Toxicity and biodegradation of formaldehyde in anaerobic methanogenic culture

Abstract

Formaldehyde is present in several industrial wastewaters including petrochemical wastes. In this study, the toxicity and degradability of formaldehyde in anaerobic systems were investigated. Formaldehyde showed severe toxicity to an acetate enrichment methanogenic culture. As low as 10 mg/L (0.33 mM) of formaldehyde in the reactor completely inhibited acetate utilization. Formaldehyde, however, was degraded while acetate utilization was inhibited. Degradation of formaldehyde (Initial concentration ≤30 mg/L) followed Monod model with a rate constant, k, of 0.35–0.46 d−1. At higher initial concentrations (≥60 mg/L), formaldehyde degradation was inhibited and partial degradation was possible. The initial formaldehyde to biomass ratio, S0/X0, was useful to predict the degradation potential of high formaldehyde concentrations in batch systems. When S0/X0 ≤ 0.1, formaldehyde was completely degraded with initial concentration of up to 95 mg/L; when S0/X0 ≥ 0.29, formaldehyde at higher than 60 mg/L was only partially degraded. The inhibition of formaldehyde degradation in batch systems could be avoided by repeated additions of low concentrations of formaldehyde (up to 30 mg/L). Chemostats (14‐day retention time) showed degradation of 74 mg/L‐d (1110 mg/L) of influent formaldehyde with a removal capacity of 164 mg/g VSS‐day. A spike of 30 mg/L (final concentration in the chemostat) formaldehyde to the chemostat caused only a small increase in effluent acetate concentration for 3 days. But a spike of 60 mg/L (final concentration in the chemostat) formaldehyde to the chemostat resulted in a dramatic increase in acetate concentration in the effluent. The results also showed that the acetate enrichment culture was not acclimated to formaldehyde even after 226 days. © 1997 John Wiley & Sons, Inc. Biotechnol Bioeng 55: 727–736, 1997.

Biotreatability of wastewater generated during machinery washing in a wood-based industry: COD, formaldehyde and nitrogen removal

“…The effects of formaldehyde on methanogenesis reversibility are to some extent reported in literature. Whereas some authors report reversible inhibition (Qu and Bhattacharya, 1997), others observed no recovery of gasification process at all (Gonzalez-Gil et al, 2002). The degree of recovery seems to be related to the concentrations of formaldehyde that microorganisms were exposed to (Vidal et al, 1999) and also the time that follows the inhibition period.…”

“…The inhibition caused by formaldehyde in biological treatment systems is widely reported in the literature, however with a broad range of critical concentrations. Qu and Bhattacharya (1997) mentioned that formaldehyde concentrations from 20 to 254 mg L À1 cause 50% reduction of methanogenesis activity, which is in agreement to Lu and Hegeman (1998) that observed 50% of anaerobic gasification inhibition in the presence of 150 mg L À1 of formaldehyde in wood glue wastewater. The influence of formaldehyde concentrations over the methanogenic activity is further discussed in the present work.…”

“…According to Gonzalez-Gil et al (2000), methanogenesis only recovers its gas production when formaldehyde is either extremely low or completely removed from the water during the following period, which was not the case of the present investigation. On the other hand, Qu and Bhattacharya (1997) reported that although completely inhibited by 150 mg L À1 of formaldehyde during the first 40 days, methane production was fully recovered after 50 days. This suggests that in the present investigation either a longer period or a complete removal of formaldehyde from the feeding wastewater would be required for methanogenesis to recover from the disturbances caused by shock loads of formaldehyde.…”

Evaluation of biodegradability and oxidation degree of hospital wastewater using photo-Fenton process as the pretreatment method

“…Aquatic organisms, for instance, respond negatively to low concentrations of formaldehyde, which is a frequently found contaminant in hospital wastewater [6]. It was reported that formaldehyde in the range of 10-100 mg/L was toxic to the microbial in wastewater treatment system [7][8][9]. In addition, the presence of organochlorine compounds in high concentrations in hospital effluent has also been reported as toxic to aquatic life [10].…”

Degradation of formaldehyde in anaerobic sequencing batch biofilm reactor (ASBBR)

“…However, degradation rates increased as the initial concentration of formaldehyde as increased. Other studies also concluded that an increase in initial formaldehyde concentrations yield inhibition [26,27].…”