Method of digesting organic wastes

Claim 1

A method for biologically digesting concentrated sewage sludge containing a plurality of anaerobic micro-organism species into compost, which comprises: (a) introducing aerobic micro-organisms by admixing the sludge with a sufficient amount of a particulate organic carbon-containing material containing predominantly aerobic micro-organisms; (b) introducing the mixture thus obtained into an aerating reactor having a top inlet and a bottom discharge so as to form an air-permeable material column in said reactor, while blowing air through the material column in an upward direction of the column, said blowing being effected in such quantities that due to the different oxygen consumption and metabolism of the different micro-organism species, the latter settle at distinct levels within the reactor space to form a plurality of distinct zones of different temperature and different oxygen content at different levels of said reactor which zones remain substantially stationary and at equilibrium so that both aerobic and anaerobic digestion take place while the method is carried out, the zone of the highest temperature being located in the uppermost third of the reactor space while the zone of the lowest temperature is located adjacent the bottom of the reactor, the temperature of said zone of highest temperature being sufficiently high so as to destroy pathogenic germs, the zone of the lowest oxygen content being located in the uppermost portion of the reactor while the zone of the highest oxygen content is located adjacent the bottom of the reactor; (c) permitting the mixture to digest until it has formed compost in the lowermost portion of the reactor space; (d) withdrawing said compost through said bottom outlet and adding fresh mixture through said top inlet to make up for said withdrawn compost, to form a continuously descending column of said mixture in said reactor which, during its descent, passes through said zones while air passes countercurrently through the column and the spent air is removed from the top of the reactor.

Claim 2

A method for biologically digesting concentrated sewage sludge containing a plurality of anaerobic micro-organism species into compost, which comprises: (a) introducing aerobic micro-organisms by admixing the sludge with a sufficient amount of a particulate organic carbon-containing material containing predominantly aerobic micro-organisms; (b) introducing the mixture thus obtained into an aerating reactor having a top inlet and a bottom discharge so as to form an air-permeable material column in said reactor, while blowing air through the material column in an upward direction of the column, said blowing being effected in such quantities that due to the different oxygen consumption and metabolism of the different micro-organism species, the latter settle at distinct levels within the reactor space to form a plurality of distinct zones of different temperature and different oxygen content at different levels of said reactor which zones remain substantially stationary and at equilibrium so that both aerobic and anaerobic digestion take place while the method is carried out, the zone of the highest temperature being located in the uppermost third of the reactor space while the zone of the lowest temperature is located adjacent the bottom of the reactor, the temperature of said zone of highest temperature being sufficiently high so as to destroy pathogenic germs, the zone of the lowest oxygen content being located in the uppermost portion of the reactor while the zone of the highest oxygen content is located adjacent the bottom of the reactor; (c) permitting the mixture to digest until it has formed compost in the lowermost portion of the reactor space; (d) withdrawing said compost through said bottom outlet and adding fresh mixture through said top inlet to make up for said withdrawn compost, to form a continuously descending column of said mixture in said reactor which, during its descent, passes through said zones while air passes countercurrently through the column and the spent air is removed from the top of the reactor.

Claim 14

A method for digesting sewage sludge into compost, which sludge contains different anaerobic and aerobic species of micro-organisms having different oxygen consumptions and metabolisms, comprising: continually introducing and passing the sludge downwardly through a reactor countercurrently with an upward flow of air, the rate of downward passage of the sludge upward passage of the air being controlled such that a series of different temperature and oxygen zones are formed in the reactor; wherein the uppermost third zone of the reactor is at a temperature sufficiently high to destroy pathogenic germs in the sludge traveling therethrough and an oxygen content between 12 to 15% which is sufficiently low to sustain anaerobic decay in the sludge traveling therethrough; and the lowermost third zone of the reactor is at the lowest temperature in the reactor and possesses an oxygen content between 18 to 20% in the reactor, which zone is at the bottom of the reactor and the intermediate third zone has an oxygen content between 15 to 18%; and wherein the residence time of the sludge in the reactor is from about 14 to 12 days and is sufficiently long such that when the sludge reaches the bottom of the reactor, it is compost; wherein the different micro-organisms settle within the reactor space at levels satisfying the requirements of each of said organisms to produce an equilibrium state as the sludge moves downwardly through the reactor such that both aerobic and anaerobic decomposition take place within the reactor; and removing the compost from the bottom of the reactor and removing the spent air from the top of the reactor.

Claim 15

A method for digesting sewage sludge into compost, which sludge contains different anaerobic and aerobic species of micro-organisms having different oxygen consumptions and metabolisms, comprising: continually introducing and passing the sludge downwardly through a reactor countercurrently with an upward flow of air, the rate of downward passage of the sludge upward passage of the air being controlled such that a series of different temperature and oxygen zones are formed in the reactor; wherein the uppermost third zone of the reactor is at a temperature sufficiently high to destroy pathogenic germs in the sludge traveling therethrough and an oxygen content between 12 to 15% which is sufficiently low to sustain anaerobic decay in the sludge traveling therethrough; and the lowermost third zone of the reactor is at the lowest temperature in the reactor and possesses an oxygen content between 18 to 20% in the reactor, which zone is at the bottom of the reactor and the intermediate third zone has an oxygen content between 15 to 18%; and wherein the residence time of the sludge in the reactor is from about 14 to 12 days and is sufficiently long such that when the sludge reaches the bottom of the reactor, it is compost; wherein the different micro-organisms settle within the reactor space at levels satisfying the requirements of each of said organisms to produce an equilibrium state as the sludge moves downwardly through the reactor such that both aerobic and anaerobic decomposition take place within the reactor; and removing the compost from the bottom of the reactor and removing the spent air from the top of the reactor.