Biosolids Decomposition after Surface Applications in West Texas

Abstract

In a semiarid environment, climate is a critical factor in the decomposition of surface-applied biosolids. This study examined the effect of 2- to 7-yr exposure times on the composition of single applications of New York, NY biosolids in western Texas. Exposure time effects on organic matter, N, P, S, Cu, Cr, Pb, Hg, and Zn were studied near Sierra Blanca, TX. Due to organic matter decomposition, total organic C decreased from 340 g kg(-1) in fresh biosolids to 180 g kg(-1) in biosolids after 82 mo of exposure, whereas the inorganic ash content of the biosolids increased from 339 to 600 g kg(-1). Total N decreased from 50 to 10 g N kg(-1) and total S decreased from 12 to 6 g S kg(-1). Bicarbonate-available P in the biosolids decreased from 0.9 to 0.2 g kg(-1). Successive H2O extractions yielded soluble P concentrations consistent with dicalcium phosphate (dical) for fresh biosolids and tricalcium phosphate (trical) for biosolids exposed for 59 months or more. Sparingly soluble phosphates, such as dical and trical, potentially yield > 0.5 mg P L(-1) in runoff waters for extended periods after biosolids applications, especially after multiple applications. Selective dissolution of the biosolids indicated that as much as 66 to 78% of P exists as iron phosphates, 16 to 21% as Fe oxides, and 5 to 12% as insoluble Ca phosphates. Chemical analyses of ash samples suggest that Cu and Zn have been lost from biosolids through leaching or runoff and no losses of Pb, Cr, or Hg have occurred since application.

Geochemical Modeling of Trace Element Release from Biosolids

“…The Chicago sample contained more FA but much less HA than the Toledo sample. The FA and HA contents of both samples were lower than those reported for New York City biosolids ( Jaynes et al, 2003). The HA content in the Chicago sample was comparable to the HA content of soils but the FA contents of both samples were much higher than those reported for soils (Dijkstra et al, 2004).…”

“…Both samples also had much higher Fe-and Mn-oxide concentrations than those reported for Brisbane, Australia biosolids (Burton et al, 2003). ( Jaynes et al, 2003). SD, standard deviation for the three replicates.…”

Phosphorus Extractability of Soils Amended with Stockpiled and Composted Cattle Manure

“…A source‐dependent correlation between agronomic and water‐extractable P in this study may relate to the water extraction method and source‐dependent P transformations throughout the incubation period. For these short‐duration water extractions, soluble forms of Ca‐P such as dicalcium phosphate dihydrate are probably not contributing much to solution P because of relatively slow dissolution rates of these minerals (Zhang et al, 1992; Jaynes et al, 2003). Consequently, surface‐adsorbed phosphate may be contributing a greater proportion to orthophosphates in water extract solutions rather than Ca‐P.…”

Residual Effects of Biosolids Application on Forage Production of Semiarid Grassland in Jalisco, Mexico

“…Residual effects on soil available nitrogen and phosphorus after 12 years have also been observed in a shortgrass prairie with biosolids application from 5 to 30 Mg ha −1 rates in Colorado [31]. However, organic matter from biosolids decreased with time, and soil nitrogen availability has been shown to decrease from 5 to 1% in a seven-year period in desert grasslands in Texas [32].…”