A laboratory study of microalgae-based ammonia gas mitigation with potential application for improving air quality in animal production operations

Figures & data

Figure 1. Schematics of the laboratory-scale algal culture system for ammonia gas mitigation.

Figure 2. Cell density and biomass productivity of continuous culture of S. dimorphus under different dilution rates. Ammonia gas loading rate 39.9 mg/L-day; medium pH 7. Data are means of five consecutive samples at the steady state (after at least three volume changes), and error bars show standard deviations.

Figure 3. Effects of dilution rate of continuous culture of S. dimorphus on ammonia gas removal performance. Ammonia gas loading rate 39.9 mg/L-day; medium pH 7. (a) ammonia removal rate, R _V; (b) overall ammonia gas removal efficiency, E; (c) cellular ammonia consumption rate, R _cell; (d) cell yield based on ammonia input, Y _X/N. Data are means of five consecutive samples at the steady state (after at least three volume changes), and error bars show standard deviations.

Figure 4. Cell density and biomass productivity of continuous culture of S. dimorphus under different inlet ammonia gas contents. Dilution rate: 0.1 day⁻¹; medium pH 7. Data are means of five consecutive samples at the steady state (after at least three volume changes), and error bars show standard deviations.

Table 1. Nitrogen distribution of inlet ammonia (N_inlet) among cell biomass (N_cell), liquid medium (N_liquid), and exhausted gas (N_outlet) at different dilution rates (D; day⁻¹) of microalgal culture

	Nitrogen Distribution of Inlet Ammonia (%)
Source	D = 0.05 day^−1	D = 0.1 day^−1	D = 0.2 day^−1	D = 0.3 day^−1
Ninlet	100	100	100	100
Ncell	47.4 ± 0.44	98.6 ± 2.16	77.8 ± 1.19	65.3 ± 3.06
Nliquid	34.7 ± 1.77	0.064 ± 0.01	10.0 ± 0.65	20.7 ± 1.03
Noutlet	7.09 ± 1.45	5.95 ± 0.16	5.67 ± 0.33	5.39 ± 0.28
ϵ (error)	10.8	−4.66	6.53	8.54
Note: Ncell, Nliquid, and Noutlet are represented as means ± SD of five consecutive samples at the steady state (after at least three volume changes).

Table 2. Nitrogen distribution of inlet ammonia (N_inlet) among cell biomass (N_cell), liquid medium (N_liquid), and exhausted gas (N_outlet) at different ammonia gas loading rates (mg/L-day) for microalgal culture

	Nitrogen Distribution of Inlet Ammonia (%)
Source	9.4 mg/L-day	19.3 mg/L-day	28.9 mg/L-day	39.9 mg/L-day	55.6 mg/L-day
Ninlet	100	100	100	100	100
Ncell	77.4 ± 2.36	90.9 ± 0.53	82.5 ± 1.32	98.6 ± 2.16	72.7 ± 0.59
Nliquid	0.172 ± 0.08	0.0941 ± 0.02	0.0564 ± 0.01	0.0637 ± 0.01	20.3 ± 0.00
Noutlet	20.4 ± 2.95	8.06 ± 0.69	10.9 ± 0.70	5.95 ± 0.16	5.43 ± 1.03
ϵ (error)	2.05	0.926	6.55	−4.66	1.56
Note: Ncell, Nliquid, and Noutlet are represented as means ± SD of five consecutive samples at the steady state (after at least three volume changes).

Figure 5. Effects of ammonia gas loading rate of continuous culture of S. dimorphus on ammonia gas removal performance. Dilution rate: 0.1 day⁻¹; medium pH 7. (a) ammonia removal rate, R _v; (b) overall ammonia gas removal efficiency, E; (c) cellular ammonia consumption rate, R _cell; (d) cell yield based on ammonia, Y _X/N. Data are means of five consecutive samples at the steady state (after at least three volume changes), and error bars show standard deviations.

Figure 6. Cell density and biomass productivity of continuous culture of S. dimorphus under different medium pH. Dilution rate: 0.1 day⁻¹; ammonia gas loading rate: 39.9 mg/L-day. Data are means of five consecutive samples at the steady state (after at least three volume changes), and error bars show standard deviations.

Figure 7. Effects of medium pH of continuous culture of S. dimorphus on ammonia gas removal performance. Dilution rate: 0.1 day⁻¹; ammonia gas loading rate: 39.9 mg/L-day. (a): ammonia removal rate, R _v; (b): overall ammonia gas removal efficiency, E; (c): cellular ammonia consumption rate, R _cell; (d): cell yield based on ammonia, Y _X/N. Data are means of five consecutive samples at the steady state (after at least three volume changes), and error bars show standard deviations.

Table 3. Nitrogen distribution of inlet ammonia (N_inlet) among cell biomass (N_cell), liquid medium (N_liquid), and exhausted gas (N_outlet) at different medium pH in microalgal culture

	Nitrogen Distribution of Inlet Ammonia (%)
Source	pH 5	pH 6	pH 7	pH 8
Ninlet	100	100	100	100
Ncell	64.4 ± 0.65	68.1 ± 2.04	98.6 ± 2.16	55.6 ± 0.92
Nliquid	31.6 ± 0.58	36.1 ± 1.82	0.0637 ± 0.01	16.6 ± 3.26
Noutlet	6.52 ± 0.65	6.52 ± 0.16	5.95 ± 0.16	26.4 ± 4.93
ϵ (error)	−2.55	−10.8	−4.66	1.43
Note: Ncell, Nliquid, and Noutlet are represented as means ± SD of five consecutive samples at the steady state (after at least three volume changes).