Pretreating Stored Human Urine for Solar Evaporation by Low-Technology Ammonia Stripping

Abstract

In order to avoid the loss of ammonia during solar drying of stored urine, low-tech stripping is suggested as a pretreatment process for ammonia recovery. The mass transfer of ammonia from stored urine with an initial pH of about 9 was tested in a simple closed vessel operated at 72˚C, 74˚C and 85˚C. The specific urine/gas interface was 16.97 m −1 . For ammonia absorption, a beaker with sulfuric acid was positioned in the gas phase of the container. After keeping the stored urine for 73 h at 85˚C, the concentration of free ammonia (NH3) was reduced by more than 99%, and the pH of the stored urine decreased to 6.4 due to ammonia volatilization. Total ammonia ( 3 NH + + 4 NH ) concentration was reduced by only 83% in the same period. At lower temperatures, the process was slower. Required treatment time can be reduced when specific gas/liquid interface is increased. Because it is known that water can be heated in solar boxes to temperatures above 90˚C, this simple stripping apparatus is feasible to be operated with solar energy in remote areas with suitable climatic conditions where no electric power is available. As the area demand for solar "low-tech stripping" is less than 1 m 2 per capita, this process can be looked at as a suitable pretreatment of stored urine prior to solar evaporation.

Sanitizing Fecal Sludge for Reuse Using Wood Ash as an Additive

“…Moreover, the reduction in pH can be attributed to ammonia volitalization because the containers were kept opened. Per available studies [35,36], desorption of ammonia from wastewater occurs at high pH when the wastewater comes into contact with large amounts of air and eventually results in a decrease in pH. The pH of all the mixtures for the 16-day monitoring period ranged between a minimum of 7.8 and a maximum of 8.38 ( Figure 1a).…”

Exploring the Potential for Concentration of Nutrients from Urine Using Solar Evaporation and Carbon Dioxide Trapping of Ammonia

“…In the evaporation process, the evaporated ammonia is trapped with acid while a residue of other nutrients is left after evaporation. It is shown that 85-99% evaporation of ammonia occurs at 85°C heating for 72 h (Gulyas et al, 2014). Stripping by contrast reportedly has low percentage recovery, being between 3 and 12% (Pinnekamp et al, 2007) in which air was used for stripping followed by wet scrubbing with sulphuric acid.…”

“…The acid requirement would be high as urine pH is around 9.0 (Udert and Wächter, 2012). Alternative proposals include biological nitrification of ammonia (Pronk and Cone, 2010) and concentration of ammonia evaporated from urine with sulphuric acid (Gulyas et al, 2014) which is expensive process. The different concentrations techniques have varying degree of concentration some partial, some complete.…”

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

“…However, due to the elemental composition of K-struvite additional chemical input of Mg 2+ and P is required for effective K recovery. 28,30 TAN recovery by ammonia stripping-acid absorption 32,34,35 and TP recovery by struvite precipitation 21,25,27,[36][37][38][39][40][41][42][43][44][45][46][47][48][49][50] have been studied extensively to recover a significant portion of N and P in urine. For example, major conclusions from previous research include >95% TP recovery using MgCl 2 and >90% TAN recovery by increasing the pH and temperature of the solution.…”

“…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.…”