Study On Sludge Earthworm Composting Technology For Municipal Sewage Treatment Plant

With the rapid developing of the municipal sewage treatment, more and more sewage sludge production, the reducing, harmless, stabilizing and recycling of municipal sludge has a widespread concern. Sewage sludge earthworms composting technology is by earthworms' special ecological features, and microorganisms' synergies to accelerate decomposition of organic matter and heavy metals absorption, and change the status of heavy metals, this technology improve sewage sludge fertility, potted plant was studied whether it could validate the effect of sewage sludge by earthworms composting, this study offers a new approach for the reducing, harmless, stabilizing and recycling of municipal sludge. The results are as follows:1. The sewage sludge earthworms composting process, the optimum temperature is approximately 20℃; the suitable humidity range between 55% and 70%; before earthworms composting, the organic matter contents control between 40% and 60%, after earthworms composting, the organic matter contents stable in the range of 25% ~ 35%; the suitable pH of sewage sludge in the range of 6.5～7.5 for earthworm composting; after earthworms composting of sewage sludge into soil have not the problem of salinity poisoning.2. Direct stacking pretreatment sludge in earthworms composting process, earthworms grow well, gain weight; on the contrary, after the hot fermentation composting stage of the pretreatment sludge in earthworms composting, earthworms don't grow and loss weight. After earthworms composting, the total weight of sewage sludge to decrease, but the former is better than the latter; In earthworms composting fully reflects the earthworms and microorganisms synergies, to maintain its small changes in the total number of bacteria, several pathogenic micro-organisms such as coliforms decrease; The results showed that the earthworms composting reduce the total nitrogen contents of sludge, and raising the available nitrogen contents, at the same time, the earthworms composting enhance the total phosphorus and available phosphorus contents of sewage sludge, total potassium and available potassium contents have small effect, basically unchanged; Research also shows that after earthworms composting sludge improve the germinability and germination percentage of the cabbage, for the germinability, rice hulls is better than sawdust; for the germination percentage, the phosphate rocks is better than fly ash, germination index showed that, the suitable after earthworms composting sewage sludge, promoting root growing development of cabbage seed.3. Earthworm composting process, earthworms can absorb heavy metals in the sewage sludge of Cu, Zn, Pb, Cd, but not enrichment; on the total contents of heavy metals, earthworm composting increased the total contents of heavy metals, in addition to Zn and some test Cd over agricultural sewage sludge standard, other heavy metals were not exceeds this standard; The status of heavy metals in sewage sludge to add fly ash and phosphate rocks to earthworms composting can be transform into each other, the exchangeable heavy metals transform towards carbonate, Fe-Mn combined oxides, organic combination state and residue state, this four kind of state not to take advantage of plant, the contents of organic combination state has decreased, the contents of Fe-Mn combined oxides increase, after earthworms composting sewage sludge land utilization can be reduce the release rate of heavy metals.4. The rational application of the earthworms composting sewage sludge can significantly increase the plant height and yields of cabbages, application of after earthworms composting sewage sludge as fertilizer, the application rates should be approach 10%, and it has appropriate to crop growth.