Effect of operating factors on the contaminants removal of a soil filter: multi-soil-layering system

Abstract

As a soil filter, the multi-soil-layering (MSL) system has several advantages over some other conventional soil-based systems, including higher hydraulic load rate (HLR) and lower probability of clogging. However, the role of operating factors on the performance of MSL is insufficiently understood, and this limits its further application to some extent. The present paper provides a holistic overview of the crucial operating parameters, including clogging and HLR, aeration, media composition and structure, temperature, and C/N ratio. In particular, clogging and HLR are discussed extensively, since they could cause much greater deterioration over the lifetime of the soil filter than the other factors. There are currently few relevant reports regarding the balance between maintaining the reasonable range of HLR and minimizing less chance of clogging. To fill this research gap, this paper proposes two applicable ways to reduce the opportunity for clogging, namely, system suspension and/or enhanced aeration, which will be time-saving and low cost. In addition, to increase the denitrification capacity of MSL, effluent recirculation is proposed, a novel recommendation based on the municipal wastewater treatment processes, which could also improve the controllability of MSL from the perspective of biochemical reaction.

Multi-Soil-Layering Systems for Wastewater Treatment in Small and Remote Communities

“…Clogging of MSL systems has been a major problem that results in total system failure (Guan et al, 2015). It was suggested that clogging can be avoided by operation planning such as using two sets of operating systems or settling the rest period of the system during the season in which water is less polluted (Masunaga et al, 2003b).…”

“…Aeration at optimal intensity and duration can significantly enhance the removal of BOD5, COD, TN and TP. As shown in Figure 3, aeration pipes can be set inside the MSL to control the aerobic and anaerobic states of the system by injections of air from outside the system (Sato et al, 2002;Masunaga et al, 2003b;Guan et al, 2015). Since BOD5 represents easily decomposable organic matter, aeration can immediately increase its removal efficiency in an MSL system.…”

Performance of multi-soil-layering (MSL) urban domestic wastewater treatment system

“…The different kinds of permeable zeolite, zeolite-resembling material, perlite, rock, and charcoal layers gave different values of efficiency in the elimination of dissolved COD, BOD5, and reactive phosphorus [3]. The efficiency of elimination also depended on the operational condition of whether or not aeration was given.…”

“…Guan et al [3] stated that the quantitative evaluation of water movement in MSL is not sufficient for understanding and suggested the use of Retention Distribution Time (RTD) as the method for the characterization of mixtures and flows in an MSL reactor using pulse tracer tests. The results of the research indicated that the level of re-dispersion of MSL is a moderate dispersion for HLR of 200, 400, 800, and 1,600 L/(m 2 .d) with the RTD showing a Continuous Stirrer Tank Reactor (CSTR) flow pattern as well as a negative correlation with the dead zone.…”

Physico‐Chemical Processes

“…The multi-soil-layering (MSL) filter system could be optimized through a few operation factors (Guan, Zhang et al, 2015). Effluent recirculation was able to increase the denitrification capacity, while system suspension and/or enhanced aeration were able to prevent system clogging.…”