Duplicate SMPs samples were taken from the reactor for the experiments of water quality measurement and MW distribution of SMPs. Chlorination of SMPs, TOX detection and mutagenicity analysis were conducted in triplicate to ensure the reproducibility and reliability of the results. Blank water samples from the reactor without the AS1404 and substrate additions were used to determine the background DBPs formation. The internal standards, 2-bromofluorobenzene (for THMs) and 1,2,3-trichloropropane (for HAAs), were used for quantification. The recoveries of DBPs ranged from 82.9% to 98.8% and the detection limits of DBPs ranged from 0.06 to 1.69 μg/L.
3. Results and discussion
3.1. Water quality of SMPs
The water quality of the SMPs samples are presented in Table 1. Among them, DOC and DON are two key parameters since DOC and DON are important precursors of C-DBPs and N-DBPs, respectively  and .
Compared with NS condition, DOC concentrations were 1.2 times, 2.6 times, 1.8 times and 8.3 times higher under the HA, HS, HM and HT conditions, respectively. This might be attributed to two reasons: first, the inhibitory effect of stressful conditions might lead to the plasmolysis and aggravate cell lysis. The release of intracellular constituents, such as polysaccharides and proteins after cell lysis contributed to DOC  and . Second, stressful conditions might also stimulate extracellular polymeric substances (EPS) production ,  and , and the slough or hydrolysis of EPS could contribute to DOC  and .