Study On The Effect Of Enhanced Treatment Of Landfill Leachate By Ochrobactrum Sp.

Landfill leachate is a kind of high-concentration organic waste water formed by the mixture of water seepage from garbage itself and rainwater during the process of landfill stacking.Due to the complex water quality of the landfill leachate and high concentration of organic components,it is difficult to treat the landfill leachate.Thus,how to develop high-efficient and low-cost technologies for treatment of landfill leachate has become one of the most important problems in the field.In this paper,the old landfill leachate was collected from a local landfill.The bacterial strains of efficiently degrade organic matter and reduce ammonia nitrogen were isolated from the landfill leachate.An efficient method for landfill leachate treatment was developed by combined process of ammonia nitrogen stripping,Fenton oxidation,and bio-enhanced SBR.The main results were as following:(1)Three strains named LL-1,LL-2 and LL-3 with high efficiency of organic matter degradation and ammonia nitrogen degradation were isolated from landfill leachate.The biological and physiological characteristics were studied.The strains of LL-1,LL-2 and LL-3 were Gram negative.The morphology of the bacterial cells was observed by scanning electron microscope.The cells were rod-shaped,with the size of about 1.6x 0.5?m.The 16S r DNA sequence analysis showed that the strains LL-1,LL-2 and LL-3 were clustered with Ochrobactrum sp.The strains were named as Ochrobactrum sp.LL-1,Ochrobactrum sp.LL-2,Ochrobactrum sp.LL-3.The bacterial cells grew well in the p H range of 5?9.The optimum growth temperature was at 25?,and the optimum salt concentration was 1.00%.(2)The landfill leachate was pretreated by ammonia nitrogen stripping.The results showed that when the landfill leachatethe was treated in the p H 11,at 35?,with the gas flow rate of 7 L/min,the best effect was obtained,with the ammonia nitrogen removal rate of 80.00%.(3)The landfill leachate was also pretreated by Fenton oxidation.The single factor was obtained by the single factor experiment.And then the best combination of the three factors was determined by orthogonal experiment.The results showed that the dosage of Fenton reagent had the most obvious effect on the experimental results,followed by p H and reaction time.Under the experimental conditions of Fe SO₄·7H₂O dosage of 15 g/L,H₂O₂of 50 ml/L,p H 4 and reaction time of 40 min,the best treatment effect was obtained by the Fenton oxidation,with the final removal rate of COD of 78.00%.(4)The activated sludge from the local sewage treatment plant was cultivated with different concentrations of Landfill leachate.After 21 days of acclimation,the activated sludge was obtained.The sedimentation ratio SV₃₀was stabled at 26.00%.The sludge concentration of the mixed liquid was 4800 mg/L,and the sludge volume index SVI was stabled at 52 ml/g.(5)The three Pasteurella strains LL-1,LL-2 and LL-3 were cultured in the laboratory and added to the acclimated activated sludge according to certain proportions for enhancement of the SBR process.The reactors were operated under the conditions of anoxia for 2 h,aerobic reaction for 14 h and standed for 2 h.The reactor temperature was controlled at about 28?and the dissolved oxygen of 4 mg/L.In the biological strengthening treatment process,the pretreated landfill leachate with the CODs of 400?600?800?1000 mg/L,and ammonia nitrogen concentration of 52?72?90?130 mg/L were used in the influent,and the SBR process was operated under the optimum reaction conditions.The experimental results showed that the CODs of the effluent in the control group,LL-1 and LL-3 groups were ranged from 240 mg/L to330mg/L,with the COD removal rates of 63.00?66.00%.The ammonia nitrogen concentrations in control group,LL-1 and LL-3 groups were from 22 mg/L to 37mg/L,with the ammonia nitrogen removal rates of 59.00?73.00%.The COD of the effluent in LL-2 treatment group was 190?260 mg/L,with the COD removal rates of70.00?72.00%.The effluent ammonia nitrogen concentration of LL-2 group was 18?20 mg/L,with the ammonia nitrogen removal rates of 65.00?83.00%.The results showed that the LL-2 group showed higher degrading effect than the blank control group,LL-1 and LL-3 groups,and the removal rates of the COD and ammonia nitrogen in LL-2 group were increased by 6.00%and 10.00%respectively.