In wireless-powered backscatter communication (WP-BackCom) networks, backscatter transmitters modulate their information on the radio frequency (RF) signals received from the power beacon (PB) and reflect the modulated RF signal to their intended receivers. To optimize delay-quality of service provisioning and network power consumption, this letter proposes an interference-aware resource allocation scheme that aims to maximize effective energy efficiency (EEE) for WP-BackCom networks. In this scheme, reflection coefficients are analytically obtained and power allocation is performed at the PB via convex optimization. Results show that the proposed scheme substantially outperforms the baseline schemes in terms of EEE.