What are the risks of surgery to remove hemorrhoids?

Several. Pain for a week or two after surgery. Bleeding after surgery. Stenosis (narrowing) from scarring. Infection (rarely). Recurrence of hemorrhoids in the future.
Several potential. Depending on the technique used and skill/experience of the surgeon, complications altho rare can including bleeding, infection, stricture or scar development and rarely some degree of incontinence. In the hands of a qualified experienced surgeon, these risks should be in the order of 1-2% at most.