A Study on Mechanism of Organic Matter Removal in a Three-step Series Constructed Rapid Infiltration System Used for Domestic Wastewater Treatment

Abstract

This study focused on domestic wastewater in a campus and investigated chemical oxygen demand (COD) removal efficiency and removal mechanism in a wastewater treatment system using three-step series constructed rapid infiltration (CRI). The experimental results indicated that the three-step series CRI system led to COD removal of 79.65%, a value 6% greater than that in a system using conventional CRI. Moreover, the effluent water quality of the three-step series CRI system met the first level criteria A as specified in Discharge Standard of Pollutants for Municipal Wastewater Treatment Plant (GB18918-2002). Total organic matter and particulate organic matter in the wastewater were removed in the first compartment of the system by 54% and 83%, respectively. The quantity of aerobic ammonifying bacteria decreased from top to bottom along the compartments in the system, and was obviously higher than in the conventional CRI system. The dehydrogenase activity showed an M-shaped variation pattern in which two peak activity values were observed. The COD removal efficiency showed a very significant correlation with the aerobic bacteria quantity (correlation coefficient r = 0.97), and showed a relatively significant correlation with the dehydrogenase activity (r = 0.64). The biofilm mass and the active biofilm mass showed M-shaped variation patterns, and were obviously higher than in the conventional CRI system. The COD removal efficiency showed a relatively significant correlation with the weight of the active biofilm mass (r = 0.73).

Regulation of Partial Nitritation in Constructed Rapid Infiltration System and Analysis of Microbial Community Structure

“…Constructed rapid infiltration (CRI) is a new ecological wastewater treatment technology developed in recent years with the advantages of less construction investment, simple operation and low operating cost [1]. It uses material such as natural river sand, zeolite sand and marble sand with good percolation performance as filter media, and the hydraulic loading is higher than the traditional soil infiltration and constructed wetland system, which made it particularly suitable for the treatment of wastewater in small towns or rural areas that are not yet covered by a municipal pipe network [2,3]. However, the concentration of organic matter in wastewater decreased gradually with the increase of filter depth, and the C/N ratio of wastewater entering the lower part of the CRI system was low.…”