Study On The Soluble Mechanism Of Activated Sludge By Ozonation Disintegration And Effect Of Performance On Activated Sludge Reduction By Simultaneous Ozonation Oxidation

The treatment and disposal of excess sludge have become a serious problem, which lead the sludge reduction to a necessary.Owing to the characteristics of high efficiency and no poisonous side effect,the ozonation reduction technology based on the lysis growth caused more and more concern all around the world.Because of the Ozone's high sterilizing ability,it can kill the bacteria by destroying the organic long chain structure once entering the cell wall.The organic products which released by cytolysis can be recycled for organism metabolism,which can cause the reduction of sludge production.Ozone can be applied to disintegrate the activated sludge,it can release the substances inside and outside cells into the liquid phase,at the meanwhile, when the sludge characteristics are totally changed,a brand new sludge reduction process will be established.In this paper,the ozone was applied to disintegrate the activated sludge in order to deeply research on some basic theoretical problems along with the possibility as well as the efficiency of ozonation simultaneous oxidation process.Use the ozone disintegration directly for the reactor to realize sludge reduction target.The mechanism of ozonation disintegration for activated sludge reduction was studied by batch test,and the dissolving laws of some indexes were analyzed.The results indicated that the indexes of soluble chemical oxygen demand(SCOD),total nitrogen(TN),ammonia nitrogen(NH₃ -N),organic nitrogen,nitrate nitrogen (NO₃^--N),total phosphorus(TP),protein and polysaccharide were accordingly raised when increase the ozone concentration and ozone dosage,on the contrary,the nitrite nitrogen(NO₂^--N),total protein,total organic carbon(TOC),pH value,specific oxygen uptake rate(SOUR)and sludge volume index(SVI)were declined obviously. The theoretical analysis was built up,It can fully prove that the dissolving value of SCOD and TN was lower than theory value due to the most part of organism was oxidized to CO₂,N₂,NH₃,which can be released from the liquid when the ozone direct reacts with the cytoplasm which enter into the liquid after the cell wall be cracked.During the whole ozonation disintegration process,the SOUR,SVI and pH value decreased from 9.92mgO₂/gVSS·h,65.4mL/g,6.38 to 5.92mgO₂/gVSS·h, 5.94mL/g,5.42,respectively.The relationship modes among the disintegration efficiency,ozone concentration, ozone dosage were established based on the method of dualistic linear regression.The results showed that the disintegrated efficiency of SCOD,solution protein, polysaccharide and TOC increased by exponential function when raises ozone concentration and ozone dosage.The ozonation reaction conditions for follow-up techniques were selected on the basis of the former theoretical analysis.Sludge reduction process based on the lysis growth can be fulfilled by ozone directly oxidize to the activated sludge in the biological reactor.The SBR and MBR were selected to study the simultaneous oxidation for sludge reduction in this experiment.The effect of ozone dosage on the performance of activated sludge reduction in SBR system was also studied.It shows the simultaneous ozonation oxidation could decrease the observed average sludge yield from 0.45gSS/gSCOD to 0.36,0.2,0.11, 0.03gSS/gSCOD when the ozone dosage was 0.01,0.02,0.025,0.03gO₃/gSS, respectively.During the 50 days process,the control system discharged about 150g dry sludge,but the ozonation system can only discharge 47.2g;the ozonation oxidation had no significantly effluence on the removal rate of COD,NH₃-N and TP, which kept 92.5%,91.1%,80.5%,respectively when the ozone dosage was below 0.03gO₃/gSS;the sludge of ozonation system also kept a sub-85.3%activity under the ozone dosage of 0.03gO₃/gSS.It proved that the SVI was declined with the increasing of ozone dosage.SBR ozonation unit run for 30 days without any sludge discharging,except sampling analysis,when ozone dosage was 0.03gO₃/gSS.The results showed that the ozonation system could significantly decrease the sludge discharge.During this period,the MLSS concentration increased 5907mg/L in control system while the ozonation unit only increased 643mg/L.However,the quality of effluent declined owing to the decrease of sludge activity after long ozonation time.The effect of ozone dosage on the performance of activated sludge reduction in MBR system was investigated.It was found that the simultaneous ozonation oxidation could decrease the observed average sludge yield from 0.32gSS/gSCOD to 0.25,0.16,0.07,0.021gSS/gSCOD when the ozone dosage was 0.01,0.015,0.02, 0.025gO₃/gSS,respectively.During the operation which lasts 50 days,the control system discharged around 143g dry sludge while the ozonation unit only slightly discharged 48g;the ozonation oxidation had no obviously effluence on the removal rate of COD,NH₃-N.Phosphorus in the MBR could not be removed effectively, which made more difficult for the ozoantion unit;the activity of sludge in ozonation unit declined with the increasing of ozone dosage.MBR ozonation unit run for 30 days without any sludge discharging except sampling analysis when ozone dosage was 0.025gO₃/gSS.The results showed that the ozonation system could obviously decrease the sludge discharge.During this period, the MLSS concentration increased 4863mg/L in control system while the ozonation unit only increased 380mg/L.