Value bet TPTK?

[Rooger]

I think value betting is still one of my problems.
Villain is 30/18 over the ~40 hands we've played. I haven't had any confrontations with him before.
Do you value bet the river? How much?

Party Poker No-Limit Hold'em (NL$100) <font color="#0000FF">(6 handed)</font> link

Preflop: Hero is UTG with K[img]/images/graemlins/diamond.gif[/img], A[img]/images/graemlins/club.gif[/img].
<font color="#CC3333">Hero raises to $4.00</font>, <font color="#666666">3 folds</font>, BB calls $3.00.

Flop: ($8.50) T[img]/images/graemlins/heart.gif[/img], K[img]/images/graemlins/heart.gif[/img], 9[img]/images/graemlins/club.gif[/img] <font color="#0000FF">(2 players)</font>
BB checks, <font color="#CC3333">Hero bets $7.00</font>, BB calls $7.00.

Turn: ($22.50) 8[img]/images/graemlins/spade.gif[/img] <font color="#0000FF">(2 players)</font>
BB checks, <font color="#CC3333">Hero bets $15.00</font>, BB calls $15.00.

River: ($52.50) 6[img]/images/graemlins/diamond.gif[/img] <font color="#0000FF">(2 players)</font>
BB checks - Bet?