LOW CARBON TECHNOLOGY FOR WASTEWATER TREATMENT
Sweaney, G.D., Gittings, C.A., Langstraat, J.W., Norton, M.R., Stephenson P.
Halcrow Group Ltd
(free)
There has been a recent trend of improvement in the standard to which wastewater is treated,
and an associated increase in the energy used in treatment. It is possible to reduce the
energy consumption of wastewater treatment by the use of treatment technologies that mimic
natural systems, such as waste stabilisation ponds and constructed wetlands. Generation of
renewable energy from biofuels manufactured from treatment byproducts may also offset
energy demand.
The potential for reduction in greenhouse gas emissions by using ‘natural wastewater
treatment’ (NWWT) systems was investigated. A lifecycle assessment was conducted for
three alternative treatment systems for a 2000 PE domestic wastewater stream in a
temperate climate:
1) Extended Aeration Plant (EA)
2) Constructed Wetland System (CWS)
3) Waste Stabilisation Ponds (WSP)
The embodied carbon of the three systems was broadly comparable; however the energy
consumption for the EA system is much greater than the NWWT systems and dominates the
whole life carbon footprint. For NWWT systems, the embodied carbon has the dominant
effect on the carbon footprint. The sensitivity of the comparison to individual components of
construction and operation are considered, and options for carbon reduction are discussed.
