Bring 2 1/2 cups water, 1/4 onion, 1 bay leaf, 1 quartered celery stalk and a few peppercorns to a boil in a large pot. Add 3 pounds scrubbed steamer clams; cover and cook until they open, about 10 minutes (discard any that do not open). Drain, then strain the liquid. To eat, remove the clams from their shells and rinse in the liquid. Dip in melted butter and serve with lemon wedges.