Nitrogen and Phosphorus Harvesting from Human Urine Using a Stripping, Absorption, and Precipitation Process

Abstract

Human urine contains significant amounts of N (nitrogen) and P (phosphorus); therefore it has been successfully used as fertilizer in different crops. But the use of urine as fertilizer has several constraints, such as, the high cost of transportation, an unpleasant smell, the risk of pathogens, and pharmaceutical residue. A combined and improved N stripping and P precipitation technique is used in this study. In this technique, Ca(OH) is used to increase the pH of urine which converts ammonium into ammonia gas and precipitate P as Ca-P compound. The ammonia gas is stripped and passed into the sulfuric acid where ammonium sulfate and hydrogen triammonium disulfate is formed. The experiment was performed using 700 mL of urine and the pH of the urine was increased above 12. Our results showed that 85-99% of N and 99% of P (w/w) can be harvested from urine in 28 h at 40 °C and in 32 h at 30 °C. The harvested N (13% N w/w) and P (1.5% P w/w) can be used as mineral fertilizer. The economic assessment of the technique showed that the extraction of N and P from 1 m of pure urine can make a profit of €2.25.

Ammonia recovery from human urine as liquid fertilizers in hollow fiber membrane contactor: Effects of permeate chemistry

“…However, this technology also has some disadvantages such as having a slow biological process and the tendency of having poor quality fertilizer. There are also studies which recovered minerals from various nitrogen-rich sources in the conventional stripping process [7][8][9][10]. This technology basically looks simple and has been extensively studied for ammonia nitrogen recovery by different scientists.…”

Review of global sanitation development

“…A combination of ammonia stripping and struvite precipitation to improve nitrogen and phosphorus recovery has been investigated. One investigation employed Ca (OH) 2 to replace NaOH to make the stripping and precipitation occur at the same time; this study showed that 85–99% of the nitrogen and 99% of the phosphorus (w/w) can be harvested from hydrolyzed urine in 28 h at 40 °C and in 32 h at 30 °C ( Pradhan et al, 2017 ). Although 90% of the phosphorus and approximately 20% of the nitrogen could be recovered through MAP crystallization, nearly all of the potassium would be lost, so magnesium potassium phosphate hexahydrate (MgKPO 4 ·6H 2 O, MPP) crystallization was developed to simultaneously recover phosphorus as well as potassium ( Xu et al, 2012 ; Xu et al, 2015 ; Zhang et al, 2017 ).…”

Integrated, multi-process approach to total nutrient recovery from stored urine

“…1). 32,33,66 Although solely increasing the temperature resulted in a higher percent of TAN recovered, operational issues such as excess foaming, precipitation, and evaporation were observed. Specific details are further explained in the ESI, † section 2.2.…”

“…In post ammonia stripping-acid absorption, the (NH 4 ) 2 SO 4 product was kept in liquid form to minimize N loss and the percent N (w/w) in the product was calculated (Table 3). 33,35 Calculation details for percent N (w/w) in the product are explained in the ESI, † eqn (S1)-(S6). The H 2 SO 4 solution used Table 3 Purity of the liquid ammonium sulfate product (% N w/w) and solid potash product (% K w/w)…”

“…Due to the high concentration of total ammonia nitrogen (TAN), NH 3IJg) + NH 4 + (aq) , in stored urine, many technologies have been investigated for the recovery of N, including air stripping-acid absorption (hereafter referred to as ammonia stripping-acid absorption) which has shown high nutrient recovery (>80% N recovery). [31][32][33][34] The ammonia stripping-acid absorption process targets N recovery by removing ammonia from solution and concentrating it in a sulfuric acid solution. This is done by shifting the solution ammonia acid/base equilibrium towards NH 3 (unionized ammonia) via a temperature and/or pH increase.…”