Skip to content
Enhancing Phosphate Removal in Woodchip Bioreactors
YEAR: 2017
INVESTIGATORS: Emily Martin, Michelle Soupir

Nutrient enrichment of Iowa’s water bodies is one of the most critical issues the state is currently facing. Intensive farming and heavy nutrient application in the Midwest coupled with an extensive subsurface tile drainage network leads to excessive nutrients entering surface waters. Of the nutrients entering Iowa’s surface waters, nitrate is one of the most critical due to its contribution to harmful algal blooms (HABs) not only in the Midwest, but also in the Gulf of Mexico. Nitrate receives attention from researchers, farmers, and the general public because it travels in subsurface tile drainage and causes HABs. There is a long history of research conducted to reduce nitrate transport to water bodies from drainage. Phosphorous (P) also contributes to HABs and at lower concentrations, but its pathways are less understood by researchers. Recent work has begun to document the significant export of phosphorous through drainage systems. Woodchip bioreactors are one of the most cost effective and least invasive methods to remove nitrate from subsurface drainage. By installing these systems at the edge-of-the field, there is potential to expand the range of pollutants removed by woodchip bioreactors to include phosphorous. The goal of the proposed project is to evaluate the ability of woodchip bioreactors to remove phosphorous by adding biochar as a P amendment to the bioreactor. Objectives of the study are (1) to assess the effectiveness of different amendments on P removal in bioreactors and (2) to analyze the effect of influent P on overall removal. The study will be carried out in the Water Quality Research Laboratory (WQRL) at Iowa State University where there are three bioreactor columns available for use to complete a P amendment column study. We will analyze a range of enhanced biochars as an amendment, including three types of pyrolysis, biochar treated with Magnesium, and organic material sourced from corn stover, hardwood, and softwood. Results of the proposed project will include identification of viable P amendments to enhance the nutrient removal of woodchip bioreactors suitable for a range of applications.