The variation characteristics of molecular weight (MW) and organic matters in the effluent were studied

respectively sampling from each unit of the advanced water treatment processes

preozonation

conventional water treatment (CWT)

and main ozonation/BAC (biological activated carbon).The relationship was established between biological stability and MW of organic matters

and the evaluation was realized for the biological stability of the drinking water quality from advanced water treatment. Results showed that the natural organic matters with high MW in raw water could be oxidized into that with MW less than 1000 by the preozonation process

and the biodegradability of raw water was improved. The CWT process has brought about rate lower in organic matters removal. Effluent organic matters from the CWT process were furthermore decomposed by the main ozonation process

and some organic matters were oxidized into the ones with MW less than 500. The biological stability of the effluent was increased by BAC process

but the removal rate of organic matters with MW less than 1000 was lower. The smaller MW and the worse biological stability of organic matters were

the more difficult they were removed.  These finds provided a theoretical basis for evaluation on biological stability of source water from advanced water treatment processes.