Study On Denitrification Biological Filter Depth Processing With Different External Carbon Source

Shenzhen City is vigorously popularizing reclaimed water reuse in recent years.With the approaches and the amount of reclaimed water constantly expanding, safety of water quality has become the primary factor in the market of reclaimed water.While the water quality index total nitrogen in the secondary effluent from WWTP and water reclamation plant is failed to meet the Shenzhen renewable water,rainwater quality standard?SZJG32-2010?. This paper carried out depth denitrification for municipal wastewater in denitrification filter with different external carbon source. It is supposed to serve as a reference for the transformation of water reclamation plant and the choose of process in new water reclamation plant.The start-up of denitrification biological filter with different external carbon source?sodium acetate, ethanol, glucose? was investigated, which provided a theoretical basis for start-up process of denitrification biological filter. After 10 days start-up, nitrite accumulation of Sodium acetate and ethanol filter disappeared and effluent quality were stable. It showed the success of start-up. After 15 days start-up,glucose filter showed the success of start-up. At the stable conditions, the NO₃^--N and TN removal rate of sodium acetate and ethanol filter could reach more than 90%,glucose filter could reach over 80%. By monitoring the water samples at different filter height of three denitrification filters on stable conditions, more than 80% of NO₃^--N and TN were removed at 0²0cm segment of three filters. At 20 cm of filter,DO concentration dropped to below 1mg/L, p H significantly increased and a small amount of nitrite was accumulated. After 40 cm height of filter, nitrite accumulation disappeared. Denitrification biological filter can remove part of the ammonia.Because concentration of dissolved is high that provides habitat for denitrifying bacteria at the bottom of filter. The ammonia is removed by denitrifying bacteria.The effect of HRT ? C/N and backwash condition for depth denitrification in denitrification filter were studied. The results showed that the denitrification biofilter had high processing load, the NO₃^--N and TN removal rate of filters with sodium acetate and ethanol reached more than 90% when HRT?10min, filter with glucose reached over 80%; The NO₃^--N and TN removal rate of filters with sodium acetate and ethanol reached more than 90% when C/N?5, filter with glucose reached over80% when C/N?8. For the experimental conditions, HRT of denitrification biofilterfor 10 min was the best; When sodium acetate or ethanol as the carbon source,keeping C/N=5:1 were appropriate. When the carbon source was glucose, maintaining the C/N of 8:1 was appropriate. Denitrification biofilter used air and water combined backwash approach. Air strength was 10L/?m2?s?, water intensity was 15L/?m2?s?,ethanol and sodium acetate filter backwash time were 10 min while glucose filter backwash time was 15 min. Under optimization condition, mean value of TN meets the Shenzhen renewable water, rainwater quality standard.The denitrification kinetics of denitrification filter with volcanic rocks had been discussed in the study. It showed that when carbon is sufficient, HRT was not less than 10 min, the denitrifying denitrification performance was better. The denitrification process was aligned with first-order kinetics. By setting up the model of denitrification process in biological filter, the simulated value was consistent with actual value under the test water quality condition.Three different external carbon source for technical and economic was analyzed,the results showed that nitrogen removal: ethanol ? sodium acetate> glucose; direct dosing cost of ethanol was the lowest as carbon source, followed by sodium acetate, a glucose; Safety and risk prevention requirements of ethanol was the highest, so the administrative costs was the highest dosing system, followed by sodium acetate and glucose; Filter backwash time for glucose was the longest, so the power consumption costs was highest; Sodium acetate was the most economically viable external carbon source for denitrification biofilter.