Application Research On Ozone Preoxidation In Yeast Wastewater Treatment

The wastewater generated during yeast producing process is typical ofthe refractory wastewater. There are few enterprises in which yeastwastewater can be treated to meet the requirements of the discharge standardfor this industry, because of high concentration of refractory organics andhigh salinity.In this paper, ozonation technology is applied to yeast wastewatertreatment. On the one hand, as pretreatment method, ozonation can improvebiodegradability of the effluent from anaerobic process and the processingcapability of subsequent aerobic biological system.On the other hand, themethod of ozone enhanced coagulation, as advanced treatment, is adopted totreat the secondary effluent in order to reach the discharge standard in thispaper. The main conclusions of this paper are as follows:(1)The results of studies on the factors,such as effective water depth、pHand ozone concentration, showed that, in a specific range, the COD removalrate would be increased along with the increase of effective water depth andpH; as ozonation process and products would be different in the same ozonedosage and different ozone concentration, the COD removal rate wasdifferent.(2)There’s a large deviation between the results of traditionalBOD5/COD evaluation and the practical wastewater treatment when being evaluated the biodegradability of yeast wastewater. In this paper, aerobicrespiration rate is adopted to build a new method to evaluate thebiodegradability of yeast wastewater.(3)Being compared to raw water, the accumulative oxygen consumptionincreased by23.0%and its reasonable time of biological treatment reduced by9h in200mg/L ozone dosage,when evaluated the biodegradability by themethod of aerobic respiration rate.(4)The results of substrate biodegradation dynamics analysis adoptedMonod equation showed that, in200mg/L ozone dosage, the wastewater wasmore favorable to biodegradation, whose inhibit coefficient dropped to85.1from466.2of raw water, and substrate biodegradation rate was maximal, was43.5mg/(L·h). It demonstrated that the right amount of ozone dosage canimprove biodegradability in view of kinetics.(5)The GC/MS analysis results of organic components before and afterozonation showed that, after ozonation, the phenol disappeared, the content ofheterocyclic and aromatic hydrocarbon decreased by11.9%and6.9%;Accordingly, the content of small molecular alcohols, aldehydes and acidsincreased respectively12.3%,8.3%and2.3%, which were the typicalozonation products. The results showed that the wastewater after ozonationwas more favorable to biodegradation.(6)The continuous running results of preoxidation with200mg/L ozonedosage combined with aerobic biological treatment system showed that the COD of effluent could stable at300mg/L basically. The COD removal ratecould reach85%, whose treatment effect was better than aerobic biologicaltreatment without ozonation and the A/O process of wastewater treatmentsystem in yeast industry significantly.(7)The treatment effect of ozone enhanced coagulation was better thanthe methods of coagulation without ozonation and first coagulation thenozonation, and the advanced treatment cost was lest, which was2.5yuan/twhen ozone generator with oxygen source, was less1.3yuan/t thancoagulation without ozonation, and less0.7yuan/t than first coagulation thenozonation. At the same time, its chemical sludge quantity was only half of theother two methods.