Patent ID: 7638056

Claim:
A method of treating sewage sludge to reduce the pathogen content of said sludge, the method comprising the steps of: (a) adding to the sludge an effective amount of a phosphorus-containing compound, wherein the phosphorus-containing compound is a phosphonium compound, wherein the phosphonium compound is either: (i) a tetrakis(hydroxyorgano)phosphonium salt; or (ii) a compound of formula (I) [R′R″(CH 2 OH) 2 P + ] n X − (I) wherein: n is the valency of X; R′ and R″, which are the same or different, are selected from an alkyl, hydroxyalkyl, alkenyl or aryl moiety and X is an anion; or wherein: the phosphorus-containing compound is an alkyl-substituted phosphine as shown in formula (II): (CH 2 OHR 2 )P (II) wherein: each R, which are the same or different, is selected from an alkyl, hydroxyalkyl, alkenyl or aryl moiety; and (b) keeping the phosphorus-containing compound in contact with the sludge for sufficient time to reduce the amount of pathogens present in the sludge by an amount equivalent to a logarithmic reduction of 2 or more.