| Urban sewage sludge is one of the main byproduct in the wastewater treatment process. It contains a lot of beneficial nutrients for plant growth, but also has some toxic and harmful substances, such as pathogens, heavy metals, etc. If the sludge disposal and improper application, it can cause serious secondary pollution of the natural environment easily. In this paper, it uses earthworms to process live sludge, analysis various substances content changes in sludge before and after treatment. It uses of sewage sludge which is processed by earthworms with soil to grow white clover and Coleus grass after matching different proportion of growing media, analyzing different ratios of matrix on effects to two different types plant.The main conclusions are as follows:(1)When the sludge is treated by earthworms, that the dry bulk density from the 0.95g/cm3 dropps to 0.58 g/cm3, porosity size ratio also becomes 1.12 from 0.32, both them are within the 0.2-0.8 g/cm3 scope of density and size of the void ratio range of 2 to 4 after treatment by earthworms, which are the most suitable for plant growth. Meanwhile sludge moisture content and pH are also declined. The physical condition of the treated sludge improved significantly, and it has provided favorable conditions for utilization.(2) After the earthworms treat sludge, the decline rate of heavy metals Pb and As in the sludge were 80.3% and 65.94%, respectively, and compared with pre-treatment it reduced significantly. There are also decline in different degrees of Hg and Zn after treatment. Polyacrylamide content fell by nearly 25 times than before treatment. Results shows hazardous substances significant reduction in handling, that provides a reliable guarantee to achieve harmless use of sludge.(3)The concent of total nitrogen, total phosphorus, nitrogen, available phosphorus decreases significantly in the sludge which is treated by earthworms, but the proportion of the nitrogen to total nitrogen increases 7.17%, and ratio of available phosphorus to the total phosphorus also increases 1.54%. Similarly, organic matter and humic acids also have some decline, but they are still far higher than normal soil. The results showed that the nutrients are still rich in treatment sludge worms, which is laid the foundation of sludge as a nutrient for plant growth matrix.(4) In the experiment which uses the treated sludge ratio into different growing media to plant clover. When matrix containing the treated sludge volume at 75%(T3), the white clover seed germination rate up to 84.0 and 16.7% higher than the whole earth control (CK),76.8% higher than the 100% sludge without earthworms treatment (T5); showed that white clover seed germination T3 treatment has some role in promoting and T5 its seeds are toxic. Under T4 (100% of earthworms after treatment sludge) treatment of white clover height, aboveground biomass and leaf size maximum; T2 (after 50% earthworm treatment sludge) belowground biomass maximum,67.9% and 29.1% higher than the T5 and CK; T1 (after 25% earthworm treatment sludge) soluble sugar and starch content were the highest; white clover blossom up to T3 treatment, the chlorophyll content of 20.5% and 31.1% higher, respectively, than CK and T5. Thus, the treated sludge ratios appropriate growing media in favor of white clover growth.(5) As use the treated sludge which was ratio of different growing media planted coleus, T4 (100% earthworms after treatment sludge) compared with CK (100% soil) anthocyanin in leaves content increased 710.57 nmol/g, and compared to T5 (100% earthworm without sludge treatment) anthocyanin levels increased five-fold; under T4 treatment, Coleus crown is 79.1% higher than T5,24.3% higher than CK; ground fresh weight in T4, respectively, higher than CK and T5 28.4g and 63.73g. Meanwhile, Coleus Root highest activity, leaf width and leaf maximum number of branching points also are the most under T4 treatment. The results showed that 100% sludge treated by earthworms as substrate for the cultivation of Coleus were the best. |
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