Treatment of domestic wastewater by an underground capillary seepage system

Organics removal of combined wastewater through shallow soil infiltration treatment: A field and laboratory study

“…The differences of COD removals between the trenches might be resulted from the different soil compositions of the four trenches and it seemed that T1 and T3 exhibited higher efficiencies (always 5-10% higher than the other two) in removing COD. Lower COD removals got in this study than those of Van Cuyk et al [8] and Sun et al [9] may be due to the more complicated wastewater treated and shallower effective depth designed for these SSIT trenches.…”

“…Thus in this study, to simplify the whole experiments, the wetting/drying period ratio was fixed at 1/2 (1/5 only in Run II) according to our preliminary experiment results with hydraulic loading rates being used and changed among the highest values in SIT systems; and the effects of hydraulic loading rate, air/water ratio in pre-aeration tank and temperature on COD removal were considered because of the field situation. with respect to temperature, indicating that temperature should be the most important factor for COD removal in SSIT trenches, which has been pointed out in SIT system by Sun et al [9].…”

“…Extensive field and laboratory studies were undertaken by Sun et al [9], Viswanathan et al [10], Reemtsma et al [11] and Quanrud et al [12,13]. The removal rates of COD, SS, and viruses were greater than 80% with phosphorus removal nearly 100%.…”

Nitrogen removal processes in deep subsurface wastewater infiltration systems

“…The advantages of SWIS over conventional activated sludge (CAS) and biofilm systems have been reported and include lower construction and operational costs, better performance for organic substance and phosphorus removal, easier management and maintenance (USEPA, 2002;Yamaguchi et al, 1996;Ye et al, 2008). Although SWIS has been successful for removing pollutants from various wastewaters, its capacity and efficiency remains low regarding nitrogen removal (Kong et al, 2004;Sun et al, 1998). According to previous research, nitrification and denitrification are the main mechanisms that are responsible for eliminating nitrogen from sewage water in the SWIS (Dong and Sun, 2007;Lance, 1986;Wang et al, 2010;Zhang et al, 2005).…”

“…However, without denitrification, NO x À -N remains in solution and is transported in the percolate because it is not held by exchange reactions. Denitrification in the conventional SWIS is usually affected by the denitrifying biomass, temperature, soil characteristics, the carbon source and the carbon/nitrogen ratio (Sun et al, 1998;Xia et al, 2008;Yamaguchi et al, 1996;Zhang et al, 2005Zou et al, 2009. Furthermore, decomposition of organic matter and nitrification mainly occur in the upper portion, where oxygen is adequate.…”