Table 14.7 - Reduction efficiencies of different wastewater treatment processes (%)

Sources: Modified from Winther et al, 1978; MiljØstyrelsen, 1990

 Heavy metals
Treatment process Suspended solids BOD P N E. coli Viruses Cd, Zn Cu, Pb, Cr
Primary 60­70 20­40 10­30 10­20 60­90 30­70 5­20 40­60
Constructed reedbeds1 ­ 60­80 20­40 25­50 ­ ­ ­ ­
Secondary 80­95 70­90 20­40 20­40 90­99 90­99 20­40 70­90
Tertiary 90­95 >95 85­97 20­402 >99 >99 40­60 80­95

Notes:

  1. Miljøstyrelsen, 1990.
  2. N-reduction increases to 85­95% with nitrification and denitrification processes included.