Abstract
In recent years, there is a trend of low C/N ratio in municipal domestic wastewater, which results in serious problems for nitrogen removal from wastewater. The addition of an external soluble carbon source has been the usual procedure to achieve denitrification. However, the disadvantage of this treatment process is the need of a closed, rather sophisticated and costly process control as well as the risk of overdosing. Solid-phase denitrification using biodegradable polymers as biofilm carrier and carbon source was considered as an attractive alternative for biological denitrification. The start-up time of the novel process using PCL (polycaprolactone) as biofilm carrier and carbon source was comparable with that of conventional process using ceramsite as biofilm carrier and acetate as carbon source. Further, the solid-phase denitrification process showed higher nitrogen removal efficiency under shorter hydraulic retention time (HRT) and low carbon to nitrogen (C/N) ratio since the biofilm was firmly attached to the clear pores on the surface of PCL carriers and in this process bacteria that could degrade PCL carriers to obtain electron donor for denitrification was found. In addition, solid-phase denitrification process had a stronger resistance of shock loading than that in conventional process. This study revealed, for the first time, that the physical properties of the biodegradable polymer played a vital role in denitrification, and the different microbial compositions of the two processes was the main reason for the different denitrification performances under low C/N ratio.
Highlights
Secondary effluent, which is produced from wastewater treatment plants (WWTPs) has to be further treated, due to increasing emission standards and water scarcity
(Figure 2a,c), respectively, and no nitrite was detected in the effluent (Figure 2b), which indicated that both reactors had the same denitrification performance attributing to sufficient the organic carbon source in the influent
Solid-phase denitrification biofilter and conventional denitrification biofilter exhibited the equivalent performance on acclimation time
Summary
Secondary effluent, which is produced from wastewater treatment plants (WWTPs) has to be further treated, due to increasing emission standards and water scarcity. Considering the feature of low turbidity and oligotrophic secondary effluent, biofiltration processes such as ceramsite grains, granular activated carbon and quartz sand were widely employed in the advanced treatment [1,2,3]. Due to limited organic carbon source in secondary effluent, denitrification of secondary effluent is usually achieved by extra organic carbon addition (e.g., acetic acid, sodium acetate, glucose, ethanol, etc.) [4]. Biodegradable polymers (BDPs), which act as both an energy source and biofilm carrier, have sparked great interest in the scientific community [7,8,9,10,11,12].
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