Overview of the anaerobic toxicity caused by organic forest industry wastewater pollutants

Numerous types of organic environmental pollutants are encountered in forest industry effluents which potentially could inhibit consortia of anaerobic bacteria. The purpose of this study was to collect anaerobic bioassay data from the literature to better estimate the impact of these pollutants on anaerobic wastewater treatment systems. The most important methanogenic inhibitors in forest industry wastewaters are wood resin, chlorophenols and tannins. These compounds account for toxicity in alkaline pulping liquors, bleaching effluents and debarking wastewaters, respectively. Adaptation to chlorophenol toxicity can be expected since they are eventually degraded in anaerobic systems. Wood resin compounds, on the other hand, are not biodegraded anaerobically and therefore their toxicity is persistent. Toxicity in forest industry wastewaters does not necessarily preclude anaerobic treatment. A variety of techniques can be employed to diminish inhibition, such as dilution and detoxification treatments.