Dissolved phosphorus removal in denitrifying bioreactors: field and laboratory studies

Denitrifying woodchip bioreactors are an edge of the field conservation practice designed to remove nitrate (N) from subsurface agricultural drainage water. However, phosphorus (P) removal has been observed in bioreactors across Illinois. Both N and P play an important role in eutrophication and hypoxia in the Gulf of Mexico. Therefore, it is important to evaluate P dynamics in denitrifying bioreactors. The objectives of the thesis were to: (1) better understand potential annual DRP removal at full-size bioreactors in Illinois using eleven site-years of monitoring data and (2) evaluate P sorption as a potential fate of DRP in woodchip bioreactors using small-scale batch testing with wood species containing varied elemental composition. Nine of the eleven site-years from the full-size bioreactors showed a DRP removal between 2-50% at the edge of the field, corresponding to 0.7-491 g P removed/ha (drainage areas of 2.8-20 ha). Two bioreactors showed P leaching (net P contribution) in their first year of operation, with losses of 180 and 382% of the inflow DRP load. For the batch testing, six wood types (specific species) were selected based on their aluminum, iron, calcium, and magnesium content, and a seventh wood type was collected from a bioreactor being monitored in Illinois. Aluminum and iron are known for their adsorption of P whereas calcium and magnesium form precipitates with P. There were few significant differences in dissolved P removal between wood types in the batch tests except for the woodchips sourced from the field bioreactor installation. These field woodchips exhibited continual P removal over 72 h which was thought to be more likely related to microbial removal than chemical P sorption. Microbial removal was further suspected when woodchips were autoclaved which showed an overall decrease in P removal (1.4-78% decrease). The full-size bioreactors being monitored showed more P removal than the laboratory batch tests (e.g., field sites averaged 55±163 mg P removed/kg with a median of 12 mg/kg; batch tests averaged 0.7±6.2 mg P removed/kg with a median of 0.6 mg/kg). Three of the full size bioreactors had woodchips that matched those used for batch tests. Further monitoring of field-scale bioreactors is recommended to better assess the environmental and design factors that may impact P behavior in denitrifying bioreactors.

Name thesis:degree_name

M.S.

Level thesis:degree_level

Thesis

Discipline thesis:degree_discipline

Crop Sciences

Grantor

University of Illinois at Urbana-Champaign

Year dc:date

2020

Author dc:creator

• Sanchez Bustamante Bailon, Ana Paula

Contributors dc:contributor

• Christianson, Laura
• Margenot, Andrew
• Cooke, Richard

• phosphorus removal
• denitrifying bioreactor
• batch test
• woodchips
• sorption
• microbial activity
• elemental content
• autoclave

Statement dc:rights

• Copyright 2020 Ana Paula Sanchez Bustamante Bailon

Language dc:language

en

Handle dc:identifier

http://hdl.handle.net/2142/108627

OAI identifier oai:identifier

oai:www.ideals.illinois.edu:2142/108627