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ABSTRACT: In the present work, the humification level of waste-derived dissolved organic matter (DOM) at different waste biostability was investigated, by using fluorescent excitation-emission matrix (EEM) scanning. Different fluorescence spectrum analysis techniques were applied and compared. Experimental results demonstrate that parallel factor (PARAFAC) analysis was sensitive to reflect DOM humification, and the most reasonable to deconstruct DOM compositions, when compared with other spectrum analysis techniques. It suggests applying the DOM-EEM-PARAFAC pipeline for rapid estimation of waste biostability.
Environmental Technology 12/2012; 33(22-24):2569-73. · 1.41 Impact Factor
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ABSTRACT: The feasibility of cultivating Chlorella vulgaris with wastewater containing high ammonia nitrogen concentrations was examined. The average specific growth rate of C. vulgaris was 0.92d(-1) at 17mgL(-1) NH(4)(+)-N, but declined to 0.33d(-1) at NH(4)(+)-N concentrations of 39-143mgL(-1). At 39mgL(-1) NH(4)(+)-N, lipid productivity reached a maximum value (23.3mgL(-1)d(-1)) and dropped sharply at higher NH(4)(+)-N levels, which demonstrated NH(4)(+)-N should be controlled for biodiesel production. C16 and C18 fatty acids accounted for 80% of total fatty acids. Increasing NH(4)(+)-N from 17 to 207mgL(-1) yielded additional short-chain and saturated fatty acids. Protein content was in positive correlation with NH(4)(+)-N content from 17mgL(-1) (12%) to 207mgL(-1) (42%). Carbohydrate in the dried algae cell was in the range of 14-45%, with a peak value occurring at 143mgL(-1) NH(4)(+)-N. The results demonstrate that product quality can be manipulated by NH(4)(+)-N concentrations of the initial feeds.
Bioresource technology 11/2012; 129C:177-181. · 4.25 Impact Factor
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ABSTRACT: To investigate the synergetic effect of pH and biochemical components on bacterial community structure during mesophilic anaerobic degradation of solid wastes with different origins, and under acidic or neutral conditions.
The bacterial community in 16 samples of solid wastes with different biochemical compositions and origins was evaluated during mesophilic anaerobic degradation at acidic and neutral pH. Denaturing gradient gel electrophoresis (DGGE) and single-strand conformation polymorphism (SSCP) were used to compare the communities. Multivariate analysis of the DGGE and SSCP results revealed that most of the dominant microbes were dependent on the content of easily degradable carbohydrates in the samples. Furthermore, the dominant microbes were divided into two types, those that preferred an acid environment and those that preferred a neutral environment. A shift in pH was found to change their preference for medium substrates. Although most of the substrates with similar origin and biochemical composition had similar microbial diversity during fermentation, some microbes were found only in substrates with specific origins. For example, two microbes were only found in substrate that contained lignocellulose and animal protein without starch. These microbes were related to micro-organisms that are found in swine manure, as well as in other intestinal or oral niches. In addition, the distribution of fermentation products was less sensitive to the changes in pH and biochemical components than the microbial community.
Bacterial diversity during anaerobic degradation of organic wastes was affected by both pH and biochemical components; however, pH exerted a greater effect.
The results of this study reveal that control of pH may be an effective method to produce a stable bacterial community and relatively similar product distribution during anaerobic digestion of waste, regardless of variation in the waste feedstocks.
Journal of Applied Microbiology 02/2009; 106(2):580-91. · 2.34 Impact Factor
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ABSTRACT: Utilizing stable carbon isotope data to account for aceticlastic and non-aceticlastic pathways of methane generation, a model was created to describe laboratory batch anaerobic decomposition of cellulosic materials (office paper and cardboard). The total organic and inorganic carbon concentrations, methane production volume, and methane and CO(2) partial pressure values were used for the model calibration and validation. According to the fluorescent in situ hybridization observations, three groups of methanogens including strictly hydrogenotrophic methanogens, strictly aceticlastic methanogens (Methanosaeta sp.) and Methanosarcina sp., consuming both acetate and H(2)/H(2)CO(3) as well as acetate-oxidizing syntrophs, were considered. It was shown that temporary inhibition of aceticlastic methanogens by non-ionized volatile fatty acids or acidic pH was responsible for two-step methane production from office paper at 35 degrees C where during the first and second steps methane was generated mostly from H(2)/H(2)CO(3) and acetate, respectively. Water saturated and unsaturated cases were tested. According to the model, at the intermediate moisture (150%), much lower methane production occurred because of full-time inhibition of aceticlastic methanogens. At the lowest moisture, methane production was very low because most likely hydrolysis was seriously inhibited. Simulations showed that during cardboard and office paper biodegradation at 55 degrees C, non-aceticlastic syntrophic oxidation by acetate-oxidizing syntrophs and hydrogenotrophic methanogens were the dominant methanogenic pathways.
Waste Management 02/2009; 29(6):1828-37. · 2.43 Impact Factor
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ABSTRACT: Distributions of six priority controlled Phthalic acid esters (PAEs), including di-methyl phthalate (DMP), di-ethyl phthalate (DEP), di-butyl phthalate (DBP), benzyl butyl phthalate (BBP), di-(2-ethylhexyl) phthalate (DEHP), di-octyl phthalate (DOP) were studied based on soluble and insoluble fractions of sludge samples collected at four wastewater treatment plants in Shanghai, China. Three sludge samples comprised hydrophilic colloidal particles of high protein contents and low aromaticity. Meanwhile, these sludges contained DBP of 4.2 to approximately 5.7 mg kg(-1) dried solids (ds) and DEHP of 21.1 to approximately 55.6 mg kg(-1) ds, respectively. Another sludge sample comprised mainly hydrophobic colloidal particles of humic substances and high aromaticity. It contained DBP of 1.18 mg kg(-1) ds and DEHP of 2.89 mg kg(-1) ds, respectively. The most abundant components noted amongst the six studied PAEs were DBP and DEHP, which mostly associated with the insoluble fraction of sludge. Specifically, the DBP and DEHP in insoluble fraction (the solid residual phase) accounted for 89.8 to approximately 98.2% and 88.6 to approximately 99.6% of those in the whole sludge. The partition coefficients of DBP and DEHP for the soluble and insoluble fractions of sludge correlated with the suspension SUVA254, suggesting that interaction between pi-electrons of DBP or DEHP and those of organic particulates in suspension contributes most of the sorption processes.
Environmental Technology 04/2008; 29(3):343-50. · 1.41 Impact Factor
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ABSTRACT: The facilitated transport of dibutyl phthalate (DBP) and di(2-ethylhexyl) phthalate (DEHP), the priority endocrine disrupting chemicals in sludge, by dissolved humic substances (HS) was evaluated by batch extraction. The DBP, much less hydrophobic than DEHP, was inclined to migrate from sludge matrix into humic substances solutions, while the DEHP could not migrate facilitated by most humic and fulvic acids solutions, except the humic acid surrogate of high humification. This result revealed that the affinity of DEHP in sludge matrix exceeded DBP and was not susceptible by weak HS. The hydrophobic property controlled the association of phthalic acid esters on sludge residual phases. Migration rate of DBP was positively correlated to the weight-average molecular weight of HS surrogates and the aromatic extents of HA. Some functional groups in HS molecules benefited to the facilitated transport of DBP.
Water Science & Technology 02/2008; 57(4):607-12. · 1.12 Impact Factor
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ABSTRACT: Two trials were established to investigate the effect of recycled effluent on hydrolysis during anaerobic co-digestion of vegetable and flower waste. Trial I evaluated the effect by regulating the flow rate of recycled effluent, while Trial II regulated the ratio of hydrolytic effluent to methanogenic effluent, which were recycled to hydrolysis reactor. Results showed that the recirculation of methanogenic effluent could enhance the buffer capability and operation stability of hydrolysis reactor. Higher recycled flow rate was favourable for microbial anabolism and further promoted hydrolysis. After 9 days of hydrolysis, the cumulative SCOD in the hydrolytic effluent reached 334, 407, 413, 581 mg/g at recycled flow rates of 0.1, 0.5, 1.0, 2.0 m3/(m3 x d), respectively. It was feasible to recycling a mixture of hydrolytic and methanogenic effluent to the hydrolysis reactor. This research showed that partially introducing hydrolytic effluent into the recycled liquid could enhance hydrolysis, while excessive recirculation of hydrolytic effluent will inhibit the hydrolysis. The flow ratio 1:3 of hydrolytic to methanogenic effluent was found to provide the highest hydrolysis efficiency and degradation rate of lignocelluloses-type biomass, among four ratios of 0:1, 1:3, 1:1 and 3:1. Under this regime, after 9 days of hydrolysis, the cumulative TOC and TN in the hydrolytic effluent reached 162 mg/g and 15 mg/g, the removal efficiency of TS, VS, C and cellulose in the solid phase were 60.66%, 62.88%, 58.35% and 49.12%, respectively. The flow ratio affected fermentation pathways, i.e. lower ratio favoured propionic acid fermentation and the generation of lactic acid while higher ratio promoted butyric acid fermentation.
Water Science & Technology 02/2008; 58(8):1637-43. · 1.12 Impact Factor
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ABSTRACT: To estimate the effect of pH on the structures of bacterial community during fermentation of vegetable wastes and to investigate the relationship between bacterial community dynamics and product distribution.
The bacterial communities in five batch tests controlled at different pH values [uncontrolled (about pH 4), 5, 6, 7 and 8] were monitored by denaturing gradient gel electrophoresis (DGGE) and single-strand conformation polymorphism (SSCP). The two fingerprinting methods provided consistent results and principal component analysis indicated a close similarity of bacterial community at pH 7 and 8 in addition to those at pH 4-6. This clustering also corresponded to dominant metabolic pathway. Thus, pH 7-8 shifted from alcohol-forming to acid-forming, especially butyric acid, whereas both alcohol-forming and acid-forming dominated at pH 5-6, and at pH 4, fermentation was inhibited. Shannon-weaver index was calculated to analyse the DGGE profiles, which revealed that the bacterial diversities at pH 7 and 8 were the highest while those at pH 5 and 4 (uncontrolled) were the lowest. According to sequencing results of the bands excised from DGGE gels, lactic acid bacteria and Clostridium sp. were predominant at all pH values, but varieties in species were observed as pH changed and time prolonged.
The bacterial community during fermentation was materially influenced by pH and the diverse product distribution was related to the shift of different bacterial population.
The study reveals that the impact of pH on fermentation product distribution is implemented primarily by changes of bacterial community. It also provides information about the comparison of two fingerprinting methods, DGGE and SSCP.
Journal of Applied Microbiology 11/2007; 103(4):1055-65. · 2.34 Impact Factor
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ABSTRACT: Five batch testing scenarios were designed to evaluate the effects of alkali metal cations on anaerobic hydrolysis and acidogenesis. These scenarios were A (c=0 g l(-1)), B (cNa+=25 g l(-1)), C (cNa+=50 g l(-1)), D (cK+=25 g l(-1)), and E (cK+=50 g l(-1), pH 7.0). A solution pH of 7.0 or above favored protein hydrolysis, higher proteinase activity and higher ammonia production. However, such a pH suppressed carbohydrate hydrolysis, as indicated by low alpha-amylase activity. Cation interference at pH 5.0-6.0 seemed not to affect carbohydrate hydrolysis, as showed by the unimpaired alpha-amylase activity at 50 g l(-1) K+. Acidogenesis was more sensitive to alkali metal cations, so acid production and the drop in pH were lowest in a 25-50 g l(-1) Na+, acidic environment (pH 4.0-6.0). It was insensitive to cations when the pH was maintained at 7.0-8.0. When the pH was uncontrolled and decreased freely to acidic values, 25 g l(-1) of cation inhibited the action of the microbes, which rapidly acclimated, as presented by the slow transformation of soluble polymers to soluble metabolites. However, acidogenetic microbes could not easily recover from inhibition by 50 g l(-1) of cation. When the pH was maintained at over 7.0, the microbes were not inhibited by cation (50 g l(-1)) as indicated by the more active acidogenesis. The metabolic pathways to lactate, acetate and alcohols were not fully coupled.
Environmental Technology 04/2006; 27(3):317-27. · 1.41 Impact Factor
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ABSTRACT: A three-compartment system, comprising a landfill column with fresh municipal solid waste, a column with a well-decomposed refuse layer as methane producer, and a sequential batch reactor as ex situ nitrifying reactor, was employed to remove nitrogen from municipal solid waste leachate. Since food waste comprised a major portion of refuse collected in Shanghai, an intense hydrolysis reaction occurred and caused the rapid accumulation of ammonia nitrogen (NH(3)-N) and total organic carbon in the leachate. This paper discusses the role of the three mentioned units and the design and operation of the proposed system. With most NH(3)-N being converted to nitrite nitrogen (NO(2)(-)-N) or nitrate nitrogen (NO(3)(-)-N) by the nitrifying reactor, and with the well-decomposed refuse layer transforming most dissolved organic compounds to CO(2), carbonates and methane, it was found that the fresh refuse column could efficiently denitrify the hydrolyzed nitrogen to N(2) gas. The role of the three mentioned units and comments on the design and operation of the proposed system are also discussed.
Waste Management 02/2006; 26(8):838-45. · 2.43 Impact Factor
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ABSTRACT: The municipal solids waste (MSW) collected at Shanghai includes a high proportion of food waste, which is easily hydrolyzed to generate ammonia-nitrogen in leachate. This study investigated the efficiency of nitrogen removal from landfill leachate employing four different treatment processes. The simulated rainfall and direct leachate recycling produced strong leachate with high ammonia-nitrogen content, and resulted in the removal of only a small amount of nitrogen. Although pretreating the leachate using an aerobic reactor removed some nitrogen, most of which was transformed to biomass because of the high organic loading applied. Using the three-compartment system, which comprises a landfill column with fresh MSW, a column with well-decomposed refuse layer as the methane generator, and a nitrifier, the ammonia-nitrogen was converted into nitrogen gas and hence removed. Experimental results demonstrated the feasibility of adopting the three-compartment system for managing nitrogen in landfill leachate generated from high-nitrogen-content MSW.
Environmental Technology 05/2005; 26(4):373-80. · 1.41 Impact Factor
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ABSTRACT: In this paper, the discussion is concentrated on the properties of the polluted sediments and the combination of clean-up and disposal process for the upper layer heavily polluted sediments with good flowability. Based on the systematic analyses of various clean-up processes, a suitable engineering process has been evaluated and recommended. The process has been applied to the river reclamation in Yangpu District of Shanghai City, China. An improved centrifuge is used for dewatering the dredged sludge, which plays an important role in the combination of clean-up and disposal process. The assessment of the engineering process shows its environmental and technical economy feasibility, which is much better than that of traditional dredging-disposal processes.
Journal of Environmental Sciences 11/2001; 13(4):435-8. · 1.66 Impact Factor
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ABSTRACT: A three-compartment system, comprising a landfill column with fresh municipal solid waste, a column with a well-decomposed refuse layer as methane producer, and a sequential batch reactor as ex situ nitrifying reactor, was employed to remove nitrogen from municipal solid waste leachate. Since food waste comprised a major portion of refuse collected in Shanghai, an intense hydrolysis reaction occurred and caused the rapid accumulation of ammonia nitrogen (NH3–N) and total organic carbon in the leachate. This paper discusses the role of the three mentioned units and the design and operation of the proposed system. With most NH3–N being converted to nitrite nitrogen or nitrate nitrogen by the nitrifying reactor, and with the well-decomposed refuse layer transforming most dissolved organic compounds to CO2, carbonates and methane, it was found that the fresh refuse column could efficiently denitrify the hydrolyzed nitrogen to N2 gas. The role of the three mentioned units and comments on the design and operation of the proposed system are also discussed.
Waste Management.
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ABSTRACT: Sewage sludge is of increasing concern in China, due to extended sewerage control and advanced wastewater treatments resulting from urbanization and economic growth. Based on the evolution of municipal sewage generation and treatment technologies in the last decade, as well as the long-term national and local plans in China, the paper elucidates production, distribution and characteristics (organics, nutrients, heat value, heavy metals, trace pollutants, pathogens) of sludge in some typical districts of China. The status and challenges of sludge management are discussed. INTRODUCTION In China, more than one thousand municipal wastewater treatment plants (WWTPs) will be put to operation in the next 10 years, most of which will adopt secondary or tertiary treatment processes. Increasing sewage treatment capacity and enhanced treatment processes will produce huge quantity of sewage sludge. Lee et al. (2006) reviewed the perspectives of sludge management in Beijing and Shanghai of China. This paper overviewed the current status of sludge management in China. SEWAGE AND SEWAGE SLUDGE In the past five years, the collected sewage in China increased in amount by 18.2%, while the sewage treatment capacity increased by 135%. At the end of 2005, 39% of the collected sewage was treated in WWTPs (Figure 1). A total of 792 sewage treatment plants located in 661 cities treated 57.25 million tons of wastewater per day (Figure 2). 87.4% of these WWTPs were operated with secondary or tertiary treatment processes. Up to June, 2005, 297 cities in China had no WWTPs for treating their sewage, indicating the potential growth of sewage treatment capability. Development in different regions of China is rather unbalanced, as evidenced by the implementations of big projects for sewage infrastructures in major provinces. The eastern regions of China have more WWTPs than the reminder area (Figure 3).
