Waste-derived volatile fatty acid production and ammonium removal from it by ion exchange process with natural zeolite

Figures & data

Table 1. Characteristics of the clinoptilolite (from Rota [25]).

Constituent	Properties/ Value (wt.%)
SiO2	65–72
Al2O3	10–12
CaO	2.4–3.7
K2O	2.5–3.8
Fe2O3	0.7–1.9
MgO	0.9–1.2
Na2O	0–0.08
MnO	0–0.08
Cr2O3	0–0.01
P2O5	0.02–0.03

Table 2. The properties of recovered AD-VFA.

Parameters	Unit	Range of the effluent during fermentation	VFA effluent used in this study
pH	/	6.02–8.18	6.8 ± 0.1
NH4-N	mg/L	1381–2262	1955 ± 135
tCOD	g/L	12.0–68.7	13.8 ± 0.6
Acetic acid	g/L	5.0–11.9	5.37 ± 0.2
Propionic acid	g/L	0.8–3.1	0.81 ± 0.1
Butyric acid	g/L	0.6–2.4	0.75 ± 0.1
Caproic acid	g/L	0.05–0.15	0.07 ± 0.0
Total VFAs	g/L	6.50–18.0	7.0 ± 0.2
Na^+	mg/L	986.3–1045.7	1016 ± 29.7
K^+	mg/L	1535.6–1572.4	1554 ± 18.4
Ca^2+	mg/L	32–33	33 ± 0.0
Mg^2+	mg/L	59.4–63.6	61.5 ± 2.1
Fe^2+	mg/L	1.8–3.2	2.5 ± 0.7

Figure 1. Schematic overview of MBR setup for AD-VFA production and fixed bed batch column setup for ammonium removal.

Figure 2. Equilibrium time profile with different initial adsorbate concentrations.

Figure 3. (a) Isotherm curve and (b) Langmuir and (c) Freundlich isotherm models of ammonium with clinoptilolite for AD-VFA solution.

Table 3. The values of isotherm model equations.

	Langmuir model				Freundlich model
	Equation	qm	KL	R^2	Equation	Kf	1/n	R^2
Pure solution (Allar [41])	$q_e=\frac{0.9438\mathrm{C}\mathrm{e}}{1+0.0345\mathrm{C}\mathrm{e}}$	27.4	0.0345	0.9826	$q_e=3.8966{{\mathrm{C}}_e}^{0.2356}$	3.8966	0.2356	0.8723
AD-VFA (This study)	$q_e=\frac{0.02628\mathrm{C}\mathrm{e}}{1+0.0017\mathrm{C}\mathrm{e}}$	15.7	0.0017	0.9998	$q_e=0.277{{\mathrm{C}}_e}^{0.5138}$	0.277	0.5138	0.9884

Figure 4. Comparison between ion exchange isotherms of pure NH₄⁺ solution, and AD-VFA with q_m values from Langmuir. The figure contains results from experiments that were done in a previous study done by Allar [41].

Figure 5. Effect of initial loading on ammonium removal with ion exchange from sVFA solution.

Figure 6. Effect of pH on ammonium removal with ion exchange from sVFA solution.

Figure 7. Effect of K⁺ ion on ammonium removal with ion exchange from sVFA solution.

Figure 8. Ammonium removal of clinoptilolite in sVFA and AD-VFA solutions (pH 6.8).

Figure 9. VFA changes on (a) sVFA and (b) waste derived AD-VFA solution.

Figure 10. Ammonium breakthrough curves in different concentrations of sVFA solution.

Rota M. Product information sheet. 2021.

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Allar AD Processing Alternatives of Urine with Clinoptilolite for Indirect Use of Human Urine as Fertilizer (İnsan İdrarının Gübre Olarak Dolaylı Kullanımında Klinoptilolitle Muamele Ve Alternatifleri) [ PhD Thesis]. (in Turkish with an extended abstract in English) Turkey: Istanbul Technical University; 2015.

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