Alfredo Garcia-Perez*, Mark Harrison PE and Bill Grant Pages 189 - 196 ( 8 )
Background: Chemical fertilizers used for field crops have three main macronutrients components: nitrogen, phosphorus and potassium. They are the limiting factor to plant growth. Effluents from treated wastewater have appropriate concentration levels of those macronutrients to support crop production.
Aim: The main purposes of this pilot case field study were: (i) to recover the valuable nutrients from sewage using a recirculating vertical flow constructed wetland planted on top with soybean (Glycine max, L.); (ii) to determine the potential of growing renewable feedstock commodities irrigated with treated effluent as a phytoremediation mechanism to clean wastewater onsite.
Method: Grab samples of effluents from both septic tank and the constructed wetland were analyzed for water quality variables.
Result: Mean treatment efficiencies (removal) were high for biochemical oxygen demand (98%), ammoniumnitrogen (97%), total suspended solids (96%), total Kjeldahl nitrogen (95%), fecal coliforms (93%), total nitrogen (85%), and total phosphorus (77%), while it was relatively low for potassium (43%). Supplementary irrigation or commercial fertilizers were not added during the growing season. The mean yield ± standard deviation (seed mean weight ± standard deviation) for fresh dried weight of soybeans crop was equivalent to 2,625 ± 1,653 kg/ha (0.21 ± 0.05 g/bean).
Conclusion: These results show that soybean growing on top of a recirculating vertical flow constructed wetland could be a sustainable alternative technology and a green mechanism to remove pollutants (nutrients) from sewage. Also, nutrients recovery through direct reuse of treated sewage effluents as source of fertilizers and water to grow first-generation biofuels commodities such as soybean is feasible.
Commodities, constructed wetland, Glycine max, nutrients, sewage, soybeans, water reclamation.
LaGrange County Health Department, Environmental Health Office, 304 North Townline Road, Ste 1, LaGrange, Indiana 46761-1319, KCI Technologies Inc., 6983 Corporate Circle, Indianapolis, Indiana 46278, LaGrange County Health Department, 304 North Townline Road, Suite 1, LaGrange, Indiana 46761