Each and every civil service employee of the city of Aberdeen, shall upon attaining the age of seventy (70) years, be mandatorily retired from further active service with the city. Such retirement shall be effective upon the first calendar day of the month next succeeding the date such member attained the age of seventy (70) years. The commission may establish minimum medical and fitness standards which must be met by employees as a condition of continued employment. Such standards need not be the same as the standards for original employment, but the standards should be job related.