take a look into the umbracoSettings.config where you can set the character replacings:

<requestHandler>
    <!-- this will ensure that urls are unique when running with multiple root nodes -->
    <useDomainPrefixes>true</useDomainPrefixes>
    <urlReplacing>
    <char org=" ">-</char>
            <char org="&quot;"></char>
            <char org="."></char>
         <char org=";"></char>
         <char org="/"></char>
         <char org=":"></char>
         <char org="#"></char>
         <char org=","></char>
         <char org="&amp;"></char>
         <char org="?"></char>
         <char org="æ">ae</char>
         <char org="ø">oe</char>
            <char org="å">aa</char>
         <char org="ä">ae</char>
          <char org="ö">oe</char>
          <char org="ü">ue</char>
          <char org="ß">ss</char>
         <char org="("></char>
         <char org=")"></char>
         <char org="["></char>
         <char org="]"></char>
         <char org="'"></char>
         <char org="\"></char>
    </urlReplacing>
  </requestHandler>

Thomas