The Board of Trustees may provide by ordinance for the levy, in addition to the taxes now authorized by law, and in addition to the amount authorized to be levied for corporate purposes, as provided by Section 12 of this Act, of a direct annual tax not exceeding .05 per cent of the value, as equalized or assessed by the Department of Revenue of the State of Illinois, of all taxable property in such sanitary district. The fund arising therefrom shall be known as a public benefit fund and shall be used solely for the purpose of paying that portion of the several amounts assessed against the district for public benefit as well as paying any such amounts as may be assessed for public benefit under any ordinance that may be adopted by the Board of Trustees.
     The foregoing limitation upon tax rate may be increased or decreased according to the referendum provisions of the General Revenue Law of Illinois.