In a stock pot, bring water and chicken bouillon granules to a boil. Stir well until bouillon is fully dissolved. Add the ham bone to the broth, reduce heat to medium-low, and mix in the lentils. Let it simmer for about 10 minutes until lentils start to soften.
Combine celery, carrots, green bell pepper, onion, marjoram, and bay leaf with broth and cook until lentils and veggies are tender, 10 to 20 minutes.
Remove the pot from heat and take out the ham bone from the soup. Cut the ham off the bone into cubes, then add the meat back into the soup and discard the bone.