bamako, Mali. At two sites the effluents were emitted directly to
the Niger River, at the third site the effluents were collected in a soakaway. The capacity of different
materials, both coagulants and adsorbents, to treat the effluents was analysed with jar tests. pH,
conductivity, total dissolved solids (TDS), turbidity and dissolved oxygen (DO) were analysed on
samples before and after jar tests, and on river water from spilling site. For some jar tests, UV-Vis
spectra and content of zinc, nickel and copper were analysed. Properties of dyestuffs were analysed
with spectrophotometry, scanning electron microscopy (SEM) and nuclear magnetic resonance
spectroscopy (NMR).
Iron(III) chloride coagulated dye effluents, efficiently removing most of the colour from water.
Activated carbon, both in granulated form and in the form of powder, showed some capacity to
adsorb compounds in dye effluents. Rice chaff, rice bran, laterite, bentonite and aluminium sulfate
did not show capacity to remove dyes from effluents.
The composition of the dyestuffs used in small scale dyeing is not known, which is a serious
problem when developing treatment methods. A significant fraction of the dyestuffs consists of
substances which are not part of the colour-yielding dye. Five dyestuffs with different colours were
analysed with SEM with X-ray fluorescence detector. These dyestuffs contained, except for carbon,
oxygen and nitrogen which can not be detected, mainly sulfur, chloride, sodium and, in the case of
green, barium. Traces of chromium, vanadium, iron, aluminium and silicon were also detected in
some of the dyestuffs. Mixed effluents from two sampling sites contained concentrations of zinc
and nickel higher than WHO guideline values for drinking water.
Further studies are needed to find a cheap treatment method since low cost materials such as
rice bran and laterite are ineffective. In addition to be able to remove polluting substances from dye
effluents, the method should include cheap and readily accessible materials, and be supported by an
infra-structure which allows the effluents to be treated locally. To find a working solution to decrease
water pollution, without threatening the livelihood for dyers, co-operation between universities,
dyers and governmental bodies is crucial. |
|---|