Heavy Metal Depletion of Sewage Sludge Ashes
Less is More
Compliance with limit values for fertilizers – current and perspective
Heavy metals, such as copper, zinc, nickel and lead, enter wastewater through various pathways. During wastewater treatment, a large proportion of the heavy metals enter the sewage sludge through the mechanical and biological treatment stages. When sewage sludge is thermally recycled, the majority of the heavy metals remain in the sewage sludge ash.
The input quantities of heavy metals vary depending on the municipal industrial input pathways. Therefore, sewage sludge ash is also contaminated with heavy metals to varying degrees. Phosphorus recyclates from this – such as fertilizers – must comply with corresponding limit values for the content of heavy metals.
Of course, this also applies to fertilizer recyclates produced using PHOS4green. Here, the fertilizer ordinances – German Düngemittelverordnung (DüMV) and Regulation EG No. 2019/1009 – set clear limits.
For sewage sludge ashes that comply with the limits of the fertilizer ordinances, the PHOS4green technology is used without heavy metal depletion.
Comparison of the pollutant content in fertilizer produced with PHOS4green with the permitted limit values according to Table 1.4 of the Fertilizer Ordinance (DüMV)
Content of copper and zinc in fertilizer produced with PHOS4green in comparison with the permitted limits
More disposal safety for sewage sludge ashes with excessive heavy metal content
Currently, a significant portion of sewage sludge ash does not meet the quality requirements of the Fertilizer Ordinance (DüMV) and Regulation EC No. 2019/1009, making heavy metal depletion necessary.
Economical heavy metal depletion increases the raw material potential (amount of usable sewage sludge ash) available for PHOS4green. The PHOS4green process, which has been modified with regard to heavy metal depletion, thus provides greater planning security with regard to possible future tighter limits or strongly fluctuating ash loads.
The ability to remove heavy metals from incoming sludge means there is no need for lot to lot selection – all available raw material can be used. This will also simplify regional and inter-municipal solutions for sewage sludge treatment, making the process viable over the long term. It is equal which ashes with which quality are used for fertilizer production from phosphorus recovery. This guarantees future disposal security and thus contributes to sustainable sewage sludge utilization.
Currently, Glatt offers various approaches to heavy metal depletion as part of a modified PHOS4green process.
Published article: ‘Striving for efficient recycling solutions’
Phosphorus recycling from sewage sludge: more fertilizer, fewer heavy metals
Phosphorus is essential as an agricultural fertilizer. Globally, this indispensable element is becoming increasingly scarce, putting an increasing focus on recovery where natural phosphate deposits are rare. Glatt Ingenieurtechnik GmbH has further developed its patented PHOS4green fertilizer production process so that sewage sludge ash from conurbations with high heavy metal contents can be used. Their removal means that fewer pollutants are released into the environment.
Glatt has expanded its PHOS4green process to facilitate the legally compliant recovery of valuable materials from sewage sludge ash contaminated with heavy metals
- author: Dr. Johannes Buchheim, Glatt Ingenieurtechnik
- originally published in the professional magazine ‘World Fertilizer’, ssue May/June 2024, Palladian Publications Ltd
Poster ‘Recovering valuable materials from sewage sludge ash – Phosphorus recycling for the production of compliant fertilisers’
Authors: Johannes Buchheim, Arne Teiwes, Michael Jacob, Glatt Ingenieurtechnik GmbH, Weimar
Phosphorus is a macronutrient for plants. It is of essential importance as a fertilizer for use in agriculture. Due to the global shortage, the recovery of phosphorus is required by law and direct soil-related recycling is no longer permitted. It is necessary to recover phosphorus through recycling and return it to reuse. Due to the increasing trend towards thermal recycling of phosphorus-containing sewage sludge, more phosphorus-containing sewage sludge ash is being produced, which can be used as a raw material for the production of phosphorus-containing fertilizers. In conurbations, sewage sludge ashes often contain high levels of heavy metals. In order to prevent excessive input into the environment, the heavy metals must be removed.
Economical heavy metal removal increases the raw material potential of the available sewage sludge ashes.
The PHOS4green process, modified with regard to heavy metal removal, thus provides greater planning security with regard to possible future stricter limit values or strongly fluctuating ash loads.
The poster provides an overview of the possibilities of optional heavy metal removal as an extension of PHOS4green.
Further information on this topic and related topics can also be found in the following publications:
Link to: Glatt builds demonstration plant for heavy metal separation from sewage sludge ash in the Rhine-Main region
Copyright: Glatt
October 2020: Glatt Ingenieurtechnik builds demonstration plant for heavy metal separation from sewage sludge ash in the Rhine-Main region
Link to: Growing the German phosphate industry
Copyright: Palladian Publications Ltd
Published article: ‘Growing the German phosphate industry’. PDF, English
Link to: Improved performance for crop protection products
Copyright: TRMG Ltd.
Published article: ‘Improved performance for crop protection products’, PDF, English
Link to: Formulation For Success – Fluid Bed Systemes as Key for the Production of Speciality Fertilizers
Copyright: Palladian Publications
Published article: ‘Fomulation For Success – Fluid Bed Systemes as Key for the Production of Speciality Fertilizers’, PDF, English
Link to: A Fluid Bed Approach for Urea-based Fertilizers
Copyright: Palladian Publications
Published article: ‘A Fluid Bed Approach – Case study on the economical production of urea-based fertilizers’ PDF, English
Copyright: Glatt
Copyright: Glatt
Copyright: Glatt
Copyright: Deutscher Fachverlag