Background data on solar heat-assisted stripping-absorption system for ammonia recovery from food waste digestate

The data presented in this paper are related to the research article “Ammonia recovery from food waste digestate using solar heat-assisted stripping-absorption” [1]. The raw and filtered data are associated to daily monitoring of NH4 concentration of food waste digestate, pH of digestate and absorption solution and temperature of food waste digestate throughout experiments at different conditions. In addition, data of temperature monitoring in different points of solar-heat assisted stripping-absorption device are presented. The data could help further studies aiming to improve this system. The detailed data of these experiments could help to improve the performance and to reduce costs of nitrogen recovery from digestate using stripping-absorption technology.


Specifications
Waste Management and Disposal Specific subject area Resource recovery from waste Type of data

Value of the Data
• This data could help to select different process parameters to improve the performance of nitrogen recovery from biogas digestate based on stripping-absorption technologies. • This data can help to select best resource recovery technologies to manage biogas digestate and other wastes. • This data can be used for further studies aiming to optimize and reduce costs for nitrogen recovery by stripping-absorption process. • This data could help to improve and foster a widespread application of stripping-absorption process for ammonia recovery, mainly aiming nitrogen fertilizer recycling.

Data Description
The data presented in this article are associated with the article (L.A.O. Melgaço et al., [1] ) and were acquired using a solar-heat assisted stripping-absorption device treating food waste digestate ( Table 1 ). The daily monitoring of food waste digestate and absorption solution pH and NH 4 concentration at different experimental conditions (25 °C and 45 °C -G/L ratios 1700 and    the column was used as an LD distribution device. The LD percolated through the packed bed inside stripping column and was collected in a reservoir at the bottom of the column for recirculation. Air was injected in the stripping column at countercurrent flow (340 L/min), and the changes in G/L ratios were achieved by decreasing LD flow rate. The top of the column was closed to prevent the release of gaseous effluent into the atmosphere. A plastic tube connected the top of the stripping column with the absorption column, where the NH 3 -rich air entered from the bottom and left from the top. Sulfuric acid solution (0.18 mol/L) was continually recycled in countercurrent flow of 0.1 L/min using a dosing pump to recover the striped ammonia as (NH 4 ) 2 SO 4 . All batch runs lasted 7 days and were carried out in duplicates.
For the tests that were performed at 45 °C, a solar heater device (vacuum glass solar collectors) was coupled to the air-stripping column, replacing the liquid digestate reservoir. Liquid digestate that came out of the stripping column flowed by gravity to the solar heater and was recycled back to the top of the stripping column using a dosing pump.
Samples from the liquid fraction of digestate and sulfuric acid solution were taken daily from the bottom of each column and analyzed for pH and ammonia-nitrogen (NH 4 -N) content. The pH was measured using a digital pHmeter (DIGIMED model DM-44) and ammonia-nitrogen analysis was made based on colorimetric phenol method described in Standard Methods for Examination of Water and Wastewater (APHA et al., 2012) [2] .
The temperature were measured daily at 12pm using a portable thermocouple digital thermometer. The measuring were made in different points of the solar-heat assisted strippingabsorption device: (i) inside vacuum glass solar collectors, (ii) inlet stripping column and (iii) outlet stripping column.

Declaration of Competing Interest
The authors declare that they have no known competing financial interests or personal relationships, which have, or could be perceived to have, influenced the work reported in this article.