Table 2.

Biological treatment characteristics of the reactors fed with municipal wastewater.

	Activated sludge (AS) with oxic post-treatment			Anaerobic stand-alone reactors						Activated sludge (AS) with anaerobic post-treatment
				Short HRT			Long HRT
	AS	Post-tr. 1	Post-tr. 2	Supplemented with		Methanogenic	Supplemented with		Methanogenic	AS	Post-tr. 1	Post-tr. 2
				Iron(III)	Sulfate		Iron(III)	Sulfate
Temperature (°C)	14–16	18–22	18–22	18–22	18–22	18–22	15–25	15–25	15–25	15–25	20–25	20–25
pH	7–8	7.0–7.2	7.4–7.8	6.7–7.5	7.3–7.5	6.9–7.2	6.5–7.5	6.5–7.5	6.5–7.5	7.0–7.5	7.0–7.5	7.0–7.5
O2 (mg/L)	0–2	0–2.5	0.2–1.5	0	0	0	0	0	0	0–3	0	0
Redox (V)	–	–	–	<−0.4	<−0.4	<−0.4	<−0.4	<−0.4	<−0.4	–	<−0.4	<−0.4
DOC Inf. (mg/L)	45	46a	115a	45	45	45	30	30	30	30	38a	8
DOC Eff . (mg/L)	6	5	6	18	15	14	12	22	23	13	8	7
NH4+—N Inf. (mg/L)	26	≤0.2	<0.2	26	26	26	42	42	42	42	<0.2	1
NH4+—N Eff. (mg/L)	≤0.2	<0.2	<0.2	29	30	33	39	40	40	<0.2	1	1
NO3−—N Inf. (mg/L)	<0.2	1.7	<0.2	<0.2	<0.2	<0.2	0.4	0.4	0.4	0.4	8	<0.23
NO3−—N Eff. (mg/L)	1.7	<0.2	<0.2	<0.2	<0.2	<0.2	<0.23	<0.23	<0.23	8	<0.23	<0.23
NO2−—N Inf. (mg/L)	<0.2	<0.2	<0.2	<0.2	<0.2	<0.2	<0.2	<0.2	<0.2	<0.2	<0.2	<0.2
NO2−—N Eff. (mg/L)	<0.2	<0.2	<0.2	<0.2	<0.2	<0.2	<0.2	<0.2	<0.2	<0.2	<0.2	<0.2
SO42− Inf. (mg/L)	29	30	35	29	270a	29	70	550a	70	70	90	70
SO42− Eff. (mg/L)	30	35	34	7	51	6	7	300	6	90	70	70
Fe3+ Inf. (mg/L)	<0.2	<0.2	<0.2	500a	<0.2	<0.2	500a	<0.2	<0.2	<0.2	<0.2	<0.2

Inf.-Influent; Eff.-Effluent; Post-tr.-Post-treatment

^aInfluent wastewater concentration plus addition.