Today\u27s chemical and physical-chemical wastewater discoloration methods do not completely meet demands regarding degree of discoloration. In this paper discoloration was performed using Fenton (FeSO4 · 7 H2O + H2O2 + H2SO4) and Fenton-like (FeCl3 · 6 H2O + H2O2 + HCOOH) chemical methods and physical-chemical method of coagulation/flocculation (using poly-electrolyte (POEL) combining anion active coagulant (modified poly-acrylamides) and cationic flocculant (product of nitrogen compounds) in combination with adsorption on activated carbon. Suitability of aforementioned methods was investigated on reactive and acid dyes, regarding their most common use in the textile industry. Also, investigations on dyes of different chromogen (anthraquinone, phthalocyanine, azo and xanthene) were carried out in order to determine the importance of molecular spatial structure. Oxidative effect of Fenton and Fenton-like reagents resulted in decomposition of colored chromogen and high degree of discoloration. However, the problem is the inability of adding POEL in stechiometrical ratio (also present in physical-chemical methods), when the phenomenon of overdosing coagulants occurs in order to obtain a higher degree of discoloration, creating a potential danger of burdening water with POEL. Input and output water quality was controlled through spectrophotometric measurements and standard biological parameters. In addition, part of the investigations concerned industrial wastewaters obtained from dyeing cotton materials using reactive dye (C. I. Reactive Blue 19), a process that demands the use of vast amounts of electrolytes. Also, investigations of industrial wastewaters was labeled as a crucial step carried out in order to avoid serious misassumptions and false conclusions, which may arise if dyeing processes are only simulated in the laboratory.Današnje kemijske i fizikalno-kemijske metode obezbojavanja otpadnih voda ne zadovoljavaju u potpunosti zahtjeve vezane uz stupanj obezbojavanja. U ovom radu obezbojavanje se provodilo pomoću Fentonove kemijske metode (FeSO4· 7 H2O + H2O2 + H2SO4) i modificirane Fentonove kemijske metode (FeCl3 · 6 H2O+H2O2+ HCOOH), te pomoću fizikalno-kemijske metode upotrebom koagulanata/flokulanata (polielektrolita-POEL), koja kombinira anionski koagulant (modificirani poliakrilamid) i kationski flokulant (produkt dušikovih spojeva) uz adsorpciju na aktivnom ugljenu. Prihvatljivost opisanih metoda ispitivana je za reaktivna i kisela bojila, s obzirom na njihovu raširenu primjenu u tekstilnoj industriji. Također, provedena su ispitivanja na bojilima različitih kromogena (antrakinon, ftalocijanin, azo i ksanten) s ciljem određivanja važnosti prostorne strukture molekule. Oksidativno djelovanje Fentonovog i modificiranog Fentonovog postupka dovodi do razgradnje obojenog kromogena i visokog stupnja obezbojavanja. Međutim, ustanovljena je nemogućnost dodavanja POEL u stehiometrijskom odnosu (također prisutno kod modificiranog Fentonovog postupka), odnosno dodavanje koagulanata u suvišku kako bi se postigao viši stupanj obezbojavanja, što u konačnici dovodi do opterećenja voda POEL-ima. Kvaliteta vode na ulazu i izlazu kontrolirana je pomoću spektrofotometrijskih mjerenja i uobičajenih bioloških parametara. U prilog tome, dio ispitivanja bio je vezan za industrijske otpadne vode bojadisaone, u kojoj se pamučni materijal bojadisao bojilom C. I. Reactive Blue 19 i to tehnološkim postupkom koji zahtijeva uporabu velike količine elektrolita. Također, ispitivanje industrijskih otpadnih voda označeno je ključnim korakom izbjegavanja niza krivih pretpostavki i zaključaka, koji bi mogli nastati u slučaju laboratorijskog simuliranja procesa bojadisanja
