Investigating The Influence Factors And Mechanism Analysis Of Dye Wastewater Decolorization By Zero-valent Iron And Anaerobic And Combined Biological Treatment

The amount of dye wastewater being discharged into the environment is nearly2billiontons in our country every year which ranks No.5among all manufactural industries. With thedevelopment of a new type of dyes and science fabric technology, various ofdegradation-resistant organisms pour into the dye wastewater which further increases thedifficulty of treatment. The zero-valent-iron（ZVI） and anaerobic biological treatmentmethods，the subject study in this paper, which specific to high concentrations and chromadye wastewater, gains optimal operation technological parameters and verify its feasibility,that lay the foundation for practical application and help to solve the problem of dyewastewater.With simulated dye wastewater as treatment object, we can cultivate bacteria which candegrade dye wastewater under the anaerobic condition with gas bath shaker. Demesticatedanaerobic sludge was aliquoted and transferred into250ml serum bottle, then controling thereaction temperature and reation time and ensuring the sludge keep suspension and contactfully with the dye wastewater. To explore the effect condition of efficient decolourization ratioin three modes: ZVI treatment、anaerobic biological treatment and ZVI-anaerobic biologicaltreatment. We have observed the influence of different conditions such as ZVI particlesize(50、250and450mesh)、ZVI dosage(0、0.5、1.0、1.5、2.0and2.5g/L)、pH(5.0、6.0、7.0、8.0and9.0)、NaCl concentration(0、30、60、90and120g/L) and shaking speed(70、100、130、160and190rpm) on decolorization rate under the ZVI treatment，and explored theinterrelation of factors by response surface methodology to gain the best test conditons; AndWe have observed the influence of different conditions such as pH(5.0、6.0、7.0、8.0and9.0)and NaCl concentration(0、20、30、40and50g/L) on decolorization rate under the anaerobicbiological treatment; And We also have observed the influence of different conditions such asZVI dosage(0、0.1、0.5and1.0g/L) and NaCl concentration(0、20and50g/L) underZVI-anaerobic biological treatment. Based above researches, we also have analysed themechanism of ZVI-anaerobic biological treatment.The results showed that Under the weak acidic environment，the decolorization efficiency increased with the increasing of ZVI dosage and shaking speed，decreased with theparticle size through the chemical treatment；Considering energy saving and workingeconomically， decolorization efficiency were investigated using response surfacemethodology and the optimal conditions of pH was5.0，ZVI dosage was1.5g/L，particle sizewas450mesh，shaking speed was160rpm, the corresponding maximal decolorizationefficiency was72.5%. And it is restraint between pH and ZVI dosage, the excessive ZVIdosage will increase the pH and decrease the decolorization rate. So it is very important tocontrol the pH. After cultured and acclimatized, the decolorization efficiency of dye was88%and pH was7.0at10hour and the NaCl concentration had a adverse effect when theconcentration is greater than50g/L through the anaerobic biological treatment. So it shouldconsider the negative effect of NaCl concentration on decoloriztion rate. Under theZVI-anaerobic biological treatment, the optimal conditions of pH was7.0，ZVI dosage was1.0g/L，particle size was450mesh，shaking speed was160rpm and the NaCl concentrationwas20g/L through the ZVI-anaerobic biological treatment; FISH test results showed that therelative contents of Bacteria had changed from62%to69%and to78%, the Achaea werefrom38%to31%and to22%at the three stages from seed sldge to anaerobic sludge toZVI-anaerobic biological sludge. It is proved that a Bacteria we cultured had betteradaptability to resist the Procion H-5R and its products’ toxic than the Achaea. At the sametime, the ZVI reduction promoted the growth of acid-producing bacteria, inhibitited themethanogens metabolism. We gained Yersinia enterocolitica and Sphaerochaeta sp. to degradethe azo dye. So we could control the growth of acid-produing bacteria to achieve higherdecolorization rete by regulating the degradation of organic matter and dosing ZVI.