Table 1.

Results of measurements of the volume and quality of wastewater and the reactor operating parameters in the Sitkówka-Nowiny wastewater treatment plant (WWTP).

Indicators	Units	Winter				Spring-Fall
		Min	Mean	Max	Standard Deviation	Min	Mean	Max	Standard Deviation
Q	m3/d	29,952	39,364	88,986	6563	30,125	41,842	94,772	8559
BOD	mgO2/l	151	290	489	81.83	132	340	557	81.2
COD	mg O2/l	384	782	1183	161.4	342	820	1703	178.2
TSS	mg/l	136	315	474	62.76	110	350	572	89.4
N-NH4	mg/l	28	48.9	62	5.68	22	54.52	66.9	7.13
TN	mg/l	56.2	82.01	95.16	8.42	39.9	95.15	124.1	11.58
TP	mg/l	3.1	7.22	12.1	1.44	3.5	7.83	12.6	1.65
T	°C	10	11.9	13.5	0.8	11.3	17.8	23	3.1
DO	mg/l	1.8	2.85	3.25	0.8	1.51	2.2	3.25	0.65
MLSS	mg/l	2.85	4.95	6.54	0.84	2.15	4.11	5.28	0.95
MLSSR	mg/l	6.62	8.7	14.92	0.72	5.03	7.81	11.86	0.1
WAS	t.s.m/d	12.69	15.35	18.35	3.51	10.02	12.35	17.25	3.77
RAS	%	85.2	102.9	152	16.25	75.2	83.06	120.5	24.4
SVI	cm3/g	154	198	291	35	90	138	200	37
mPIX	m3/d	0	0.81	1.75	0.27	0	0.84	1.82	0.28

where: Q—inflow to wastewater treatment plant, BOD, COD—biochemical/chemical oxygen demand, TSS—total suspended solids, N–NH4—ammonium nitrogen, TN—total nitrogen, TP—total phosphorus, T—temperature in the activated sludge chambers, DO—oxygen concentration in the bioreactor, MLSS—concentration of activated sludge, MLSSR—concentration of return sludge, WAS—excess amount of sludge, RAS—degree of recirculation, mPIX—dosage of PIX, SVI—sludge volumetric index.