In a saucepan, bring broth and 2 cups (500 mL) water to a boil; reduce heat to low and keep warm.
Heat oil in a large deep skillet over medium heat; fry onion, stirring, until softened, about 3 minutes. Add rice, stirring to coat grains for about 1 minute. Stir in wine until absorbed.
Using ladle, add ½ cup (125 mL) hot broth mixture; cook, stirring constantly, until liquid is absorbed, 2 to 3 minutes, and adjusting heat as necessary to maintain a simmer. Continue to cook, stirring constantly, adding hot broth ½ cup (125 mL) at a time and waiting until liquid is absorbed before adding more, for about 15 minutes.
Stir in shrimp, scallops and remaining broth (should be around ½ cup/125 mL); cook, stirring, until shrimp are pink and scallops are opaque, about 3 minutes.
Stir in peas, dill and lemon zest; cook, stirring, for 1 to 2 minutes. Rice should be tender with a firm centre and risotto should be creamy.
Remove from heat. Stir in lemon juice, butter and cheese. Serve sprinkled with more cheese and garnished with dill sprigs, if desired.
Per Serving: 344 calories, 21 g protein, 8 g fat (3 g saturated fat), 42 g carbohydrates, 2 g fibre, 90 mg cholesterol, 223 mg sodium