Abstract: A method for reducing or preventing the formation of scale in a municipal or industrial waste water treatment facility comprising introducing an antiscalent composition which comprises: A) A water soluble polymer of molecular weight below 20,000 and containing anionic groups, and B) A sequesterant compound, selected from the group consisting of phosphonates, phosphates, metaphosphates and orthophosphates including derivatives and salts thereof. Preferred antiscalent compositions include a blend of A) a polymer of acrylic acid and/or maleic acid and B) diethylentriamine penta (methylenephosphonic acid) or salts thereof. The invention is of particular value for the treatment of struvite scale in sewage treatment works.