PHYSICAL CHARACTERISTICS OF ALKALINE STABILIZED SEWAGE-SLUDGE (N-VIROSOIL) AND THEIR EFFECTS ON SOIL PHYSICAL-PROPERTIES

The N-Viro process for alkaline stabilization of municipal sewage slud ge combines dewatered sludge with one or more alkaline industrial bypr oducts and destroys pathogens by a combination of high pH, heat, and d rying. The final product, N-Viro Soil, is a soil-like material that is being used as an agricultural lime substitute, soil amendment, and so il substitute. Physical characteristics of 28 N-Viro Soils were determ ined and compared to those of mineral soils. The N-Viro Soils have an average solids content of 62%, particle density of 1.96 Mg/m(3), bulk density of 0.59 Mg/m(3), and total porosity of 70%. Mean moisture rete ntion was 66, 58, 34, and 31% (v/v) at saturation, 5.9, 33, and 1.5 MP a, respectively. Available water content was 27% by volume (60 cm wate r tension, 1.5 MPa). Noncompacted and compacted saturated hydraulic co nductivities were high, 3 x 10(-2) and 9 x 10(-4) cm/s, respectively. Mean weight diameter (MWD) of water stable aggregates was 2.0 mm. Fift y-six percent of the materials were >2 mm in diam., almost all of this (88%) in sizes <16 mm. Of the <2-mm fraction, 69% was >0.5 mm. The N- Viro Soils have a shrinkage of 58%, and Atterberg liquid limit, plasti c limit, and plasticity index of 76, 64, and 18% water (w/w), respecti vely. The N-Viro Soils are similar in physical attributes to those of medium to fine textured, porous soils with granular, stable aggregates , and nonplastic consistency. The moisture retention characteristics a re those of a fine textured soil dominated by fine pores and low to me dium available water holding capacity, and these materials are highly permeable, even when compacted. N-Viro Soil was applied to the Miamian silt loam (fine, mixed, mesic Typic Hapludalf) in the field at a rate of 500 Mg/ha (dry solids), and changes in physical properties were me asured 1 yr after application. All effects of N-Viro Soil were statist ically significant (P = 0.01), except total porosity, 33 KPa moisture holding capacity, 0.5- to 0.25-mm water stable aggregates, and pocket penetrometer measurements, and all of the effects were beneficial.