Chemical Oxygen Demand and Ammonia Nitrogen Removal in a Non-saturated Layer of a Strengthened Constructed Rapid Infiltration System

Abstract

A strengthened constructed rapid infiltration (SCRI) system is a sewage treatment system derived from a constructed rapid infiltration (CRI) system. The SCRI tank structure primarily includes saturated and non-saturated layers. The degradation of the chemical oxygen demand (COD) and the conversion of ammonia nitrogen (NH4 +-N) are primarily performed in a non-saturated layer. To study the COD and NH4 +-N removal process in a non-saturated layer, two organic glass columns with a radius of 2.5 cm and a height of 70 cm were loaded with layers of soil from the Shunyi district of Beijing. The primary goal of this research is to quantify the removal effect factors and the relationship of the COD and NH4 +-N in the non-saturated layer. The SCRI system functioned successfully under a wetting-drying ratio of 1:5 with hydraulic loading at 1.0 m3/ (m2·d) for over 2 months. Our results show that the removal rate of NH4 +-N is approximately 69.11%, and the removal efficiency of COD is approximately 90.46%. The removal of COD is only slightly affected by pH, while the removal of NH4 +-N is greatly influenced by pH.