Effects of composting process and fly ash amendment on phytotoxicity of sewage sludge

• Published in: Archives of environmental contamination and toxicology 2001-02, Vol.40 (2), p.184-191
• Main Authors: LAU, S. S. S, FANG, M, WONG, J. W. C
• Format: Article
• Language: English
• Subjects: Animal, plant and microbial ecology; Applied ecology; Biological and medical sciences; Carbon - analysis; Carbon - pharmacology; Coal Ash; Composting; Composts; Ecotoxicology, biological effects of pollution; Effects of pollution and side effects of pesticides on plants and fungi; Environmental restoration; Fly ash; Fundamental and applied biological sciences. Psychology; Germination - drug effects; Humans; Industrial Waste; Lagoons; Metal concentrations; Metals; Oxidation-Reduction; Particulate Matter; Phytotoxicity; Seed germination; Seeds - drug effects; Seeds - growth & development; Sewage - analysis; Sewage - chemistry; Sewage disposal; Sewage sludge; Sludge
• ISSN: 0090-4341; 1432-0703
• DOI: 10.1007/s002440010162

With the increasingly growing global production of sewage sludge, evaluation of its applicability in agriculture and land restoration is essential. This study assessed the potential effects of composting process and fly ash amendment on soil-ameliorating properties of sewage sludge. The metal availability and phytotoxicity of ash-amended sludge compost (AS, mature sewage sludge compost mixed with fresh lagoon ash) and sludge-ash co-compost (SA, co-composted mixture of sewage sludge and lagoon ash) were compared. The results of this work suggested that both composts favored the applicability of sewage sludge for land application by reducing Cd, Cu, Pb, and Zn availability. The SA co-compost stimulated seed germination at ash amendment rates of < or = 10%, whereas various treatments of AS compost inhibited germination at an extract dilution of 50%. Amendment of lagoon ash before or after sludge composting increased electrical conductivity (EC) and volatilization of NH4-N, but lowered availability of PO4-P. Together with the results of phytotoxicity, an optimal ash amendment rate of 5% for AS and 10% for SA were most desirable. Alkaline amendment prior to sludge composting was recommended, because it could be more effective in reducing soluble and plant-available metal concentrations through the composting process.