Changes in the phosphorus availability of a chemically precipitated urban sewage sludge as a result of different dewatering processes

• The objective of this study was to compare the effects of different dewatering processes on the phosphorus (P) availability of an FeCl3precipitated and limeconditioned sludge having an initial dry matter content (DMC) of 4%. The sludge was dewatered by either drying (D), freezing/thawing (FT) or centrifugation (C) until a DMC of about 15% was reached. Thereafter the FT and D sludges were gently dried to obtain a DMC increasing up to 50 to 60%. The plantavailable sludge P was assessed by the change in the isotopic dilution of P taken up by ryegrass (Lolium perenne[L]) after sludge amendments to one soil. After the plant experiment, the soiltosolution transfer of P ions and bicarbonateand ammonium lactate extractable P were determined in selected soil samples. The amount of plantavailable P (Lvalue) and the contribution of sludge P to plant nutrition (%Pdfsl) in soil amended with nondewatered sludge (ND) were not significantly different from the L and percentage Pdfsl values of soils amended with FT, D and C sludges. Nor did the subsequent drying of D and FT sludges significantly change the L and percentage Pdfsl values. Hence, the dewatering processes did not significantly alter the initial sludge P availability. The soiltosolution transfer of P ions and the chemically extracted P did not significantly differ between the different sludgeamended soil samples. The percentage Pdfsl values can be predicted by percentage ΔE1, since the overall average relative increase (%ΔE1) in the immediate soiltosolution transfer of P ions did not significantly differ from the percentage Pdfsl values.

Ämnesord

TEKNIK OCH TEKNOLOGIER  -- Samhällsbyggnadsteknik -- Vattenteknik (hsv//swe)

ENGINEERING AND TECHNOLOGY  -- Civil Engineering -- Water Engineering (hsv//eng)

Nyckelord

VA-teknik

Urban Water Engineering

Publikations- och innehållstyp

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