Potential of acetic acid to restore methane production in anaerobic reactors critically intoxicated by ammonia as evidenced by metabolic and microbial monitoring

Table 1 Treatments applied to the free ammonia intoxicated reactors, HNR1, HNR2 and HNR3

Stage	Phase	Weeks	Treatment
Process reconditioning	I	0 (day 0–1)	pH reduction with acetic acid (15 g_VS L⁻¹ in total)
	II	0 (days 2–5) and 1	Dilution with tap water at 37°C (25 mL L⁻¹ d_feed⁻¹)
	III	2 to 3	Re-inoculation with LNR effluents (6.5 mL L⁻¹ d_feed⁻¹); Water dilution*
Process recovery	/	4 to 7	Re-inoculation with LNR effluents (6.5 mL L⁻¹ d_feed⁻¹); Feeding with sugar beet pulp (0.5 → 2 g_VS L⁻¹ d_feed⁻¹); Water dilution*
Process stability test	/	8 to 11	Feeding with sugar beet pulp (2 g_VS L⁻¹ d_feed⁻¹); Water dilution*

The reactors were fed on working days, usually five consecutive days (i.e., d_feed) per week; * inputs suspended in tap water at 37°C to reach a hydraulic retention time of 56 days (total fed volume: 25 mL L−1 d_feed−1); LNR: low nitrogen input reactor used as a reference reactor; VS: volatile solids

ISSN: 2731-3654