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At least 505 records · Page 28Linked to original sources
PubMed2003

[Evaluation of Fenton process for the treatment of sanitary landfill leachate with Response Surface Methodology].

Response Surface Methodology (RSM) was employed to investigate the effect of TOC ratio of high molecular weight organic matter (HMWOM) to low molecular weight organic matter (LMWOM), the LMWOM concentration and hydrogen peroxide to ferrous ion molar ratio on COD removal during the treatment of sanitary landfill leachate with Fenton reagents. The high and low levels of HMWOM/LMWOM, the LMWOM concentration and H2O2/Fe2+ were from 14 to 38, 975 to 3000 mg/L, and 1.75 to 4.00 respectively. Using the software of Design--Expert 5, a response surface quadratic model in terms of actual factors was obtained based on the experimental data, and COD removal contour plots were derived from the model accordingly. It showed that COD removal increased with the increase of HMWOM to LMWOM ratio, but decreased with increasing LMWOM concentration. There existed an optimal hydrogen peroxide to ferrous ion molar ratio so that the highest COD removal efficiency could be achieved.

Environmental Pollution↗
PubMed2003

[A study on ANAMMOX A2/O process for ammonium-rich leachates].

The ANAMMOX reaction could be realized by recycling the aerobic effluent to the anaerobic fluidized bed. A TN removal rate of 32% could be reached in ANAMMOX A2/O process for the ammonium-rich leachate. It is increased by 15%-20% compared to the A2/O process without ANAMMOX. NO2(-)-N concentration and NO2(-)-N/NOx(-)-N ratio in the aerobic effluent are decreased significantly. The effluent quality is improved. The ANAMMOX reaction has a total reaction order of 3, and the reaction orders for NH4(+)-N, NO2(-)-N and NO3(-)-N are 1. The reaction constant is -3.43E-5 L2.(mmol2.h)-1.

Anaerobiosis↗
PubMed2004

Sequenced anaerobic-aerobic treatment of high strength, strong nitrogenous landfill leachates.

As a first step in treatment of high strength, strong nitrogenous landfill leachates (total COD--9.66-20.56 g/l, total nitrogen 780-1,080 mg/l), the performance of laboratory UASB reactors has been investigated under sub-mesophilic (19+/-3 degrees C) and psychrophilic (10+/-2 degrees C) conditions. Under hydraulic retention time (HRT) of around 1.2 days, when the average organic loading rate (OLR) was around 8.5 g COD/l/day, the total COD removal accounted for 71% (on average) for sub-mesophilic regime. The psychrophilic treatment conducted under the average HRT of 2.44 days and the average OLR of 4.2 g COD/l/day showed an average total COD removal of 58% giving effluents more suitable for subsequent biological nitrogen removal. Both anaerobic regimes were quite efficient for elimination of heavy metals by concomitant precipitation in the form of insoluble sulphides inside the sludge. The subsequent submesophilic aerobic-anoxic treatment of submesophilic anaerobic effluents led to only 75% of total inorganic N removal due to COD deficiency for denitrification created by too efficient anaerobic step. On the contrary, psychrophilic anaerobic effluents (richer in COD compared to the submesophilic ones) were more suitable for subsequent aerobic-anoxic treatment giving the total N removal of 95 and 92% at 19 and 10 degrees C, respectively.

Bacteria, Aerobic↗
PubMed2004

Treatment of leachate from the anaerobic fermentation of solid wastes using two biofilm support media.

Biofilms growing on different carrier media have a different response to the nutrients contained in wastewater. Biofilms have proven to be an alternative to the treatment of wastewater containing higher concentrations of contaminants. The main objective of this research was to compare two biofilm support media for the treatment of leachate from the anaerobic fermentation of solid wastes. The removal of organic matter and ammonia was achieved in two fixed bed biofilm reactors containing Kaldnes and Linpor support materials with specific surface areas of 490 and 270 m2/m3, respectively, and operating under the sequencing batch procedure during 204 days. The Linpor reactor achieved higher total COD removal than the Kaldnes reactor (47% and 39%, respectively). Linpor was shown to be less sensitive to influent COD changes than Kaldnes. The effluent total COD values of Kaldnes were higher than Linpor. The dissolved COD removal was 21% for both reactors. The average ammonia removal for Linpor was 72% and 42% for Kaldnes. The matrix of Linpor allows higher concentrations of microorganisms (as dry mass) than Kaldnes. The dry mass concentration was related to the "active" exposed surface area of the biofilm. This is considered to be the cause for the better performance of Linpor when compared with Kaldnes.

Ammonia↗
PubMed2004

Treatment of landfill leachate by a pilot-scale modified Ludzack-Ettinger and sulfur-utilizing denitrification process.

Nitrogen removal efficiency of a pilot-scale system consisted of Modified Ludzack-Ettinger (MLE) followed by sulfur-utilizing denitrification (SUDNR) process was evaluated with a landfill leachate. For SUDNR, a down-flow mode sulfur packed bed reactor (SPBR) filled with sulfur and limestone particles was used. Although total nitrogen removal efficiency of the MLE process was about 80% at the recycle ratio of 4, effluent contained 350-450 mg/L NO(3-)-N. Up to a loading rate of 1.2 kg NO(3-)-N/m3-day, the SPBR could achieve complete removal of nitrate, and nitrate removal rate was kept to that level even at higher loading rate. When a COD/N ratio of MLE process was maintained at 2 instead of 4, more organics with molecular weight less than 500 were utilized for heterotrophic denitrification although denitrification was not complete with the lack of electron donors. Clogging in the SPBR, mainly by the accumulation of nitrogen gas in the pores, could easily be removed by introducing the effluent in an upward direction for 1 min at 1 hr intervals. The proposed treatment system could achieve nitrate free effluent with a slight increase in chemical cost. Furthermore, depending on further COD removal requirement after biological treatment, the proposed treatment system can be an economical solution.

Bioreactors↗
PubMed2005

Landfill leachate treatment by an experimental subsurface flow constructed wetland in tropical climate countries.

Municipal leachate was treated in an experimental unit of constructed wetlands of subsurface flow type. The parameters studied were organics (BOD and COD), solids and heavy metals (Zn, Ni, Cu, Cr and Pb). Using two types of emergent plants of Scirpus globulosus and Eriocaulon sexangulare, more than 80% removal was achieved for all the parameters. E. sexangulare removed organics and heavy metals better than Scirpus globulosus. A higher concentration of heavy metals in the influent did not change the removal efficiency.

Cyperaceae↗
PubMed2006

[Study on redox zones of landfill leachate plume in subsurface environment].

A soil column filled with sandy soil was constructed to investigate biogeochemical process of leachate pollutants degradation and redox zones in subsurface environment, and variation of Fe3+, Fe2+, oxidation capacity (OXC) and reduction capacity (RDC) of fresh and contaminated soil were analyzed. Experimental results indicated that four sequent redox zones are appear in pollution plume, and different terminal electron acceptors (they are CO2, Fe3+, NO3- and O2) were used by microbes in different zones; Zones can be named methanogenic zone, iron reduction zone, nitrate reduction zone and oxygen reduction zone correspondingly; the indicator of the different zone is HCO3-, Fe2+, NO2- and DO, and its highest concentration is 10,353 mg/L, 13.61 mg/L, 0.097 mg/L and 5.8 mg/L respectively. OXC of the soil is increased sequentially, its lowest value is 14.18 micromol/g in methanogenic zone and highest value is 24.45 micromol/g in oxygen reduction zone; RDC of the soil is reduced sequentially, its highest value is 14.18 micromol/g in methanogenic zone and lowest value is 24.45 micromol/g in oxygen reduction zone. With the more serious contamination, Fe3+ minerals of the soil are reduced by biogeochemical process, and dissolved Fe2+ is produced. Some of the Fe2+ is released to water and the other is precipitated as sediments. Therefore, it is significant for the in situ remediation and risk assessment of the landfill contaminated site to investigate of the redox zones.

Environmental Monitoring↗
PubMedDate not supplied

Cancer incidence following exposure to drinking water with asbestos leachate.

In November 1985, the New York State Department of Health was altered to extraordinary concentrations of asbestos leachate in the drinking water in the Town of Woodstock. Concentrations of 3.2 million fibers per liter (MFL) to 304.5 MFL were found, depending on location. An investigation of cancer incidence in the area was conducted for the period 1973-83 using the State Cancer Registry to compute standardized incidence ratios. No evidence was found of elevated cancer incidence at sites associated with asbestos exposure. A statistically non-significant excess of kidney cancer was seen among men, but not women. Colon cancer among men was significantly low, but incidence among women was similar to that expected. Lung cancer incidence was lower than expected for both sexes. Ovarian cancer rates were not different from expected rates. At sites not previously related to asbestos exposure, cancer of the oral cavity was significantly high, with most affected persons having a history of cigarette smoking. Surveillance of the community is continuing because of an insufficient latent period for some exposed groups.

Asbestos↗
PubMed1991

Toxicity to estuarine organisms of leachates from chromated copper arsenate treated wood.

The effects of chromated copper arsenate (CCA), used for treating wood in docks, pilings, and bulkheads, were studied in several estuarine organisms. Leaching of metals from treated wood into sea water was assayed by atomic absorption spectrophotometry. Fiddler crabs (Uca pugilator) were subjected to limb removal and were placed in containers with treated wood of various sizes or control wood. Limb regeneration rate was retarded in a dose-dependent fashion and mortality occurred with the treated wood, reaching 100% in the tank with the largest piece of wood. Embryos of the mummichog (Fundulus heteroclitus) were allowed to develop in culture dishes in which CCA-treated or untreated wood was soaking. Mortality was noted in the dishes with treated wood and to a smaller extent in those with untreated wood. Containers containing CCA-treated wood, control wood, or no wood were stocked first with the alga Ulva lactuca, the snails (Nassarius obsoletus). Chlorophyll content of the algae was reduced with the treated wood within a few days, and snails with the treated wood became moribund and died within a few days. In the controls containing untreated wood or no wood, no such effects were seen. Studies with individual or combination of two or three of the metals with snails and algae indicated that the copper was primarily responsible for the snail mortality and algal bleaching seen in the treated wood experiments. In all experiments, the toxicity of the wood decreased over time; when the experiments were repeated with the same pieces of wood, effects were diminished.

Animals↗