(Art. 6 para. 1)
1Communal wastewater includes:
2The following requirements apply to communal wastewater from wastewater treatment plants treating in excess of 200-population equivalent (PE1). They apply at the site of discharge and for the standard operation of the plant, subjectto exceptional situations such as unusually heavy rainfall.
3For communal wastewater from wastewater treatment plants with 200 PE or fewer and for wastewater from overflows from combined systems , the authorities determine the requirements from case to case taking local conditions into consideration.
4If the wastewater from a central wastewater treatment plant also contains industrial wastewater (Annex 3.2) or other polluted wastewater (Annex 3.3), the authorities shall specify the requirements for discharge into waters in their authorisation, if necessary in derogation from the requirements listed in Nos 2 and 3, in such a way that no more potential water pollutants are discharged with the wastewater than would be the case if the different wastewaters were treated separately in compliance with the requirements of the corresponding Annexes.
| No. | Parameter | Requirements |
|---|---|---|
| 1 | Total suspended solids | For wastewater from plants of less than 10 000 PE the following requirements apply: – discharge concentration: 20 mg/l For wastewater from plants from 10 000 PE the following applies: – discharge concentration: 15 mg/l |
| 2 | Chemical oxygen demand*(COD)* | For wastewater from plants of less than 10 000 PE the following requirements apply: – discharge concentration: 60 mg/l O |
| 3 | Dissolved organic carbon*(DOC)* | For wastewater from plants of 2000 PE or over the following requirements apply: – discharge concentration: 10 mg/l and – removal efficiency: 85%, expressed as If the value is not complied with, the authorities shall assess the substances, determine their origin and if necessary specify the required procedures in accordance with Annexes 3.2 and 3.3. |
| 4 | Transparency*(Snellen method)* | 30 cm |
| 5 | Ammonium*(sum of NH* | If the ammonium concentrations in the wastewater are potentially detrimental to the water quality of a watercourse, the following requirements apply if the wastewater temperature is higher than 10 °C; In these cases nitrification must be carried out throughout the year: Remark : Kjeldahl nitrogen is the sum of the nitrogen inform the ammonium, ammonia and organic nitrogen. |
| 6 | Nitrite*(NO* | 0.3 mg/l N (guide value) |
| 7 | Adsorbable organic halogen*(AOX)* | 0.08 mg/l X. If the value is not complied with, the authorities shall assess the substances, determine their origin and if necessary specify the required procedures in accordance with Annexes 3.2 and 3.3. |
| 8 | Organic substances that can pollute waters even in low concentrations*(organic trace substances)* | The removal efficiency with respect to raw wastewater and measured using selected substances must amount to 80 % for wastewater from: – plants with 80 000 or more connected residents; – plants with 24 000 or more connected residents in the catchment area of lakes; the canton may authorise exceptions if the benefit of removal for the environment and for the drinking water supply is negligible; – plants with 8000 or more connected residents that discharge into a watercourse containing more than 10 % wastewater untreated for organic trace substances; the canton shall identify the plants that must take measures as part of a plan for the catchment area; – other plants with 8000 or more connected residents if removal is required due to special hydrogeological conditions; – .2 The Department shall specify the substances to be used to measure the removal efficiency in an ordinance, and how efficiency is calculated. |
| 9 | Biochemical oxygen demand*(Bod* | and and |
| No. | Parameter | Requirements |
|---|---|---|
| 1 | Total phosphorus (after conversion to dissolved orthophosphate) | For wastewater from plants – in the catchment area of lakes, – situated on watercourses downstream of lakes, if this is required for the protection of the watercourse, and – of 10.000 PE or over, situated on watercourses in the catchment area of the Rhine downstream of lakes, the following requirements apply: – discharge concentration: 0.8 mg/l P and – removal efficiency, with respect to raw wastewater: 80% |
| 2 | Total nitrogen | In plants for which no discharge concentration and no removal efficiency for total nitrogen is specified, must be operated in such a way that during wastewater purification and sludge treatment as much nitrogen as possible is eliminated. All structural modifications which are possible at no great cost must be undertaken; this applies particularly to plants that already carry out nitrification. Prior to 28 February 2002, cantons in the catchment area of the Rhine shall work out a plan on how to reduce discharges of nitrogen by 2600 tonnes compared to 1995 with effect from the year 2005 onwards. Plants that are earmarked in this plan for nitrogen elimination must be operational by 2005 at the latest. |
1The requirements under Nos 2 and 3 refer to an examination period of one year and to continuous sampling, conducted at regular intervals on different days of the week. With regard to organic trace substances, the samples must be taken over 48 hours and with regard to other parameters over 24 hours.
2The number of samples per year depends on the size of the plant:
| a. Plants of less 2000 PE | The cantonal authorities shall specify the minimum number of samples to be analysed on a case by case basis. |
|---|---|
| b. Plants of 2000 PE or over | In the first year after the commissioning or extension of the plant at least twelve samples. In the following years at least four samples if the wastewater complied with the requirements in the first year. If the wastewater does not comply with the requirements in any year, a further twelve samples at least must be analysed the following year. With regard to organic trace substances, at least eight samples must be analysed instead of at least twelve. |
| c. Plants of 10 000 PE and over | At least twelve samples per year. With regard to organic trace substances, from the second year after the commissioning or extension of the plant at least six samples must be analysed if the wastewater complied with the requirements in the first year; If the wastewater does not comply with the requirements in any year, a further twelve samples at least must be analysed the following year. |
| d. Plants of 50 000 PE and over | At least 24 samples per year. With regard to organic trace substances, from the second year after the commissioning or extension of the plant at least twelve samples must be analysed if the wastewater complied with the requirements in the first year; If the wastewater does not comply with the requirements in any year, a further 24 samples at least must be analysed the following year. |
1The maximum number of non-compliant samples admissible depends on the total number of samples as indicated in the table below.
2The following values must never be exceeded:
– Total suspended solids 50 mg/l
– Chemical oxygen demand (BOD5) 120 mg/l
– Dissolved organic carbon (DOC) 20 mg/l
– Biochemical oxygen demand (BOD5) 40 mg/l
3The following annual averages must not be exceeded: – Phosphorus in plants of 10 000 PE and over 0.8 mg/l P
Table: admissible number of non-compliant samples
| Number of samples per year | Admissible number of non‑compliant samples | Number of samples per year | Admissible number of non‑compliant samples |
|---|---|---|---|
| 4– 7 | 1 | 172–187 | 14 |
| 8– 16 | 2 | 188–203 | 15 |
| 17– 28 | 3 | 204–219 | 16 |
| 29– 40 | 4 | 220–235 | 17 |
| 41– 53 | 5 | 236–251 | 18 |
| 54– 67 | 6 | 252–268 | 19 |
| 68– 81 | 7 | 269–284 | 20 |
| 82– 95 | 8 | 285–300 | 21 |
| 96–110 | 9 | 301–317 | 22 |
| 111–125 | 10 | 318–334 | 23 |
| 126–140 | 11 | 335–350 | 24 |
| 141–155 | 12 | 351–365 | 25 |
| 156–171 | 13 |
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