Study On Chemical Fiber Wastewater Treatment Method And Process Design

Chemical fiber is one of the chemical industries which develop rapidly, but the wastewater always contains lots of organic matters, such as alcohols and aromatic compounds. Because of the strong acid, it belongs to the refractory wastewater which is harmful to human health and ecological system. According to the characteristics of the wastewater, the combined process of enhanced reduction, advanced oxidation, anaerobic, hydrolysis acidification and contact oxidation was used for the treatment of chemical fiber wastewater. Take COD, pH, etc. as the key indicators to the treatment effect on processing unit and combined process.During the enhanced reduction, the effects of dosages of zero-valent iron (ZVI) and humic acid (HA), initial pH, aeration intensity and temperature were investigated. It was found that the treatment with reduction with ZVI enhanced by HA had obvious effect. And maximum COD removal of 69.4% was observed after 6 h under the optimum conditions of ZVI dosage for 1.0 g/L, HA dosage for 0.5 g/L, initial pH for 2, aeration intensity for 0.8 m3/(L-h) and temperature for 60 ℃, respectively. Further, by comparing the efficiencies of different processes in advanced oxidation, Fe(Ⅱ)/persulfate(PMS) oxidation technology was used as the second pretreatment. Through several single factor experiments, it was identified that the COD removal of 62.0% at optimal conditions:sodium persulfate dosage 2.0 g/L, ferrous sulfate dosage 4.0 g/L, pH= 5, reaction time for 6 hours. The effluent COD was from 45.9 g/L to 17.5 g/L.Pretreated wastewater by HA-ZVI/Air and Fe(Ⅱ)/PMS was pumped into biochemical unit. Anaerobic granular sludge was seeded into anaerobic reactor and acclimated in a low organic load. Start-up period, COD volume loading increased from 0.5 kgCOD/(m3-d) to about 44 kgCOD/(m3-d), and completed within 45 days. During stable period, when influent COD was 17.5 g/L, the effluent COD from anaerobic reactor was about 3887.6 mg/L and COD removal was about 78% with HRT for 10 h. As for hydrolysis acidification and contact oxidation ponds, activated sludge inoculation method was made for starting and culturing for several days. Experimental study shows that the COD removal stable at the average on 53.0% for hydrolytic acidification with HRT=30 h and 89.0% for contact oxidation with HRT=16 h, air/water ratio 20:1, respectively.At the same time, the effluent COD of the whole process is 200.9 mg/L, which could meet the second discharge standard (GB8978-1996).