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4/2/2019 Effect of C/N Ratio on the Removal of Nitrogen and Microbial Characteristics in the Water Saturated Denitrifying Section of a Two-Stage C... <br /> S-EPS <br /> ,� y Cell <br /> Ce/I } <br /> Y C'el] <br /> Cell <br /> AS LB-EPS <br /> Figure-2 <br /> Schematic stnicture of EPS composition. <br /> The goal of the current study was to use simulation columns of a two-stage CRI system to study the <br /> nitrifying simulation column(the first stage)and the water-saturated denitrifying simulation column <br /> (the second stage)separately, during treatment simulation of artificial sewage. The effect of variable <br /> CN ratios in the second-stage influent on pollutant removal was determined,and the microbial <br /> community and biofilm EPS concentrations were quantified in the water-saturated denitrifying section. <br /> This addressed the influence of different ON ratios in influent on the pollutant removal performance of <br /> CRI from a microcosmic perspective,which provides insights to improve nitrogen removal. <br /> 2. Materials and Methods <br /> 2.1. Experimental Design <br /> A schematic diagram of the simulation columns representing the two stages of the CRI system used in <br /> this study is shown in Figure 3. The model is composed of two parts: a nitrifying simulation column <br /> (the first stage)and a water-saturated denitrifying simulation column that represents the second stage; <br /> these were connected in series. The temperature of the columns was kept constant at 30 f 1.2 °C by <br /> means of a temperature-controlled insulation mantle. The columns were made of polyvinyl chloride <br /> (PVC)with a diameter of 8 cm and a height of 30 cm. The filling medium consisted of two layers: a 4 <br /> cm high supporting layer of pebbles(5.0-10.0 mm)mixed with gravel(3.0-4.0 mm)was covered by a <br /> 21 cm high treatment layer of 90%river sand(0.25-0.30 mm grain size),mixed with 5%marble sand <br /> (1.0-2.0 mm) and 5%zeolite sand(1.5-1.7 mm). The sampling outlet of the first stage column was <br /> positioned 1 cm above the bottom of the column,while the sampling outlet of the second-stage column <br /> was fitted at a height of 26 cm. In this way,the second stage remained continuously submerged. The <br /> influent sewage was pumped up so that it entered from the top of the column, moved through the <br /> https://www.ncbi.nim.nih.gov/pmc/articles/PMC6069465/ 4/18 <br />