This quote comes towards the beginning of the novel and describes the machine that Montag sees that is used to flush out his wife's system after she has taken an overdose and tried to kill herself. This quote helps establish how impersonal and regular the system is, as we discover that such a process occurs very often in this dystopian world of emptiness and despair. Note what Montag thinks just before this quote is said:
The entire operation was not unlike the digging of a trench in one's yeard. The woman on the bed was no more than a hard stratum of marble they had reached.
Note the slightly ironic note in the quote you have mentioned. Can it really "slush up the emptiness," which is, of course, the real reason behind Mildred's attempted suicide? Thus this quote seems to point towards the limits of technology and the way that it is unable to meet the needs of humans--a key factor of this society.