Implementation of partial nitrification in wastewater treatment systems by modifications in operational strategies– a review

Figures & data

Figure 1. Optimum range of the DO/TAN ratio and corresponding nitrite accumulation ratio reported in the literature.

Table 1. Performance of PN in real and synthetic wastewater-based reactor systems using pH as an operational strategy.

Wastewater	Reactor Type	Volume (L)	Biomass Type	In Ammonia (mg/L)	DO/TAN	In COD (mg/L)	pH	Nitrite Accumulation (%)	Reference
Real wastewater
Landfill Leachate	SBR	48.5–52.0	Activated Sludge	1170 ± 220	0.0006	2180 ± 252	8.16–8.25	97 ± 2	[19]
Municipal wastewater	SBR	135	Activated Sludge	65 ± 15	0.038	300 ± 100	7.5 ± 0.5	>90	[9]
Landfill leachate	PN-SBR	190	PN sludge	3096			7.9-8.7	>90	[20]
Domestic wastewater	SBR	7.0 m^3	Activated Sludge	41.2–78.3	0.04	160–300	7-7.8	90	[21]
pig slurry pre-treated	CSTR	2	Nitrifying Activated sludge	399 ± 25	0.005	103 ± 43	7.4 ± 1.4	>95	[22]
Domestic wastewater	SBR	14	Activated Sludge	79	0.03	220	6.85–7.62	95.6	[23]
Real sewage	SPNDPR	11	Nitrifying Activated sludge	35.8–57.5	0.03	84.1–186.3	7.0-8.2	90.3	[24]
Domestic wastewater	SBR	3		44.5–72.6		159.1–241.5	7.08–7.82	97.9	[25]
Urine wastewater	CFR	12	Activated Sludge	100–400	0.016		5.0-6.0	95	[26]
Synthetic Wastewater
Synthetic wastewater	SBR	2.15	Activated Sludge	300	0.013	600–1000	7.5-8.5	91.5-93.7	[15]
Synthetic wastewater	SBR/Continuous	8		150	0.033		7.5-8.6	>80	[27]
Synthetic Nitrogen rich mining wastewater	SBR	2,7	Activated Sludge	150–400	0.004		7.5-8.9	90.08	[28]
Synthetic wastewater	SBR	8	Activated Sludge	1000	0.0008		6.0-8.5	>95	[29]
Synthetic  wastewater	SBR	5	Activated Sludge	300–1000	0.002		6.3-8.3	>95	[30]
Synthetic wastewater	SBR	8	Activated Sludge	19–84	0.04		6,06	>90	[31]
Synthetic wastewater	SBR	10	PN seed sludge	50–170	0.007	70–100	8.2-8.5	87.25	[32]
Synthetic wastewater	Biofilm Reactor	1	Activated Sludge	30–280	0.008		7.8 ± 0.	>95	[33]
Synthetic municipal wastewater	SBR	2	Activated Sludge	150–990	0.0024		7.9–8.2	93.0 ± 0.7	[34]
Synthetic wastewater	ALR	5	Nitrifying biomass	>1000	0.0021		8.2–8.3	80	[35]

SBR: – Sequential Batch Reactor – SBR: – Partial nitrification Sequential Batch Reactor; CSTR: – Continuous stirred tank reactor; CFR: – Continuous Flow reactor; SPNDPR: – simultaneous partial nitrification, denitrification and phosphorus removal; ALR: – Airlift reactor.

Table 2. Performance of PN in real and synthetic wastewater-based reactor systems using Temperature as operational strategy.

Reactor Type	In Ammonia (mg/L)	Temp°C	Nitrite Accumulation (%)	Remarks	References
Synthetic wastewater
Low temperature (<15°C)
Aerobic Granular Reactor.	70	12.5	>95	At 12.5°C, the average nitrogen loading rate was 0.7 ± 0.3 g N/l/d, with a nitrate concentration of just 2.5 ± 0.7 mg NeNO3/ effluent. Because of the bulk ammonium concentration imposed by the control method, a lower specific growth rate of NOB was preserved in the biofilm (even at 12.5 °C).	[8]
SBR	60–65	14–16	90.1	Pre-treatment with high-ammonia seeding sludge resulted in a high-rate and stable PN method for treating low-ammonia sewage at low temperatures.	[52]
MBBR	60	12	98.78	The C/N = 1 and C/N = 2 were found to be essential for culturing biofilms and achieving partial nitrification at 12 °C, which can be accomplished successfully (NAR was 85% and 96%).	[53]
SBR	60–65	14–16	98.2	Both reactors had high levels of ARE and NAR, indicating that AOB has good bioactivity and effectively suppresses NOB. At a temperature of 14–16 °C, both systems in this study achieved stable PN. The pre-treatment with high ammonia effectively suppressed the NOB in seed sludge, which may be the cause.	[52]
SBR	60–65	14–16	90.1
SBR	40	14	>87	For partial nitrification at low temperatures, low dissolved oxygen and a long solids retention period were recommended.	[16]
Continuous airlift reactor	70	10	>98	Long-term operation of the granular reactor at 10°C with a high residual ammonium concentration reduced microbial diversity and increased the AOB content of the granular sludge.	[54]
Real wastewater
Low temperature (<15°C)
SBR	41.2–78.3	11–16	90	A real-time control strategy based on pH and Blower frequency at lower temperatures was used to create PN.	[21]
SBR	39.3–78.7	11.8–16.9	97.3	At lower temperatures, the alternate A/O mode, aerobic phosphorus uptake, specific granule structure, and short SRT could effectively suppress NOB, resulting in stable PN process activity.	[55]
SBR	58.1	18–25, 12–17	90 and 95 respectively	The nitrifying microorganism population was designed for long-term activity by aeration period control, which resulted in a higher nitrite accumulation ratio at low temperatures.	[56]
Synthetic wastewater
High temperature (>15°C)
ZBFB	50	36	95	Stable nitrite accumulation was only achieved by biological desorption at 36.0 °C.	[57]
PNA-SBR	74.5 ± 3.2	25–15	>90		[58]
SBR	120	35.25 and 15	83.72,40.82 and 8.50 respectively	Nitrite accumulation was weakened by low temperatures, and partial nitrification could easily switch to full nitrification at 15 °C.	[59]
Swim Bed Reactor	200–1000	(20-30) and (10-20)	95.7 and 95.8 respectively	This study found that at lower temperatures, PN output was stable and satisfactory, and that AOB could show high activity and robust resistance.	[60]
SBR	6000	25 and 35	>90	At 25 and 35 °C, partial nitritation was achieved with leachate containing 6 g of N-NH4/L. At 25°C, FNA was the key source of AOB inhibition. The combined action of FA and FNA inhibited AOB at 35 degrees Celsius.	[6]
Real wastewater
High temperature (>15°C)
SBR	39.0–76.4	22.6 and 28.6			[61]
SBR	60–90	25	95	The use of PN and granulation at the same time could cut the start-up time in half, and the addition of granular sludge could cut it even further. The presence of organic matter aided the PN granulation process.	[62]

ZBFR: Zone based failure recovery: SBR: – Sequential Batch Reactor; MBBR: – Membrane Biofilm Bioreactor; MBBR: – Moving bed biofilm reactor.

Figure 2. Optimum range of SRT and corresponding nitrite accumulation percentages reported in literature.

Table 3. Performance of PN in real and synthetic wastewater-based reactor systems using FNA and FA operational strategies.

Wastewater	Reactor Type	FNA or FA (mgN/L)	Inlet Ammonia (mg N/L)	Inlet COD (mg/L)	HRT (h)	Nitrite Accumulation (%)	Reference
Control strategy: – Free Nitrous Acid (FNA) dosing
Synthetic domestic wastewater	SBR	4.23 & 3.07	50	300	24	>95	[78]
Synthetic domestic wastewater	SBR	1.82	57		13.2	80	[79]
Synthetic wastewater	SBR	0.004-4.1	300–1000		24		[30]
Synthetic wastewater	SBR	0.24–1.35	50	300	24	>80	[80]
Synthetic wastewater	SBR	1.35 & 4.23	50	300	24	90	[76]
Synthetic wastewater	CNSBR	<0.01	200–1000		6–10		[48]
Synthetic wastewater	SBR	0.308, 0.770 and 1.230				88–90	[81]
Synthetic wastewater		0.55	45.5 ± 1.49			>83.8	[82]
Synthetic wastewater	MBR	0.39, 0.51 and 0.61	200–650		9 ± 1	96	[41]
Real wastewater
Landfill leachate	SBR	0.12,0.47	6000		4.5& 12		[6]
Real sewage wastewater	SBR	1.2	50.28 ± 4.93	365.2 ± 40.5	11.7	96	[9]
Urine wastewater	ASP	2	100–400		1.5-3	95	[49]
Control strategy: – Free ammonia (FA) Dosing
Synthetic wastewater
Synthetic wastewater	SBR	210	40	300	24	>90	[83]
Synthetic wastewater	SBR		200	600	16	87.6	[84]
Synthetic wastewater	ZBAF	15.48	250 - 550		4.7-35	>98.0	[85]
Synthetic wastewater	MBR	9.84 ± 1.81,34.34 ± 6.85	100–200		12	58.6	[41]
Synthetic wastewater	SBR	10–46	100–1500		20	82	[86]
Synthetic wastewater	MBBR	1068	63.2 ± 2.3		12	100	[87]
Synthetic wastewater	SBR	38-97.1	700–800	600		87.8	[88]
Synthetic wastewater	SBBR	70	200	600		93.77 ± 1.04	[89]
Synthetic domestic wastewater anaerobic digestion liquor	SBR	210	50	300	24	>95	[78]
Synthetic wastewater	CSTR	3.5–17.6	175.5		30.0-7.0	87	[90]
Real wastewater
Landfill Leachate	A/O	70–30	300–1550		1.5-4.1	90–99	[91]
Sludge digester liquor	CFR	0.7-8.4	1150		16–24	>98	[92]
Domestic wastewater	SBR	222–225	44.0 ± 11.5	300.6 ± 123.0	18	60	[26]
Reject water	SBR	10–8	30–70	150–200	2.5	99.9	[93]
Landfill Leachate	SBR	18.8-0.21	155	665		91.7	[94]

ZBAF: Zeolite biological aerated filter: SBR: – Sequential Batch Reactor; CNSBR: – Complete Nitrification Sequential Batch Reactor; MBR: – Membrane Bioreactor; SBBR: – Sequencing Batch Biofilm reactor; MBBR: – Moving bed biofilm reactor; CSTR: – Continuous stirred tank reactor; CFR: – Continuous Flow reactor; A/O: – Anaerobic Oxic

Table 4. Performance of PN in real and synthetic wastewater-based reactor systems using other operational strategy.

Control strategy	Wastewater	Reactor Type	Volume (L)	Biomass Type	Concentration (mg/L)	In Ammonia (mg/L)	SRT(d)	pH	Temp°C	NAR (%)	Refrences
Benzethonium chloride	Synthetic wastewater	Flask	200mL	Activated Sludge	0, 10, 30, 50, 70, 90 and 110	26.3 ± 4.5		7.5–7.7	22 ± 2	97.46	[109]
Salinity	Real Sewage	SBR	11	floc sludge and small granular sludge	0.5 wt% (5 g NaCl/L) and 0.75 wt% (7.5 g NaCl/L),	32.6–53.2	15		22 ± 1	98.9	[24]
Real-time control, FNA treatment, NH2OH addition	Municipal wastewater	SBR	10			67.7 ± 5.1			27.4 - 15.0	66.1	[110]
Salinity	Synthetic wastewater	UASB	5	Nitrifying sludge	0,5,10,20,30,50 g/L	100		7.5–8.0	30	81.03	[11]
Effect of TC and Zn(II) on PN	Synthetic wastewater	ALR	3.8	Activated Sludge	TC:0-100-200-300-400-500 Zn(II):0-40-80-120-160-200	100			30 ± 1	>90	[111]
Hydroxylamine (NH2OH)	Domestic Sewage	SBR	10	Activated Sludge	4.5	70.5 ± 6.6	20		25 ± 1	97	[42]
low intensity ultrasound	synthetic sewage	SBR	5	Activated Sludge	(0.25 W·m/L)	60	20–30	7.5–8.5	18–28	>80	[112]
Response surface methodology	Synthetic wastewater	SBR	8	AOB & Anammox Sludge		50–100			30	88	[113]
Salinity	Synthetic wastewater	ZBAF	10	Activated sludge	5.0, 7.5, 10.0, 12.5, 15.0, 20.0 and 25.0 g/L	150–250		8.5 ± 0.1	25.0 plusmn; 1.0	99	[114]
Nitrite Stress	Domestic wastewater	SBR	3	Activated Sludge	5& 30	44.5–72.6			26.6–16.6	97.9 ± 2.1	[25]
Salinity	Synthetic wastewater	SBBGR	5	SNAP seed sludge	0.5% to 5.0			7.5–7.8	31 ± 1		[115]
Salinity	Synthetic wastewater	SBBR	5.7	biofilm system	5.0–20.0 as NaCl	200				90.6	[89]
Pulse aeration strategies	Digested effluent of swine wastewater	SBR	4	aerobic sludge		400–900		08	35 ± 1	>90	[116]
Intermittent Aeration/Salinity	Industrial Wastewater	SBR	25	granular biomass	1.75 to18.00 g-NaCl /L	112–267			29 ± 1		[117]

SBR: – Sequential Batch Reactor; SBBGR: – Sequencing Batch Biofilm granular reactor; ZBAF: Zeolite biological aerated filter: MBR: – Membrane Bioreactor; UASB: – Up flow anaerobic sludge blanket; SBBGR: – Sequencing Batch Biofilm granular reactor; SBBR: – Sequencing Batch Biofilm reactor; ALR: – Airlift reactor.

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Data availability statement

All data and information are mentioned in the manuscript.