Acceleration Of Sludge Reduction And Carbon Source Solubilization Using Micro- Bubble Ozonation

With the rapid growth of excess sludge and carbon source shortage in wastewater treatment porcess,sludge reduction and carbon source solubilization is one of promising technologies.Ozonatoin treatment is got wide attention due to its strong oxidizing property and high decomposition efficiency.To enhance sludge reduction and carbon source solubilzation process by ozonation,ozonation treatment combined with micro-bubble technology was implemented here.At the same time,the effects of ozone concentration,initial sludge concentration and initial pH of sludge on micro-bubble ozonation were investigated and the operation conditions were optimized.Meanwhile,the porcess and effects of micro-bubble ozonation on sludge and its solubilization were analyzed under optimal oparatoin conditions.It was found that micro-bubble was helpful for ozonation treatment and improved the reduction and solubilization of sludge.The removal efficiency of MLSS and MLVSS was nearly doubled compared with normal bubble ozonation process.Soluble Chemical Oxygen Demand?SCOD?increased to1964 mg/L,which was 2.1 times higher than traditional one;the sludge disintegration degree(DD_COD)reached 41.5%,while it was only 18.1%by normal bubble ozonation.In order to avoid sludge mineralizatin,ozone dosage set to 160 mgO₃/gSS was reasonable.Ozone concentration,sludge concentration and initial pH of sludge could affect sludge reduction and solubilization significantly.To improve micro-bubble ozonation efficiency,the optimal operation conditions were determined as follows:ozone concentration is 100 mg/L,sludge concentration is 5 g/L and initial pH is 9.Under the optimal operation conditions,the removal efficiency of MLSS and MLVSS could rise to 37.5%and 49.4%,respectively;the average of sludge particle size decreased 23%;the sedimentation of sludge was improved,while the dewatering performance got worse.The carbon source solubilization and biodegradability was significantly improved:SCOD rose to 2008 mg/L and DD_COD reached 41.6%,BOD₅/SCOD increased from 0.10 to 0.30.Total nitrogen,organic nitrogen,nitrate,total phosphorus,polysaccharide and protein increased through ozonation treatment process.The molecular weight distribution and 3-D fluorescence spectrum was used to explore the Changes of dissolved organic matters in sludge supernatant.Some macromolecular organic matters,such as fulvic acid-like and humic acid like matters,released from sludge flocs with the ozone dosage of 40 mgO₃/gSS.As Ozone dosage rose to 80 mgO₃/gSS,aromatic protein and soluble microbial by-product-like matters were decomposed by ozonation,while fulvic acid-like and humic acid-like matters accumulated.When the ozone dosage reached 160 mgO₃/gSS,except for part of humic acid-like matters,most of fluorescent matters were oxidized into non-fluorescent matters and the average molecular weight was decreased significantly.The mechanism of micro-bubble ozonation process was further explored.Compared with normal bubble ozonation,microbubble ozonation could improve the mass transfer efficiency and hydroxyl radical reaction intensity of ozone,which contributed to the solubilization of carbon source from sludge.