Chrome Removal from Wastewater Using Water Treatment Plant Sludge as An Adsorbent
No Thumbnail Available
Date
2015-06
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
Addis Ababa University
Abstract
Industries produces large amount of waste and the effluent of these wastes are often
hazardous in polluting the environment and affecting human health. Tanneries are among
industries which release large amount of waste which contains hazardous heavy metals such
as chromium. Hexavalent chromium in the environment is often harmful and it should be
treated before releasing to the environment. Chromium carcinogenicity to humans and other
living organisms has promulgated extensive research on its treatment technologies with
varying levels of success.
The present study deals with removal of Cr(VI) by alum based water treatment sludge (Al-
WTS) through batch and fixed bed column study. Response surface methodology (RSM) was
applied in batch wise experiment for designing and analysis of experiment. Cr(VI)
concentration and pH increase, is shown to decrease chrome removal percent, while
adsorbent dose and shaking time increase, is shown to increase chrome removal. Factor
interaction terms: Cr(VI) concentration with pH shows that maximum chrome removal
95.62.1% was obtained at Cr(VI) concentration of 2.4mg/l and pH 2.45, while interaction of
Cr(VI) concentration and adsorbent dose shows, 97.06% chrome removal was obtained at
chrome concentration of 3.3mg/L and adsorbent dose of 6.3g. Interaction of pH and
adsorbent dose also shows that maximum chrome removal 92.2 was obtained at pH 2.44 and
adsorbent dose of 6.17g. Theoretical Langmuir, Freundlich isotherms are subjected to
adsorption data to estimate adsorption capacity. The results gained from this study were well
described by the theoretical Langmuir and maximum adsorptive capacity of 33.33mg/g was
obtained.
The removal of Cr(VI) by Al-WTS was also investigated in a fixed bed column study.
Experiments were conducted to study the effect of bed depth (10–30cm), flowrate (5–
15mL/min) and initial concentration (10-30mg/L). The column data was fitted by BDST,
Thomas and Yoon-Nelson models. Adsorption capacity increases with increase in initial Cr(VI)
concentration and bed depth. Thomas model well fits the experiment and gives high
adsorptive capacity of 14.8mg/L. Al-WTS was used for the Cr(VI) removal from tannery
wastewater in fixed bed column study and showed a high potential for the wastewater
treatment.
Key words: Alum based water treatment sludge, batch adsorption, response surface
methodology, Cr(VI), fixed bed column
Description
Keywords
Alum based water treatment sludge, Batch adsorption, Response surface methodology, Cr(VI), Fixed bed column