The Athens Water and Sewage Company (EYDAP) asked residents of Piraeus and its surrounding areas to be patient for a few more weeks after they complained yesterday about the return of a foul smell in the air from the waste treatment plant on the nearby islet of Psyttaleia. EYDAP said that there remain some 25,000 tons of unprocessed sewage on the island and that it aims to treat the waste by the end of the spring. Psyttaleia was burdened by some 160,000 tons of sewage about a year ago but a drying unit began operating on the islet last summer and that has helped reduce the backlog. The drying unit, which allows the sewage to be compressed and shipped away, treats some 500 tons of sewage a day. There are still some 15,000 tons of dried sewage on the island that have yet to be transported.