Greywater Recycling: Field Experience
367
I.
II.
III.
IV.
Fig. 6. Greywater Recycling System: Water Samples from I) raw water, II) after
flocculation, III) after filtration and IV) after Nanofiltration and UV
After severe initial problems probably due to cross-connection with the
blackwater system, finally good water quality for use as toilet flush has been
obtained. After the treatment microbiological contamination could not be detected.
This is the result of the three consecutive processes nanofiltration, UV
disinfection, and chlorination, which act as a multiple barrier to microorganisms
and pathogenic germs.
Table 2. Quality of greywater and recycled water (n.d. = not detected)
Unit
Greywater
Recycled Water
pH
7.5 - 8.5
6.5 -7.0
Temperature
°C
15 - 20
15 - 20
COD
mgr!
200 - 300
10 - 100
Coliforms
CFU (100 ml)
10 3 _2*10 6
n.d.
E-Coli
CFU (100 ml)
10 3 - 3*10 4
n.d.
Coliphague
MPN (1 liter)
10 2 - 3*10 4
n.d.
S.3 Nanofiltration
The real condition of greywater is different on various sites. For every installation
an adaptation of the treatment process to actual conditions was required. A key
issue is to stabilize the flux of the nanofiltration units which showed severe