Home sewage treatment plant discharge?

My 3 chamber treatment plant discharges onto the surface of the ground about 145' from my pond.  The ground between the discharge and the pond stays wet.  We have HEAVY clay soil so a leach field is a no go.  Septic systems here are required to have sprinklers to spray the waste water over a wide area.  Mine didn't have the sprinklers when we moved in and I don't want them now.  

I am thinking about digging a ditch down the side of my pond for waste water to filter through instead of straight into the pond.  The ditch would be 10' wide and 1.5' deep approximately 220' long.  The waste water would enter one end and filter down the length before connecting to the pond at the spillway.  This would keep the water level of the ditch and the pond the same.  Heavy rain events would force the ditch water down to the spillway, mix it with pond water and discharge it.  

I would plant reeds, cattails,  and maybe even hidrilla in the ditch to collect the nutrients from the waste water.  These could be collected for compost and returned to the top of the hill where our or orchards and gardens are.

As a side note,  we get about 48" of rain per year and the total drainage area to the pond is probably 10 acres. With the heavy clay soil there is very little seepage of water into the soil. They pond stays full except for about  3 months during the summer and then it only drops a few inches.  The pond frequently overflows during rains.  

Here is a crude drawing of what I am planning.  The new ditch dam is in red.  

i like it i like it, keep it coming!

I'm on here learning and studying so I really don't have much to weigh in as far as affirmation and confirmation goes...my mind goes to a small series of 2-3 smaller ponds connecting into the the pond (close to sppillway) and have its own spillway into the drainage of the big pond. So, 1-2-3 ponds with the third having both mouth to big pond and a spillway connecting to pond spillway drain. Definitely using every bit of that 220 ft.

My poke here is to ask,

I get the feeling its full sun, but just to be clear and fresh: How much sun? Any partial shade? What is the coldest in winter time (rough)?

And how close is the ditch from the pond?
What grade or slope are we talking?

Regards

You might want to look into something called a "Subsurface flow constructed wetland"  Basically similar to what you described, but filled with gravel until the water level is about an inch or two below the surface.  

The gravel provides lots of surface area for beneficial bacteria to grow on, the reeds/cattails help (a little) to bring oxygen down below the surface and having the gravel above the water keeps the mosquitoes from breading in it plus helps to prevent people/animals from coming into contact with the raw waste water.

Wouldn't this ditch work better if it were built as a meandering flow instead of a straight line flow?
By making the ditch have some turns in it and opting for a "wetlands" type system like Peter mentions you could clean that water with not only the plants you mentioned but bacteria and fungi would be put into play on a much larger scale as well.
This would make the discharge water much cleaner before it reached your pond.

Redhawk

Here are some pics of what I an dealing with.  I could dig a trench zigzaged down the hill and back fill with gravel and sand. This would give at least 150 feet of travel and filtering before it reaches the pond.  As you can see in the pics I have lots of diversity in plants and trees to absorb nutrients before it reaches the pond.  The added ditch among the bank would allow reeds and willows to absorb the rest.  

These pics were taken after a heavy rain.  I don't want any standing water above ground as I have now. The gravel and sand in the transition ditch should prevent standing water. Plants would be replanted in all areas after the earth works were completed.

It is hard to tell from these pics but the plants in the ditch are 5 to 6 feet tall and loving life.