Is Veolia Water available as an online biller?

Until the new Bill Manager service supports your biller, IMHO, you have these alternatives (in no particular order of preference):
1. Use Quicken Bill Manager's Check Pay making sure to submit payment early enough (at least 3 weeks before due date) to allow time for delivery and processing of a paper check.
Note: limited number of free transactions per month. See Quicken Bill Manager: How many payments can I make each month?

2. Every month logon to your bank's website and, using the bank's Bill Pay service, schedule your bill pay payments to be executed by the bank from your checking account. In parallel to that, in Quicken use a regular Scheduled Reminder to record your payment. Repeat both actions every time another payment is due.

3. Bypass Bill Manager. Automate the process. Let the biller's (or credit card company's) computer system do all the work for you. Logon to the biller's website once and set up their Autopay (or APS, Direct debit, etc.) service to make the current payment and all future payments on Due Date directly from your checking account. In parallel to that, in Quicken, every month, record a regular Scheduled Reminder to keep track of your payments before they come due.

4. Write (or print with Quicken) a paper check and mail it to the biller, making sure to mail payment early enough (at least 10 days before due date) to allow time for delivery and processing.

I've been using method #3, Autopay, for decades, since before the Internet and transaction download capabilities were even introduced. It's easy to get used to this process. And I have yet to miss a single payment.