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3.2        Energy use and efficiency

3.2.1        Sustainable use of resources

Minimising unnecessary use of resources is the first step towards sustainability, and often can provide monetary savings to operators. In the context of water, efficient use of this essential resource should be high priority, both because water can be in short supply, and because pumping and treatment are expensive in both energy and financial terms. Water saved from use also does not become waste water. The circular economy under the Green Deal sets out the EC’s ambitions for resource use, focusing on certain product chains and recognising the relationship between circularity and climate neutrality (EC, 2020).

Figure 3.1 summarises the inputs and outputs of a) urban waste water treatment, and b) sewage treatment separated at source, such as in certain types of decentralised treatment. While many of the products are similar, the main difference is scale – typically, (a) might apply from 50 people to millions, while currently (b) would mainly apply in Europe to pilot studies. This chapter mainly focuses on conventional treatment (a) as the dominant approach. However, the importance of smaller scale approaches (b) is increasing in innovative towns and operators.

Figure 3‑1 Inputs and outputs of sewage treatment

a) at WWTP, b) source separation sewage treatment