Toxicity Effects of Formaldehyde on Methanol Degrading Sludge and Its Anaerobic Conversion in Biobed® Expanded Granular Sludge Bed (EGSB) Reactors

Abstract

Methanogenesis from formaldehyde mainly occurred via intermediates as confirmed by the increased concentrations of methanol and H2 in the liquid and gas phases respectively during formaldehyde conversion. While formaldehyde was readily transformed, the methane production rate was immediately and strongly inhibited. Formaldehyde toxicity was in part reversible since the methane production rate recovered after formaldehyde depletion. This recovery can not be explained by biomass growth. The toxicity of formaldehyde was also in part irreversible, since the degree of recovery was not complete. This loss in the methane production rate likely can be attributed to biomass decay as suggested by its linear relation with the amount of formaldehyde dosed, as well as by scanning electron microscopy observations. The addition of the same amount of formaldehyde either in a slug or in a continuous mode caused the same loss in the methane production rate. Thus for the treatment of formaldehyde-containing streams, a balance between loss in the rate (formaldehyde-related decay) and bacterial growth should be attained. By combining good biomass retention and internal dilution of the wastewater, industrial streams containing formaldehyde can still be treated anaerobically.

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

“…Other industrial wastewater can reach concentrations as high as 10 g/L [3]. Such formaldehyde-rich industrial wastewater may cause microbial activity inhibition in biological processes [4]. Formaldehyde can react directly with DNA, RNA and proteins, thereby damaging cells and causing the death of microorganisms [5].…”

“…These studies do not point to any consensus about the concentrations that can inhibit microbial activity [5,[12][13][14]. In addition, the pathways of anaerobic formaldehyde degradation and the microorganisms involved in this process are still discrepant [4,10,14].…”

Degradation and detoxification of formaline wastewater by advanced oxidation processes

“…The contact of this toxic substance with aquatic ecosystems leads to a risk directly related to the existence of hazardous substances, which could have potential negative effects on the biological balance of natural environments [2,3]. The direct discharge to the biological wastewater treatment plant is also ceased the bacteria activity causing the failure of such a system [4]. However, little research work has been done to find the practical way to degrade the organic contaminants and reduce the toxicity of formaline wastewater.…”

Influence of pH shocks on trace metal dynamics and performance of methanol fed granular sludge bioreactors

“…A pH controller maintained the pH at 7.0 (±0.2) by the addition of NaOH in the effluent recycle tube. The produced biogas was led through a water lock filled with a NaOH (15%) solution in order to remove CO 2 and H 2 S. The produced methane volume was measured by water displacement from mariot-flasks using an on-line balance system as described by Gonzalez et al (1999). Due to a problem with the data collection system, no gas production data are available from day 41 until day 49 and from day 163 onwards.…”