— 2 000 to 9 999 p.e.:,  12 samples during the first year.    four samples in subsequent years, if it can be shown that the water during the first year complies with the provisions of the Directive; if one sample of the four fails, 12 samples must be taken in the year that follows.  ,
— 10 000 to 49 999 p. e.:,12 samples.,
— 50 000 p.e. or over:,24 samples.,
    Reduction in relation to the load of the influent.    ,
    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.    ,
    This requirement is optional.    ,

Biochemical oxygen demand (BOD5 at 20 °C) without nitrification ,25 mg/l O 2 ,  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 O 2 ,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     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 μm 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    ,
     Reduction in relation to the load of the influent.     ,
     Total nitrogen means the sum of total Kjeldahl nitrogen (organic and ammoniacal nitrogen) nitrate-nitrogen and nitrite-nitrogen.     ,
     These values for concentration are annual means as referred to in Annex I, paragraph D.4(c). However, the requirements for nitrogen may be checked using daily averages when it is proved, in accordance with Annex I, paragraph D.1, that the same level of protection is obtained. In this case, the daily average must not exceed 20 mg/l of total nitrogen for all the samples when the temperature from the effluent in the biological reactor is superior or equal to 12 °C. The conditions concerning temperature could be replaced by a limitation on the time of operation to take account of regional climatic conditions.     ,

 Total phosphorus ,  2 mg/l (    10 000    —    100 000    p.e.)  , 80 , Molecular absorption spectrophotometry ,
 1 mg/l (more than  100 000  p.e.) ,
 Total nitrogen  , 15 mg/l (  10 000  -  100 000  p.e.)  , 70-80 , Molecular absorption spectrophotometry ,
 10 mg/l (more than  100 000  p.e.)  ,

4-7,1,
8-16,2,
17-28,3,
29-40,4,
41-53,5,
54-67,6,
68-81,7,
82-95,8,
96-110,9,
111-125,10,
126-140,11,
141-155,12,
156-171,13,
172-187,14,
188-203,15,
204-219,16,
220-235,17,
236-251,18,
252-268,19,
269-284,20,
285-300,21,
301-317,22,
318-334,23,
335-350,24,
351-365,25,