In view of the general public benefits resulting from the elimination of pollution from the public waters of the state, the governor and council are authorized in the name of the state of New Hampshire to guarantee unconditionally, but at no time in excess of the total aggregate sum for the entire state of $50,000,000, the payment of all or any portion, as they may find to be in the public interest, of the principal of and interest on any bonds or notes issued by any municipality, town, city, county or district for construction of sewerage systems, sewage treatment and disposal plants, or other facilities necessary, required or desirable for pollution control, and the full faith and credit of the state are pledged for any such guarantee. The outstanding amount of principal and interest on such bonds and notes, the payment of which has been guaranteed by the state under the provisions of this section, shall at no time exceed the amount of $50,000,000. The state’s guarantee shall be endorsed on such bonds or notes by the state treasurer; and all notes or bonds issued with state guarantee shall be sold at public sealed bidding to the highest bidder. Any and all such bids may be rejected and a sale may be negotiated with the highest bidder. In the event of default in payment of any such notes or bonds, the state may recover any losses suffered by it by action against the municipality, town, city, county or district as provided in RSA 530. Provided, further, that in accordance with N.H. Rev. Stat. § 35-A:29, the foregoing requirement for public sealed bidding shall not be applicable to any bonds or notes or both so guaranteed which are sold to the New Hampshire municipal bond bank, and any bonds or notes or both so guaranteed may be sold to the New Hampshire municipal bond bank at private sale in accordance with the provisions of RSA 35-A.