Experimental study on zero excess sludge production process with ozonation unit in MBR process

In order to investigate the influence factors of zero excess activated sludge (EAS) process by ozona tion, a 100 L membrane bioreactor coupled with a sludge ozonation unit (MBR-SO) was performed for 80 d without EAS wasting. Some mathematical models were developed to elucidate the relationship between process parameters and the operating effects. It is considered that the sludge lysing ratio (ζ) , produced COD per unit mass lysed MISS (η), observed sludge yield coefficient (Y_(obs)) and intrinsic yield coefficient for COD produced by lysed sludge (Y_2) significantly affect the flowrate to ozonation unit (q). When q is 0. 0067 times of influent flowrate (Q) and ζ is about 0. 72 for each batch ozonation, a relatively stable MISS concentration of 8168 mg/L and zero Y_(obs) are achieved in the MBR-SO system. The calculation of sludge disintegration number indicates that the high ζ can apparently decrease the sludge amount needed for ozonation. At the same ozone dose, the low input ozone concentration and high flowrate can enhance the sludge lysing effects and a low energy consumption of 0. 041 Yuan/m~3 wastewater is obtained.