TITLE:
A Life Cycle Assessment Based Evaluation of a Coupled Wastewater Treatment and Biofuel Production Paradigm
AUTHORS:
Monica C. Rothermel, Amy E. Landis, William J. Barr, Kullapa Soratana, Kayla M. Reddington, Matthew K. Weschler, Grace Witter, Willie F. Harper
KEYWORDS:
Wastewater; Biofuels; Life Cycle Assessment; Nitrogen; Carbohydrate
JOURNAL NAME:
Journal of Environmental Protection,
Vol.4 No.9,
September
27,
2013
ABSTRACT: A laboratory experiment
was performed to determine the feasibility of coupling a conventional
wastewater treatment system with an algal photobioreactor (PBR) for the removal
of nutrients from wastewater and production of renewable resources. An
activated sludge batch reactor was set up in series with an algal PBR to feed
synthetic wastewater to Chlorella
vulgaris. The nutrient concentration in the water as well as lipid content,
carbohydrate content, and growth rate of the algal biomass were tested over 10
cycles to determine the capabilities of the coupled system. The study revealed
complete nutrient removal in some cycles, with the average final nutrient
content of 2 mg-P/L and 3 mg-N/L in effluent of the PBR. The algae biomass
contained 24% ± 3% lipids and 26% ± 7% carbohydrates by dry weight. A life
cycle assessment revealed the highest energy demand occurred during harvesting
of the algal mixture through centrifugation or filtration, but the highest
global warming and eutrophication impacts were due to CO2 use and PBR
construction material production. It is feasible for the system to treat
wastewater while generating renewable resources, but the system must be
optimized to reduce life cycle environmental impacts and result in a net energy
gain before large-scale implementation is possible.