Dwelling Performance Standards

5.1 Performance Standards

I.S. EN 12566-3:2005 and prEN 12566-6 specify the test procedures to be followed in the measurement of a range of parameters relevant to treatment efficiency for packaged and/or site-assembled treatment plants and for prefabricated treatment units for septic tank effluent, respectively. These standards do not specify treatment efficiency to be achieved for any of these parameters. However, the standards provide for the declaration of test performance in relation to some or all of the parameters, as may be required by national regulations.

Table 4.1 sets out the influent characteristics for the testing of these systems. Due to the more concentrated influent in Ireland, wastewater treatment systems being tested for use on the Irish market should be tested according to the I.S. EN 12566-3:2005

standard using the upper values for influent sewage and their performance stated in terms of percentage removal efficiency for the entire test parameters. The design should be based on 60g BOD/person/day and the recommended influent test range should be 300–500 mg/l.

Table 5.1 sets out performance effluent standards for specific parameters, which are considered to be the minimum acceptable levels that should be achieved by these types of treatment systems. Compliance with the standard should be at a sampling chamber following the treatment process.

Local authorities may set stricter performance standards and they should be conditional on the results of a proposed impact assessment on the receiving waters.

In nutrient-sensitive locations, the local authority should consider more stringent performance standards for nitrogen and phosphorus (Table 5.1), particularly where measures are needed to achieve the objectives of the Water Framework Directive.



Standard1 (mg/l)


Biochemical oxygen demand (mg/l)


Suspended solids (mg/l)


NH4 as N (mg/l)


Unless otherwise specified by local authority

Total nitrogen2 as N (mg/l)


Only for nutrient-sensitive locations

Total phosphorus2 (mg/l)


Only for nutrient-sensitive locations

1.  95 percentile compliance is required for site monitoring carried out after installation.

2. Only required to be achieved in nutrient-sensitive locations.

3. 24-h composite samples.

O.S.C Environmental Engineering and Percolation Testing