Removal of potentially toxic metals from sewage sludge using EDTA



Sewage sludge has the potential to be used as a fertilizer in agriculture because of its high nutritional value, but it is often contaminated with toxic metals (TM). This study investigated whether ReSoil® technology, based on the use of EDTA (50, 70, and 100 mmol l-1), efficiently removes TM from sewage sludge collected after aerobic (blato1) and anaerobic (blato2) treatment. The highest removal efficiency of Pb was achieved in blato1 (up to 60 %) and of Zn and Cu in blato2 (up to 55 and 29 %, respectively). The content of nutrients did not change significantly after remediation, only available phosphorus decreased up to 1.7-times in blato2, but its content remained high (489-510 mg 100-1 g-1). After remediation, the concentration of all metals, except Zn, in the leachates was below the limit for non-hazardous substances. To demonstrate the possibility of recycling process solutions and EDTA, blato2 was washed in 5 consecutive batches with 50 mmol l-1 washing solution, removing on average 28 % Pb, 48 % Zn, 35 % Cu, 30 % Mn, and 10 % Fe. ReSoil® technology removes metals from sludge and preserves its nutritional value. However, the efficiency of the technology depends on the treatment process used in the wastewater treatment plant.


EDTA; toxic metals; remediation; sewage sludge; wastewater treatment plants; aerobic biological treatment; anaerobic biological treatmen


/278/EGS. (1986). Directive 86/278/EEC on the protection of the environment, and in particular of the soil, when sewage sludge is used in agriculture. Official Journal L, 6-12.

Ali, H., Khan, E., Ilahi, I. (2019). Environmental chemistry and ecotoxicology of hazardous heavy metals: Environmental persistence, toxicity, and bioaccumulation. Hindawi Journal of Chemistry, 2019, 6730305.

Babel, S., del Mundo Dacera, D. (2006). Heavy metal removal from contaminated sludge for land application: A review. Waste Management, 26, 988-1004.

Bloem, E., Haneklaus, S., Haensch, R., Schnug, E. (2017). EDTA application on agricultural soils affects microelement uptake of plants. Science of The Total Environment, 577, 166-173.

Buta, M., Hubeny, J., Zielinski, W., Harnisz, M., Korzeniewska, E. (2021). Sewage sludge in agriculture – the effects of selected chemical pollutants and emerging genetic resistance determinants on the quality of soil and crops – a review. Ecotoxicology and Environmental Safety, 214, 112070.

Chen, H., & Cutright, T. (2001). EDTA and HEDTA effects on Cd, Cr, and Ni uptake by Helianthus annuus. Chemosphere, 45, 21-28.

Collivignarelli, M.C., Abbà, A., Frattarola, A., Carnevale Miino, M., Padovani, S., Katsoyiannis, I., Torretta, V. (2019). Legislation for the reuse of biosolids on agricultural land in Europe: Overview. Sustainability, 2019(11), 6015.

Černe, D. (2017). Izzivi trajnostne rabe fosforja. J. Pihler (Ur.), 26. mednarodno posvetovanje »Komunalna energetika 2017« (str. 87-96). Maribor: Univerzitetna založba Univerze v Mariboru. Pridoblejno s

DIN Standards. (1984). German standard procedure for water, wastewater and sludge analysis, sludge and sediments (Group S); determination of water leachability (DIN 38414-S4).

Geng, H., Xu, Y., Zheng, L., Gong, H., Dai, L., Dai, X. (2020). An overview of removing heavy metals from sewage sludge: Achievements and perspectives. Environmental Pollution, 266, 115375.

Gluhar, S., Kaurin, A., Finžgar, N., Gerl, M., Kastelec, D., Lestan, D. (2021). Demonstrational gardens with EDTA-washed soil. Part I: Remediation efficiency, effect on soil properties and toxicity hazards. Science of The Total Environment, 792, 149060.

Hamdi, H., Hechmi, S., Khelil, M.N., Zoghlami, I.R., Benzarti, S., Mokni-Tlili, S., Hassen, A., Jedidi, N. (2019). Repetitive land application of urban sewage sludge: Effect of amendment rates and soil texture on fertility and degradation parameters. Catena, 172, 11-20.

Hanay, O., Hasar, H., Kocer, N.N. (2009). Effect of EDTA as washing solution on removing of heavy metals from sewage sludge by electrokinetic. Journal of Hazardous Materials, 169, 703-710.

Hanum, F., Yuan, L.C., Kamahara, H., Aziz, H.A., Atsuta, Y., Yamada, T., Daimon, H. (2019). Treatment of sewage sludge using anaerobic digestion in Malaysia: Current state and challenges. Frontiers in Energy Research, 2019(7), 19.

Hudcova, H., Vymazal, J., Rozkošný, M. (2019). Present restrictions of sewage sludge application in agriculture within the European Union. Soil and Water Research, 14(2), 104-120.

Iglesias, M., Marguí, E., Camps, F., Hidalgo, M. (2018). Extractability and crop transfer of potentially toxic elements from mediterranean agricultural soils following long-term sewage sludge applications as a fertilizer replacement to barley and maize crops. Waste Management, 75, 312-318.

International Organization for Standardization. (2000). Characterization of sludges – Determination of dry residue and water content (ISO Standard No. 12880).

International Organization for Standardization. (2001). Characterization of sludges - Determination of trace elements and phosphorus - Aqua regia extraction methods (ISO Standard No. 13346).

International Organization for Standardization. (2012). Sludge, treated biowaste and soil - Determination of total nitrogen using dry combustion method (ISO Standard No. 16168).

International Organization for Standardization. (2012). Sludge, treated biowaste, soil and waste - Determination of total organic carbon (TOC) by dry combustion (ISO Standard No. 15936).

International Organization for Standardization. (2020). Soil, treated biowaste, sludge and waste - Digestion of aqua regia soluble fractions of elements (ISO Standard No. 54321).

Islam, K.R., Roth, G., Rahman, M.A., Didenko, N.O., Reeder, R.C. (2021). Cover crop complements flue gas desulfurized gypsum to improve no-till soil quality. Communications in Soil Science and Plant Analysis, 52, 926–947.

Jenkins, R.L., & Scheybeler, B.J. (1981). Metals removal and recovery from municipal sludge. Journal of the Water Pollution Control Federation, 5, 25-31.

Jez, E., Leštan, D. (2016). EDTA retention and emissions from remediated soil. Chemosphere, 151, 202-209.

Jez, E., Bravo, C., Lestan, D., Gluhar, S., Martin-Neto, L., De Nobili, M., Contin, M. (2021). Changes in organic matter composition caused by EDTA washing of two soils contaminated with toxic metals. Environmental Science and Pollution Research, 28, 65687-65699.

Kaurin, A., Gluhar, S., Tilikj, N., Leštan, D. (2020). Soil washing with biodegradable chelating agents and EDTA: Effect on soil properties and plant growth. Chemosphere, 260, 127673.

Kim, C., Lee, Y., Ong, S.K. (2003). Factors affecting EDTA extraction of lead from lead-contaminated soils. Chemosphere, 51, 845-853.

Kolbl Repinc, S., Bizjan, B., Budhiraja, V., Dular, M., Gostiša, J., Brajer Humar, B., Kaurin, A., Kržan, A., Levstek, M., Arteaga, J.F.M., Petkovšek, M., Rak, G., Stres, B., Širok, B., Žagar, E., Zupanc, M. (2022). Integral analysis of hydrodynamic cavitation effects on waste activated sludge characteristics, potentially toxic metals, microorganisms and identification of microplastics. Science of The Total Environment, 806, 151414.

Kou, Y., Zhao, Q., Cheng, Y., Wu, Y., Dou, W., Ren, X. (2020). Removal of heavy metals in sludge via joint EDTA-acid treatment: Effects on seed germination. Science of the Total Environment, 707, 135866.

Kowalik, R., Latosinska, J., Gawdzik, J. (2021). Risk analysis of heavy metal accumulation from sewage sludge of selectedwastewater treatment plants in Poland. Water, 2021(13), 2070.

Leštan, D. (2017). Novel chelant-based washing method for soil contaminated with Pb and other metals: A pilot-scale study. Land Degradation and Development, 28, 2585–2595.

Li, S., Li, R., Tang, Y., Chen, G. (2019). Microwave-induced heavy metal removal from dewatered biosolids for cost-effective composting. Journal of Cleaner Production, 241, 118342.

Morales Arteaga, J.F., Gluhar, S., Kaurin, A., Leštan, D. (2022a). Simultaneous removal of arsenic and toxic metals from contaminated soil: Laboratory development and pilot scale demonstration. Environmental Pollution, 294, 118656.

Morales Arteaga, J.F., Kaurin, A., Leštan, D. (2022b). Removal of toxic metals from sewage sludge by EDTA in a closed-loop washing process. Chemosphere, 307, 135917.

ÖNORML1087 (1993). Chemical analysis of soils: Determination of plant-available phosphate and potassium by calcium-acetate-lactate. Österreichisches Normungsinstitut, Austria.

Parveen, T., Hussain, A., Rao, M.S. (2015). Growth and accumulation of heavy metals in turnip (Brassica rapa) irrigated with different concentrations of treated municipal wastewater. Hydrology Research, 46(1), 60-71.

Pei, D., Xiao, C., Hu, Q., Tang, J. (2016). Electrokinetic gathering and removal of heavy metals from sewage sludge by ethylenediamine chelation. Procedia Environmental Sciences, 31, 725-734.

PIS. (2008). Uredba o uporabi blata iz komunalnih čistilnih naprav v kmetijstvu. Ur. l. RS, št. 62. Pridobljeno s

PIS. (2014). Uredba o odlagališčih odpadkov. Ur. l. RS, št. 10. Pridobljeno s

Roig, N., Sierra, J., Martí, E., Nadal, M., Schuhmacher, M., Domingo, J.L. (2012). Long-term amendment of Spanish soils with sewage sludge: Effects on soil functioning. Agriculture, Ecosystems and Environment, 158, 41-48.

Rorat, A., Courtois, P., Vandenbulcke, F., Lemiere, S. (2019). Sanitary and environmental aspects of sewage sludge management. Industrialand Municipal Sludge, Emerging Concerns and Scope for Resource Recovery, 2019, 155-180.

Ren, X., Yan, R., Wang, H.C., Kou, Y.Y., Chae, K.J., Kim, I.S., Park, Y.J., Wang, A.J. (2015). Citric acid and ethylene diamine tetra-acetic acid as effective washing agents to treat sewage sludge for agricultural reuse. Waste Management, 46, 440-448.

Roš, M. (2001). Biološko čiščenje odpadne vode. Prvi natis. Ljubljana, GV založba.

Suanon, F., Sun, Q., Dimon, B., Mama, D., Yu., C.P. (2016). Heavy metal removal from sludge with organic chelators: Comparative study of N,N-bis(carboxymethyl) glutamic acid and citric acid. Journal of Environmental Management, 166, 341-347.

Tytła, M., Widziewicz, K., Zielewicz, E. (2016). Heavy metals and its chemical speciation in sewage sludge at different stages of processing. Environmental Technology, 37(7), 899-908.

Ubukata, Y. (2006). Fundamental mechanisms of phosphate removal by anaerobic/aerobic activated sludge in treating municipal wastewater. Phosphate removal from wastewater. Engineering in Life Sciences, 6(1), 51-56.

Wang, J., Yu, J., Kong, X.Z., Hou, L. (2013). Spectrophotometric determination of EDTA in aqueous solution through ferroin formation using sodium sulfite as the reducer. Chemosphere, 91, 351–357.

Wei, H., Gao, B., Ren, J., Li, A., Yang, H. (2018). Coagulation/flocculation in dewatering of sludge: A review. Water Research, 143, 608-631.

Wei, L., Zhu, F., Li, Q., Xue, C., Xia, X., Yu, H., Zhao, Q., Jiang, J., Ba, S. (2020). Development, current state and future trends of sludge management in China: Based on exploratory data and CO2-equivaient emissions analysis. Environment International, 144, 106093.

Wen, Y., Cheng, Y., Tang, C., Chen, Z. (2013). Bioleaching of heavy metals from sewage sludge using indigenous iron-oxidizing microorganisms. Journal of Soils and Sediments, 13, 166-175.

Wuana, R., Okieimen, F., Imborvungu, J. (2010). Removal of heavy metals from a contaminated soil using organic chelating acids. International Journal of Environmental Science and Technology, 7(3), 485-496.



  • There are currently no refbacks.

Copyright (c) 2022 Anela Kaurin, Juan Francisco Morales Arteaga, Domen Leštan


Acta agriculturae Slovenica is an Open Access journal published under the terms of the Creative Commons CC BY License.


eISSN 1854-1941