EFFECT OF SOIL TYPE ON WATER-QUALITY IMPROVEMENT DURING SOIL AQUIFER TREATMENT

Bench-scale soil column experiments were performed at The University o f Arizona to examine the effects of soil type and infiltration rate on the removal of wastewater organics during soil aquifer treatment (SAT ), The suitability of such waters for potable uses following a combina tion of above-ground treatments and SAT polishing was under investigat ion, SAT was simulated in 1-meter soil columns containing repacked hom ogenized soils ranging from poorly graded sands to silty sands. Soils were obtained from existing and potential effluent recharge sites in A rizona. All columns received chlorinated/dechlorinated secondary efflu ent, ponded to a 25-cm depth above the soil surface, under alternating wet/dry conditions. Treatment efficiencies in biologically active and inhibited columns were compared to determine the mechanism(s) of wate r quality improvements and the sustainability of SAT. Water quality pa rameters included: (i) non-purgable dissolved organic carbon and (ii) UV absorbance at 254 nm (used as a measure of disinfection-by-product precursors). Differences in through-column removal of non-purgable dis solved organic carbon were significant for columns containing sandy lo am (56%), sand (48%) and silty sand (44%), Removal of UV-absorbing org anics was not significantly different for columns containing sand and sandy loam (22 and 20%, respectively). There was no significant correl ation between infiltration rate and removal efficiency of either organ ic parameter for both soils. Copyright (C) 1996 IAWQ. Published by Els evier Science Ltd.