关键词:
Wastewater treatment
Macroalgae
Nutrient management
Bioextraction
Life cycle assessment
Techno-economic analysis
摘要:
Advanced nutrient removal in water resource recovery facilities (WRRFs) can reduce coastal eutrophication, but can increase economic costs and indirect environmental impacts associated with energy and materials usage for WRRF construction and operation. A strategy of interest to reduce coastal eutrophication is the cultivation of seaweeds in proximity to WRRF discharge plumes to bioextract nutrients from coastal waters. We report economic and environmental trade-offs of this proposed strategy for a 1,170 m(3).d (-1) (0.31 mgd) WRRF in Boothbay Harbor, Maine, targeting a Water Environment Research Federation (WERF) level 2 effluent nitrogen goal of 3 mg-N.L-1. The scenarios investigated include WRRF upgrade and year-round nutrient bioextractive aquaculture (Saccharina latissima and Gracilaria tikvahiae cultivation) with end uses of bioenergy feedstock, fertilizer, or food. Based on biomass production characteristics and tissue nitrogen contents in Boothbay Harbor, an aquaculture site of 5.4 hectares would bioextract equivalent nitrogen mass as WRRF upgrade to meet level 2 nitrogen effluent goals. Using a techno-economic analysis, the cost of a WRRF upgrade was estimated to be $0.31 m 3 wastewater treated. The cost of bioextractive seaweed aquaculture depended on beneficial use of seaweed. If dried and sold as sea vegetables (for human consumption), a net revenue of $0.72 m(-3) wastewater treated could be generated. If dried and sold as commercial fertilizer, the net cost of nutrient removal would be $0.26 m(-3) wastewater treated, less than the WRRF upgrade. However, if anaerobically digested to produce biogas, the net cost of treatment was estimated to be $0.499 m(-3) wastewater treated. WRRF upgrade and bioextractive aquaculture significantly reduced marine eutrophication. Bioextractive aquaculture with use as biofuel feedstock had the best performance on human carcinogenic toxicity, global warming, and fossil resource scarcity, marine ecotoxicity, and freshwater e