Cow Dung Compost Maturity Evaluation And Metals Speciation Change

Cattle manure and straw were important resource. This paper was to study : (1) , the effect of different pretreatment time on cattle manure and straw mixture composting, the feasibility of using biochemical parameters and Fuzzy comprehensive assessment to evaluate the composting maturity,(2) the effect of different pretreatment time of composting on speciation of heavy metal, by using the DTPA and BCR sequential extraction, to explore the law of changes of heavy metal speciation during cattle manure composting, by utilizing PCA. The experiments were divided into four treatments followed by the pretreatment periods, which were 0 day, 5 days, 10 days and 15 days (marked 0#, 5#, 10#, 15#), respectively. Experiment of composting periods started from 4-13-2007 to 6-15-2007, totally 63 days. During the periods, the temperature, pH, TOC, TN, C/N, total bacteria, germination index (GI), concentration and speciation of heavy metal were detected.The results showed that:(1) Pretreatment periods were able to rise the composting temperature, to prolong the time of high temperature and promote compost to reach the stability quickly.(2) According to compare the correlation of composting parameters, and to use the multiple stepwise regression analysis, The GI value, greater than 105%, were proposed to be the threshold of evaluation index of composting maturity.(3)Fuzzy comprehensive assessment, which was used to evaluate the composting maturity, was able to avoid unilateral and to integrate quantificational maturity.(4) Following the DTPA and BCR sequential speciation analysis, bioavailability of heavy metals were decreased, the main reason was that composting material concentrated and volatilize.(5) The data showed that the change of heavy metal speciation correlated with species. Different laws were existed between different heavy metals. The fraction of Cu-oxidizable and Cu-residual were the dominant speciation, while the fractions of exchangeable and reducible were dominant speciation for Zn in composted sludge.