Quelltext der Seite Ablaufwasser aus Kleinkläranlagen/en

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In Europe, the quality of water discharged from small treatment plants is governed in 91/271/EEC directive. 

{| class="wikitable"
|-
! Class !! CSB mg/l !! BSB5 mg/l !! NH4-N mg/l !! N<sub>anorg.</sub> mg/l !! P mg/l !! Faecal coliforme Keime je 1000 ml !! AFS mg/l
|-
| C || 150<sup>*</sup>/100<sup>**</sup>* || 40<sup>*</sup>/25<sup>**</sup> || - || - || - || - || 75<sup>*</sup>
|-
| N || 90<sup>*</sup>/75<sup>**</sup>*|| 20<sup>*</sup>/15<sup>**</sup> || 10<sup>**</sup> || - || - || - || 50<sup>*</sup>
|-
| D || 90<sup>*</sup>/75<sup>**</sup>*|| 20<sup>*</sup>/15<sup>**</sup> || 10<sup>**</sup> || 25<sup>**</sup> || - || - || 50<sup>*</sup>
|}

<sup>*</sup> obtained from certified sample, ordinary sample of faecal coliform bacteria

<sup>**</sup> ** determined from 24 h mixed sample; NH<sub>4</sub>-N and N<sub>anorg.</sub>. with temperature of discharged water T &ge; 12°C

Most modern water treatment plants have improved over BOD<sub>5</sub>   discharge values of < 25 mg/l.