The resilience of a treatment facility should be an important part of its design and operation throughout its service life to ensure it meets compliance and production expectations. This has traditionally been difficult to assess and quantify, and as a consequence its management has largely been ignored, or has been reduced to a function of how many treatment stages are provided with redundancy and/ or backup ‘stand-by’ facilities. Without proper resilience assessment there will always be a tendency to undertake ‘gold-plate’ engineering producing specifications much higher than the business need. This consequently leads to higher capital and operational expenditure over the life of a treatment asset. Value engineering then ends up an art form, where negotiating the line between risk and cost is often more to do with good luck than judgement. Resilience assessment makes value engineering a science rather than an art, as well as providing a critical means of influencing and assessing investment decisions and operational and maintenance planning to minimise the overall cost of compliance. Asset resilience assessment techniques have been developed in other industries over the last 15 years. Recently the authors have applied these tried and tested approaches to water and wastewater treatment assets.