The method of treating sewer scum including combustibles and debris includes the steps of collecting the scum from sewage, delivering it to a perforated filter drum, continuously rotating the drum upon an inclined longitudinal axis, applying heated air under pressure to the exterior of the drum along...http://www.google.com.au/patents/US4248709?utm_source=gb-gplus-sharePatent US4248709 - Method of filtering sewer scum and apparatus therefor
