Performance evaluation of wastewater treatment plants in Southern Brazil

Camelo, Luana; Brito, Daniel Oliveira de; Almeida, Maria Cristina de

doi:10.1590/S1413-415220230060

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Engenharia Sanitaria e Ambiental

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Scientific Paper • Eng. Sanit. Ambient. 29 • 2024 • https://doi.org/10.1590/S1413-415220230060 copy

Performance evaluation of wastewater treatment plants in Southern Brazil

Análise de desempenho dos sistemas de esgotamento sanitário do Sul do Brasil

Authorship SCIMAGO INSTITUTIONS RANKINGS

ABSTRACT

This study assesses the influent and effluent characteristics and the removal efficiency of 56 wastewater treatment plants (WWTPs) operating in Brazil’s southern region, in the Rio Grande do Sul state. The analysis encompasses the main secondary wastewater treatment processes used in the country, such as septic tank and anaerobic filter, activated sludge with sequencing batch reactor and with extended aeration, upflow anaerobic sludge blanket reactor followed by trickling filter, anaerobic and facultative ponds, and the combination of anaerobic, facultative, and maturation ponds. The parameters evaluated were biochemical oxygen demand (BOD), chemical oxygen demand (COD), ammoniacal nitrogen (NNH₃), total phosphorus (TP), total suspended solids (TSS), and Escherichia coli. The influent concentrations of BOD, COD, and TSS were considerably lower than other values reported in studies in Brazil, indicating that the analyzed WWTPs operate with a diluted influent, with respective average ranges of 38–189, 203–416, and 75–242 mg∙L⁻¹. The effluent concentrations were also lower than the reference values, although the differences were not as pronounced as in the influent. No significant distinctions were observed between the removal efficiencies obtained and other results in the literature, except for TSS, which had a weaker performance. Concerning the technologies, lower performance was observed for BOD, COD, and TSS removal in the septic tank and higher removal rates of TP for the activated sludge systems. This study represents the first comprehensive dataset on the performance of WWTPs in Brazil’s southern region, contributing to the understanding of wastewater management practices in the country by indicating potential points for improvement.

Keywords:
performance evaluation; removal efficiency; wastewater treatment plants; statistic; wastewater treatment technologies

Variable	Factor	ST+AF	SBR	EA	UASB+TF	AFP	AFMP
BOD₅	No. of WWTPs	16	6	6	15	3	10
	influent (mg∙L⁻¹)	188.5 ± 139.9	129.5 ± 80.9	102.3 ± 49.4	77.3 ± 67.3	38.4 ± 41.1	81.4 ± 31.6
	Effluent (mg∙L⁻¹)	79.2 ± 52.2	8.5 ± 12.8	7.2 ± 6.2	11.6 ± 11.2	10.6 ± 7.3	19.6 ± 19.9
	Removal efficiency (%)	49.7 ± 35.7	93.3 ± 5	94.6 ± 3.7	80.2 ± 10.7	61.3 ± 29.8	77.9 ± 13.3
COD	No. of WWTPs	16	6	6	15	3	10
	influent (mg∙L⁻¹)	415.9 ± 233.4	396.9 ± 203.4	298.8 ± 116.9	203.8 ± 141.5	208.5 ± 206.3	202.5 ± 69.1
	Effluent (mg∙L⁻¹)	230.9 ± 135.9	36.2 ± 12.1	53.6 ± 18.2	57.3 ± 35.1	80.5 ± 18.3	118.7 ± 46.5
	Removal efficiency (%)	47.7 ± 29.5	87.1 ± 11	81 ± 7.2	66.2 ± 16.1	33.1 ± 40	35.5 ± 22.1
NNH3	No. of WWTPs	10	4	5	14	3	7
	influent (mg∙L⁻¹)	60.6 ± 21.9	33 ± 9.4	39.3 ± 12.3	36 ± 22.2	27.7 ± 11.9	27.2 ± 7.3
	Effluent (mg∙L⁻¹)	52.5 ± 25.3	9.1 ± 8.3	16.3 ± 14.3	18.1 ± 16.2	5.8 ± 6.2	6.3 ± 8.6
	Removal efficiency (%)	14 ± 23	65.2 ± 35.7	50.9 ± 39.9	50 ± 33.4	81.7 ± 13	78.5 ± 27
TP	No. of WWTPs	5	3	2	10	3	7
	influent (mg∙L⁻¹)	9.6 ± 5.2	4.9 ± 1.9	5.1 ± 1.2	4.8 ± 2.9	3.3 ± 1.2	3.2 ± 0.5
	Effluent (mg∙L⁻¹)	6.4 ± 5.1	1.8 ± 1.8	1.4 ± 0.2	2.7 ± 1.9	2 ± 0.9	1.8 ± 1.4
	Removal efficiency (%)	40.8 ± 30.8	66.2 ± 22.4	72.7 ± 9.8	35.8 ± 32.2	37.8± 12.5	37.2 ± 37
TSS	No. of WWTPs	16	6	6	15	3	9
	influent (mg∙L⁻¹)	241.9 ± 295.4	133.8 ± 58.7	93.7 ± 41.1	75.3 ± 47.4	81.2 ± 76.9	69.7 ± 28.2
	Effluent (mg∙L⁻¹)	50.9 ± 30.5	8.5 ± 5.9	19.2 ± 8.2	19.3 ± 15.1	44 ± 11.5	60.1 ± 20.9
	Removal efficiency (%)	54.3 ± 34.1	94.1 ± 6.3	74 ± 21.1	68.1 ± 22.6	18 ± 44.1	11.2 ± 30.3
E. coli	No. of WWTPs	7	6	4	11	3	9
	influent (10⁶∙ MPN∙100 mL⁻¹)	5.1 ± 5.9	10.5 ± 8.5	7.4 ± 0.9	6.5 ± 6.0	4.3 ± 5.1	3.6 ± 1.4
	Effluent (10³∙ MPN∙100 mL⁻¹)	2440.0 ± 3020.0	128.0 ± 153.0	270.0 ± 324.0	608.0 ± 871.0	21.2 ± 34.7	0.4 ± 0.6
	Removal efficiency (log. units)	0.4 ± 0.3	2.3 ± 0.8	1.9 ± 0.9	1.6 ± 1.3	3.1 ± 0.8	4.3 ± 0.8

Variable	Factor	ST+AF	SBR	EA	UASB+TF	AFP	AFMP
BOD₅ (%)	Median	57.76	95.37	95.59	81.04	75.8	79.91
	95% CI¹ 1Obtained by the resampling bootstrap method with 10,000 iterations;	39–72	87–97	91–97	72–83	27–76	65–88
	Typical values² 2based on von Sperling (2014).	80–85	90–97	90–97	80–93	75–85	80–85
	WWTPs below the typical range	88%	33%	17%	50%	47%	33%
COD (%)	Median	49.24	92.18	83.06	70.40	29.88	27.32
	95% CI¹ 1Obtained by the resampling bootstrap method with 10,000 iterations;	28–70	74–94	70–86	50–76	(−5)–75	16–51
	Typical values² 2based on von Sperling (2014).	70–80	83–93	83–93	73–88	65–80	70–83
	WWTPs below the typical range	69%	33%	50%	90%	60%	67%
NNH3 (%)	Median	12.87	75.15	30.77	42.55	88.39	93.75
	95% CI¹ 1Obtained by the resampling bootstrap method with 10,000 iterations;	(−6)–28	16–92	14–91	27–78	67–88	25–95
	Typical values² 2based on von Sperling (2014).	<45	>80	>80	<50	<50	50–65
	WWTPs below the typical range	0%	50%	60%	14%	0%	0%
TP (%)	Median	30.91	77.80	72.65	32.02	35.03	46.40
	95% CI¹ 1Obtained by the resampling bootstrap method with 10,000 iterations;	21–33	40–78	66–73	15–47	27–51	(−6)–65
	Typical values² 2based on von Sperling (2014).	<35	<35	<35	<35	<35	>50
	WWTPs below the typical range	0%	0%	0%	57%	0%	0%
TSS (%)	Median	64.53	95.76	81.56	72.69	20.59	7.41
	95% CI¹ 1Obtained by the resampling bootstrap method with 10,000 iterations;	31–78	87–99	31–83	58–82	(−27)–21	(−6)–29
	Typical values² 2based on von Sperling (2014).	80–90	87–93	87–93	87–93	70–80	73–83
	WWTPs below the typical range	75%	17%	100%	100%	80%	100%

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[1] * Corresponding author: mariacristinaas@gmail.com