Methane production from food waste leachate in laboratory-scale simulated landfill

Due to the prohibition of food waste landfilling in Korea from 2005 and the subsequent ban on the marine disposal of organic sludge, including leachate generated from food waste recycling facilities from 2012, it is urgent to develop an innovative and sustainable disposal strategy that is eco-friendly, yet economically beneficial. In this study, methane production from food waste leachate (FWL) in landfill sites with landfill gas recovery facilities was evaluated in simulated landfill reactors (lysimeters) for a period of 90 d with four different inoculum–substrate ratios (ISRs) on volatile solid (VS) basis. Simultaneous biochemical methane potential batch experiments were also conducted at the same ISRs for 30 d to compare CH₄ yield obtained from lysimeter studies. Under the experimental conditions, a maximum CH₄ yield of 0.272 and 0.294 L/g VS was obtained in the batch and lysimeter studies, respectively, at ISR of 1:1. The biodegradability of FWL in batch and lysimeter experiments at ISR of 1:1 was 64% and 69%, respectively. The calculated data using the modified Gompertz equation for the cumulative CH₄ production showed good agreement with the experimental result obtained from lysimeter study. Based on the results obtained from this study, field-scale pilot test is required to re-evaluate the existing sanitary landfills with efficient leachate collection and gas recovery facilities as engineered bioreactors to treat non-hazardous liquid organic wastes for energy recovery with optimum utilization of facilities.     

Flood Risk Perceptions and Overdevelopment in the Floodplain1

ABSTRACT: There is a long standing hypothesis that overdevelopment has occurred in the nation's floodplains due to imperfect information about the potential flood hazard, an expectation of disaster relief and anticipation of future structural protection. This hypothesis is investigated with multiple regression analysis of data for a case study area. In particular the question of whether floodplain residential property values are fully discounted for expected flood damages is addressed by considering the impact of the National Flood Insurance Program on property values. The extent to which flooding risk perceptions are based on low cost information such as distance from and elevation above the river is also considered. Finally, implications for floodplain management policy are discussed.     

Estrogenic effects of phenolic compounds on glucose-6-phosphate dehydrogenase in MCF-7 cells and uterine glutathione peroxidase in rats

In this study, we tested phenolic compounds such as bisphenol A (BPA), 4-nonylphenol (NP), 4-octylphenol (OP) and 4-propylphenol (PP) by using glucose-6-phosphate dehydrogenase (G6PD) in estrogen sensitive human breast cancer cells (MCF-7 cells) and glutathione peroxidase (GPx) in female immature Sprague-Dawley (SD) rats. This study was designed to investigate whether phenolic compounds have estrogenic effects in these useful screening methods for endocrine disruptors. We chose 6 h as the incubation period for the G6PD assay through a preliminary experiment using 17beta-estradiol (E2). Above the concentration of 1 x 10(-8) M, BPA significantly increased the G6PD activity in a concentration-dependent manner, relative to the control. NP (over the concentration of 1 x 10(-9) M) also enhanced the G6PD activity by about 1.8 times that of the control. OP produced weaker effects on G6PD than NP, and showed a tendency to increase the G6PD activity. PP did not affect the G6PD activity. These results show that BPA and NP have the effect of enhancing G6PD activities in MCF-7 cells. In the in vivo GPx assay, both BPA and E2 significantly increased the uterus wet weights and dramatically enhanced uterine GPx activities in immature female rats in a dose-dependent manner. Treatment with NP (500 mg/kg/day) increased significantly both the uterine GPx activity and the uterus wet weights in immature female rats. OP (500 mg/kg/day) also caused a significant increase in uterine GPx activity, but had no effect on the uterus wet weights. This finding indicates that the change in uterine GPx activities could be a more sensitive parameter than that of uterus wet weights in immature rats. This study implies that phenolic compounds have a weak estrogenic effects.     

No bioavailability of 17α-ethinylestradiol when associated with nC60 aggregates during dietary exposure in adult male zebrafish (Danio rerio)

The C(60) fullerene is a manufactured carbon nanoparticle (CNP) that could pose a risk to humans and other organisms after release into the environment. In surface waters, C(60) is likely to be present as aggregates of nC(60) and these aggregates can associate with other substances that are toxic. Our goal was to evaluate the association of a model contaminant [17α-ethinylestradiol (EE2)] with nC(60) and determine bioavailability of EE2 after accumulation by a filter feeding organism [Brine shrimp (BS) Artemia sp.] and subsequent dietary exposure in zebrafish. Aqueous suspensions of nC(60) were prepared (600 mg C(60)/900 mL, 6-month water stirred method) with/without EE2 (1 μg/L) and BS were exposed to these preparations. Accumulation of nC(60) in gut of BS was assessed by light microscopy, and C(60) were extracted from BS and concentration analyzed by HPLC. Adult male zebrafish were fed (5d) live BS according to the following treatments: BS (control); BS containing nC(60); BS containing nC(60)+EE2; or BS containing EE2. Liver was excised from exposed fish and total RNA was extracted for assessment of vitellogenin gene (vtg1A/B) expression. The vtg1A/B was highly up-regulated in fish exposed to BS containing EE2, but expression of vtg1A/B did not differ from controls in other treatments. The EE2 associated with nC(60) did not become bioavailable in zebrafish during passage through the intestinal tract of zebrafish. Results have implications on the effect of nC(60) on the bioavailability of co-contaminants in organisms during dietary exposure.     

Determination of oxidative metabolism in Collembolan Proisotoma minuta (Tullberg)

An oxidative metabolism of Collembolan Proisotoma minuta was determined with a model compound of aldrin and dieldrin in this paper. The seven-day LD(50) values for aldrin, dieldrin, and piperonyl butoxide in salt solution were 0.496, 0.367, and 8.346 mg L(-1), respectively. When P. minuta were exposed to aldrin, dieldrin was the sole metabolite. The conversion of aldrin to dieldrin was known to be catalyzed by P450 monooxygenases system. It has been shown that the synergist piperonyl butoxide inhibited the metabolism of aldrin in P. minuta.     

The digestibility of waste activated sludges.

Laboratory digestion studies using waste activated sludges (WAS) were conducted to compare the digestion performance between anaerobic and aerobic processes. Nine samples of WAS from seven wastewater treatment plants were collected and batch-digested under both anaerobic and aerobic conditions for 30 days at 25 degrees C. The cation content of wastewater (both floc and solution phases) and solution biopolymer (protein and polysaccharide) was measured before and after digestion and compared with volatile solids destruction data. The study revealed that each digestion process was associated with a distinct biopolymer fraction, which accounted for differences in volatile solids reduction under anaerobic and aerobic conditions. The anaerobic digestion data showed strong correlations between soluble protein generation, ammonium production, percent volatile solids reduction, and floc iron (Fe). These data suggest that the amount of volatile solids destroyed by anaerobic digestion depends on the Fe content of floc. In aerobic digestion, polysaccharide accumulated in solution along with calcium and magnesium. For aerobic digestion, correlations between divalent cation release and the production of inorganic nitrogen were found. This implies that divalent cation-bound biopolymer, thought to be lectin-like protein, was the primary organic fraction degraded under aerobic conditions. The results of the study show that the cation content in wastewater is an important indicator of the material that will digest under anaerobic or aerobic conditions and that some of the volatile solids will digest only under either anaerobic or aerobic conditions.     

Distribution and pollution sources of polycyclic aromatic hydrocarbons (PAHs) in reclaimed tidelands and tidelands of the western sea coast of South Korea

The wide-scale reclamation of tidal flats distributed throughout the western and southern coastal areas in Korea has been completed, in an effort to expand the available arable land. The present studies were conducted in order to characterize the concentrations and compositional patterns of selected PAHs, in order to obtain more information regarding environmental risk assessments for sustainable and environment-friendly agriculture in reclaimed tidelands and tidelands in South Korea. The PAH contents were low to moderate, relative to other urbanized regions of the world. Sigma PAHs ranged from 69.8 to 1,175.2 ng g(-1) in dry weight, with a mean value of 394.4 ng g(-1). Differences were observed in the Sigma PAHs concentrations between industrial complex areas and rural regions. The two dominant PAHs were identified as fluoranthene and pyrene. These compounds constituted 1.4 to 55.0% (mean, 33.4%) and 2.7 to 45.6% (mean, 22.0%) of the Sigma PAHs. Our correlation analysis revealed that the Sigma PAHs contents were associated significantly with the organic carbon content (R(2) = 0.86, P < 0.01) and the cation exchange capacity (CEC; R(2) = 0.89, P < 0.01) in the reclaimed tidelands and tidelands.     

Simultaneous sorption of lead and chlorobenzene by organobentonite

Clays or organoclays have been used as a barrier to prevent the transport of hazardous contaminants in landfills. However, clays are known to effectively sorb mostly inorganic contaminants, while organoclays are mainly used for organic contaminants. Since the organoclays are basically clay particles modified with cationic surfactants, there might exist an optimal coverage of cationic surfactant on the clay particles to sorb both inorganic and organic contaminants. In order to determine the optimal mass of cationic surfactants on the bentonites, sodium bentonites were treated with various ratios of hexadecyltrimethylammonium (HDTMA) to bentonites. Chlorobenzene and lead were selected as representative contaminants. When either chlorobenzene or lead exists as a single contaminant, chlorobenzene sorption increased with increasing HDTMA to bentonite ratios, and lead sorption decreased with increasing HDTMA to bentonite ratios. Sorption of chlorobenzene was a function of HDTMA coverage on the bentonites, while lead sorption was much more influenced by the initial lead concentration rather than the mass of HDTMA added to the bentonites.     

Detrital control on the release of dissolved organic nitrogen (DON) and dissolved inorganic nitrogen (DIN) from the forest floor under chronic N deposition

The role of detrital quantity and quality in forest floor N leaching was investigated in a litter manipulation experiment at a deciduous forest under chronic N deposition. Dissolved inorganic nitrogen (DIN) comprised the bulk of nitrogen leaching from the control except a short period following autumn litterfall. The dominance of DIN was strengthened by litter exclusion, whereas the addition of glucose or fresh litter led to a small increase in dissolved organic nitrogen (DON) and either a temporary or gradual reduction in NO(3)(-) release, respectively. Changes in soluble organic C and microbial C in the forest floor implied that increased availability of C sources might have enhanced microbial immobilization of DIN, either temporarily following glucose application or over the longer term following litter addition. The results suggest that detrital quantity and quality can play a crucial role in determining the balance between DIN and DON in N-enriched forest soils.