One of the key aspects of planning and designing a water reuse scheme (see Chapter 6) is to define the quality needed according to the use planned that will then determine the level of required treatment and the choice of treatment technology. Scheme design needs to take into account the quality (and the variability of the quality) of the influent wastewater (secondary effluents), the quality requirements of the purpose of use and reliability of operation. Design and implementation of an under-performing treatment system could lead to unacceptable or unreliable water quality for water reuse purposes (defeating the object of improved resilience and water security). Risks from treatment choices There might be risks posed by the treatment process (e.g. formation of sub products, deficits in the removal of pollutants). In rare cases of areas with low environmental risk and for specific reuse purposes with low health risk, an advanced treatment could pose a higher risk than the use of treated wastewater with a lower treatment (e.g. discharge of disinfection by-products such as trihalomethanes). Such risks should be assessed in the planning processes where risks are analysed and the decisions made on the treatment required (see Chapter 6). The choice of appropriate treatment should in any case be based on the best available technology, standards, legislation and sound knowledge. Risks to species and habitats Ecosystems, species and habitats have all their needs related to water quality and quantity. When planning water reuse it should be ensured that conservation status of species and habitats, including requirements of the Birds and Habitats Directives, in the area are not compromised by the changes in availability / quality of water resources, e.g. ecological flows are still ensured.
One of the key aspects of planning and designing a water reuse scheme (see Chapter 6) is to define the quality needed according to the use planned that will then determine the level of required treatment and the choice of treatment technology. Scheme design needs to take into account the quality (and the variability of the quality) of the influent wastewater (secondary effluents), the quality requirements of the purpose of use and reliability of operation. Design and implementation of an under-performing treatment system could lead to unacceptable or unreliable water quality for water reuse purposes (defeating the object of improved resilience and water security). Risks from treatment choices There might be risks posed by the treatment process (e.g. formation of sub products, deficits in the removal of pollutants). In rare cases of areas with low environmental risk and for specific reuse purposes with low health risk, an advanced treatment could pose a higher risk than the use of treated wastewater with a lower treatment (e.g. discharge of disinfection by-products such as trihalomethanes). Such risks should be assessed in the planning processes where risks are analysed and the decisions made on the treatment required (see Chapter 6). The choice of appropriate treatment should in any case be based on the best available technology, standards, legislation and sound knowledge. Risks to species and habitats Ecosystems, species and habitats have all their needs related to water quality and quantity. When planning water reuse it should be ensured that conservation status of species and habitats, including requirements of the Birds and Habitats Directives, in the area are not compromised by the changes in availability / quality of water resources, e.g. ecological flows are still ensured.