[{'role': 'USR', 'utterance': 'Well, no one could survive without water, but you see pollution has been making more and more water unable for drinking.'}
 {'role': 'SYS', 'utterance': 'Yeah. Water pollution has for a long time been a major concern among the environmental issues.'}
 {'role': 'USR', 'utterance': 'But what are the sources of water pollution?'}
 {'role': 'SYS', 'utterance': 'They could generally be divided into two categories'}
 {'role': 'USR', 'utterance': "Well, direct ones are the pollution directly from factories, refineries waste treatment plants etc. , aren't they?"}
 {'role': 'SYS', 'utterance': 'Yeah. They are emitted directly into urban water supplies.'}
 {'role': 'USR', 'utterance': 'But what about the indirect ones?'}]
{'role': 'SYS', 'utterance': 'Indirect sources include contaminants that enter the water supply from soils or groundwater systems and from the atmosphere via rainwater.'}