Improved Performance of Membrane Bioreactor by Sludge Ozonation for Reduction of Excess Sludge Production

To seek for an alternative solution for the treatment and disposal of excess activated sludge, a hybrid system of membrane bioreactor ( MBR) coupled with ozonation process (i.e., ozonation run) was set up to treat the domestic wastewater. A reference run without ozonation was also preformed as a control. The optimal ozone dose of solubilization in the ozonation run was firstly determined through the batch sludge ozonation tests. A 40-day continuous operation of the two parallel systems demonstrated that circulation of ozonized sludge as lysate did not impact the performance of MBR in terms of organic and ammonia removal. On the contrary, an improvement in TN removal (by 7.7%) and sludge reduction (by 54%) was observed in the ozonation-combined MBR, and it was furthermore illustrated by the calculation of the mass balance based on the COD and TN substances. In addition,ozonation did not deteriorate the sludge activities for the ozonation run, indicating that not much inert organic materials built up in the bioreactor. Decreased VSS/SS ratio and lower amount of filamentous bacteria after ozonation treatment on the other hand improved the sludge settleability, as lower and constant Sluge Volume Index (SVI) values were detected in the ozonation run.     

Enhanced Biological Phosphorus Removal in SBR Using Glucose as a Single Organic Substrate

Enhanced biological phosphorus removal （EBPR） was investigated in an anaerobic/aerobic sequencing batch reactor （SBR） supplied with glucose as a single organic substrate. The results illustrated that EBPR process could also occur successfully with glucose other than short chain fatty acids （SCFAs）. High phosphorus release and polyhydroxyalkanoate （PHA） accumulation in the anaerobic phase was found vital for the removal of phosphorus during the aerobic phase. The measurement of intracellular reserves revealed that glycogen had a higher chance to replace the energy role of poly-P under anaerobic conditions. Moreover, glycogen was also utilized as the carbon source for PHA synthesis, as well as a reducing power as reported earlier. The accumulated PHA in this system was mainly in the form of poly-hydroxyvalerate （PHV） instead of poly-hydroxybutyrate （PHB）, and was inferred to be caused by the excess reducing power contained in glucose. Lactate as a fermentation product was also found released into the bulk solution. Applying fundamental biochemistry knowledge to the experimental results, a conceptual biochemical model was developed to explain the metabolism of the glucoseinduced EBPR.