Physical, chemical and biological treatment of textile wastewater for removal of dyes and heavy metals

Abstract

The water consumption by textile industries is millions of gallons per day. Discharge of untreated wastewater causes environmental, health, and aquatic life problems. This study aims to remove the dyes and heavy metals in textile wastewater by three different methods. In physical treatment, adsorption includes rice husk and sawdust and coagulation includes lime and alum, in chemical treatment AOPs and biological treatment Pistia stratiotes and Eichhornia crassipes macrophytes were utilized. Results showed that the maximum removal efficiency of azo dyes AY-17, AY-36, DY-4, DR-28, EBT, AB-1 was 35 %, 87 %, 89 %, 95 %, 94 %, 78 % and basic dyes MV-10B, BG-4, BB-9 was 80 %, 76 %, 94 % and reactive dyes RO-4, RO-16 and RB-5 was 89 %, 78 %, 95 % after physical treatment. The maximum removal efficiency of heavy metal Cu was detected 28.46 % with alum compared to other materials used in the physical treatment. The maximum removal efficiency of azo dyes AY-17, AY-36, DY-4, DR-28, EBT, AB-1 was 74 %, 91 %, 94 %, 88 %, 89 %, 92 % and basic dyes MV-10B, BG-4, BB-9 was 89 %, 87 %, 94 % and reactive dyes RO-4, RO-16 and RB-5 was 82 %, 68 %, 86 % after chemical treatment. H2O2/O3 and ozonation yielded a maximum removal efficiency of 31.35 % and 26.36 %, respectively, for Cu metal after chemical treatment. The maximum removal efficiency of azo dyes AY-17, AY-36, DY-4, DR-28, EBT, AB-1 was 62 %, 78 %, 80 %, 92 %, 89 %, 69 % and basic dyes MV-10B, BG-4, BB-9 was 90 %, 80 %, 80 % and reactive dyes RO-4, RO-16 and RB-5 was 90 %, 84 %, 62 % after biological treatment on dilutions. The maximum removal efficiency of Zn was 69.4 %, 53.5 %, and 61.7 % with Eichhornia crassipes, Pistia stratiotes, Pistia stratiotes + Eichhornia crassipes respectively. Overall, the biological treatment showed the best results for the removal of dyes and heavy metals so for this reason, this technique could be integrated into the industrial management plan for treating wastewater.