Phosphorus in Sewage Sludges as a Fertilizer

Abstract

A knowledge of the value of the phosphorus in a sewage sludge relative to a conventional phosphorus fertilizer such as superphosphate can provide a strong economic incentive for farmers to accept sewage sludge as an application to agricultural land. A study of the literature showed a range of values. These appeared to be modified by method of assessment, by type of sludge, and by its metal content. An incubation study of soil-sludge mixtures showed that changes occurred in the values for solubility of phosphorus in 0.5 M sodium bicarbonate. A study of six crops and three soils indicated that the most suitable crop to indicate availability of phosphorus in sludge was spinach ( Spinacea oleracea cv.) with ryegrass ( Lolium perenne cv.) as the next best. Soil of any texture was suitable provided the initial bicarbonate solubility of phosphorus in the soil was less than 10 mg P kg -1 . Data from the three studies carried out indicated that phosphorus in fresh undigested sludge was as available as that in superphosphate. Phosphorus in the digested sludge used was 60% as available as that in superphosphate.

Direct Chemical Speciation of P in Sequential Chemical Extraction Residues Using P K-Edge X-Ray Absorption Near-Edge Structure Spectroscopy

“…This is consistent with the observation that triple super phosphate P is four to seven times more available to plants than common P forms in biosolids (McCoy et al, 1986). The relatively small percentages of labile P in biosolid-applied soils may be due to the presence of different elements and surfaces that can react with biosolids (Coker and Carlton-Smith, 1986;Kashem et al, 2004;Kyle and McClintock, 1995). In support of this, NaOH-extractable P, which is typically considered to be Fe-and Al-associated P (Bowman and Cole, 1978;McLaughlin et al, 1977), was higher in all biosolid-amended plots.…”

Influence of long-term fertilizer application on changes of the content of Mehlich-3 estimated soil macronutrients

“…That resulted in a total application dose of 201 kg P/ha per crop rotation (SS) and only 70 kg P/ha per crop rotation (FYM), respectively. Sewage sludge phosphorus availability is comparable with superphosphates (Coker and Carlton-Smith 1986). Therefore, such a big increase of bioavailable P content during the experiment was observed.…”

Comparative environmental impacts of source-separation systems for domestic wastewater management in rural China

“…A nitrogen plant availability of 100% relative to mineral fertilizers was assumed for urine (Jönsson et al, 2004), as nitrogen is mostly in the form of urea; and for the treated effluent, as nitrogen is almost completely in the form of NH 4 + or NO 3 − , which are readily available to plants. For phosphorus, plant availability of 60% was assumed relative to mineral fertilizers for liquid anaerobically digested sludge and dried sludge from SDRBs, based on the literature review undertaken by Coker and Carlton-Smith (1986). Phosphorus plant availability of 100% relative to mineral fertilizers was assumed for urine (Jönsson et al, 2004) and treated effluent, as phosphorus is mostly in the form of phosphate that is readily available to plants.…”