5. Conclusions
This study presented two modified septic tank systems considered
to represent efficient technologies domestic sewage
(pre) treatment at sewage temperature conditions found in
northern China during winter months. At an HRT of 36 h,
the CODtot removal of the ABR-septic tank and the YDTcarrier-
septic tank were improved by 10–20% as compared
to the conventional septic tank.
For newly constructed septic tanks, an ABR-septic tank
design is recommended for an efficient and stable CODtot
and TS removal. However, for rebuilt septic tanks, existing
conventional septic tanks can be modified into an