查看更多>>摘要：As the nitrogen concentration in the sewage flowing into the sewage treatment plant and water system increases, the degree of negative influence, such as eutrophication, decrease in dissolved oxygen and toxicity to the aquatic ecosystem increases. As the nitrogen concentration in sewage increases, a biological nitrogen removal process for high nitrogen concentration is attracting attention, and research is being conducted in various fields. The nitrification-denitrification process at a low carbon-to-nitrogen ratio is not cost effective because of aeration and external carbon source supplement. Accordingly, an economic improvement of biological nitrogen removal process is required and economical and efficient anaerobic ammonium oxidation (ANAMMOX) process has been proposed. This study analyze operation factors for a stable ANAMMOX process. ANAMMOX reactor was operated to evaluate the appropriate ratio or concentration for each operation factor, such as seeding sludge, mixed liquor suspended solids (MLSS), substrate ratio. In seeding sludge, 3 sludges have a high proportion of ANAMMOX bacteria and are suitable for process implementation. In MLSS, it was challenging to secure the stability of the ANAMMOX process at 4000 mg/L over. In substrate ratio, the ammonia nitrogen and total nitrogen removal efficiency were increased when the nitrite to ammonia ratio was increased. Consequently, the results of this study could be used as basic data for the ANAMMOX process in high nitrogen concentration wastewater and mainstream.
Wadnerkar, Praktan D.White, Shane A.Morris, Shaun A.Conrad, Stephen R....
9页
查看更多>>摘要：Agricultural hothouses are intensive food production systems relying on high fertilization and irrigation. Runoff from hothouses can contain high levels of nitrogen (N) and drain into streams. Here, we investigate the effectiveness of buried, inline woodchip bioreactors constructed using PVC pipes in removing nitrate (NO3--N) and the possibility of pollution swapping from nitrate to the greenhouse gas nitrous oxide (N2O). Mean dissolved NO3--N removal and N2O gas production were 6.0 +/- 5.2 g N m(-3) h(-1) (0.9-12.3 g N m(-3) h(-1)), and 35.1 +/- 31.4 mg N L-1 h(-1) (14-83 mg N L-1 h(-1)) respectively, across five surveys. NO3--N removal and N2O-N production occurred primarily in hypoxic to anoxic conditions. Overall, these inline pipe bioreactors achieved nitrate removal efficiencies (NRE) of 14.5 +/- 6.8% (8.2%-25.0%) and N2O production equivalent to 0.7 +/- 0.6% (0.3-1.4%) of nitrate removal. Comparisons to the literature indicate that our bioreactors have a low NRE but a very high nitrate removal rate (NRR) on a woodchip volume basis. The bioreactor was operating at 21% water capacity. Therefore, increasing the bioreactor water height would be needed to maximize nitrate removal. Our results imply that these bioreactors can efficiently remove NO3-N without major N2O release to the atmosphere.
Knappenberger, ThorstenJayakaran, Anand D.Stark, John D.
13页
查看更多>>摘要：Bioretention is a green stormwater infrastructure practice that has been shown to reduce some of the harmful effects of urban stormwater on downstream receiving waters. Typically, media used for bioretention consist of high percentages of sand to realize high hydraulic conductivities and smaller percentages of soil or organic materials to improve the retention of stormwater pollutants. The objectives of this study were to evaluate four bioretention media mixes that differed in sand, compost, and water treatment residuals content and to predict pollutant removal based on realistic stormwater concentrations using Bayesian statistics. Pollutants of interest were chemical oxygen demand, ammonia, nitrite, nitrate, total Kjeldahl nitrogen, as well as total and dissolved forms of phosphorus, copper, lead, and zinc. Water quality data were collected for eleven storms, and cumulative rainfall after construction was used as a measure for the media age. The data were evaluated for the probability to observe pollutant reduction and for the probability to observe high-performance reduction (HPR) with a minimum pollutant reduction of 60%. The chemical oxygen demand had a probability for reduction of P = 0.09 and HPR of P = 0.00, resulting in pollutant export in the majority of storms. HPR reduction goals were met for total lead, zinc, and copper, and reduction probabilities were generally P > 0.5 for all total and dissolved metals. Age and media composition affected phosphorus and nitrogen removal, with increased pollutant retention observed as the media aged. Lower compost percentages resulted in less nutrient export. This probabilistic model of realistic stormwater concentrations in combination with bioretention pollutant removal experiments results in a holistic view of credible pollutant outflow concentrations that can be used by stormwater managers to alleviate the effects of stormwater on surface water quality.
NSTL
Elsevier