Investigation of Removal Efficiency of Blended Cactus Mucilage and Alum Coagulants In Textile Wastewater Treatment
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Date
2019-06
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Addis Ababa University
Abstract
Textile wastewater treatment is one the most difficult environmental issues because it contains
high color, high suspended solids, chemical oxygen demand (COD), pH, temperature, turbidity
and toxic chemicals. The direct discharge of this wastewater without previous or proper
treatment into the water bodies, like lakes, rivers, etc. pollutes the water affecting directly and
indirectly the water. This indicated urgent need to develop cost effective and efficient treatment
method. In this connection, coagulation is one of the most effective and simple to operate
treatment methods to remove colloidal and suspended solid pollutants of textile wastewaters that
technically need adding of either chemical or natural coagulant. However, use of chemical
coagulants has been criticized to have some limitations. Consequently, recently there is an
interest to replace chemical coagulants by natural materials. The overall objective of this study
was to investigate the removal efficiencies of blended inorganic and natural coagulants namely
alum and cactus mucilage. The evaluation of removal efficiency of the blended coagulants was
done for color, COD, TSS, and TDS before and after treatment. The raw textile wastewater was
collected from Arbaminch textile Investment group. The treatment process was carried out using
a jar test at different coagulant dose, pH and mixing time values for constant other parameters.
The coagulant dose, pH and mixing time were the three factors considered in the treatment
process. The dose of the coagulants were 0.5-3 g per 500ml textile waste water whereas pH was
set at 3-11 and mixing time (flocculation time) 20-60 minutes. The pH was adjusted using
hydrochloric acid and sodium hydroxide (1M). The maximum removal efficiency of the blended
coagulant was obtained at coagulant dose of 1.75g, pH 7 and mixing time of 40minuties for
Color, TSS and TDS removal but 3g, pH 3, 40minutes for COD removal and the removal
efficiency was 74.3%, 73.9%, 62.3, and 74.5 % respectively and from the observed results the
optimum conditions were at 2.194g of coagulant dose, pH 3.840 and 38.992 minutes of mixing
time with rapid mixing 100 rpm for 2 minutes and slow mixing 40 rpm for 20-60 minute and 60
minutes of settling time. At these optimum conditions 74.3 % color reduction, 71.177% COD
reduction, 73.094 % TSS and 62.930 % TDS reduction was obtained.
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Keywords
Blended Cactus, Wastewater Treatment, Textile, Mucilage, Alum Coagulants