as in
*occasional wastewater discharge*; not specific enough, but should point you in the right direction

http://www.dtsc.ca.gov/PollutionPrevention/P2_REP_Petroleum_...
Steam boilers in the refinery require **occasional discharge**
of boiler water as wastewater to maintain the mineral content of the boiler water within target operating limits. The refinery directs the discharged boiler wastewater, or “blowdown,” to the process sewer.


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Note added at 2 hrs 8 mins (2005-09-26 12:20:55 GMT)
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check this out
*production campaign* is also used when speaking of refineries

http://www.ftc.gov/os/2001/03/mwgasrpt.htm
Once a refiner has decided what formulations of gasoline it will produce in an upcoming **production campaign**, it becomes increasingly difficult to alter the planned output of the refinery as the **production campaign** approaches

and this looks like *it*

http://www.owr.ehnr.state.nc.us/ref/23/22860.pdf
Companies usually produce a range of different substances simultaneously with effluents discharged as **dictated by the production campaign.**

So I guess you could say *occasional wastewater discharge, as dictated by production campaigns*