  The discovery of a kilonova (KN) associated with the Advanced LIGO
(aLIGO)/Virgo event GW170817 opens up new avenues of multi-messenger
astrophysics. Here, using realistic simulations, we provide estimates of the
number of KNe that could be found in data from past, present and future surveys
without a gravitational-wave trigger. For the simulation, we construct a
spectral time-series model based on the DES-GW multi-band light-curve from the
single known KN event, and we use an average of BNS rates from past studies of
$10^3 \rm{Gpc}^{-3}/\rm{year}$, consistent with the $1$ event found so far.
Examining past and current datasets from transient surveys, the number of KNe
we expect to find for ASAS-SN, SDSS, PS1, SNLS, DES, and SMT is between 0 and
$0.3$. We predict the number of detections per future survey to be: 8.3 from
ATLAS, 10.6 from ZTF, 5.5/69 from LSST (the Deep Drilling / Wide Fast Deep),
and 16.0 from WFIRST. The maximum redshift of KNe discovered for each survey is
z = 0.8 for WFIRST, z = 0.25 for LSST and z = 0.04 for ZTF and ATLAS. For the
LSST survey, we also provide contamination estimates from Type Ia and
Core-collapse supernovae: after light-curve and template-matching requirements,
we estimate a background of just 2 events. More broadly, we stress that future
transient surveys should consider how to optimize their search strategies to
improve their detection efficiency, and to consider similar analyses for GW
follow-up programs.
