Neil Wragg, head of DNV GL’s Performance Forecasting team Sewerage networks, Wastewater treatment, Water, Water networks, Water treatment, Opinion

Neil Wragg says water companies can more effectively allocate resources by not over-engineering their technical solutions.

With agreement from the regulator, water companies can plan investments appropriately for the provision of services. Outside investment allows the replacement of deteriorated assets and improvements to the quality of drinking water and water courses.

Ofwat recently reported on how water and wastewater companies have approached asset health and how this contributes to resilience. Key challenges include driving innovation, adopting a long-term mindset and understanding how asset health affects service.

Ofwat describes resilience as “the ability to cope with, and recover from, disruption, and anticipate trends and variability in order to maintain services for people and protect the natural environment, now and in the future”. Water companies recognise these parameters and know their treatment facilities must comply. The evaluation of the resilience of a treatment facility should be an important part of its design and operation.

Resilience modelling allows the effective selection of processes and treatment schemes. It also provides a critical means of influencing and assessing investment decisions and operational and maintenance planning in order to minimise the overall cost of compliance.

Without proper resilience assessment, there will always be a tendency to default to a “belt and braces” approach as a means of managing the compliance risk, leading to “gold-plated” engineering, with specifications much higher than the business need. This in turn leads to higher total cost over the life of a treatment asset.

Resilience can be assessed across the full water cycle, encompassing drinking water treatment, sewage and trade effluent treatment, and sludge treatment and disposal. Typical uses of resilience modelling have included the following:

• comparison of proposed schemes and alternative technologies in design phase;

• identification of critical and non-critical equipment;

• risk-ranking of treatment works;

• development of investment, operational, maintenance and spares holding strategies;

• operational troubleshooting and identification of capacity bottlenecks.

Using resilience modelling in this way, key factors can be brought together and assessed, including equipment reliability, system capacity and criticality, operations and maintenance strategy, flowrates and discharge consents – and maintenance resources and spares holding.