title: The impact of alum based advanced nutrient removal processes on phosphorus bioavailability.
abstract: Because eutrophication is a widespread consequence of wastewater discharges, there is a strong impetus to develop new approaches to remove phosphorus (P) from wastewater treatment plant (WWTP) effluents. We examined the effluents from a pilot plant that is testing various alum based processes for achieving>99% P removal, however, it is not known how these advanced P removal technologies affect the bioavailability of P (BAP). We tested how the percent BAP (%BAP) varied with different P removal levels using an algal growth bioassay methodology. This facility reduced total P concentrations from ≈ 500μgL(-1) in the pilot plant influent to 19±4 (±SD)μgL(-1) in the final effluent, and our results showed that as the level of P removal increased, the %BAP of the product declined sharply, r(2)=0.98. Prior to alum treatment, the influent had an average %BAP of 79±13%, and after three steps of alum-based removal the %BAP averaged 7±4%. Thus, this alum based P removal process was very effective at sequestering the P forms that most readily stimulate algal growth. Further, our results show the final BAP of the effluent was only ≈ 50% of the "reactive" P concentration. These results have important implications for nutrient management and trading schemes.
authors.affiliation: Civil & Environmental Engineering, University of Washington, Seattle, WA 98105, USA. libo@u.washington.edu
authors.forename: Bo
authors.initials: B
authors.lastname: Li
authors.forename: Michael T
authors.initials: MT
authors.lastname: Brett
mesh_terms: D000534:Alum Compounds / Q000737:chemistry*; D001673:Biodegradation, Environmental; D001682:Biological Availability; D010758:Phosphorus / Q000302:isolation & purification*; D012621:Seasons; D014865:Waste Disposal, Fluid; D018508:Water Purification / Q000379:methods*
chemical_list: D000534:Alum Compounds; D010758:Phosphorus