In case any contracting municipality shall request sewage capacity in excess of what would be allotted to it for sewage, including ten per cent of factory waste, provision may be made in the contract for the enlargement of the sewer, plant and works, in order to accommodate and dispose of a larger quantity of factory waste, such increase in accommodation to be made at the expense of the municipality making requisition therefor.
N.J.S. § 58:14-14