The Urban Waste Water Treatment (England and Wales) Regulations 1994

PART II REFERENCE METHODS FOR MONITORING AND EVALUATION OF RESULTS

1.—(a) The Authority shall apply a monitoring method which corresponds at least with the level of requirements described below.

(b) Alternative methods to those mentioned in paragraphs 2, 3 and 4 may be used provided that it can be demonstrated that equivalent results are obtained.

(c) The Authority shall provide the Secretary of State with all relevant information concerning the applied method.

2.—(a) Flow-proportional or time-based 24-hour samples shall be collected at the same welldefined point in the outlet and if necessary in the inlet of the treatment plant in order to monitor compliance with the requirements for discharged waste water laid down in these Regulations.

(b) Good international laboratory practices aiming at minimising the degradation of samples between collection and analysis shall be applied.

3.  The minimum annual number of samples shall be determined according to the size of the treatment plant and be collected at regular intervals during the year:

— 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 these Regula tions; 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.

4.  The treated waste water shall be assumed to conform to the relevant parameters if, for each relevant parameter considered individually, samples of the water show that it complies with the relevant parametric value in the following way:

(a) for the parameters specified in Table 1 and sub-paragraph (b) of regulation 5(8), a maximum number of samples which are allowed to fail the requirements, expressed in concentrations and/or percentage reductions in that Table and that sub-paragraph, is specified in Table 3;

(b) for the parameters of Table 1 expressed in concentrations, the failing samples taken under normal operating conditions must not deviate from the parametric values by more than 100%;

(c) for those parameters specified in Table 2 the annual mean of the samples for each parameter shall conform to the relevant parametric values.

5.  Extreme values for the water quality in question shall not be taken into consideration when they are the result of unusual situations such as those due to heavy rain.

TABLE 3

Series of samples taken in any year	Maximum permitted number of samples which fail to conform
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