Recipient Organization
OKLAHOMA STATE UNIVERSITY
(N/A)
STILLWATER,OK 74078
Performing Department
Biosystems & Ag Engineering
Non Technical Summary
Uncontrolled runoff from urban, suburban and rural areas is a prevalent environmental problem. These non-point sources are responsible for the pollution of 39% of the rivers, 45% of the lakes, and 51% of the estuaries in assessed water bodies in the United States. Bioretention cells (BRC), a type of stormwater filter technology used in Low Impact Development, are intended to address this problem. BRC are basically large, hi-tech holes in the ground, fill with sand, soil and other additives. Stormwater is directed into the BRC and filtered before being released to surface waters. Some of the pollutants are degraded by biological processes in the BRC, while some are trapped and held in the cell. While this technology is growing in use, there is little data on how long BRC will remove water pollutants, specifically nutrients, heavy metals, and oil. Water and filter soil sampling at cells that have been in operation for more than six years in Oklahoma will provide conclusive data. This will enable the formation of defendable recommendations suitable for stormwater engineers, landscape architects, municipal stormwater professionals and state regulators. In addition, new soil additives that may provide better pollutant trapping will be explored by laboratory testing. While the research will be directed at urban landscapes, it is expected the results will be applicable to agricultural applications.
Animal Health Component
70%
Research Effort Categories
Basic
20%
Applied
70%
Developmental
10%
Goals / Objectives
Quantify long-term pollutant sorption and transformations in BRC filter media.Identify and quantify the performance of new filter media additives that will increase filter media sorption and/or transformations of pollutants.
Project Methods
MethodsDue to the broad range of the goals, specific procedures and methods for all the research cannot be defined here. The following provides a general framework of the work that will be conducted. In all of these procedures, it is assumed that the existing BRC in Grove and Stillwater, the permeable pavement at the Botanical Garden, and the new BRC and vegetated waterways in OKC will be available for testing.Goal 1Long term treatment performance will be determined by two methods. First, sampling of cell influent and effluent will provide a time series of water quality. Both grab sampling and automated samplers will be used. The second effort will be focused on core sampling of the cells as they age. Analysis of adsorbed concentrations with depth will provide insight on the sorption mechanisms and ultimate BRC performance.Water Quality SamplingWater quality samples will be collected by automated samplers on five of the existing BRC. Those cells will be selected based on their perceived pollution loading and access. Influent, drain flow and effluent (cell overflow) will be sampled. Sampling will use equipment acquired under previous EPA 319 h funding. Autosamplers will record flow using a small flume and a pressure transducer. Total, aggregated, flow-weighted samples will be the collected to provide single storm, total pollution removal. On selected BRC and times, multiple samples will be collected to provide a time series of water quality during a storm. This data will determine if the influent demonstrates a "first flush" characteristic, or if the effluent exhibits the effects of water storage in the BRC. Water quality parameters to be determined are listed in Table 1. Water quality analysis will be performed by the Soil, Water and Forage Analytical Laboratory (SWFAL). SWFAL employs state-of-the-art equipment capable of handling a wide range of analytical tasks. Accuracy and precision of test results are assured through daily analysis of quality control samples, a three step internal data review process and participation in external certification and sample exchange programs. All instruments are calibrated with certified standards and maintained according to the specification.Table 1. Water Quality Parameters.Common indicatorspH, EC, TSS, HardnessCationsNa, Ca, Mg, KAnionsCl-, SO4-2,Heavy MetalsFe, Zn, Cu, Mn, Pb, Cd, CrNutrientsNO3-N-, P (total dissolved), P (total)OrganicOil and greaseSpecific tasks for water sampling are:Install autosamplers, flumes and enclosures on the influent and effluent of five BRC.Collect water samples and deliver to the OSU-SWFAF laboratory for analysis.Analyze water quality data to quantify pollution removal.Remove autosamplers at the end of the project.Core Sampling of Filter MediaThe concentration of non-degrading, adsorbed pollutants as a function of depth will be determined in the existing BRC. At each sampling event, two to four, 2" cores will be taken by a Gidding's sampler for the full depth of the cells following the procedures in Brown and Garbrecht (2007). After sampling, the sample hole will be backfilled with sand. The cores will be visually inspected and then sectioned into 6" intervals. Analysis for dissolved and total nutrients and common ions will be performed on each section. Depending on the results, addition chemical analysis of the samples may be performed to identify the sorption mechanism and ultimate sorption capacity of the filter media. Specific analytical procedures for extraction will be determined with the assistance of Dr. Chad Penn, and will be a function of the pollutant, media and the sorption mechanism being investigated. Chemical analysis of leachate will be performed by SWFAL. Specific adsorbed pollutants of concern are phosphorous and heavy medals.Specific tasks for core sampling are:Notify property owners and arrange for access to each of the BRC. Note, as a condition of the original installation, property owners agreed to provide future access.Using a Giddings soil sampler in push mode, collect two, 2" cores from each of the 10 BRC. Backfill sample holes as needed and return cores to the BAE Groundwater Lab.In the laboratory, remove the filter material from the core tubes and describe. Slice each core in half among the axis and store one half for possible future use. Subsection the remaining half into 6" subsamples.Perform 10:1 water extractions and total digestions on each subsample. Extracts will be submit to SWFAL for analysis for the same parameters as the water samples.Goal 2There is great industrial and public agency interest in the development of "custom" blends of materials for optimum filtering of storm water pollutants. As an example, the addition of fly ash to sand filter media has been shown to greatly increase phosphate and heavy metal adsorption (Zhang, et al, 2006 and 2008). However, no known filter media can provide long term treatment for the range of pollutants commonly encountered in storm water. Allred (2008) has screened over 50 different industrial byproducts for their potential to adsorb or degrade, nitrate, metals and organic pesticides. Based on his recommendation, Midgley, et al. (2009), conducted exploratory tests of nitrate losses with sulfur modified iron and fly ash mixtures, which performed better than expected. Storm (2014) conducted simple tests of biochar to reduce nitrate in sand filter applications. His findings showed only modest reductions in nitrate.This developing area of research will be pursued as opportunities are discovered. Evaluations will follow a four step process. First, when a promising media is identified, batch adsorption/degradation for a pollutant of interest will be conducted with the pure material and mixtures of sand, following ASTM (2004) and Zhang et al. (2006 and 2008). Second, if those results are positive, additional batch tests will be performed with other contaminants and media additives to determine if the media sorption is impacted by competitive reactions or solution composition more typical of field conditions. Those results will be evaluated for performance in total pollutant removal and cost effectiveness. Third, materials passing the second phase will be subjected to long duration column testing. Depending on the size of the media, 2" to 6" diameter columns, 6" to 12" in length will be packed with prospective media mixtures. Columns will be subjected to multiple simulated storm event hydrographs. Each event will consist of ten pore volumes of influent, followed by one week of drying. This will be repeated until the column effluent concentrations reach 50% of the influent concentration. It is conceivable that a test may last up to a year. At the completion of the test, the column will be sectioned and the distribution of pollutants will be determined using the same analytical methods developed for Objective 1. Finally, if a media mixture shows promise after column testing, a field demonstration will be pursued. Field testing will require the cooperation of outside agencies, local governments and/or developers.