The problem with the banana circle is that its ONE big hole. The (mulch filled) pond is in my opinion anaerobic for two long. The pond is too deep and the soil metabolizes less efficiently down there. Infiltration is that much closer to the aquifer. Then, eventually, the bananas fill in the hole. Bananas can only be on one side or at the bottom end of a system. We used a grey water system for the kitchen of a restaurant for ten years and it worked like this.
Make sure you have the strainer in the sink. make sure the are no dips and adequate slope in the plumbing. The pipe has to branch three times to three ditches. We use un-glued tee´s and adjust them so that gravity sorts for only one pipe at a time. The top of each ditch needs a solids trap with is a box with a hole in the top where the pipe goes in, and open bottom for drainage, and an outlet on the downhill side six inches below the soil level. Below that there is a ditch maybe 14" by 14" running down hill. This is filled with
compost heap quality carbon compost, dry grass , corn cane etc. Use each ditch for three days then switch. The solids box is cleaned out intermittently with a hoe, grade for composting. The ditch is cleaned out once or twice a year, grate compost.
The slope is important, best if over thirty percent. The soil will decide how much it wants to metabolize in a given area and send the rest on. This is a system for what Art would call dark grey water. A laundry machine can function on something as simple as a mulch filled hole or ditch, but we have good drainage. ps. Hungry fruit trees love grey water but might not like having recently cut or damaged roots drowned in grey water.