What causes ripples on part of first layer?
First layer rippling is usually caused by a too low of a first layer height (for the amount of extruded filament).

Are you sure that:


Your bed is leveled as good as possible, and
the initial height between the nozzle and the bed is correct when Z=0 (A4 paper thickness, when moved should be giving some drag), and
the bed is flat. (This is most probably your actual problem!)


To minimize the effects, you could try to:


increase the first layer height, or
set an additional Z offset in the slicer, or 
reduce the filament flow for the first layer, or
install an automatic bed leveling sensor, or
perform a manual bed levelling mesh procedure (if you have Marlin Firmware).


This usually helps fighting these ripples.