phosphorus recovery from polish sewage sludge ash
PHOSPHORUS RECOVERY FROM POLISH SEWAGE SLUDGE ASH – POTENTIAL OF FERTILIZER PRODUCTION B. TARKO*, K. GORAZDA*, Z. WZOREK* * Faculty of Chemical Engineering and Technology, Cracow University of Technology, ul. Warszawska 24, 31-155 Kraków, Poland
SUMMARY: In the paper the capacity of Polish Thermal Utilization Plants producing incinerated sewage sludge ash (ISSA) was presented. The potential of this waste as an alternative phosphorus source in the context of phosphorus recovery was evaluated. The sewage sludge incinerated in micro-technical rotary kiln was taken under consideration as well. The extraction process with nitric acid was conducted and the analysis of the main ash components, S/L ratio and the amount of extractant per selected components mass versus phosphorus extraction efficiency was presented. As a second part of the experiment the neutralization process was conducted in order to obtain fertilizer products in the form of granules and pellets. These materials fulfilled the guidelines for the merchant fertilizers according to the law regulation.
1. INTRODUCTION Sewage sludge ash is one of the most promising alternative phosphorus source due to its high phosphorus content (up to 12 %P), easy collection system and stable, sterile form. Phosphorus can be recovered from SSA via relatively simple wet extraction process, which allows obtaining high quality fertilizer products (Herzel et al., 2016, Gorazda et al. 2017). Phosphorus recovery form waste materials such sewage sludge ash is highly desired according to circular economy (CE) strategy, which emphasizes sustainable resources utilization, their recycling as well as waste reuse and proper management (Skulimowska, 2015, EC 2016). In Poland in 2015 there were 568 thousand tons of sewage sludge produced (GUS, 2016). Assuming, that whole produced amount of sludge had been subjected to thermal utilization process, it would be possible to obtain ca. 62 thousand tons of ash that is an equivalent to 5.5 thousand tons of P (average P concentration in ash equal to 9%). According to the Best Available Technics (BAT) the best method of sewage sludge utilization is its combustion (IPPC, 2006). However, the most common sewage sludge utilization methods in our country are accumulating on the treatment plant area (43%) and agricultural disposal (19%). Thermal utilization (with 14% share) is on the third place (GUS 2016). What is more, not all thermal utilization plants produce material that could be directly used in a typical recovery process. As a result, huge amount of phosphorus that could be recovered in Poland from ISSA is just a theoretical value at the moment. In this paper evaluation of real potential for phosphorus recovery in Poland was discussed.
Proceedings Sardinia 2017 / Sixteenth International Waste Management and Landfill Symposium/ 2 - 6 October 2017 S. Margherita di Pula, Cagliari, Italy / © 2017 by CISA Publisher, Italy
Sardinia 2017 / Sixteenth International Waste Management and Landfill Symposium / 2 - 6 October 2017
2. POTENTIAL OF SEWAGE SLUDGE ASH PRODUCTION IN POLAND 2.1 Polish sewerage system There are 3268 municipal wastewater treatment plants (WWTPs) operating at the area of The Republic of Poland (data for 2016). Their numbers have been raised up to 11% during 12 years (there were 2931 WWTPs operating in 2005). From 2000 to 2003, 181 plants were modernized. Currently nearly 1,742,174 thousand cubic meters are subjected to the treatment process. As a result, about 556 thousand tons (dry solid, d.s.) of sewage sludge are formed each year. It is estimated that there will be a constant increase of the amount of sewage sludge equal 2-3% per year (Bień 2009, GUS 2016, KPGO, 2017). Former predictions from 2010 were foretelling dramatic increase of sewage sludge production up to 700 thousand tons d.s. in 2018 due to the fact that each year more households were introduced to the central sewerage system. Fortunately, these forecast appeared to be unfounded. Nevertheless, the amount of sewage sludge produced each year is still problematic especially towards new law regulations. According to the Ministry of Economics regulation, only sewage sludge with specific properties (e.g. Total organic compound (TOC) below 5 wt.% , lost on ignition (LOI)
SUMMARY: In the paper the capacity of Polish Thermal Utilization Plants producing incinerated sewage sludge ash (ISSA) was presented. The potential of this waste as an alternative phosphorus source in the context of phosphorus recovery was evaluated. The sewage sludge incinerated in micro-technical rotary kiln was taken under consideration as well. The extraction process with nitric acid was conducted and the analysis of the main ash components, S/L ratio and the amount of extractant per selected components mass versus phosphorus extraction efficiency was presented. As a second part of the experiment the neutralization process was conducted in order to obtain fertilizer products in the form of granules and pellets. These materials fulfilled the guidelines for the merchant fertilizers according to the law regulation.
1. INTRODUCTION Sewage sludge ash is one of the most promising alternative phosphorus source due to its high phosphorus content (up to 12 %P), easy collection system and stable, sterile form. Phosphorus can be recovered from SSA via relatively simple wet extraction process, which allows obtaining high quality fertilizer products (Herzel et al., 2016, Gorazda et al. 2017). Phosphorus recovery form waste materials such sewage sludge ash is highly desired according to circular economy (CE) strategy, which emphasizes sustainable resources utilization, their recycling as well as waste reuse and proper management (Skulimowska, 2015, EC 2016). In Poland in 2015 there were 568 thousand tons of sewage sludge produced (GUS, 2016). Assuming, that whole produced amount of sludge had been subjected to thermal utilization process, it would be possible to obtain ca. 62 thousand tons of ash that is an equivalent to 5.5 thousand tons of P (average P concentration in ash equal to 9%). According to the Best Available Technics (BAT) the best method of sewage sludge utilization is its combustion (IPPC, 2006). However, the most common sewage sludge utilization methods in our country are accumulating on the treatment plant area (43%) and agricultural disposal (19%). Thermal utilization (with 14% share) is on the third place (GUS 2016). What is more, not all thermal utilization plants produce material that could be directly used in a typical recovery process. As a result, huge amount of phosphorus that could be recovered in Poland from ISSA is just a theoretical value at the moment. In this paper evaluation of real potential for phosphorus recovery in Poland was discussed.
Proceedings Sardinia 2017 / Sixteenth International Waste Management and Landfill Symposium/ 2 - 6 October 2017 S. Margherita di Pula, Cagliari, Italy / © 2017 by CISA Publisher, Italy
Sardinia 2017 / Sixteenth International Waste Management and Landfill Symposium / 2 - 6 October 2017
2. POTENTIAL OF SEWAGE SLUDGE ASH PRODUCTION IN POLAND 2.1 Polish sewerage system There are 3268 municipal wastewater treatment plants (WWTPs) operating at the area of The Republic of Poland (data for 2016). Their numbers have been raised up to 11% during 12 years (there were 2931 WWTPs operating in 2005). From 2000 to 2003, 181 plants were modernized. Currently nearly 1,742,174 thousand cubic meters are subjected to the treatment process. As a result, about 556 thousand tons (dry solid, d.s.) of sewage sludge are formed each year. It is estimated that there will be a constant increase of the amount of sewage sludge equal 2-3% per year (Bień 2009, GUS 2016, KPGO, 2017). Former predictions from 2010 were foretelling dramatic increase of sewage sludge production up to 700 thousand tons d.s. in 2018 due to the fact that each year more households were introduced to the central sewerage system. Fortunately, these forecast appeared to be unfounded. Nevertheless, the amount of sewage sludge produced each year is still problematic especially towards new law regulations. According to the Ministry of Economics regulation, only sewage sludge with specific properties (e.g. Total organic compound (TOC) below 5 wt.% , lost on ignition (LOI)
