Survey of the Anaerobic Biodegradation Potential of Organic Chemicals in Digesting Sludge

Abstract

The degradation potential of 77 organic chemicals under methanogenic conditions was examined with an anaerobic digesting sludge from the United Kingdom. Degradation was assessed in terms of net total gas (CH4 plus C02) produced, expressed as a percentage of the theoretical production (ThGP). The compounds tested were selected from various chemical groups and included substituted phenols and benzoates, pesticides, phthalic acid esters, homocyclic and heterocyclic ring compounds, glycols, and monosubstituted benzenes. The results obtained were in good agreement with published surveys of biodegradability in U.S. digesting sludges and other methanogenic environments. In general, the presence of chloro or nitro groups inhibited anaerobic gas production, while carboxyl and hydroxyl groups facilitated biodegradation. The relationship between substituent position and susceptibility to methanogenic degradation was compound dependent. The following chemicals were completely degraded (.80% ThGP) at a concentration of 50 mg of carbon per liter: phenol, 2-aminophenol, 4-cresol, catechol, sodium benzoate, 4-aminobenzoic acid, 3-chlorobenzoic acid, phthalic acid, ethylene glycol, diethylene glycol, triethylene glycol, sodium stearate, and quinoline. 3-Cresol, 4-chlorobenzoic acid, dimethyl phthalate, and pyridine were partially degraded. Although the remaining chemicals tested were either persistent or toxic, their behavior may differ at more environmentally realistic chemical-to-biomass ratios. Our findings suggest that biodegradability assessments made with sludge from one source can be extrapolated to sludge from another source with a reasonable degree of confidence and should help in predicting the fate of an organic chemical during the anaerobic digestion of sewage sludge. * Corresponding author. zoates, phthalic acid esters, pesticides, homocyclic and heterocyclic ring compounds, glycols, and monosubstituted benzenes. The results of this study are compared with those reported for municipal sludges in the United States and may help in predicting the fate of organic chemicals during anaerobic digestion.

Toxicity and degradability of nitrophenols in anaerobic systems

“…Abiotic transformation of 2nitrophenol and 2,4-dinitrophenol, under reducing conditions (with sulfide or cysteine), has also been reported by Gorontzy et al (1993). Biological degradation of 4-nitrophenol confirms the findings of other researchers (Horowitz et al, 1982;Boyd et al, 1983;Battersby and Wilson, 1989;Haghighi et al, 1995).…”

“…In (1995) and Sluder (1994). Battersby and Wilson (1989) reported that 2-nitrophenol was not inhibitory while 4-nitrophej:…”

“…Biodegradation studies of the nitropheno]s with digesting sludge under methanogenic conditions and in the bottom sediments of lakes and rivers have shown that the compounds are not easily biodegraded and that 4-nitrophenol at high concentration is inhibitory to methanogenic microorganisms (Horowitz et al 1982;Siragusa and Delaune, 1986;Battersby and Wilson, 1989). In anaerobic screening tests using digester sludge inocula, complete removal of 4-nitrophenol occurred in ] week in one study (Boyd et at., 1983), and> 75% removal in 56 days in another study (She]ton and Tiedje, ] 984).…”

Enzymes involved in the anaerobic degradation of ortho‐phthalate by the nitrate‐reducing bacterium Azoarcus sp. strain PA01

“…Aftring et al, showed that phthalate isomers can be degraded under anoxic conditions (Aftring et al, 1981). Although less understood than aerobic phthalate degradation, anaerobic degradation of phthalate isomers and phthalate esters was reported for numerous pure and mixed cultures under nitrate-or sulfate-reducing or methanogenic conditions (Battersby and Wilson, 1989;Kleerebezem et al, 1999;Qiu et al, 2006;Cheung et al, 2007;Liang et al, 2008), but no decisive studies on the degradation pathways have been published so far.…”

Utilization of a bioluminescence toxicity assay for optimal design of biological and physicochemical wastewater treatment processes

“…The preliminary anaerobic contact stage served to equalize and partially degrade the raw compounds. Such an environment has been reported to facilitate subsequent aerobic degradation by transforming complex organic compounds into readily degradable molecules (Young, 1981 ;Battersby and Wilson, 1989). At the beginning of the study, a screening system composed of four reactors in series (two anaerobic and two aerobic) was operated for several months with no attempt at sludge concentration.…”