. 2017 Jul 14;7:5477. doi: 10.1038/s41598-017-05555-y

Table 3.

The comparisons of TN, NO₃ ⁻N, NO₂ ⁻N, NH₄ ⁺-N concentrations in wastewater for all eight monitoring stations (W1–sewage outflow from the WWTP; W2–W8–sewage after treatment in particular zones of the Sequential Biofiltration System).

Parameter	Station	Median	Mean concentration [mg dm⁻³]	N	S.D.
TN, p = 0.000*	W1	33.9	40.6	36	20.9
	W2	36.6	40.5	36	20.3
	W3	35.3	40.9	36	22.6
	W4	32.5	38.9	36	26.0
	W5	33.1	38.4	36	25.9
	W6	31.3	36.7	36	22.1
	W7	28.4	35.1	36	21.7
	W8	26.2	34.7	36	27.1
% Reduction of TN between W1–W8		Mean	15
		Max.	97
		Min.	−88
NO ₃ ⁻-N, p = 0.000*	W1	31.3	36.5	36	22.9
	W2	34.1	36.7	36	22.8
	W3	31.9	35.9	36	22.5
	W4	27.1	33.7	36	24.6
	W5	27.2	33.2	36	24.2
	W6	28.7	32.7	36	23.4
	W7	26.6	31.3	36	23.2
	W8	19.0	30.2	36	24.1
% Reduction of NO ₃ ⁻-N between W1–W8		Mean	17
		Max.	98
		Min.	−70
NO ₂ ⁻-N, p = 0.419	W1	0.00629	0.430	36	1.038
	W2	0.00985	0.431	36	1.013
	W3	0.00918	0.441	36	1.047
	W4	0.00503	0.388	36	0.978
	W5	0.00977	0.380	36	0.894
	W6	0.00815	0.368	36	0.862
	W7	0.00512	0.347	36	0.832
	W8	0.00488	0.298	36	0.746
% Reduction of NO ₂ ⁻-N between W1–W8		Mean	31
		Max.	100
		Min.	−933
NH ₄ ⁺ - N, p = 0.341	W1	1.576	3.66	36	6.18
	W2	0.303	3,45	36	6,56
	W3	0.376	4,59	36	8,93
	W4	0.572	4,82	36	9,53
	W5	0.772	4,86	36	9,89
	W6	0.442	3,63	36	6,09
	W7	0.872	3,46	36	5,76
	W8	0.825	4,20	36	9,22
% Reduction of NH ₄ ⁺ - N between W1–W8		Mean	−15
		Max.	99
		Min.	−3998

Friedman ANOVA test (*significance at p < 0.05). Percentage reduction of TN, NO₃ ⁻N, NO₂ ⁻N^, NH₄ ⁺-N concentrations between stations W1 and W8 during the study period. A negative vale in % Reduction indicates concentration increased in outflowing wastewater. Thirty-six samples were taken from each of eight stations (total number of analysed samples = 288).