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Fertiliser properties of wastewater sludge and sludge ash - a case study from the Finnish forest industry

Oksanen Juha, Pöykiö Risto, Dahl Olli

Ecological Chemistry and Engineering. S

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2023

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Vol. 30, nr 1

63--78

EN

In this case study we compared the fertiliser properties of an industrial wastewater treatment sludge and a sludge ash to the requirements of the Finnish Fertiliser Product Decree. The sludge was obtained from the activated sludge wastewater treatment plant of a Finnish non-integrated pulp mill. The sludge was furthermore incinerated at a laboratory in a muffle furnace (850 °C) to obtain sludge ash. The total Cd (4.9 mg/kg d.m.) concentration in the pulp sludge exceeded the Finnish limit value (1.5 mg/kg d.m.) for fertiliser products used in agriculture. In the sludge ash, the total concentration of Cd (39 mg/kg; d.m.) exceeded the Finnish limit value (25 mg/kg d.m.) for ash fertilisers used in forestry. These results restrict the potential reuse options of these residues. However, from the utilisation point of view, the enrichment of essential plant macro-nutrients was most notable, resulting to the following total concentrations of these elements in the sludge ash: P (26,000 mg/kg d.m.), S (40,000 mg/kg d.m.), K (11,000 mg/kg d.m.), Ca (83,000 mg/kg d.m.) and Mg (10,000 mg/kg d.m.). Therefore, we conclude that, the converting of sludge into ash may promote the reuse of this wastewater treatment residue to a more value-adding fertiliser by-product to be used as a soil improver and growing medium in landscaping or landfills sites or other closed industrial areas, where heavy metal limit values for fertilisers are not applied in Finland.

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Comparison of Untreated, Lime-Stabilised and Composted Wastewater Sludges from a Pulp, Board and Paper Mill Integrate as a Fertiliser Product

Oksanen Juha, Pöykiö Risto, Dahl Olli

Journal of Ecological Engineering

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2021

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Vol. 22, nr 5

47--58

EN

In this study, the physical and chemical properties of untreated, lime-stabilised and composted wastewater sludges from a Finnish pulp, board and paper mill integrate were compared in order to assess their fertiliser properties based on the requirement of the Finnish Fertilizer Product Decree. Furthermore, the extraction properties of heavy metals in the sludges were assessed by the three-stage sequential extraction procedure of the Community Bureau of Reference (BCR) and the solubility indices for heavy metals were calculated in order to evaluate the release potential of elements from the sample (sludge) matrix. The results of this study indicated that the total heavy metal (As, Cd, Cr, Cu, Hg, Ni, Pb and Zn) concentrations in all sludges were lower than the statutory Finnish limit values for fertiliser products. However, the untreated sludge required either lime-stabilisation or composting in order to fulfil the Finnish maximum concentrations of pathogens (coliforms and Escherichia coli) for fertiliser products.

3

Characterisation of used traction sand for utilization aspects in earth construction based on the requirements of Finnish environmental legislation

Pöykiö Risto, Grönvall Mika, Watkins Gary, Välimäki Ilkka, Perämäki Paavo, Dahl Olli

Geology, Geophysics and Environment

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2019

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Vol. 45, no. 2

99--109

EN

Finland launched a new Government Decree, the so-called MARA-regulation, on the utilization of certain wastes in earth construction on 1.1.2018. This statutory regulation sets limit values for the solubility of heavy metals (Sb, As, Ba, Cd, Cr, Cu, Pb, Mo, Ni, Se, Zn, V, Hg), chloride, sulphate, fluoride and dissolved organic carbon, as well as for organic substance (petroleum hydrocarbons, benzene, naphthalene, TEX (toluene, ethylbenzene and xylene), PAH-, phenolic- and PCB-compounds). In this case study, the concentrations of these harmful substances in the used traction sand collected in the city of Kemi, Northern Finland, were lower than their limit values set in the MARA-regulation. Therefore, this residue is a potential material to be used at earth construction sites such as in roads and roadways, in field and embankment structures, as well as in floor structures of industrial or storage buildings. However, if the used traction sand is to be utilized for these kinds of civil engineering purposes, an environmental permit is still needed because this material is not yet included in the scope of the MARA-regulation. This paper also gives an overview of the relevant Finnish environmental legislation on the utilization of wastes as an earth construction material.

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Characterisation of municipal sewage sludge as a soil improver and a fertilizer product

Pöykiö Risto, Watkins Gary, Dahl Olli

Ecological Chemistry and Engineering. S

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2019

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Vol. 26, nr 3

547--557

EN

In this study, we have determined the main important physical and chemical properties of municipal sewage sludge and compared them to the requirements of the Finnish Fertilizer Product Act and Fertilizer Product Decree in order to assess the potential utilization of this by-product as a fertilizer. Except for Hg (1.4 mg/kg d.m.), the total concentrations of Cd, Cu, Ni, Pb, Zn, Cr and As in our sewage sludge were lower that the Finnish maximum permissible heavy metal concentrations for sewage sludge used as a fertilizer products. However, the sewage sludge may be utilized as a soil improver, a growing media or as a fertilizer product in landfill sites (e.g. surface structures) or in other closed industrial areas, because the above mentioned Finnish limit values are not applied at these sites. If the sewage sludge is to be utilized in these kinds of areas, an environmental permit may be needed. According to BCR-extraction, the lowest release potential (solubility) from the sample matrix was observed for sulphur (58.4 %) and the highest for Cd (100 %).