Description
The main objective of this current project is the development of vermicomposting technology of sewage sludge, which is based on the foundations of conventional composting. An alternative to conventional sewage sludge composting technology can be vermicomposting, when manure worms are placed into the starting material, so the efficiency of breakdown and transformation of organic matter is increased by the activity of worms. Compared to conventional composting, higher-quality product can be produced with vermicomposting concerning agronomical value. Municipal sewage sludge from Érd has very high TPH content (5000-6000 mg/kg), which inhibits agricultural use. The exceedance in case of Cu content is 3-fold (Cu limit value is 100 mg/kg) and for TPH it is 50-fold (TPH limit value is 100 mg/kg). Based on previous experiments, treatment of municipal sewage sludge from Érd solely by vermicomposting has not proved to be effective enough mainly due to the high TPH content of sludge, despite the positive attributes of the produced material. The developed technology can greatly promote the recycling of sewage sludge, which is a very significant problem not only in Hungary but also in the European Union. Expected outcome of the project is the development of a viable technology, which allows the production of a better quality material compared to dewatered sewage sludge and conventional compost, which as a product can also get out of waste status. The importance of the latter is also given by the fact that more than 15% of soils in agricultural areas of Hungary are currently classified as less favored. Due to site conditions in the vicinity of Érd, raw materials to be included in the experimentation are available and potential users (farmers, growers) are accessible which are determining factors in terms of business plan and sustainability of the project.
Summary of project results
The main objective of the project was to transform the sewage sludge that is currently considered as waste into vermicompost, which can be utilized as soil improver or yield-increasing material. The biologically treated sewage sludge can become the soil organic matter supply in Hungary. Vermicomposting, when manure worms are placed into the starting material, the breakdown and transformation of organic matter is increased by the activity of worms. Compared to conventional composting, higher-quality product can be produced. In addition, worms are able to extract certain inorganic contaminants and accumulate them in their bodies, as well as to promote the breakdown of organic pollutants. Municipal sewage sludge from Érd has very high TPH content (5000-6000 mg/kg), which inhibits agricultural utilization even according to Decree 50/2001. (IV. 3.) (TPH limit value: 4000 mg/kg). Based on the Decree 36/2006. (V. 18.) the exceedance of Cu limit is 3-fold (Cu limit value is 100 mg/kg) and for TPH it is 50-fold (TPH limit value is 100 mg/kg). The technology development is achieved through small-scale and semi industrial experiments in prisms, the impact of the vermicompost was studied on less favoured soils of Hungary and Norway in pot experiments under laboratory conditions. Both the earthworms and the TPH degrading vaccine could reduce the amount of the hydrocarbon contamination of the substance. It could be observed in respect of plant hormones that the life-activity of earthworms enriched the plant cell division controlling kinetin content in the matter mixture. A prototype was developed prism to realize vermicompost technology in industrial conditions. This is a dynamic model with daily feeding of raw matter and taking-away of vermi-humus. The prototype could provide 60 tonnes of vericompost in every 4 week. During vermicomposting, the TPH and Cu content was reduced significantly compared to the initial sludge. The investigated vermicompost sample can be classified to the 2nd category according to the Norwegian legislation. This can be utilised in agricultural areas, private gardens and parks in amounts of 20 t/ha/10 years.
Summary of bilateral results
The NIBIO team's involvement in the project was built around the following activities: data collection and literature; technical consultation, comprehensive evaluation of the data; know-how; culture vessels experiments; mathematical modeling of water flows in vermicompost treated soil; substrate experiments; contribution of the project results to scientific and other circles, disseminating, popularizing.