Biodecolorization of the azo dye Reactive Red 2 by a halotolerant enrichment culture.

The decolorization of the azo dye Reactive Red 2 (RR2) under anoxic conditions was investigated using a mesophilic (35 degrees C) halotolerant enrichment culture capable of growth at 100 g/L sodium chloride (NaCl). Batch decolorization assays were conducted with the unacclimated halotolerant culture, and dye decolorization kinetics were determined as a function of the initial dye, biomass, carbon source, and an externally added oxidation-reduction mediator (anthraquinone-2,6-disulphonic acid) concentrations. The maximum biomass-normalized RR2 decolorization rate by the halotolerant enrichment culture under batch, anoxic incubation conditions was 26.8 mg dye/mg VSSxd. Although RR2 decolorization was inhibited at RR2 concentrations equal to and higher than 300 mg/L, the halotolerant culture achieved a 156-fold higher RR2 decolorization rate compared with a previously reported, biomass-normalized RR2 decolorization rate by a mixed mesophilic (35 degrees C) methanogenic culture in the absence of NaCl. Decolorization kinetics at inhibitory RR2 levels were described based on the Haldane model (Haldane, 1965). Five repetitive dyeing/decolorization cycles performed using the halotolerant culture and the same RR2 dyebath solution demonstrated the feasibility of biological renovation and reuse of commercial-strength spent reactive azo dyebaths.     

The anaerobic biodegradability of municipal sludge and fat, oil, and grease at mesophilic conditions.

The anaerobic biodegradability of municipal primary and secondary sludge with increasing levels of partially dewatered fat, oil, and grease (FOG) was assessed using a mixed methanogenic culture at 35 "C. Under batch conditions with an acclimated and enriched microbial population, the sludge loading was 3 kg volatile solids/m3 and the highest FOG loading tested was 1.5 kg volatile solids/m3, resulting in a methane yield of 245 mL methane/g sludge volatile solids added at 35 degrees C and 1010 mL methane/g FOG volatile solids added at 35 degrees C. Under semicontinuous feeding conditions, the sludge and sludge plus FOG loading tested were 3 and 3.75 kg volatile solids/m3-d, respectively. Within 23 days of operation, the volatile fatty acid concentrations were reduced below 200 mg chemical oxygen demand/L (187 mg/L as acetic acid). Enhancement of sludge digestion was observed in those reactors where codigestion of sludge and FOG took place, which was attributed to a higher level of microbial activity maintained in these reactors as a result of FOG degradation. The results of this study demonstrate that beneficial use of FOG through codigestion with municipal sludge is feasible.     

市政污泥与高浓度废弃物的厌氧共消化：一种生物质能源净产生的途径

厌氧共消化是一种绿色、实用的回收废弃物中能源的技术。本文介绍了厌氧共消化技术的原理，并介绍了美国佐治亚州F. Wayne Hil水资源处理中心采用油脂废弃物（FOG）和含糖工业废水与市政污泥进行连续流厌氧共消化的实际应用案例。结果表明，厌氧共消化可显著提高甲烷产量达2倍以上，甲烷产量随着高浓度有机废弃物负荷率及厌氧消化反应器停留时间的延长而增加，且COD和VS降解率可保持在合理范围内，经济效益显著。     

Estimation of environmentally relevant chemical properties of veterinary ionophore antibiotics

Environmental Science and Pollution Research - Monensin (MON) and salinomycin (SAL), known as polyether ionophore antibiotics (IPAs), are extensively used in livestock industry and can enter the...     

Biological decolorization of reactive anthraquinone and phthalocyanine dyes under various oxidation-reduction conditions.

The decolorization of two anthraquinone dyes (Reactive Blue 4 [RB4] and Reactive Blue 19 [RB19]) and two phthalocyanine dyes (Reactive Blue 7 [RB7] and Reactive Blue 21 [RB21]) was investigated at an initial dye concentration of 300 mg/L using an unacclimated, enrichment culture. The culture was fed a mixture of organic compounds and maintained initially under aerobic conditions, and then progressively developed anoxic/ anaerobic conditions. Biotransformation-related decolorization of the dyes did not take place under aerobic conditions, but use of the feed organic mixture and biomass production by the enrichment culture were not affected. Complete ammonia removal occurred in the control and all dye-amended cultures. The development and extent of nitrification were much lower in the latter cultures, in which ammonia removal via air stripping was the dominant mechanism. Prolonged incubation of the culture under anoxic/anaerobic conditions with multiple carbon source additions resulted in a high decolorization extent of anthraquinone dyes (over 84%) and only partial decolorization of phthalocyanine dyes (49 to 66%). Development of significant methanogenic activity took place in the control and, to a lesser extent, in the two phthalocyanine dye-amended cultures, but the anthraquinone dyes severely inhibited the development of methanogenic activity. The RB4 and RB19 decolorization was attributed to nonreversible, microbially mediated dye transformation(s), demonstrated by the accumulation of decolorization products with absorbance maxima in the 420- to 460-nm region. The decolorization of RB4 and RB19 followed Michaelis-Menten kinetics. At an initial dye concentration of 300 mg/L, the observed maximum decolorization rate per unit biomass was 9.1 and 37.5 mg dye/mg volatile suspended solids x day for the RB4 and RB19, respectively. Thus, partial decolorization of reactive phthalocyanine dyes and extensive biological decolorization of reactive anthraquinone dyes is feasible only under anoxic/anaerobic conditions.     

Potential and Limitations of Microbial Reductive Dechlorination for Bioremediation Applications

Current knowledge and recent advances in the area of microbial reductive dechlorination of polychlorinated organic compounds are summarized. Factors which may limit the efficacy of the dechlorination process for the in situ bioremediation of contaminated soil and sediment systems are identified. Results of recent studies on the anaerobic biotransformation of soil-sorbed chlorinated ethenes and sediment-sorbed chlorinated benzenes are provided to illustrate how low contaminant bioavailability may control the rate and extent of dechlorination in subsurface systems, especially those with long-term contamination. Use of nonionic, polysorbate surfactants as the sole electron donors of a mixed, methanogenic culture supported the microbial sequential reductive dechlorination of either free or sediment-bound hexachlorobenzene (HCB) to primarily 1,3-dichlorobenzene, but did not enhance the bioavailability of sediment-bound HCB as compared to microcosms, which used glucose. Because current knowledge on the interactions of dechlorinating populations with other microbial populations in the presence of alternative terminal electron acceptors (e.g., nitrate, Fe³⁺ , Mn⁴⁺) is limited, such interactions and their effect on the dechlorination process in subsurface systems need to be further explored to improve our understanding of the reductive dechlorination process in complex environmental systems and lead to the development of more efficient in situ bioremediation technologies and strategies.