A university student has been treated to a surprise 21st birthday party at one of Britain's largest sewage treatment plants. Joanne Bushell was given the unexpected party during a visit to Yorkshire Water's Knostrop waste water treatment works near Leeds. Ms Bushell and her fellow third-year students on the Leeds environmental bio-geo science degree course had asked for a tour of the site to help them with their studies. But when she arrived she was presented with a birthday cake, party hats, balloons and streamers. She told the Yorkshire evening Post: "A sewage works wasn't exactly what I had in mind for my 21st birthday but it was a great laugh and I really enjoyed it." She added: "It made me feel a little queasy and that's even before I had enjoyed a drink or two." The party was organized by Joanne's tutor and the plant bosses who thought it would be a novel way of celebrating a landmark birthday.