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Abstract:
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The aim of this study was to compare conventi
onal and natural wastewater treatment systems
appropriated for India considering the environmental and socio-economic dimensions. To this end,
Life Cycle Assessment (LCA) of a
conventional Wastewater treatment
Plant (WWTP) (1,500 p.e) and
5 configurations of two stages co
nstructed wetlands (CWs) (i.e Li
ne 1: horizontal+horizontal flow;
Line 2: horizontal+vertical flow; Line 3: vertical+horiz
ontal flow; Line 4: vertical+vertical flow; Line 5:
one aerated wetland) was carried out using
SimaPro 8
software. The comparison was
complemented by a Multi Criteria Analysis (M
CA) which considered technical, socio-economic and
environmental aspects.
The results obtained from conventional WWTP
LCA showed that for all impacts categories
considered (i.e Abiotic Depletion, Acidification, Eutrophication and Global Warming) between 89 and
93 % of the contribution was due to system operat
ion (i.e.: energy consumption, ferric chloride used
for phosphorous precipitation and polyelectrolyte
used for sludge treatment) while the construction
phase (e.g: earth movings, excavation, materials an
d manufacturing) accounts for 7-11 % of the total
impacts. According to that for CWs LCA only system operation was taken into account.
The results obtained from the LCA of the CWs sy
stems showed that for all impacts categories
considered (i.e Abiotic Depletion, Acidification, Eutrophication and Globla Warming) between 10 and
37 % of the contribution was due to energy
consumption while sludge production and its
transformation in compost (biowaste process) accounts
for 62-90 % of the total impacts. In particular,
Line 1 configuration has the smallest impact for all categories considered. Indeed, it had the lowest
energy consumption compared to other configurati
ons. On the other hand, Line 5 scenario presents
the highest impact due to the high blower
energy consumption in the aereted wetland.
Comparing all scenarios, the impacts of WWTP operation was between 5 and 21 times higher than
the impacts of CWs operat
ion, for all lines and categories considered. It is mainly due to the high
energy consumption in WWTP with res
pect to CWs (1.26 and 0.0243-0.0738 kWh/m
3
, respectively).
The MCA emphasized the high costs and energy consumption as well as the low land occupation
and waste production of WWTP. The opposite was observed for CWs scenarios.
Finally, MCA results showed that the most appropri
ated alternatives for wa
stewater treatment in
India were Line 2 (horizontal+vertical flow CW),
Line 3 (vertical+horizontal flow CW) and Line 4
(vertical+vertical flow CW), thanks to
lowest energy consumption and costs. |
