Research has shown that the Hollandse Delta Water Board can achieve annual energy savings of 3 mln kWh in its Dokhaven underground water treatment plant by applying fine-bubble aeration. The environmental gains require a relatively high investment, though, and the Board therefore wanted an integrated appraisal of all the factors involved before going forward with such an investment. This report examines all the relevant business aspects along with social and environmental factors, and weighs these up.