Alum application to improve water quality in a municipal wastewater treatment wetland

Document Type

Article

Publication Date

3-1-2009

Abstract

Nutrient removal in treatment wetlands declines during winter months due to temperature. A 3-mo (wintertime) mesocosm study was conducted to determine the effectiveness of alum in immobilizing P as well as other nutrients during this period of reduced treatment efficiency. Eighteen mesocosms, triplicate alum, and three controls or no alum were established with either Typha spp., Schoenoplectus californicus, or SAV (Najas guadalupensis-dominated). Alum was delivered by timer at a rate of 0.81 g Al m -2 d -1 and parameters measured included: pH, soluble reactive phosphorus (SRP), total phosphorus (TP), dissolved organic carbon (DOC), dissolved inorganic nitrogen (DIN), total kjeldahl nitrogen (TKN), and soluble aluminum (Al). Alum-treated mesocosms had signifi cantly lower pH values (8.1) than controls (8.8), but well within the elevated pH range for aluminum toxicity. Alum signifi cantly reduced all measured water column nutrients with the exception of ammonium N, which remained unaff ected, and particulate P, which increased. This study demonstrated that seasonal low-dosage alum application to different vegetation communities in a treatment wetland can significantly improve treatment efficiencies for SRP (87 vs. 58%) and TP (62 vs. 44%) but also increase DOC (19 vs. 0%) and TKN (12 vs. -3%) removal capacity to a lesser degree. Alum applications within close proximity of the treatment wetland effluent points should be implemented with caution due to the production of alum floc-bound P which could potentially aff ect discharge permit compliance for total suspended solids or total P. Copyright © 2009 by the American Society of Agronomy, Corp Science Society of America, and soil Science of America. All right reserved.

Publication Source (Journal or Book title)

Journal of Environmental Quality

First Page

814

Last Page

821

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