Doctoral Dissertations

Date of Award

5-1995

Degree Type

Dissertation

Degree Name

Doctor of Philosophy

Major

Biosystems Engineering

Major Professor

C. Roland Mote

Committee Members

Bobby L. Bledsoe, James L. Smoot, Tim N. Burcham

Abstract

This research attempted to evaluate the applicability of constructed-wetland wastewater treatment technology to a dairy lagoon supernatant, and assess the utility and applicability of a commonly used kinetic based design equation. A laboratory-scale system of ten wetlands was used to investigate the impacts of select operational and design parameters. These included organic loading rate, OLR (three levels) and microbial attachment sites, MAS (Vegetated, Inert, and None); experimental treatments were combinations of these parameters. The study included two phases. During Phase One, the system was loaded semi-continuously at relatively higher influent concentrations. During Phase Two, the system was batch loaded at relatively lower influent concentrations. MAS were consistent during both phases. Sample analysis included total organic carbon (TOG), various nitrogen compounds, ortho-phosphate and other inorganic ions, and bacteria (total and fecal coliform, and fecal strep). Assessment of the applicability of this technology was based on the extent of waste renovation within the system. Waste treatability and the effectiveness of a particular treatment were based on net and relative removal, effluent concentrations, and the rate of substrate utilization. Statistical comparisons were used to quantify any treatment effects. This system was able to sustain only about one quarter of the MAS specific surface area currently considered the design standard. Effects attributable to either the Vegetated or Inert MAS were not distinguishable from the effects of a detritus layer that developed on the bottom of all test cells. Based on waste constituent removal results, it was concluded that this detritus layer (an unanticipated site for microbial activity) played a significant role in waste treatment, and was particularly active in facilitating nitrogen removal. Results presented here also question that the utility of the evaluated design relationship and its applicability to constructed wetland systems. The design relationship's reliance on quantifying microbial attachment site media-specific parameters is questioned. Results from this study suggest that the role of constructed wetlands in an animal waste management system may be as a treatment component prior to traditional land application, rather than the stand-alone treatment alternative as has been proposed to date.

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