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The Urban Waste Water Treatment Regulations (Northern Ireland) 1995

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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 I

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

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

Reference method of measurementMinimum percentage of reduction(1)ParametersConcentration
(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.

Biochemical oxygen demand (BOD5 at 20°C) without nitrification(2)25 Mg/l O270-90Homogenized, 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 O275Homogenized, unfiltered, undecanted sample Potassium dichromate.

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 SUB-PARAGRAPH (a) OF PART 1 OF SCHEDULE I

One or both parameters may be applied depending on the local situation. The values for concentration or for the percentage of reduction shall apply.

ParametersConcentrationMinimum 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 phosphorus2 mg/l P (10,000-100,000 p.e.) 1 mg/1 P (more than 100,000 p.e.)80Molecular 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.)70-80Molecular absorption spectrophotometry

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