A diffuser useful for sparging to remove contaminant in situ is described. The diffuser includes a first elongated member having a sidewall with a first portion of the length of the sidewall being microporous, and a second portion of the length of the sidewall having well screen sized openings with the first elongated member defining an interior hollow portion of the diffuser, a second elongated member having a second sidewall having a plurality of microscopic openings, said second member being disposed through the hollow region of said first member and a third elongated member having a third sidewall having a plurality of microscopic openings, said third member being disposed coaxial with the first and second members. An end cap is disposed to seal a first end of the third elongated member, and being in contact with the second elongated member forms a chamber. The diffuser has an inlet arrangement disposed at a second end of diffuser for supporting a first inlet fitting to coupled to an peripheral interior portion of the diffuser adjacent the first member, a second fitting to couple to the chamber, and a third fitting coupled to the third member.