Frontiers of Environmental Science & Engineering

ISSN 2095-2201

ISSN 2095-221X(Online)

CN 10-1013/X

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Research articles
Challenges of a feasible route towards sustainability in environmental protection
Front.Environ.Sci.Eng.. 2010, 4 (2): 123-134.

Abstract   PDF (293KB)
Anaerobic processes for treatment of low and high strength wastewaters and solid wastes constitute the core method in the natural biological mineralization (NBM) treatment concept. When adequately combined with the complementary NBM-systems and modern clean water saving practices in wastewater collection and transport, they represent a feasible route to sustainable environmental protection (EPsus), in essence even towards a more sustainable society. Despite the development and implementation of modern high rate Anaerobic Wastewater Treatment (AnWT-) systems and complementary innovative NBM-processes, the considerable progress made since the seventies in fundamental insights in microbiology, biochemistry and process technology, still numerous challenging improvements in the NBM-field can be realized. This contribution is mainly based on the insights attained from wide ranging literature evaluations and the results of experimental research conducted by numerous PhD students who participated in our group over the last four decades. An attempt is made here to identify major facets on which an improved insight can, and consequently should, be obtained in order to accomplish more optimal operation and design of various types of Anaerobic Degradation (AnDeg-) processes.
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Increasing the performance of anaerobic digestion: Pilot scale experimental study for thermal hydrolysis of mixed sludge
Front.Environ.Sci.Eng.. 2010, 4 (2): 135-141.

Abstract   PDF (319KB)
The performance of a pilot plant operation combining thermal hydrolysis (170°C, 30 min) and anaerobic digestion (AD) was studied, determining the main properties for samples of fresh mixed sludge, hydrolyzed sludge, and digested sludge, in order to quantify the thermal pretreatment performance (disintegration, solubilisation, and dewaterability) and its impact on the anaerobic digestion performance (biodegradability, volatile solids reduction, and digester rheology) and end product characteristics (dewaterability, sanitation, organic and nitrogen content). The disintegration achieved during the thermal treatment enhances the sludge centrifugation, allowing a 70% higher total solids concentration in the feed to anaerobic digestion. The digestion of this sludge generates 40% more biogas in half the time, due to the higher solids removal compared to a conventional digester. The waste generated can be dewatered by centrifugation to 7% dry solids without polymer addition, and is pathogen free.
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Effect of wastewater composition on the calcium carbonate precipitation in upflow anaerobic sludge blanket reactors
Shucheng YANG, Yanling HE, Charles CHOU, Pengxiang ZHANG, Dongqi WANG, Yonghong LIU,
Front.Environ.Sci.Eng.. 2010, 4 (2): 142-149.

Abstract   PDF (526KB)
Calcium carbonate often precipitates in anaerobic reactors treating wastewater with high calcium content. The aim of this paper is to study the effect of wastewater composition on calcium carbonate precipitation in upflow anaerobic sludge blanket (UASB) reactors. Two laboratory-scale UASB reactors were operated with calcium-containing influents using acetate and carbohydrate as substrate, respectively. There was an obvious accumulation of inorganic precipitate observed in the biogranules. Observations via scanning electron microscope (SEM) and energy dispersive spectroscopy (EDS) showed that the acclimated biogranules in the two reactors differed in microstructure. Calcium carbonate was found to have precipitated on the surface of acetate-degrading biogranules, but precipitated at the core of the carbohydrate-degrading biogranules. The results indicated that substrates had significant influence on the location of calcium carbonate precipitation in anaerobic granular sludge, which was expected due to the different methanogens distribution and pH gradient within the granular sludge degrading various substrates. Moreover, the location of calcium carbonate precipitation substantially affected the specific methanogenic activity (SMA) of the granular sludge. The SMA of the acetate-degrading biogranules dropped from 1.96 gCODCH4·gVSS−1·d−1 to 0.61 gCODCH4·gVSS−1·d−1 after 180-d of operation in the reactor. However, the SMA of the carbohydrate-degrading biogranules was not adversely affected by calcium carbonate precipitation.
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Effect of short-term atrazine addition on the performance of an anaerobic/anoxic/oxic process
Changyong WU, Xiaoling LI, Zhiqiang CHEN, Yongzhen PENG,
Front.Environ.Sci.Eng.. 2010, 4 (2): 150-156.

Abstract   PDF (422KB)
In this study, an anaerobic/anoxic/oxic (A2O) wastewater treatment process was implemented to treat domestic wastewater with short-term atrazine addition. The results provided an evaluation on the effects of an accidental pollution on the operation of a wastewater treatment plant (WWTP) in relation to Chemical Oxygen Demand (COD) and biological nutrient removal. Domestic wastewater with atrazine addition in 3 continuous days was treated when steady biological nutrient removal was achieved in the A2O process. The concentrations of atrazine were 15, 10, and 5mg·L−1 on days 1, 2 and 3, respectively. The results showed that atrazine addition did not affect the removal of COD. The specific NH4+ NO3— reduction rate decreased slightly due to the short-term atrazine addition. However, it did not affect the nitrogen removal due to the high nitrification and denitrification capacity of the system. Total nitrogen (TN) removal was steady, and more than 70% was removed during the period studied. The phosphorus removal rate was not affected by the short-term addition of atrazine under the applied experimental conditions. However, more poly-hydroxy-alkanoate (PHA) was generated and utilized during atrazine addition. The results of the oxygen uptake rate (OUR) showed that the respiration of nitrifiers decreased significantly, while the activity of carbon utilizers had no obvious change with the atrazine addition. Atrazine was not removed with the A2O process, even via absorption by the activated sludge in the process of the short-term addition of atrazine.
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Complexation of iron by salicylic acid and its effect on atrazine photodegradation in aqueous solution
Xiaoxia OU, Chong WANG, Fengjie ZHANG, Yan MA, He LIU, Xie QUAN,
Front.Environ.Sci.Eng.. 2010, 4 (2): 157-163.

Abstract   PDF (283KB)
The photodegradation of atrazine and the photochemical formation of Fe(II) and H2O2 in aqueous solutions containing salicylic acid and Fe(III) were studied under simulated sunlight irradiation. Atrazine photolysis followed first-order reaction kinetics, and the rate constant (k) corresponding to the solution of Fe(III)-salicylic acid complex (Fe(III)-SA) was only 0.0153 h−1, roughly one eighth of the k observed in the Fe(III) alone solution (0.115 h−1). Compared with Fe(III) solution, the presence of€ salicylic€ acid€ significantly€ enhanced€ the€ formation€ of Fe(II) but greatly decreased H2O2 generation, and their subsequent product, hydroxyl radical (·OH), was much less, accounting for the low rate of atrazine photodegradation in Fe(III)-SA solution. The interaction of Fe(III) with salicylic acid was analyzed using Fourier-transform infrared (FTIR) spectroscopy and UV-visible absorption, indicating that Fe(III)-salicylic acid complex could be formed by ligand exchange between the hydrogen ions in salicylic acid and Fe(III) ions.
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Preparation of ceria-zirconia solid solution with enhanced oxygen storage capacity and redox performance
Lijing MENG, Licheng LIU, Xuehong ZI, Hongxing DAI, Hong HE, Zhen ZHAO, Xinping WANG,
Front.Environ.Sci.Eng.. 2010, 4 (2): 164-171.

Abstract   PDF (429KB)
A new method called ultrasonic-assisted membrane reaction (UAMR) was reported for the fabrication of ceria-zirconia solid solution. A series of ceria-zirconia solid solutions with different Ce/Zr molar ratios were prepared by the UAMR method and characterized by X-ray diffraction (XRD), N2 adsorption, hydrogen temperature-programmed reduction (H2-TPR), scanning electron microscope (SEM), and transmission electron microscopy (TEM) techniques. The UAMR method proved to be superior, especially when the Ce/Zr molar ratio was lower than 1, in fabricating ceria-zirconia solid solutions with large BET surface area, high oxygen storage capacity (OSC), and low reduction temperature.
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Effects of a dynamic membrane formed with polyethylene glycol on the ultrafiltration of natural organic matter
Boksoon KWON, Noeon PARK, Jaeweon CHO,
Front.Environ.Sci.Eng.. 2010, 4 (2): 172-182.

Abstract   PDF (866KB)
The formation of a dynamic membrane (DM) was investigated using polyethylene glycol (PEG) (molecular weight of 35000 g/mol, concentration of 1 g/L). Two natural organic matters (NOM), Dongbok Lake NOM (DLNOM) and Suwannee River NOM (SRNOM) were used in the ultrafiltration experiments along with PEG. To evaluate the effects of the DM with PEG on ultrafiltration, various transport experiments were conducted, and the analyses of the NOM in the membrane feed and permeate were performed using high performance size exclusion chromatography, and the effective pore size distribution (effective PSD) and effective molecular weight cut off (effective MWCO) were determined. The advantages of DM formed with PEG can be summarized as follows: (1) PEG interferes with NOM transmission through the ultrafiltration membrane pores by increasing the retention coefficient of NOM in UF membranes, and (2) low removal of NOM by the DM is affected by external factors, such as pressure increases during UF membrane filtration, which decreases the effective PSD and effective MWCO of UF membranes. However, a disadvantage of the DM with PEG was severe flux decline; thus, one must be mindful of both the positive and negative influences of the DM when optimizing the UF performance of the membrane.
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Evaluation of groundwater quality in the Xinjiang Plain Area
Jinlong ZHOU, Xinguang DONG, Yiping WANG, Guomin LI, Xiaojing GUO,
Front.Environ.Sci.Eng.. 2010, 4 (2): 183-186.

Abstract   PDF (247KB)
Groundwater is the main source of drinking water for the urban and rural residents in the plain area of the Xinjiang Uygur Autonomous Region, China. The quality of groundwater has a direct relationship with human health. Thus, 386 groundwater samples collected from April to August in 2003 were analyzed. The samples were collected in basic evaluation units which are determined on the basis of watersheds. Total dissolved solids, total hardness, pH value, NH3–N, C6H5OH, Chemiluminescence detection of permanganate index (CODMn) and intestinal germ group were evaluated according to the guidelines of Groundwater Quality Standard (GB/T14848-93). The quality of the groundwater in each evaluation unit was classified by using the One Veto Method (a unified approach stipulated by the Ministry of Water Resources). The results indicate that the groundwater in the mainstream area of the Tarim Basin and the Yerqiang River Sub-basin belongs to Category V; the groundwater in the Wulungu River Sub-basin, the Kaidu-Kongque River Sub-basin, the Kashgar River Sub-basin, the Cherchen River Sub-basin and the Hotan River Sub-basin belongs to Category IV; the groundwater in the Aibi Lake System belongs to Category II, and the groundwater of other evaluation units belongs to Category III. The causes of water quality formation were concisely analyzed. The results can be useful for the evaluation and management of water resources in the Xinjiang Plain Area.
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Ultrasound-assisted emulsification solidified floating organic drop microextraction for the determination of trace amounts of copper in water samples
Qingyun CHANG, Jingwen ZHANG, Xin DU, Jingjun MA, Jingci LI,
Front.Environ.Sci.Eng.. 2010, 4 (2): 187-195.

Abstract   PDF (213KB)
A simple and efficient liquid-phase microextraction (LPME) technique was developed using ultrasound-assisted emulsification solidified floating organic drop microextraction (USAE-SFODME) combined with flame atomic absorption spectrometry, for the extraction and determination of trace copper in water samples. 1-(2-Pyridylazo)-2-naphthol (PAN) was used as chelating agent. Microextraction efficiency factors (including extraction solvent type, extraction volume, time, temperature, and pH), the amount of the chelating agent, and salt effect were investigated and optimized. Under the optimum extraction conditions, figures of merit of the proposed method were evaluated. The calibration graph was linear in the range of 20–600 mg·L−1 with a detection limit of 0.76 mg·L−1. The relative standard deviation (R.S.D) for ten replicate measurements of 20 and 400 mg·L−1 of copper was 3.83% and 2.65%, respectively. Finally, the proposed method was applied to tap water, river water, and sea water, and accuracy was assessed through the analysis of certified reference water or recovery experiments.
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Exposure-response of Cr(III)-organic complexes to Saccharomyces cerevisiae
Nivedita CHATTERJEE, Zejiao LUO,
Front.Environ.Sci.Eng.. 2010, 4 (2): 196-202.

Abstract   PDF (154KB)
Hexavalent chromium [Cr(VI)] bioreduction produces soluble Cr(III)-organic complexes. The Cr(III)-organic complexes are relatively stable once they are formed, and no data about their toxicity were reported. Therefore, this study aims to investigate the bioavailability and toxicity of the soluble Cr(III)-organic complexes. Saccharomyces cerevisiae L-1 wild type yeast strain was chosen as the model organism and Cr(III)-citrate was selected as the representative compound of the Cr(III)-organic complexes. The short-term chronic aquatic toxicity tests of the Cr(III)-citrate was explored by measuring growth inhibition, direct viable cell count, dry biomass, biosorption, and the amount of CO2 production. Cr(III)-citrate exerted a toxicity of 51mg/L with an EC50, which was calculated from the percent growth inhibition. These toxicity data would be helpful to define the toxic potential of the organo-chromium-III compounds in the environment.
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EMERGY analysis for sustainability evaluation of the Baiyangdian wetland ecosystem in China
Weiqing MENG, Cui HAO, Hongyuan LI, Meiting JU,
Front.Environ.Sci.Eng.. 2010, 4 (2): 203-212.

Abstract   PDF (251KB)
This study presents a quantitative and ecological benefit evaluation of the Baiyangdian wetland in China between the years 2000 and 2006. Methods of EMERGY analysis were applied to illustrate the wetland ecosystem, to evaluate the economic and environmental inputs and consequent yields, and to assess the sustainability of the Baiyangdian wetland. The indicators for the integrated ecological and economic system, such as EMERGY yield ratio (EYR) (7.51), EMERGY investment ratio (EIR) (4.52), environmental loading ratio (ELR) (2.92), EMERGY exchange ratio (0.41), and EMERGY sustainable indicator (ESI) (2.57) were calculated, compared, analyzed, and discussed. The non-renewable investment in Baiyangdian was greater than renewable investment, leading to the unsustainable development of the system. High EYR indicated that the Baiyangdian integrated system had created huge profits for its people, while ELR and ESI revealed that human behavior has been a heavy burden on the environment, and countermeasures should be taken by the Chinese government to relieve and resolve these problems. Potential management methods were also proposed in this paper.
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Evaluation of aquatic rehabilitation technologies for polluted urban rivers and the case study of the Foshan Channel
Haifeng JIA, Nan DONG, Hongtao MA,
Front.Environ.Sci.Eng.. 2010, 4 (2): 213-220.

Abstract   PDF (441KB)
An index system for evaluation of technologies for urban river rehabilitation was proposed and discussed. The index system includes indicators of cost, resources, environmental improvement, and social effects. The calculation method for an objective value of each index based on its attributes and weights was presented. The Foshan Channel, which is a seriously polluted, black and malodorous urban river in Foshan City, China, was selected as a case study. The values of the attributes and the weights of the indices for the Foshan Channel were determined. The technologies for the rehabilitation of the Foshan Channel were evaluated based on this index system. Finally, a rehabilitation scheme for the Foshan Channel was proposed.
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Evaluating and structuring indicators for wetland assessment
Xuehua LIU, Yan SUN,
Front.Environ.Sci.Eng.. 2010, 4 (2): 221-227.

Abstract   PDF (323KB)
Wetland assessment has been a popular field of research worldwide. However, various indicators have been used in wetland assessment for different purposes and backgrounds and also because of the research limitations. Therefore, a more comprehensive, sound, and efficient indicator system is needed for researchers’ referencing to evaluate wetlands. After an extensive review of wetland assessment literatures, the reported indicators were evaluated using the developed assessment system, based on the Analytical Hierarchy Process (AHP) with three main goals: nature protection, function utilization, and sustainable development. Each indicator was evaluated using two methods. The first method was to study the percentage of the indicator application, and the second was to assess the weighted ratios assigned to the indicators according to principles of comparability, typicality, sensibility, and availability. The results of these two methods were compared to study the commonalities and specialties of the indicators. They also showed that some indicators were widely used, including biodiversity, weather and climate, hydrological change, and the output of wetland. On the other hand, other sustainable indicators were easily ignored, such as environmental carrying capacity and wetland planning. Furthermore, an indicator system for wetland assessment was structured and strategized to discuss how to choose indicators for wetland assessment under different conditions. The proposed approach can be used to guide the process of wetland assessments in the future.
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Nitrogen-retaining property of compost in an aerobic thermophilic composting reactor for the sanitary disposal of human feces
Fan BAI, Xiaochang WANG,
Front.Environ.Sci.Eng.. 2010, 4 (2): 228-234.

Abstract   PDF (222KB)
Aerobic composting is a method for the sanitary disposal of human feces as is used in bio-toilet systems. As the products of composting can be utilized as a fertilizer, it would be beneficial if the composting conditions could be more precisely controlled for the retention of fecal nitrogen as long as possible in the compost. In this study, batch experiments were conducted using a closed aerobic thermophilic composting reactor with sawdust as the bulk matrix to simulate the condition of a bio-toilet for the sanitary disposal of human feces. Attention was paid to the characteristics of nitrogen transformation. Under the controlled conditions of temperature at 60°C, moisture content at 60%, and a continuous air supply, more than 70% fecal organic removal was obtained, while merely 17% fecal nitrogen loss was observed over a two-week composting period. The nitrogen loss was found to occur mainly in the first 24 h with the rapid depletion of inorganic nitrogen but with an almost unchanged organic nitrogen content. The fecal NH4–N which was the main component of the inorganic nitrogen (>90%) decreased rapidly in the first day, decreased at a slower rate over the following days, and finally disappeared entirely. The depletion of NH4–N was accompanied by the accumulation of NH3 gas in the ammonia absorber connected to the reactor. A mass balance between the exhausted NH3 gas and the fecal NH4–N content in the first 24 hours indicated that the conversion of ammonium into gaseous ammonia was the main reason for nitrogen loss. Thermophilic composting could be considered as a way to keep a high organic nitrogen content in the compost for better utilization as a fertilizer.
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Recycling combustibles from aged municipal solid wastes (MSW) to improve fresh MSW incineration in Shanghai: Investigation of necessity and feasibility
Dezhen CHEN, Zhenzhen GUAN, Guangyu LIU, Tong ZHU, Gongming ZHOU,
Front.Environ.Sci.Eng.. 2010, 4 (2): 235-243.

Abstract   PDF (421KB)
Aged municipal solid wastes (MSW) excavated from landfills and dumpsites were characterized to analyze their fraction composition, moisture content, and lower heat value (LHV). The necessity and feasibility of recycling combustibles from aged MSW to improve the incineration of fresh MSW were investigated. The results showed that combustibles in aged MSW were easily separated from other components and than LHV of the separated combustibles are higher than 11000 kJ/kg. The fresh MSW are of high moisture contents with average LHV below 6500 kJ/kg, making their stable combustion difficult to maintain in MSW incinerators. For both fresh MSW and aged MSW, plastics are the main contributor to their LHV. To improve incineration of fresh MSW that are characterized with low LHV, combustibles separated from aged MSW were made into refuse derived fuel (RDF) pellets and were then added to fresh MSW by 2% wt.– 5% wt. LHV variation and air supply resistance change of the MSW layer on the incinerator grate caused by the addition of RDF was checked, and no significant changes were found. No obvious difference was observed for the ‘burn-out time’ between RDF pellets and fresh MSW either. RDF made from aged MSW combustibles is found to be a promising auxiliary fuel to improve the incineration of fresh MSW, and aged MSW from old landfill cells and dumpsites can be finally disposed of jointly with fresh MSW by recycling combustible from the former to be co-incinerated with the latter in the incineration plants.
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15 articles