Use Array#delete_if:
arr = [{"k1"=>"v1", "k2"=>"75.1%"}, {"k1"=>"v2", "k2"=>"-NA-"}, {"k1"=>"v3", "k2"=>"5.1%"}]
arr.delete_if { |h| h["k1"] == "v3" }
#=> [{"k1"=>"v1", "k2"=>"75.1%"}, {"k1"=>"v2", "k2"=>"-NA-"}]
If there is no hash matching the condition, the array is left unchanged.