Phosphorus Recovery and Bioavailability from Chemical Extraction of Municipal Wastewater Treatment’s Waste Activated Sludge: A Case of Bangkok Metropolis, Thailand

Abstract

This study evaluated the extractability and bioavailability of Phosphorus (P) recovered from waste activated sludge (WAS) so as to reduce dependence on the import of non-renewable P resources. P extraction was carried out using sulfuric acid (H2SO4). A response surface methodology was used to optimize conditions for the chemical leaching of WAS. The results showed the optimum condition for leaching WAS with 0.1 mol/L H2SO4 for 30 min, resulting in 97% P released. The efficiency of P recovery by P precipitation was associated with pH value and Mg:P. At pH 7, 9, and 11, P recovery was 92, 92, and 91% with uncontrolled Mg and 93, 93, and 92% with sea salt (Mg:P, 2:1), respectively. However, the yield of the produced struvite was much lower compared with that of added sea salt. From elemental analysis, the yield of struvite precipitated at pH 9 of Mg:P, 2:1 was about 26%, and the total P content of the precipitate was 12%. Available P was almost 80% after 35 days of operation, which was higher than that of commercial fertilizers. Results of this study are expected to provide fully comprehensive information to decision-makers regarding the suitability of implementing P-composite matter recovered from WAS. This will also help close the loop of the P cycle for food cultivation in the human ecosystem.

Optimization and Kinetic Study of Phosphorus Dissolution from Primary Settled-Nightsoil Sludge

“…This optimum condition is also comparable to what other studies obtained from different leaching methods of P from wastes. Compared with organic acid, inorganic acid approaches, especially H2SO4, have been more widely investigated to extract P from wastes because of high leaching efficiency, up to 82-100% (Table 6) (Khaing et al, 2022;Shiba and Ntuli, 2017;Wang et al, 2018;Fang et al, 2018). Similarly, due to the double concentration of H + ions, sulfuric acid can release more P than nitric acid at the same concentration (Fang et al, 2018).…”

“…However, pre-treatment is needed to release P from PSNS into solution thereby enhancing P availability for P recovery. The common method widely used to extract phosphorus from wastes is acid or acid-based leaching (Fang et al, 2020;Khaing et al, 2022). Moreover, influencing factors including pH, extraction time, liquid to solid ratio (L:S ratio), molar concentration of acid solution, and sludge concentration have also been investigated (Ali and Kim, 2016;Shiba and Ntuli, 2017).…”

Recovering Phosphate from Complex Wastewater Using Macroporous Cryogel Composited Calcium Silicate Hydrate Nanoparticles

“…Various phosphorus-rich residues have been reported for phosphorus recovery, most of them related to the municipal wastewater treatment sector [ 4 ], including wastewater [ 9 , 10 , 11 , 12 ], sewage sludge [ 13 , 14 ], and sewage sludge char ash [ 15 ]. From the liquid phase (wastewater treatment plant influent), the phosphorus recovery rate can reach 10–60%, whereas high rates are obtained from sludge (35–70%) and sludge ashes (70–98%) [ 4 , 9 ].…”