[kidd]

While you correctly note that non-point sources are the number one source of phosphate in the Bay, I think you have it backwards regarding which source that dishwasher detergent falls into.

Point sources include those sources that have known and permitted phosphate discharges. These include industrial sources and waste water treatment plants. Urban area water is generally sourced to water treatment plants, thus nearly all dishwasher phosphates would be a point source (not a non-point source).

Non-point sources are from runoff. Non-point sources include agriculture, erosion, wildlife poo, etc.

(see http://www.water-research.net/phosphate.htm)

[JerseyHighlander]

Much less than half the dish dtergent goes through water treatment in the Chesapeake Bay watershed,... lots and lots of suburbs, exurbs and rural areas with septics and leech fields.