With the plant manager's concurrence, and supported by some sampling data to quantify the problems, I prefer Quickcrete in the drains, coupled with building a curb around the perimeter of the process to guarantee that nothing gets washed to the drains.  (When the operators start swimming in their own wastes, they will stop generating them.  The principle is that you have to remove the drain as a safety valve for non-performance!) 

If this is too radical a solution, try replacing hoses with high pressure cleaning or steam cleaning guns.  The issue is cleaning and there are several ways to manage that.  Dry cleaning is also very effective, and it is zero water use, as is vacuuming  (shop vac) the results of the cleaning at the shift end or during the shift.  

One plant instituted a management policy change.  After they sealed the drains, they told the lead operators that they would be held accountable for all materials they generated on the shift, and that their bonus would be tied to the reducing the cost of operations.  That meant that if an operator left something for the next shift, the second shift operator would have to cover the cost, and lower his profitability.  The operators were encouraged to provide a shift audit walk through involving the lead operators from each shift.  In that manner, the operator taking over the shift performs an walk-through audit of the facility to make sure that the wastes which should have been disposed of were accounted for and properly credited to the previous shift.  This tends to work very well.

The first solution proposed also has its strong points.  As long as you provide an escape route, or an "away," the shift personnel will utilize it to get rid of bad batches, and spills.  This discourages re-work and reprocessing and wastes product.  It also sets a precedent to provide the wastewater treatment plant operator with an unmanagable situation where he cannot control any deliberate dumping of off spec. chemicals, but he is responsible for recieving and treating the products of that dumping.