Abstract
The use of readily available water treatment residuals (WTR) as a low-cost material for removal of colour from real textile wastewater was investigated. WTR was used in three forms, namely in raw wet form as a coagulant, in the dried form as an adsorbent and as a filtration media in column tests. The results showed a maximum colour removal of 55 and 36% by coagulation and adsorption, respectively, and the corresponding COD removals were 35 and 37%. Coagulation and batch sorption tests showed the effect of initial pH on the colour removal, and maximum colour removal was obtained at an initial pH of 3.0. Long-duration continuous-flow column test using WTR as a filtration/sorption media showed that a maximum colour removal of 60% can be achieved. In column studies, complete exhaustion of the media occurred at 180 and 120 bed volumes, respectively, for initial pHs of 3.0 and 6.2. The study thus shows the potential of WTR for primary treatment of real textile dye wastewater.
Highlights
With the increasing demand for textile products, management of huge quantity of textile and dyeing wastewater generated from textile industries has become a major concern as it contains a variety of pollutants and toxic substances such as dyes (Kadam et al 2015)
Most of the studies reported are based on alum-based water treatment residuals (WTR), but the present study was carried out employing polyaluminium chloride (PACl)-based WTR
Shi et al (2007) investigated the colour removal performance with different aluminium species and found that coagulation efficiency significantly increased with decrease in pH and complete dye removal was obtained at sufficiently lower pH of 5.6
Summary
With the increasing demand for textile products, management of huge quantity of textile and dyeing wastewater generated from textile industries has become a major concern as it contains a variety of pollutants and toxic substances such as dyes (Kadam et al 2015). The synthetic origin of dyes to produce strong fastness has produced several detrimental effects on the environment and human health. Very low concentration of dyes in water makes water highly coloured and unpleasant (Paz et al 2017; Sultan 2017), and the discharge of coloured wastewater and their metabolites in aquatic ecosystems reduces sunlight penetration to cause inhibitory effects on photosynthesis (Hassine et al 2016). Several treatment processes used for colour removal are based on physiochemical and biological processes. Compounds produced when textile wastewater undergoes anaerobic degradation for colour removal are reported to be toxic, carcinogenic and mutagenic (Paz et al 2017; Ponraj et al 2017).
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