Abstract
Domestic sewage sludge and cattle manure are rich in nutrition elements, but without proper disposal, are harmful to the environment. Here with an indoor culture method, we used Eisenia fetida to dispose different ratios of sewage sludge and cattle manure, and thereby investigated the effects and acting rules of these sludge-manure mixtures on the growth and reproduction of E. fetida. We find these mixtures are food sources for E. fetida, and their physiochemical properties are significantly changed after disposal by earthworms. Paired samples t-test shows the average change after different treatments is -20.37% for total organic carbon, 85.71% for total Kjeldahl N, -6.67% for total P, 8.33% for pH, -24.78% for EC (ms·cm-1), and -57.10% for C/N ratio. The average growth rate after treatment CD-70 is 9.20 mg·worm-1·day-1; the average growth rates of E. fetida on day 0–28, day 29–56, and day 57–91 are 9.33, 11.90 and 6.95 mg·worm-1·day-1, respectively, indicating a trend of "rapid—rapidest—slow" growth. Other treatments all show this trend. Though all earthworms developed reproductive rings during the test periods, the appearing time and the cocoon production time both differed among these treatments. The cocoon production amount is maximized to 233 after treatment CD-70. The cocoon production rates are significantly different among these treatments, and the maximum and mean are 0.32 and 0.17–0.32, cocoons·worm-1· day-1, respectively. E. fetida can modestly enrich Cd, but is not very effective over Sb or other heavy metals. E. fetida can remove a part of heavy metals from sewage sludge and cattle manure. Generally, the mixtures of sewage sludge and cattle manure can largely affect the growth and propagation of E. fetida in a ratio-dependent way.
Highlights
As is well-known, a huge amount of organic solid wastes, including urban sludge, crop straw, cattle manure, sheep manure and pig manure, is produced from planting, breeding, and PLOS ONE | DOI:10.1371/journal.pone.0156492 June 3, 2016Different Food Affecting Physiological Characteristics of Eisenia Fetida industrial fields
Paired-samples T-test shows the Total organic carbon (TOC) are significantly changed after treatment CD-0 (t = 10.17), CD-30 (t = 15.65), CD-50 (t = 15.78), CD-70 (t = 62.50), CD-100 (t = 25.85), and especially after CD-70, the reduction degree is maximized to 33.65%
In earthworm composting experiments, the Cd, Zn and Pb contents are 7.64±0.35, 109.85±7.18 and 51.33±1.97 mg/kg, respectively, and the bio-enrichment factors of Cd, Zn and Pb are 2.973, 1.316, and 0.443, respectively [45]. These results indicate E. fetida can modestly enrich Cd and Zn and helps to remove some heavy metals from sludge
Summary
As is well-known, a huge amount of organic solid wastes, including urban sludge, crop straw, cattle manure, sheep manure and pig manure, is produced from planting, breeding, and PLOS ONE | DOI:10.1371/journal.pone.0156492. Different Food Affecting Physiological Characteristics of Eisenia Fetida industrial fields. These wastes, without recycled use, will deteriorate the environment, so their disposal and management become urgent [1,2]. China is challenged by the inappropriate and arbitrary disposal of solid wastes. The common disposal methods, including burning and land use, cause severe pollution to air, soil and groundwater. Earthworm composting is an environmental-friendly and sustainable technique, as it can efficiently decompose organic waste, save energy resources and avoid secondary pollution [3,4]
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