Any district heretofore established pursuant to the provisions of this chapter is hereby declared and determined to have been validly established, regardless of the failure of the county government or any of its officials or employees to comply with the requirements as to the establishment of such district set forth in this chapter, and notwithstanding that any of the proceedings taken to establish such district were not validly taken, and notwithstanding that the area of the district is less than the area in which the proposed sewage improvements are to be constructed and that such sewage improvements will serve an area greater than the area of such district; provided, however, that any assessment levied on the lots and parcels of land in such district or any extension thereof shall be in proportion as nearly as may be to the benefit which each parcel would derive from such proposed sewage improvements, regardless of the total cost of such sewage improvements. Sewage disposal systems may be constructed on behalf of any such district either within or without the area of the district, to serve the district, any other district heretofore or hereafter established, and any municipality or other political subdivision of the State or agency which may contract for the use and services of the sewage system. Bonds of the county government may be issued to finance the cost of such sewage system whether authorized by bond resolutions heretofore or hereafter adopted by the county government. The bonds shall be payable in the manner provided by § 4656 of this title.