Reducing Nutrient Pollution using Woodchips: Reaction Surface Area Matters!
|Affiliation||Civil and Environmental Engineering|
|Project title||Reducing Nutrient Pollution using Woodchips: Reaction Surface Area Matters!|
|Background||Woodchips are a low cost media used in water treatment reactors. Woodchip bioreactors can be installed adjacent to agricultural fields to catch and treat agricultural runoff, to reduce nutrient pollution in receiving water bodies. The reactors are designed to remove nitrogen from the runoff via denitrification (nitrate-reduction) (Figure 1). Because treatment is carried out by microorganisms living on the surface of the woodchip media, the surface area of the woodchips in the reactor is important. However, the average surface area of woodchips, and their distribution, varies widely depending on the source of the woodchips. The challenge of appropriate reactor design is compounded by the fact that measuring specific surface area of woodchips in the field is not a straightforward task.
We envision an easy-to-use app for a farmer who would like to install a woodchip bioreactor at their agricultural site to reduce nutrient pollution. The input to the app would be measurements conducted by the farmer (woodchip porosity as measured through a bucket test), and the output from the app would be a recommended hydraulic retention time for the reactor. This design project would compliment an ongoing study in Civil & Environmental Engineering (CEE) at UC Davis that developing Best Management Practices for the implementation of woodchip bioreactors. Two components are needed for the app development: 1) characterizing the relationship between bulk woodchip porosity and specific woodchip surface area; 2) contaminant removal rates per surface area. The first of these components would be developed by the student team using data provided by UC Davis researchers. The second of these components would be data made available to the student team by the research team. The project will help farmers better operating conditions to improve treatment results.
|Description||Project Description: The client needs an efficient and accurate tool to estimate the total surface area of the woodchips based on more easily measured parameters. We propose that bulk reactor volume and media porosity (i.e. volume of reactor occupied by water; see Equation 1) will allow surface area to be calculated.This project will likely involve (though is not limited to) image analysis (e.g., ImageJ), simple model building, and simple program-building. The student team will be provided with a series ‘training set’ images from different woodchip types (Figure 2) from which they would obtain a series of 2-dimensional measurements of surface area. The training sets will be accompanied by provided porosity and bulk volume measurements. At this stage, for each woodchip type the following questions should be answered:
1. Which particle dimensions attained from the image analysis may be used to accurately describe woodchip particle volume?
2. What [optimized] mathematical function can accurately describe the relationship between porosity and surface area for the provided type of woodchip media?
From the obtained image data, students would then construct a model relating the provided porosity measurements to the surface area of the set. Knowing nutrient removal reaction rates (per surface area), construction of an easy-to-use computer app would follow. Ideally, this tool will allow for rapid calculations of treatment (or reaction rate) per unit area, providing the client with information on how the contact time between the media and the runoff water effects performance. In such an app, the user may input a known porosity, bulk volume and woodchip type, and the related surface area will be calculated for them.
|Deliverable||Outcome: The specific deliverables may include the following:
1. Students will use image analysis to determine the relationship between particle volume and 2-D particle dimensions.
2. For each woodchip type (i.e., different training sets), the students will model total surface area of the woodchip media as a function of bulk volume and porosity.
3. Students will program an application that will allow users to input woodchip type, porosity, and bulk volume of a woodchip media to receive the total surface area of the woodchips in their given reactor.
|Skill set desirable||image analysis, app development|
|Client time availability||30-60 min weekly or more|
|IP requirement||Client wishes to keep IP of the project|