Denitrification of Aquaculture Wastewater using Agricultural by-products as Biofilter Media

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dc.contributor.advisor Dr. Philip W. Westerman, Committee Co-Chair en_US
dc.contributor.advisor Dr. Francis L. de los Reyes III, Committee Member en_US
dc.contributor.advisor Dr. Thomas M. Losordo, Committee Co-Chair en_US Saliling, Willie Jones Bayotlang en_US 2010-04-02T17:52:44Z 2010-04-02T17:52:44Z 2005-07-27 en_US
dc.identifier.other etd-03312005-180604 en_US
dc.description.abstract This research evaluated wood chips and wheat straw as inexpensive and readily available biofilter media for denitrification as alternatives to commonly used plastic media. Nine 3.6-L laboratory scale reactors (40 cm packed height x 10 cm dia) were built to evaluate performance of wood chips, wheat straw, and Kaldnes plastic media to reduce nitrate from synthetic and real aquaculture wastewater. The upflow bioreactors were loaded at a constant flow rate and three influent concentrations of 50, 120, and 200 mg NO&#8323;-N/L each for at least four weeks, in sequence. Experiments showed that both wood chips and wheat straw are comparable to Kaldnes plastic media in terms of reducing nitrate. As high as 99% of nitrate (as high as 200 mg NO&#8323;-N/L) were reduced. Pseudo-steady state denitrification rates at 200 mg NO&#8323;-N/L influent averaged 1365 &#177; 39 g NO3-N/m&#179;/day for wood chips, 1361 &#177; 80 g NO&#8323;-N/m&#179;/day for wheat straw, and 1326 &#177; 74 g NO&#8323;-N /m&#179;/day for Kaldnes. These values were not even the maximum potential since nitrate profile along reactors showed substantial reduction in the lower half of the reactors with rates more than double than what was estimated for the whole reactor. Treatment of real wastewater also showed comparable performance with that at the 50 mg NO&#8323;-N /L synthetic experiments. COD consumption per NO&#8323;-N removed was highest in Kaldnes media (3.41 to 3.95) compared to wood chips (3.34 to 3.64) and wheat straw (3.26 to 3.46). COD/NO&#8323;-N ratios for the real wastewater were low (<2.0). Effluent ammonia concentrations were close to zero while nitrites were around 2.0 mg NO&#8322;-N/L for all reactor types. There was alkalinity production and pH increased corresponding to NO&#8323;-N removed. On the other hand, the oxidation-reduction potential also decreased with nitrate removal. Wood chips and wheat straw lost 16.2% and 37.7% of their masses, respectively over 140 days. There were physical signs of degradation like discoloration and structural transformation. Carbon/Nitrogen (C/N) ratio and lignin mass of the media also decreased. Considerable amount of microbial biomass also developed inside the reactors decreasing porosity. By Polymerase Chain Reaction &#8212;Denaturing Gradient Gel Electrophoresis (PCR-DGGE) analysis, it was shown that the bacterial populations differed among reactor types and with column height. en_US
dc.rights I hereby certify that, if appropriate, I have obtained and attached hereto a written permission statement from the owner(s) of each third party copyrighted matter to be included in my thesis, dissertation, or project report, allowing distribution as specified below. I certify that the version I submitted is the same as that approved by my advisory committee. I hereby grant to NC State University or its agents the non-exclusive license to archive and make accessible, under the conditions specified below, my thesis, dissertation, or project report in whole or in part in all forms of media, now or hereafter known. I retain all other ownership rights to the copyright of the thesis, dissertation or project report. I also retain the right to use in future works (such as articles or books) all or part of this thesis, dissertation, or project report. en_US
dc.subject lignin en_US
dc.subject wheat straw en_US
dc.subject biofilter en_US
dc.subject Kaldnes en_US
dc.subject C/N en_US
dc.subject ribotypes en_US
dc.subject ammonia en_US
dc.subject aquaculture wastewater en_US
dc.subject nitrite en_US
dc.subject nitrate en_US
dc.subject wood chips en_US
dc.subject denitrification en_US
dc.title Denitrification of Aquaculture Wastewater using Agricultural by-products as Biofilter Media en_US MS en_US thesis en_US Biological and Agricultural Engineering en_US

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