Colour removal from biologically treated textile dyeing wastewater with natural and novel pre-hydrolysed coagulants

Abstract

In this paper, natural (chitosan and starch) and novel pre-hydrolysed coagulants (PACl, PAFC, PFS and PFC) were performed with coagulant aid for colour removal from a biologically treated textile wastewater including multiple dyes (indigo and reactive). According to the experimental results, optimum coagulant dosages which provide the best colour removal for PACl, PAFCl, PFS (%10) and PFCl (%10), were determined as 80 mg/L, 10 mg/L, 3 mg/L and 40 mg/L, respectively, at pH 4 and pH 6,98 (natural pH of studied wastewater, pHnww). Maximum colour removal was determined as 97% for PAFCl, minimum removal was 23% for PFCl at pH 4, while it was calculated as 75% and 52% at pHnww. COD removal was observed as 45% at pH 4 and 55% at pHnww for maximum colour removal. Sludge production rate was measured as 71 kg/d while this rate was found as 60 kg/d at pHnww. On the other hand colour removal efficiencies were determined in the range of 55-88% at pHnww and pH 3 for chitosan while it was calculated as 52% for starch at pHnww and pH 9. According to the results, PAFCl and chitosan were found as the best coagulants for colour removal of investigated textile wastewater. According to the economic analysis results, the best colour effiency were found as 97% with PAFCl and the second best colour removal were found as 88% with Chitosan. Due to lower sludge production than PAFCl and lower chemical costs; Chitosan can be considered as a reasonable alternative for this wastewater. © 2018, Turkish Chemical Society. All rights reserved.