Patent ID: 7740762

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 tetrakis(hydroxyorgano)phosphonium salt or compound of formula (I) [R′R″(CH 2 OH) 2 P + ] n X n− (I) wherein: n is the valency of X; R′ and R″, which may be the same or different, are each an alkyl, hydroxyalkyl, alkenyl or aryl moiety and X is an anion; and (b) keeping the tetrakis(hydroxyorgano)phosphonium salt or compound in contact with the sludge for sufficient time to give rise to a finally treated sludge wherein the total reduction in the amount of pathogens present is by an amount equivalent to a logarithmic reduction of 2 or more compared to the amount of pathogens present in untreated sludge.