Yes. You can remove a submission from a Challenge by removing the Challenge hashtag from the image. To remove the hashtag:
- Go to the image (either in your Profile or your collections)
- Select the three dots in the top right-hand corner
- Select "Edit Details
- Remove the Challenge hashtag from the caption (Tip: The Challenge hashtag will usually start with "#ec," "#pc," "#sc," or "#irc")
- Select "Save"