Phosphorus availability in soils amended with dewatered water treatment residual and metal concentrations with time in residual

The objective of this laboratory study was to measure the effect of dewater ed Hater treatment residual (WTR) on extractable P and AI in soils with abo ve-optimum P concentrations. A secondary objective Has to document the vari ability of the metal content of WTR during 1 Sr. Two soils, a Paxton fine s andy loam (coarse-loamy, mixed, active, mesic Oxyaquic Dystrudept) and an E nfield silt loam (coarsesilty over sandy or sandy-skeletal, mired, active, mesic Typic Dystrudept) with above-optimum Mehlich 3 P concentrations (833 mg kg(-1) and 630 mg kg(-1), respectively) were amended with four dewatered WTRs. The WTRs were dewatered using three treatments: (i) WTR dewatered at 40 degreesC in a forced-air oven (DRY), (ii) WTR dewatered by freezing at -4 degreesC and then dried at 40 degreesC in a forced-air oven (FROZEN)I an d (iii) WTR dewatered to 4.5% solids at 40 degreesC in a forced-air oven (R AW). The WTRs were added to the soils at rates of 20 or 60 g kg(-1) and inc ubated far 21 d. The WTRs in the RAW treatment significantly reduced Mehlic h 3 P concentrations compared with the DRY and FROZEN treatments. The RAW t reatment reduced soil P concentrations an average of 64% compared with a re duction of 28% for the DRY treatment and 23% for the FROZEN treatment. The results suggest that the method used to dewater WTR will alter its ability to decrease Mehlich 3 P soil concentrations. The secondary objective involv ed collection of two of the WTRs every 3 wk for 1 Sr and subsequent analysi s for metal concentrations. The metal concentrations changed little during the year and only Cu, due to its use as an algicide, Has elevated.