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Wastewater Directives
- Urban waste water treatment
- Directive 91/271/EEC
| Parameters |
Concentration |
Minimum percentage of reduction (1) |
Reference method of measurement |
| Biochemical oxygen demand (BOD5 at 20 °C) without nitrification (2) |
25 mg/l O2 |
70-90 40 under
Article 4 (2) |
Homogenized, unfiltered, undecanted sample. Determination of dissolved oxygen before and after five-day incubation at 20 °C ±
1 °C, in complete darkness. Addition of a nitrification inhibitor |
| Chemical oxygen demand (COD) |
125 mg/l O2 |
75 |
Homogenized, unfiltered, undecanted sample Potassium dichromate |
| Total suspended solids |
35 mg/l 35 under
Article 4 (2)
(more than 10 000 p.e.)
60 under
Article 4 (2)
(2 000-10 000 p.e.) |
90 (3) 90 under
Article 4 (2)
(more than 10 000 p.e.)
70 under
Article 4 (2)
(2 000-10 000 p.e.) |
- Filtering of a representative sample through a 0,45 ìm filter membrane. Drying at 105 °C and weighing - Centrifuging of
a representative sample (for at least five mins with mean acceleration of 2 800 to 3 200 g), drying at 105 °C and weighing |
(1) Reduction in relation to the load of the influent.
(2) The parameter can be replaced by another parameter: total organic carbon (TOC) or total oxygen demand (TOD) if a relationship can be established between
BOD5 and the substitute parameter.
(3) This requirement is optional.
Analyses concerning discharges from lagooning shall be carried out on filtered samples; however, the concentration of total suspended solids in unfiltered water
samples shall not exceed 150 mg/l.
Table 2:
Requirements for discharges from urban waste water treatment plants to sensitive areas which are subject to eutrophication as identified in Annex II.A
(a). One or both parameters may be applied depending on the local situation. The values for concentration or for the percentage of reduction shall apply.
| Parameters |
Concentration |
Minimum percentage of reduction (1) |
Reference method of measurement |
| Total phosphorus |
2 mg/l P
(10 000 - 100 000 p. e.)1 mg/l P
(more than
100 000 p. e.) |
80 |
Molecular absorption spectrophotometry |
| Total nitrogen (2) |
15 mg/l N (10 000 - 100 000 p. e.)
10 mg/l N
(more than
100 000 p. e.) (3) |
70-80 |
Molecular absorption spectrophotometry |
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