Put a months worth of your meals into a tote and return what you dont eat to the tote, dont wash your plate between meals..thats the equivalent of a recirculated res
If plants could pick and choose what they took from a res you wouldnt need to worry about ph, EC or the elemental make up. The solution PH depends on its makeup, the direction of ph swing depends on the plants. PH will rise as plants remove nitrate in veg, it will fall when they remove potassium in bloom. The ph imbalance goes back to the recirc res, with dtw the imbalance goes out with the runoff. PH adjustment usually involves phos acid and potassium hydroxide which will increase P and K respectively (ph up and down affects the elemental makeup). With DTW you dont need to add anything, the elemental content remains the same for the life of the res, you simply replace it when its gone. Maintenance wise, recirc is a pita with daily checks and adjustments. Ultimately you have to guess when to dump a recirculated res or dump it on a set schedule. The first thing most folks do when noticing a slight issue with the plants is to dump and replace the entire res just to be safe...now thats wasteful
If you wait for a 900ppm res to drop to 150ppm the micro`s will be long gone, The plants will try to make up the deficeit from the fresh res which will leave it short.
The point is a recirculated res starts to become an unknown quantity from day one and only gets worse the longer its in use. A DTW res is a known quantity until its gone. If you dump 70gal of recirculated nutes a week, you can run 10gal a day dtw and waste exactly the same amount. The dtw will be less work and provide better results.