Abstract
In this study, an integrated multi-soil-layering and subsurface wastewater infiltration (MSL-SWI) system was developed for decentralized domestic sewage treatment under high hydraulic loading rates (HLRs). To improve sustainable nitrogen removal, the influence of intermittent operation and shunt distributing wastewater on the performance of MSL-SWI systems was investigated. The optimal performance—with removal efficiencies of 93.41% for chemical oxygen demand, 97.91% for total phosphorus, 74.02% for ammonia nitrogen, and 73.56% for total nitrogen—was achieved using both intermittent operation and shunt distributing wastewater under an HLR of 0.3 m3 m−2 d−1. The activity of microbial nitrogen functional genes (i.e., amoA, nirK, nirS, nosZ, and anammox 16S rRNA) and their relationships with nitrogen transformation rates were further analyzed in different layers of the system. The results imply that nitrification and anaerobic ammonium oxidation in the MSL section coupled with nitrification and denitrification in the SWI section contribute to main the mechanisms of sustainable nitrogen removal. In summary, MSL-SWI systems not only operate with high efficiency under high HLRs, but the contaminant removal is also stable and sustainable, which are promising properties for domestic sewage treatment in areas where land resources are limited.
Highlights
Accepted: 2 February 2021Because of limited local budgets to construct sewer networks and centralized sewage systems in small and remote communities, domestic wastewater is often discharged into the environment without treatment, resulting in serious water pollution [1,2]
This paper focuses on pilot-scale experiments in four MSL-Subsurface wastewater infiltration (SWI) systems treating domestic wastewater under high hydraulic loading rates (HLRs)
In a soil infiltration system, physicochemical reactions such as filtration and adsorption are considered the major initial processes of organic matter removal, which are gradually replaced by microbial action over time [11,26]
Summary
Because of limited local budgets to construct sewer networks and centralized sewage systems in small and remote communities, domestic wastewater is often discharged into the environment without treatment, resulting in serious water pollution [1,2]. Subsurface wastewater infiltration (SWI) systems have gained considerable attention in this context due to their advantages of low cost, easy maintenance, and satisfactory performance in domestic sewage treatment [3]. The large operational footprints resulting from low hydraulic capacity restrict the wider application of SWI systems in areas with land resource shortages. The SMBs are a mixture of local soil and other materials which can improve pollutant removal performance, such as iron with high
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