The Urban Waste Water Treatment Regulations (Northern Ireland) 2007

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 7(1) and (2) shall, subject to paragraphs 4 and 5 of Part II, meet the requirements shown in Table 1.

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, also meet the requirements in Table 2.

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 minimize the effects on receiving waters.

TABLE 1

REQUIREMENTS FOR DISCHARGES FROM URBAN WASTE WATER TREATMENT PLANTS SUBJECT TO REGULATION 7(1) AND (2)

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

Parameters	Concentration	Minimum percentage of reduction(001)	Reference method of measurement
(001) Reduction in relation to the load of the influent.
(002) 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.
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(002)	25 mg/l O2	70-90	Homogenized, unfiltered, undecanted sample. Determination of dissolved oxygen before and after five-day incubation at 20°C ± 1°C, incomplete darkness. Addition of a nitrification inhibitor.
Chemical oxygen demand (COD)	125 mg/l 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(003)	Reference method of measurement
(003) Reduction in relation to the load of the influent.
(004) Total nitrogen means: the sum of total Kjeldahl-nitrogen (organic N + NH3), nitrate (NO3)-nitrogen and nitrite (NO2)-nitrogen.
(005) These values for concentration are annual means as referred to in Schedule 3, Part II, paragraph 4(c). However, the requirements for nitrogen may be checked using daily averages when it is proved, in accordance with Schedule 3, Part II, paragraph 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 P (10,000-100,000 p.e.) 1 mg/1 P (more than 100,000 p.e.)	80	Molecular absorption spectrophotometry
Total nitrogen(004)	15 mg/1 N (10,000-100,000 p.e.)(005) 10 mg/1 N (more than 100,000 p.e.)(005)	70-80	Molecular absorption spectrophotometry