Supplementary Information (SI)
Table SI-1 Comparison of the observed yield coefficients of activated sludge process (ASP),
methanogenic anaerobic bioreactor (MAB) and sulfate reduction up-flow sludge bed
(SRUSB)
Process
Y
(kg VSS/kg COD)
θc
(d)
Kd
(d-1)
Yobs
(kg VSS/kg COD)
ASP
MAB
SRUSB
0.42
0.08
0.07a
10
60
90
0.06
0.03
0.04
0.25
0.05
0.02
References
Metcalf and Eddy Inc. 1991
van Lier et al., 2008
Lu et al., 2009 and 2011
a: fcv=COD/VSS=1.52 kg COD/kg VSS of the sludge in the SRUSB,
thereby Y=Y’/fcv=0.113/1.52=0.07 kg VSS/kg COD, where Y’=0.113 kg COD/kg COD
In order to evaluate the sludge minimizing effectiveness of the SANI® process, the observed
yield coefficient (Yobs) was determined from the following equation (Metcalf and Eddy, 1991),
which is the same as that determined in the steady state BSR model (Poinapen and Ekama,
2010).
Yobs 
Y
(1   c  K d )
where, Yobs=observed yield coefficient (kg VSS/kg COD); Y=yield coefficient (kg VSS/kg
COD); θc=cell retention time or sludge retention time (SRT, day); and Kd=endogenous decay
coefficient (d-1).
SSi
SSi-inorg
SSi-org
SSe-inorg
SSr-inorg
SSe-u
SSi-b
RBCOD
FSS
BPO
UPO
RBO
USO
Mass of SS flowing into SRUSB per day (kg SS/day);
Mass of inorganic SS flowing into SRUSB per day (kg SS/day);
Mass of organic SS flowing into SRUSB per day (kg SS/day);
Mass of inorganic SS flowing out of SRUSB via effluent per day (kg SS/day);
Mass of inorganic SS retained in SRUSB per day (kg SS/day);
Mass of un-biodegradable organic SS in effluent of the SRUSB per day (kg SS/day);
Mass of biodegradable organic SS flowing into SRUSB per day (kg SS/day);
Readily biodegradable COD (kg COD/day);
Fixed-inorganic suspended solids;
Biodegradable particulate organics;
Un-biodegradable particulate organics;
Readily biodegradable organics; and
Un-biodegradable soluble organics;
Figure SI-1 Composition of suspended solids and soluble organics flowing into the SRUSB
at the steady state.
Calculation premise for energy consumption and fossil CO2 emission:
Some assumptions and basic parameters are applied for the calculation of energy
consumption and fossil CO2 emission of the SANI® process and conventional biological
nitrogen removal (CBNR) process as follows:
1) Each wastewater treatment process (WWTP) treats 100,000 m3/day, and the influent COD
and removal efficiency are set at 500 mg/L and 80%, respectively. So each WWTP
removes about 14,600,000 kg COD/year;
2) Sludge treatment of CBNR process involves sludge thickening, dewatering, anaerobic
digestion and ultimate disposal by sludge incineration which adopts a typical fluidized
bed incinerator. Since 84% of excess sludge from SANI® is inorganic, sludge incineration
could be waived. The sludge treatment in this process includes sludge thickening,
dewatering, and landfill only;
3) Energy generation efficiency from methane gas in the sludge anaerobic digestion of
CBNR is 1.5 kWh/kg COD removed (Van Lier et al., 2008), while the methane gas per
unit energy converts to CO2 per unit energy of coal (Ausubel et al., 1988);
4) Energy consumption in sludge dewatering and storage is 131 kWh/tonne dried mass (tDM)
(Houillon and Jolliet, 2005);
5) Energy consumption in sludge incineration=2.1 GJ/tDM or 583.8 kWh/tDM, and its CO2
emission=0.132 ton CO2 /tDM (Lu et al., 2009);
6) Electricity energy is obtained from coal driven power station;
7) η=CO2 generation coefficient for producing 1 kWh of electricity at a typical coal-driven
power station, which is determined by (Van Lier et al., 2008):

21tonCO2 / d
 8.75 104 (tonCO2 / kWh)
1000kW  24h
(18)
Reference:
Ausubel JH, Grubler A, Nakicenovic N. 1988. Carbon dioxide emissions in a methane
economy. Climatic Change 12(3):245-263.
Houillon G, Jolliet O. 2005. Life cycle assessment of processes for the treatment of
wastewater urban sludge: Energy and global warming analysis. Journal of Cleaner Production
13(3):287-299.
Metcalf and Eddy Inc. 1991. Wastewater engineering: treatment, disposal, and reuse. New
York: McGraw-Hill.
Poinapen J, Ekama GA. 2010. Biological sulfate reduction with primary sewage sludge in an
upflow anaerobic sludge bed (UASB) reactor-Part 5: Steady state model. Water SA
36(3):193-202.
Van Lier JB, Mahmoud N, Zeeman G. 2008. Anaerobic wastewater treatment in Biological
wastewater treatment: Principles, modelling and design. Henze M, van Loosdrecht MCM,
Ekama GA, Brdjanovic D, editors. London: IWA Pub. p 415-456.