Upflow anaerobic filter for the degradation of adsorbable organic halides (AOX) from bleach composite wastewater of pulp and paper industry.

The removal of AOX from bleach plant effluent of pulp and paper industry was studied using upflow anaerobic filter. In this paper biodegradation of AOX at different concentrations and effect of electron donors like acetate and glucose thereon in an upflow anaerobic filter at 20 d HRT is described. Results showed significant improvement in AOX degradation when electron donors such as acetate and glucose were supplemented to the influent. AOX degradation was 88% at 28 mg AOX L(-1) and 28% at 42 mg AOX L(-1). The percent degradation efficiency was enhanced to 90.7, 90.2, and 93.0 at 28 mg AOX L(-1) when the influent was supplemented with glucose, acetate and both glucose and acetate, respectively. Similarly, the efficiency was 57, 56.6 and 79.6 at 42 mg AOX L(-1) when the influent was supplemented with glucose, acetate and both glucose and acetate, respectively. The GC-MS analysis data indicated that supplementation of the influent with electron donor increased the biodegradability of number of chlorinated organic compounds.

Anaerobic degradation of adsorbable organic halides (AOX) from pulp and paper industry wastewater.

Adsorbable organic halides (AOX) are generated in the pulp and paper industry during the bleaching process. These compounds are formed as a result of reaction between residual lignin from wood fibres and chlorine/chlorine compounds used for bleaching. Many of these compounds are recalcitrant and have long half-life periods. Some of them show a tendency to bioaccumulate while some are proven carcinogens and mutagens. Hence, it is necessary to remove or degrade these compounds from wastewater. Physical, chemical and electrochemical methods reported to remove AOX compounds are not economically viable. Different types of aerobic, anaerobic and combined biological treatment processes have been developed for treatment of pulp and paper industry wastewater. Maximum dechlorination is found to occur under anaerobic conditions. However, as these processes are designed specifically for reducing COD and BOD of wastewater, they do not ensure complete removal of AOX. This paper reviews the anaerobic biological treatments developed for pulp and paper industry wastewater and also reviews the specific micro-organisms reported to degrade AOX compounds under anaerobic conditions, their nutritional and biochemical requirements. It is imperative to consider these specific micro-organisms while designing an anaerobic treatment for efficient removal of AOX.

Application of Methanobrevibacter acididurans in anaerobic digestion.

To operate anaerobic digesters successfully under acidic conditions, hydrogen utilizing methanogens which can grow efficiently at low pH and tolerate high volatile fatty acids (VFA) are desirable. An acid tolerant hydrogenotrophic methanogen viz. Methanobrevibacter acididurans isolated from slurry of an anaerobic digester running on alcohol distillery wastewater has been described earlier by this lab. This organism could grow optimally at pH 6.0. In the experiments reported herein, M. acididurans showed better methanogenesis under acidic conditions with high VFA, particularly acetate, than Methanobacterium bryantii, a common hydrogenotrophic inhabitant of anaerobic digesters. Addition of M. acididurans culture to digesting slurry of acidogenic as well as methanogenic digesters running on distillery wastewater showed increase in methane production and decrease in accumulation of volatile fatty acids. The results proved the feasibility of application of M. acididurans in anaerobic digesters.

Methanobrevibacter acididurans sp. nov., a novel methanogen from a sour anaerobic digester.

A novel acid-tolerant, hydrogenotrophic methanogen, isolate ATMT, was obtained from an enrichment performed at pH 5.0 using slurry from an acidogenic digester running on alcohol distillery waste. The original pH of the slurry was 5.7 and the volatile fatty acid concentration was 9000 p.p.m. Cells of isolate ATMT were Gram-positive, non-motile and 0.3-0.5 microm in size. They did not form spores. The isolate could grow in the pH range 5.0-7.5, with maximum growth at pH 6.0. The optimum temperature for growth was 35 degrees C. Formate, acetate, methanol, trimethylamine, 2-propanol and 2-butanol were not utilized as growth substrates. Rumen fluid and acetate were required for growth on H2/CO2. Coenzyme M and 2-methylbutyric acid were not required in the presence of rumen fluid. 16S rDNA sequence analysis confirmed the signature sequence of the genus Methanobrevibacter. Morphological and biochemical characteristics of the isolate, together with the 16S rDNA sequence analysis, clearly revealed that the isolate could not be accommodated within any of the existing species of the genus Methanobrevibacter. Therefore, it is proposed that a novel species of the genus Methanobrevibacter should be created for this isolate, Methanobrevibacter acididurans sp. nov., and the type strain is