title: Controlled field studies on soil aquifer treatment in a constructed coastal sandfill.
abstract: A controlled artificial recharge experiment was conducted to investigate the effect of soil aquifer treatment during percolation of secondary and tertiary (ultrafiltered) treated wastewater through the shallow vadoze zone of a newly constructed coastal sandfill. The sandfill is a reclaimed land constructed from marine sand dredged from the seabed. To obtain 1-D flow, a stainless steel column was driven to a depth of 2.5 m, penetrating the phreatic surface. Wastewater was percolated through the column under fully-saturated and unsaturated conditions. Infiltration rates, dissolved organic carbon (DOC) and ultra-violet absorption (UVA) were monitored. The wastewaters were recharged at similar infiltration rates of approximately 5.5 m/day and 3.5 m/day under fully-saturated and unsaturated conditions, respectively. In both cases, clogging occurred 40 days after the start of recharge, under saturated conditions. For secondary treated wastewater, DOC concentration (mg/l) reduced by 28% and 13% under unsaturated and saturated conditions, respectively. The corresponding UVA reduction was 19.4% and 14.1%. Similar reductions in DOC were observed for the tertiary treated wastewater; however, the reduction in UVA was higher; 28% and 22% under unsaturated and saturated conditions, respectively. On an mass removal (mg/m(2) DOC) basis, DOC reduction appeared to be more significant under unsaturated conditions. This is attributed to the presence of interstitial oxygen.
authors.affiliation: Division of Environmental and Water Resources Engineering, School of Civil and Environmental Engineering, Nanyang Technological University, Singapore. chcchua@ntu.edu.sg
authors.forename: Lloyd H C
authors.initials: LH
authors.lastname: Chua
authors.forename: Melvin C M
authors.initials: MC
authors.lastname: Leong
authors.forename: Edmond Y M
authors.initials: EY
authors.lastname: Lo
authors.forename: Martin
authors.initials: M
authors.lastname: Reinhard
authors.forename: Alexander P
authors.initials: AP
authors.lastname: Robertson
authors.forename: T T
authors.initials: TT
authors.lastname: Lim
authors.forename: E B
authors.initials: EB
authors.lastname: Shuy
authors.forename: S K
authors.initials: SK
authors.lastname: Tan
mesh_terms: D000042:Absorption; D002244:Carbon / Q000737:chemistry / Q000302:isolation & purification; D005374:Filtration; D009792:Oceans and Seas; D009930:Organic Chemicals / Q000737:chemistry / Q000302:isolation & purification; D012822:Silicon Dioxide / Q000737:chemistry; D012987:Soil; D012995:Solubility; D013499:Surface Properties; D014466:Ultraviolet Rays; D014865:Waste Disposal, Fluid / Q000379:methods*; D014867:Water / Q000737:chemistry
chemical_list: D009930:Organic Chemicals; D012987:Soil; D014867:Water; D002244:Carbon; D012822:Silicon Dioxide