Table 1.

Comparison of WWTP parameters at the different sample collection times ^a

Parameterb, c, d	May 03 - Aug 04e	May 07 f	Dec 07g	Comment
Tempb	15 ± 3	15 ± 1	11 ± 1 **
SRTb	3 ± 1	3 ± 0	2 ± 0
F/Mb	0.008 ± 0.002	0.014 ± 0.004 **	0.008 ± 0.002	Max value in May 2007
CODb	1058 ± 240	999 ± 194	1068 ±97±
NO23-Nb	48 ± 8	46 ± 9	42 ± 22	Min and max values in Dec 07
SSVIc	80 ± 15	54	79
Effluent NSSc	23 ± 17	26	31

^a The three periods were compared using the Kruskal-Wallis test. A statistically significant difference, p(same) < 0.05, is marked with asterisks (**). ^b Average values (± standard deviation) from all sample dates and the six days preceding the sample dates. ^c Data only from sample dates, not including the six preceding days. ^d The parameters are water temperature (Temp, °C), solids retention time (SRT, days), food to mass ratio (F/M, g/kg*s), COD going into the activated sludge tanks (COD, g/s), nitrite/nitrate levels going in to the activated sludge tanks (NO23-N, g/s), standardized sludge volume index (SSVI, ml/g) and effluent non-settleable solids (Effluent NSS, mg/l). ^e Samples collected during this period were used for T-RFLP analysis. ^f A sample collected during this period was used for T-RFLP and clone library analysis. ^g A sample collected during this period was used for FISH analysis.