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 reduction1 | Reference method of measurement |
|---|---|---|---|
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 nitrification2 | 25 mg/l O2 | 70—90 | Homogenized, unfiltered, undecanted sample. Determination of dissolved oxygen before and after five-day incubation at 20° ±1°C, in complete darkness. Addition of a nitrification inhibitor |
| Chemical oxygen demand (COD) | 125 mg/l O2 | 75 | Homogenized, 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 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 reduction1 | 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/l P (10,000—100,000 p.e.) 1 mg/l P (more than 100,000 p.e.) | 80 | Molecular absorption spectrophotometry |
| Total nitrogen2 | 15 mg/l N (10,000—100,000 p.e.) 10 mg/l N (more than 100,000 p.e.) | 70—80 | Molecular absorption spectrophotometry |