Study on the Recovery of Phosphorus from Waste-Activated Sludge Incinerator Ash

Abstract

Several batch studies that were made up of the acid extraction and the solvent extraction were performed to recover phosphorus from the waste-activated sludge (WAS) incinerator ash. In the acid extraction, the extraction efficiency of phosphorus relied on the acid type, liquid(acid)-to-solid (L(acid)S) ratio, and acid concentration. Phosphorus in the WAS incinerator ash was completely extracted by 1 M HCl at the L(acid)S ratio of 6.4:1. Subsequently, the solvent extraction was conducted to separate and concentrate phosphorus further from the acid extract. The efficiency of solvent extraction was affected mainly by the solvent type, liquid (solvent)-to-liquid (the acid extract) (L(solv)L(acid ext)) ratio, and hydrogen ion concentration. Under the appropriate condition, 76% of phosphorus in the acid extract was extracted to 1-butanol phase, which corresponded to 80.1% as the mass fraction of phosphorus to total elements. Prior to the solvent extraction, the addition of bis (2-ethylhexyl) phosphoric acid (D2EHPA), which was available for removing aluminum from the acid extract, led to an additional increase in the term of the mass fraction of phosphorus to total elements. Overall results indicated that phosphorus in the WAS incinerator ash could be efficiently recovered and be a potential renewable resource.

Phosphorus recovery as struvite from farm, municipal and industrial waste: Feedstock suitability, methods and pre-treatments

“…Apart from liquid waste, ash from municipal sewage sludge generated by incineration is P-rich and has potential for struvite recovery (P constitutes 13-25% of the total mass) (Hong et al, 2005;Xu et al, 2012). However, it requires mechanical, thermal (incineration) or chemical (acid/base leach) pre-treatments to allow for P recovery because of its strong retention with other elements like Ca, Mg, Al and Fe (Hong et al, 2005).…”

“…However, it requires mechanical, thermal (incineration) or chemical (acid/base leach) pre-treatments to allow for P recovery because of its strong retention with other elements like Ca, Mg, Al and Fe (Hong et al, 2005).…”

Investigation of phosphorus desorption from P-saturated alum sludge used as a substrate in constructed wetland

“…For example, Takahashi et al [17] have found that phosphorus and various heavy metals in the incinerated wastewater treatment sludge can be extracted when the pH of the ash fell below 2.0 by adding sulfuric acid. Hong et al [10] revealed that phosphorus in the waste-activated sludge incinerator ash was completely extracted by 1 M HCl at the L acid S ratio of 6.4:1. Liao et al [18,19] have reported that by using microwave treatment for only 5 min, about 80% of total phosphorus in the sewage sludge could be released into solution.…”

“…Recently, studies on P recovery technologies by the application of the solvent-extraction method have attracted considerable attention [10]. However, these methods not only use a large amount of organic solvent such as butyl-alcohol or tri-butyl phosphate to extract P but also require a very complicated procedure.…”

Management of Phosphorus Resources – Historical Perspective, Principal Problems and Sustainable Solutions

“…Another process for phosphorus recovery involving dissolution of ash from sewage sludge in acid using ion exchange and recovering the phosphorus in the form of phosphoric acid has been suggested by Jensen (2000). Hong et al (2005) describe how phosphoric acid can be extracted with organic solvents after dissolution of incinerated sewage sludge ash with sulphuric or hydrochloric acid. Another process is based on heating the ash up to 1,400 o C to vaporise elemental phosphorus, which is condensed in water and oxidised to phosphoric acid (Japanese patent 9145038, 1997).…”