is alkaline or or acidic? plant accordingly. i would avoid drought tolerant natives.
Depends on the grey water. From laundry it would be mostly soap. (soap=alkaline) perhaps sodic also. might do well with oceanfront plants.
You can go to:
Are you just interested in planting something to be green until changed by a contractor, to make folk more amenable to dropping their wallet at the mall and go home maybe, or is there some kind of vision? Is it to reflect local flora in a natural habitat or be forward looking, say to support elfin figures like a fairy lustre plate as a backdrop to a kids playground? How long is the project, during which time you can grow/try various species. Is it a home garden, do the owners want herbs? or trees? or a drop-in lit cave for their iguana collection with a water cascade? How much can be spent on filtering or cleaning the water? Is there room for a 3 pond reed bed cleaning system? Are composting toilets wanted? Perhaps the 3rd pond would be for game fish as an income? Are the owners/staff able to work the area or has it to be maintenance free? Finally, does it all come together without asking the question as you may need to plant what you need to to fit the brief, even if that means changing the geology or substrate to promote a natural cycle in an unnatural setting whatever the cost (like a life support unit on Mars).
PS A cool Yule to one and all
Gray water from laundry is probably best oriented toward an area with various salt tolerant species of trees, shrubs, and groundcover. There are books on Greywater design by Art Ludwig and Brad Lancaster that show detailed diagrams for building such a system.(pipe dumps into a mulch filled ditch next to woodlands)
If you're looking to establish something quick and easy. Sudan grass is crazy strong, but maybe rye would tolerate in winter time, Sun Hemp(crotalari junica) would also be a good summer crop soil builder. Swiss chard grows huge and is very salt tolerant. They use that for bio-remediation of saline soils. I once consulted for a guy who couldn't get anything but swiss chard and beets to grow in his garden.(Beets and Swiss Chard are closely related) I tested his soil to have 4000ppm TDS which is about 4 times the level most plants will tolerate.
Don't forget to use a phosphate-free detergent or you are doing the soil surface a dis-service and will eventually see the results in anything you try to grow there.
If it's in full sun, I would plant Rainbow swiss chard for shrub like effect with radiant color, various mint species for smell and tolerance, and Dymondia in areas you want to be able to walk over.
If its not in full sun you might simply dig a ditch and fill it with compost next to the treeline.