The Urban Waste Water Treatment (Scotland) Regulations 1994

Regulations 5, 6 and 11

SCHEDULE 3

PART I REQUIREMENTS FOR DISCHARGES FROM TREATMENT PLANTS

1.  Treatment plants shall be designed or modified so that representative samples of the incoming waste water and of treated effluent can be obtained before discharge to receiving waters.

2.  Discharges from urban waste water treatment plants subject to treatment in accordance with regulation 5(1) and (2) shall, subject to paragraphs 4 and 5 of Part II of this Schedule, meet the requirements shown in Table 1 below.

3.  Discharges from urban waste water treatment plants to those sensitive areas which are subject to eutrophication as identified in sub-paragraph (a) of Part I of Schedule 1 shall, subject to paragraphs 4 and 5 of Part II of this Schedule, also meet the requirements in Table 2 below.

4.  More stringent requirements than those shown in Table 1 and/or Table 2 shall be applied where required to ensure that the receiving waters satisfy any other relevant Community Directives.

5.  The points of discharge of urban waste water shall be chosen, as far as possible, so as to minimise the effects on receiving waters.

TABLE 1 REQUIREMENTS FOR DISCHARGES FROM URBAN WASTE WATER TREATMENT PLANTS SUBJECT TO REGULATION 5(1) AND (2)

The values for concentration or for the percentage of reduction shall apply.

Parameters	Concentration	Minimum percentage of reduction	Reference method of measurement
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.
Biochemical oxygen demand (BOD5 at 20°C) without nitrification	25 mg/1 O2	70-90	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/1 O2	75	Homogenized, unfiltered, undecanted sample Potassium dichromate.

TABLE 2 REQUIREMENTS FOR DISCHARGES FROM URBAN WASTE WATER TREATMENT PLANTS TO SENSITIVE AREAS WHICH ARE SUBJECT TO EUTROPHICATION AS IDENTIFIED IN SUB-PARAGRAPH (a) OF PART I OF SCHEDULE 1

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
(1) Reduction in relation to the load of the influent.
(2) Total nitrogen means: the sum of total Kjeldahl-nitrogen (organic N+NH3), nitrate (NO3)-nitrogen and nitrite (NO2)-nitrogen.
Total phosphorus	2 mg/1 P (10,000–100,000 p.e.) 1mg/1 P (more than 100,000 p.e.)	80	Molecular absorption spectrophotometry
Total nitrogen(2)	15 mg/1 N (10,000–100,000 p.e.) 10 mg/1 N (more than 100,000 p.e.)	70-80	Molecular absorption spectrophotometry

PART II REFERENCE METHODS FOR MONITORING AND EVALUATION OF RESULTS

1.—(a) Every river purification 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) Every 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 well-defined 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 Regulations; 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