Användning av komposterat rötslam i anläggningsjord: En undersökning av innehåll och läckage till recipienten
Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
Preventing climate change and taking care of today's environmental problems in a way future generations can meet their own needs without inhibiting is one of the biggest challenges that humanity faces. Part of the problem is to reduce the dependence on extraction of new resources and instead reuse the resources that are already integrated into society in order not only to promote, but also create, effective recycling. For instance, nutrients such as phosphorus and nitrogen that are present in digested sewage sludge can be recycled. Falu Energy and Water is the municipal company working with these issues in Falun, Sweden. However, due to its high concentration of metals, digested sewage sludge alone, it is not suitable for reusing as a nutrient on productive land. To compost the digested sewage sludge with other materials in order to create plant soil has been identified as an alternative solution.
The aim of this study is to evaluate the leach of nutrients and metals from plant soil to the recipient from the soil manufactured with the digested sewage sludge from Främby sewage treatment plant. The goal is to compare results from water samples with existing limits to investigate if they are met, along with other impact aspects. Samples have been collected from the recipient water at the Kemslam-landfill. The target group is Falu Energy and Water, who can use the report as a decision-making support document, although even other operators in the field may benefit from the report. Methods used to evaluate the problem are literature review, personal communication, samplings, comparison of the samples with existing limits and site visits in Falun. The authors have carried out appropriate calculations.
A common way of using sewage sludge in Sweden today is by creating plant soil. There are some requirements the plant soil has to meet unlike other soils used in window boxes and pots. Plant soil should be able to be used on green areas and thus it is required to have a higher carrying capacity and permeability of water. All soil has to meet the requirements in the Swedish laws and regulations. Limit values for surface water are not compiled today. Therefore, limit values for drinking water from the Swedish National Food Agency were used as indicators, along with guidance values from the Swedish Agency for Marine and Water management and the Swedish Environmental Protection Agency. The digested sewage sludge from Främby sewage treatment plant contains high levels of metals, partly due to former mining in Falun. High levels of metals are not shown in the samples and when the samples are compared with limit values for drinking water, all values meet the limits required by the Swedish National Food Agency.
Despite the high level of nutrients, it is not possible to determine that the leakage to the recipient is only caused from the plant soil. Certification of plant soil is one way to increase the demand of it. This can be done in two ways, REVAQ certification at the treatment plant or SPCR 148 certification of the plant soil. Due to the high content of metals in both sewage sludge and the plant soil, neither REVAQ certification nor the SPCR 148 certification are possible to implement at the moment. It is still possible to use the plant soil within the Falu city borders. From an economic perspective the production of plant soil with both Samuelsdal- and Kemslam mixture is possible but it is holding soil with Samuelsdals-mixture that is the cheaper approach and the one that is intended for commercial soil in the future. As for future studies, a need for upstream work has been identified; among others inspection programs for infection control and investigation of the impact other substances in the sewage sludge that impact on the possibility of using the soil and introducing a certification in the future.
Place, publisher, year, edition, pages
2015. , 50 p.
rötslam, anläggningsjord, läckage, metaller, näringsämnen, avloppsvatten
Engineering and Technology
IdentifiersURN: urn:nbn:se:hig:diva-20011OAI: oai:DiVA.org:hig-20011DiVA: diva2:841220
Subject / course
Study Programme in Environmental Engineering
2015-06-04, Gävle, 15:42 (Swedish)
Hillman, Karl, Universitetslektor miljöteknik
Norrman Eriksson, Ola, Universitetslektor (docent)