Boring blind defense A high river decision (Bellagio 15/30)

[felson]

button open-raises, i have A9o in SB and threebet. BB is tight so i know he will get out of the way, although he might come along if i flat call. button is typical player, nothing unusual about his play so far.

flop is twotone rags, ten-high. i have none of the flush suit. i bet, he calls.

turn is another rag, putting the third flush card out there. i bet, he checks his cards and calls.

river is rag non-flush card. bet or check? if i bet, is it mostly for value or mostly bluffing? if i check, i have to call, right?