Comparison of Clay Ceramsite and Biodegradable Polymers as Carriers in Pack-bed Biofilm Reactor for Nitrate Removal

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.

Optimize the Preparation of Novel Pyrite Tailings Based Non-sintered Ceramsite by Plackett-Burman Design Combined With Response Surface Method for Phosphorus Removal

“…The adsorption equilibrium was observed at 16 h, where the TP concentration decreased to 0.43 mg/L, meeting the V level of "Surface water Environmental Quality Standard" (GB 3838-2002), and the equilibrium adsorption capacity was 0.2864 mg/g. As the mostly using models for description of adsorption kinetic, pseudo first-order and pseudo second-order models (Text S1) were used to fit the experimental data (Supplementary Table S8) (Chen et al, 2019). Although the correlation coefficients of both two kinetic models were similar (>0.9), the predicted adsorption capacity with pseudo first order model is 0.2995 mg/g which is close to the experimental value (0.2864 mg/g).…”

“…The adsorption thermodynamics was investigated through three isotherms at different temperatures (Figure 5B), through the data fitting with Langmuir and Freundlich isotherm models (Text S2) (Chen et al, 2019). It can be found that Langmuir model fitted better with the isotherms, and indicated the mono- layer adsorption process (Supplementary Table S9).…”

“…Ceramsite was generally prepared with various active materials such as clay ( Zhang et al, 2019 ), activated sludge ( Nie et al, 2021 ) and fly ash ( Mi et al, 2021 ) by high temperature calcination, which not only aim to improve the material properties and safety, but also promote the recovery and utilization of waste resource. However, the calcination is a high energy consumption process, and the crystal structure of raw material would be destroyed leading to the decrease of active adsorption sites.…”