Abstract
Subsurface wastewater infiltration (SWI) is an environmentally friendly technology for the advanced treatment of domestic sewage. Clogging (including physical, chemical and biological clogging) of the porous medium not only directly reduces the hydraulic load (treatment efficiency), but also reduces the service life. Although clogging has become one of the key issues discussed in several reports, there are still several gaps in understanding, especially in its occurrence process and identification. SWI clogging causes, development process and solutions are different from those of constructed wetlands. This article quotes some reports on constructed wetlands to provide technical ideas and reference for revealing SWI clogging problems. Based on the analysis of the clogging genesis, this review gathers the main factors that affect the degree of clogging, and new methods for the identification of clogging conditions. Some preventive and unclogging measures/strategies are presented. Finally, it is suggested that to effectively alleviate the clogging phenomenon and extend the service life, priority should be given to the comprehensive analysis of wastewater quality and solid constituents accumulated in the pores. Then, the effectiveness of in-situ strategies, such as alternating operation will be the main focuses of future research.
Highlights
Up to dated methods for the identification of clogging conditions were compared. Main factors that affect the probability and degree of clogging were gathered. Different preventive and unclogging measures/strategies were compared. Priority unclogging measurements are proposed
Subsurface wastewater infiltration (SWI) technology is an improved process of soil capillary infiltration trench, as shown in Figure 1 (Li et al ; Lopez-Peña et al )
Starting from the internal principles, this review comprehensively reveals the causes of SWI clogging and the main factors
Summary
To minimize the clogging in SWI beds, it is important to identify the degree of obstruction in the porous medium. The hysteresis factor R can be calculated using the following equation (Perujo et al ): The mathematical model can predict the zone, time and simulate the process of porous clogging. In 2019, Wang et al ( ) used DO and KBr’s migration curve model to simulate the process of SWI clogging caused by the air carried by water. About 2% to 20% of the pore space in the middle of the SWI bed was occupied by gas, indicating that the air carried by the water mainly affected the permeability of the middle zone, where gas clogging was most likely to occur. Since the wastewater continuously supplies the nutrients needed for the growth of microorganisms, the newly formed microbial biomass in the pores is greater than the amount of attenuation, so that the pores are continuously occupied by biofilms, resulting in a decrease in permeability. The main task of clogging prevention and remediation is to ensure uniform
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