In a large Dutch oven, bring the water, clam juice and peppercorns to a boil.
If necessary, remove the beards from the mussels.
Add the mussels to the boiling liquid.
Return just to a boil, then reduce the heat.
Cover and simmer about 5 minutes or until the shells open.
Drain and discard the liquid and any mussels that did not open.
Cool until easy to handle.
Remove the mussels from their shells and transfer to a medium bowl.
Reserve 16 of the shell halves.
Add the roasted peppers, capers, vinegar, thyme, lemon juice, lemon peel and black pepper to the bowl.
Toss until well mixed.
If desired, cover and chill in the refrigerator for up to 6 hours.