Examination of synergism in nitrate and orthophosphate removal in bioreactors

Bioreactor;Nutrient removal

Goodwin, Gregory ; Cooke ; Richard A.

关键词: Bioreactor;    Nutrient removal;   

Others  :  https://www.ideals.illinois.edu/bitstream/handle/2142/31188/GOODWIN_GREGORY.pdf?sequence=1&isAllowed=y

美国|英语

来源: The Illinois Digital Environment for Access to Learning and Scholarship

【 摘 要 】

The use of fertilizer on agricultural cropland to replenish soil nutrients removed by crops is one of the most important steps to continually producing healthy, highyielding crops. However, the historic overuse of these fertilizers has had a detrimentaleffect on the receiving waters of agricultural watersheds. Due to their important role inplant nutrition, the two main nutrients generally associated with these impacts are nitrogen and phosphorus resulting from high application rates as well as high potential for transport to receiving waters. For these reasons, there is a demand for better management practices and remediation techniques to reduce and potentially eliminate the transport of nutrients from agricultural lands. To aid in this effort, this study evaluated materials suitable to convert orthophosphate into a non-bioavailable form as well as examine the synergistic effects of using this material in conjunction with a woodchip bioreactor known to have a high affinity for nitrate-N removal. The evaluation of materials was conducted via a bench-top batch study and led to the selection of a locally available iron-based scrap steel material, which was able to remove over 99% of orthophosphate from solution at the 24 hour retention time. A laboratory-scale column reactor was then constructed using the iron-based material and woodchips as reactor media. Synergism was displayed as a result of alternating mediaarrangement with the observation of 25% higher reduction in nitrate-N concentrations, on average, as a result of interaction with woodchips when woodchips were downstream of steel turnings as opposed to upstream. This was also demonstrated in the orthophosphateresults, where woodchips reduced orthophosphate concentrations by 8.54% on average when upstream of steel turnings, but yielded a net increase in orthophosphate concentration (23.8% of initial concentration on average) by converting bound phosphate back to orthophosphate when downstream of steel turnings. This led to a final experiment where the steel turnings were placed both upstream and downstream of woodchips. This confirmed earlier findings of enhanced nitrate-N removal by woodchips downstream of iron, while showing that the second iron section downstream of woodchips could once again remove orthophosphate from solution down to nondetectable concentrations.