Treatment of embalming fluid using domestic wastewater as co-substrate in anaerobic filter

Abstract

Simultaneous formaldehyde (FA) and phenol, the main ingredients of embalming fluid, biodegradation using domestic wastewater as the co-substrate in anaerobic filter was investigated. Experiments were conducted in two anaerobic filters operated at 6h and 12h HRT for 215 days. FA and phenol concentrations of 22-1,373 mg/l and 5.4-208 mg/l, corresponding to COD concentration of 207-1,756 mg/l, were fed to both reactors. FA removal efficiencies of 97.0% and 97.2% were obtained in the 6h and 12h reactors at all applied FA concentrations. On the other hand, phenol was observed to be completely removed when initial concentrations were not higher than 15 mg/l and 33 mg/l (with FA concentrations of 64 and 128 mg/l) in 6h- and 12h-HRT reactors, respectively. It was possible that high concentration of FA affected some microorganisms responsible in degrading phenol. Results obtained also indicated that anaerobic filter operated at longer HRT (12h) could achieve higher performance in removing studied toxic substances than that of the shorter one (6h). This could possibly be attributed to the decrease of microorganisms activity from the acute toxic of FA and phenol. Moreover, presence of embalming fluid in the influent caused the decrease of specific methane yield. The maximum treatable ratio of embalming fluid to domestic wastewater were found to be 0.004 : 1 and 0.002 : 1 by volume at the HRTs of 6h and 12h, respectively. Using the microscopic technique, dominant microorganisms were observed in the rods, cocci, filament, and helices forms. The organisms similar to Methanosarcina and Methanoseata were observed to dominate in all studies among the methanogenic archaea. DGGE profile revealed the appearances and losses of bands in response to the improvement and deterioration of reactor’s performance in removing FA and phenol. Differences of the bands number were also visualized implying differences of microbial diversity in anaerobic reactors treating wastewater contaminated with different FA and phenol concentrations