Abstract: Sludge is composted by arranging the sludge in a pile over a conduit and air is forced into the pile in spaced time intervals and air is drawn from the pile into the conduit in alternate time intervals.The perforated conduits are adapted to be placed under and extend the length of two windrow compost piles. A reversible blower is connected to blow air to and withdraw air from each of the conduits. The blower is timed and controlled to blow air from a first pile through the conduits and into a second pile in spaced time intervals and in alternate time intervals to withdraw air from the second pile through the conduits and into the first pile.

Abstract: Process for treating sewage by using algal photosynthesis for removing cominants from sewage. The sewage is treated in a channelled algae pond while the sewage meanders through the channels in the pond. The process includes integrated day-time and night-time cycles enabling continuous operation over a 24 hour period. An essential step in the process involves varying the flow rate between the day-time and night-time cycles with a cage aerator. The flow rate during the day-time cycle is controlled by the cage aerator so as to increase the amount of algae in the sewage that is exposed to light and bring about nutrient exchange between the bottom and surface of the sewage in the channels without stirring up the sludge in the channels. The rotational speed of the cage aerator is increased during the night-time cycle so as to agitate the sewage to stir up the sludge and beat air into the sewage to increase its oxygen content.