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PubMed2000

Comparison of the spatial homogeneity of physico-chemical parameters and bacterial 16S rRNA genes in sediment samples from a dumping site for dredging sludge.

The homogeneity of the microbial community structure of a sediment landfill was examined by a culture-independent method and compared with physico-chemical parameters, i.e. organic matter, CaCO3 content, pH, and texture. Total genomic DNA was extracted from samples derived from different places and depths. After amplification with two different primer sets of partial bacterial 16S rRNA genes, the products were separated by denaturing gradient gel electrophoresis (DGGE). The DGGE fingerprints of different sediment samples taken in regular patterns at the same depth were similar, which indicates a spatial homogeneity in the numerically dominant bacterial populations in a landfill over 10,000 m2 in size. In a vertical column of approx. 10 m, only some differences in a few bands of the bacterial community structure were observed between samples taken from different depths. This DNA homogeneity coincided with a similar homogeneity of the physico-chemical parameters in the landfill at this site. Nevertheless, the DGGE technique revealed small differences in less prominent bacteria and was capable of separating the upper and lower samples of one column into two clusters. It therefore seems more sensitive than the physico-chemical approach for characterising the homogeneity of an environmental habitat.

Belgium↗

PubMed1998

Treatment of cyanide-containing wastewater from the food industry in a laboratory-scale fixed-bed methanogenic reactor.

During the process of producing cassava starch from Manihot esculenta roots, large amounts of cyanoglycosides were released, which rapidly decayed to CN- following enzymatic hydrolysis. Depending on the varying cyanoglycoside content of the cassava varieties, the cyanide concentration in the wastewater was as high as 200 mg/l. To simulate anaerobic stabilization, a wastewater with a chemical oxygen demand (COD) of about 20 g/l was prepared from cassava roots and was fermented in a fixed-bed methanogenic reactor. The start-up phase for a 99% degradation of low concentrations of cyanide (10 mg/l) required about 6 months. After establishment of the biofilm, a cyanide concentration of up to 150 mg CN-/l in the fresh wastewater was degraded during anaerobic treatment at a hydraulic retention time of 3 days. All nitrogen from the degraded cyanide was converted to organic nitrogen by the biomass of the effluent. The cyanide-degrading biocoenosis of the anaerobic reactor could tolerate shock concentrations of cyanide up to 240 mg CN-/l for a short time. Up to 5 mmol/l NH4Cl (i.e. 70 mg N/l = 265 mg NH4Cl/l) in the fresh wastewater did not affect cyanide degradation. The bleaching agent sulphite, however, had a negative effect on COD and cyanide removal. For anaerobic treatment, the maximum COD space loading was 12 g l-1 day-1, equivalent to a hydraulic retention time of 1.8 days. The COD removal efficiency was around 90%. The maximum permanent cyanide space loading was 50 mg CN- l-1 day-1, with tolerable shock loadings up to 75 mg CN- l-1 day-1. Under steady-state conditions, the cyanide concentration of the effluent was lower than 0.5 mg/l.

Ammonia↗

PubMed1998

Degradation of cyanide in agroindustrial or industrial wastewater in an acidification reactor or in a single-step methane reactor by bacteria enriched from soil and peels of cassava.

During cassava starch production, large amounts of cyanoglycosides were released and hydrolysed by plant-borne enzymes, leading to cyanide concentrations in the wastewater as high as 200 mg/l. For anaerobic degradation of the cyanide during pre-acidification or single-step methane fermentation, anaerobic cultures were enriched from soil residues of cassava roots and sewage sludge. In a pre-acidification reactor this culture was able to remove up to 4 g potassium cyanide/l of wastewater at a hydraulic retention time (tHR) of 4 days, equivalent to a maximal cyanide space loading of 400 mg CN- 1(-1) day-1. The residual cyanide concentration was 0.2-0.5 mg/l. Concentrated cell suspensions of the mixed culture formed ammonia and formate in almost equimolar amounts from cyanide. Little formamide was generated by chemical decay. A concentration of up to 100 mmol ammonia/l had no inhibitory effect on cyanide degradation. The optimal pH for cyanide degradation was 6-7.5, the optimal temperature 25-37 degrees C. At a pH of 5 or lower, cyanide accumulated in the reactor and pre-acidification failed. The minimal tHR for continuous cyanide removal was 1.5 days. The enriched mixed culture was also able to degrade cyanide in purely mineralic wastewater from metal deburring, either in a pre-acidification reactor with a two-step process or in a one-step methanogenic reactor. It was necessary to supplement the wastewater with a carbon source (e.g. starch) to keep the population active enough to cope with any possible inhibiting effect of cyanide.

Aerobiosis↗

PubMed1999

Aerobic 4-nitrophenol degradation by microorganisms fixed in a continuously working aerated solid-bed reactor.

Studies of microbial purification of a model waste water containing 4-nitrophenol were carried out in a continuously working aerobic solid-bed reactor. The main emphasis was on the dynamic behaviour of the system after a sudden change in cultivation conditions and on the steady state performance of the reactor as a function of the pollution load. A change from ammonium-free to ammonium-containing medium hardly influenced the nitrophenol degradation. The reactor responded differently to an increase in pollutant load, which was brought about by increasing either the 4-nitrophenol content or the flow of the waste water. Up to a load of 270 mg l-1 h-1 the pollutant was stably and almost completely degraded. At a higher load, only a partial 4-nitrophenol degradation took place. A mathematical model was derived to describe the processes that occurred in the reactor. By segregation into two compartments--the aqueous phase and the biofilm--account was taken of the fact that the pollutant is carried into the biofilm by diffusion and is degraded there. The observed relations between the pollutant load, the pollutant concentration in the outlet of the reactor and the reactor performance agreed with the simulated process behaviour. As the model simulation showed, the incomplete pollutant degradation at a higher reactor load was caused by oxygen limitation.

Aerobiosis↗

PubMed2001

Investigations into the application of a process for the determination of microbial activity in biofilms.

The formation of biofilms in a waste paper medium was studied in a pilot plant by analysing the redox potential in the biofilm. Miniaturised redox electrodes were applied at the reactor wall/biofilm phase boundary. With this measurement set-up, it was possible to demonstrate the effectiveness of biocides and thus to avoid under- and over-doses with these agents. The redox signals measured were correlated with reference methods, such as colony-forming units and dehydrogenase activity.

Bacteria↗

PubMed2002

Acid-base enrichment enhances anaerobic hydrogen production process.

This study offers a novel and quick enrichment technology that can be used as a preliminary method to obtain a hydrogen-producing species from the biological sludge produced by wastewater treatment. The influences of acid-base enrichment (by sludge pH adjustment) on the anaerobic hydrogen-producing micro-organisms were investigated using serum bottle assays. The enrichment pH values were controlled at 3, 4, 5, 7, 10, 11 and 12 with 1 N hydrochloric acid and 1 N sodium hydroxide. For each enrichment pH, the cultivation pH values were controlled at 5, 6 and 7. Based on the experimental results, hydrogen accumulation from sludge with acid or base enrichment is higher than that of the control. The hydrogen-production potential of the sludge with acid or base enrichment is 200 and 333 times enhanced, compared with the control, when the enrichment pH is 10 and 3, respectively. The enhancement is due to a shortening of the micro-organisms' lag-time which occurs at a proper cultivation-pH level.

Anaerobiosis↗

PubMed2001

Analysis of the microbial communities on corroded concrete sewer pipes--a case study.

Conventional as well as molecular techniques have been used to determine the microbial communities present on the concrete walls of sewer pipes. The genetic fingerprint of the microbiota on corroded concrete sewer pipes was obtained by means of denaturing gradient gel electrophoresis (DGGE) of 16S rRNA gene fragments. The DGGE profiles of the bacterial communities present on the concrete surface changed as observed by shifts occurring at the level of the dominance of bands from non-corroded places to the most severely corroded places. By means of statistical tools, it was possible to distinguish two different groups, corresponding to the microbial communities on corroded and non-corroded surfaces, respectively. Characterization of the microbial communities indicated that the sequences of typical bands showed the highest level of identity to sequences from the bacterial strains Thiobacillus thiooxidans, Acidithiobacillus sp., Mycobacterium sp. and different heterotrophs belonging to the alpha-, beta- and gamma-Proteobacteria, Acidobacteria and Actinobacteria. In addition, the presence of N-acyl-homoserine lactone signal molecules was shown by two bio-assays of the biofilm on the concrete under the water level and at the most severely corroded places on the concrete surface of the sewer pipe.

Bacteria↗

PubMed2006

Two measured parameters correlated to participation rates in curbside recycling schemes in the UK.

Local authorities in the United Kingdom are currently changing their approach towards recycling as they attempt to meet legislative targets. An important part of this drive is the provision of an effective curbside recycling service and it is vital to understand the parameters that influence the performance of the system offered. In this article, three primary datasets, collected from over 1400 households each, are examined for parameters correlated to participation rates. Two measured parameters were found that are not commonly identified in previous studies of curbside recycling schemes, and they are shown to merit further investigation as useful tools for planning purposes. One is the number of types of material collected; participation rates are greater for schemes collecting more materials. The second is the number of households situated on the same road; the lower the number, the higher the participation rate. In both cases, evidence of the measured correlation is presented, justifying their usefulness for planning. The multiple underlying factors causing the correlations are not identified here, but suggestions are made for further studies.

Conservation of Natural Resources↗

PubMed2005

Science, policy, and stakeholders: developing a consensus science plan for Amchitka Island, Aleutians, Alaska.

With the ending of the Cold War, the US Department of Energy is responsible for the remediation of radioactive waste and disposal of land no longer needed for nuclear material production or related national security missions. The task of characterizing the hazards and risks from radionuclides is necessary for assuring the protection of health of humans and the environment. This is a particularly daunting task for those sites that had underground testing of nuclear weapons, where the radioactive contamination is currently inaccessible. Herein we report on the development of a Science Plan to characterize the physical and biological marine environment around Amchitka Island in the Aleutian chain of Alaska, where three underground nuclear tests were conducted (1965-1971). Information on the ecology, geology, and current radionuclide levels in biota, water, and sediment is necessary for evaluating possible current contamination and to serve as a baseline for developing a plan to ensure human and ecosystem health in perpetuity. Other information required includes identifying the location of the salt water/fresh water interface where migration to the ocean might occur in the future and determining groundwater recharge balances, as well as assessing other physical/geological features of Amchitka near the test sites. The Science Plan is needed to address the confusing and conflicting information available to the public about radionuclide risks from underground nuclear blasts in the late 1960s and early 1970s, as well as the potential for volcanic or seismic activity to disrupt shot cavities or accelerate migration of radionuclides into the sea. Developing a Science Plan involved agreement among regulators and other stakeholders, assignment of the task to the Consortium for Risk Evaluation with Stakeholder Participation, and development of a consensus Science Plan that dealt with contentious scientific issues. Involvement of the regulators (State of Alaska), resource trustees (U S Fish and Wildlife Service), representatives of the Aleut and Pribilof Island communities, and other stakeholders was essential for plan development and approval, although this created tensions because of the different objectives of each group. The complicated process of developing a Science Plan involved iterations and interactions with multiple agencies and organizations, scientists in several disciplines, regulators, and the participation of Aleut people in their home communities, as well as the general public. The importance of including all parties in all phases of the development of the Science Plan was critical to its acceptance by a broad range of regulators, agencies, resource trustees, Aleutian/Pribilof communities, and other stakeholders.

Alaska↗

PubMed2001

Evolving policies to regulate pollution from animal feeding operations.

Due to concentrations of animals at large facilities, animal feeding operations (AFOs) have emerged as a major potential source of water pollution. The federal government regulates concentrated animal feeding operations under its point-source pollution permitting regulations. A major determinant of whether an operation must apply for a permit is the number of animals at an individual lot or facility. This paper examines federal mandatory controls and voluntary guidelines that seek to reduce contaminant pollution from AFOs. Land treatment practices are delineated due to their importance in reducing the injurious by-products of agricultural production. An evaluation of proposed revisions to federal regulations on confined animal feeding operations suggests they diverge from their goal of controlling water pollution. Federal regulations focus on the size of operation and amount of manure governed by the permitting process to the exclusion of other criteria related to the impairment of water quality. Given the uncertainties about the amount of pollution from AFOs, lack of enforcement of existing regulations, localization of problems, and possible alternatives for addressing the pollution, more demanding federal regulations may not form an appropriate response.

Animal Feed↗

PubMed1996

Nuclear waste repositories in salt mines: a new approach to safety assessment.

The long-term safety of radioactive waste repositories in rock-salt mines in the deep underground benefits significantly from the barrier effect of overlying rocks. The concentrations of radioactive substances released from the repository and migrating in the aquifer up to the biosphere are greatly reduced during passage through these rocks. In former safety analyses of waste repositories this transport has generally been modelled as a combination of the involved phenomena, e.g. convection, dispersion, adsorption, etc. The data required for a numerical evaluation of the overall effect are obtained either as (conservative) estimates based on experience or are empirical, based mainly on laboratory experiments. The approach presented here is much simpler and entirely empirical, and therefore more transparent. It makes use of the fact that the groundwater in the overlying rocks always contains dissolved salt from the salt formation and carries it continuously into the receiving channels or the drainage system. The relation between the total amount of dissolved solids present in a certain subsurface catchment area and their steady-state concentration in the receiving channels is assumed to be equivalent to the relation between the given amount of radionuclides released from the repository and their concentration in the receiving channels, the latter leading to a certain radiation exposure of the population. Two versions of this approach are discussed: version (a) assumes a continuous stream of radionuclides released from the repository, and version (b) assumes a pulse release of radionuclides from the repository. A simple calculation using data from the Gorleben exploration leads to the inequality [equation: see text] where Cmax is the maximum radionuclide concentration (with respect to time) in the receiving channels and W (Bq) is the amount of radionuclides released from the respository in a very short time. Cmax obtained from (1), is supposed to be an upper limit of the radionuclide concentration in the receiving channel and, therefore, a conservative estimate. In some catchment areas the salt concentration in a small region near the surface is higher by a factor of < 2 to 3 than the concentration in the receiving channel. In order to be conservative, this empirical factor may be used to calculate the concentration of radioactive substances. Surprisingly, the values of radiation exposure resulting from both versions of the new approach are far below those calculated by applying elaborated models of the transport processes. The respective factors are 10-100 in case (a) and as much as 1000 in case (b). The reasons for these significant differences are discussed.

Radioactive Waste↗

PubMed2002

Biological monitoring of metals and organic substances in hazardous-waste incineration workers.

OBJECTIVES: To determine blood and urine concentrations of a number of metals and organic substances in workers at a hazardous-waste incinerator (HWI) 1 year after regular operations in the facility, and to compare these concentrations with the baseline levels. METHODS: The employees were divided into three groups according to their workplaces. Plasma analyses of hexachlorobenzene (HCB), polychlorinated biphenyls (PCBs 28, 52, 101, 138, 153 and 180) and polychlorinated dibenzo- p-dioxins and dibenzofurans (PCDD/Fs), and urinary analyses of 2,4- and 2,5-dichlorophenol (DCP), 2,4,5- and 2,4,6-trichlorophenol (TCP), pentachlorophenol (PCP) and 1-hydroxypyrene (1-HP) were carried out. The blood concentrations of beryllium, manganese, mercury and lead, and the urine levels of cadmium, chromium, nickel and vanadium were also determined. RESULTS: The current plasma HCB, PCB and PCDD/F levels, and the urine levels of chlorophenols (CLPs) and 1-HP did not show significant differences between workplace groups or the baseline concentrations. Moreover, no significant differences between metal levels could be observed. DISCUSSION AND CONCLUSION: The lack of differences between the current levels of metals and organic substances and the respective baseline concentrations, together with the absence of differences depending on the workplace indicate that the potential exposure of HWI workers to the analyzed compounds was insignificant. According to these results, 1 year of potential exposure to the above metals and organic substances would not mean any specific health problem for the workers at the HWI.

Adult↗

PubMed2003

Morbidity among municipal waste incinerator workers: a cross-sectional study.

OBJECTIVES: In order that the occupational exposures and health risks for municipal waste incinerator operators be better determined, a study was carried out in three centres. METHODS: A transversal study was carried out for 102 male incinerator workers matched for age with 94 male workers from other industrial activities. Three groups of exposed workers were considered (group 1: "crane operators" and "equipment operators"; group 2: "furnace " workers; group 3: "maintenance" and "effluent-treatment" workers). Data were collected through a questionnaire and medical examination. The respiratory function was explored and blood samples were taken for biological analysis. Statistical analysis using chi(2) or Student's test, and calculation of odds-ratio (OR) using logistic regression analysis were performed. RESULTS: There were no significant differences in general symptoms between the two groups. Skin symptoms (OR =4.85; 2.04-11.51 for the "maintenance and effluent" workers) were more often observed in the exposed group. An excess of respiratory problems was also encountered: daily coughing ["maintenance and effluent" groups (OR =2.55; 0.84-7.75); "furnace men" (OR =6.58; 2.18-19.85)]. A significant relationship between exposure and the decrease of several pulmonary parameters was observed. The liver and haematological tests were well within the normal range; nevertheless, a slight but significant increase in the white blood cells was observed in the exposed group. Higher blood lead levels were found for exposed workers. CONCLUSION: There were few adverse health effects in our morbidity study but skin irritation and cough were more frequent in the exposed workers. A slight decrease in pulmonary function was observed. These findings are in agreement with those of several other studies.

Accidents, Occupational↗

PubMed1997

Chemical degradation of wastes of antineoplastic agents: cyclophosphamide, ifosfamide and melphalan.

Handling genotoxic compounds commonly used in cancer chemotherapy generates contaminated wastes that require decontamination before disposal. Chemical methods are an alternative and/or a complement to incineration for the treatment of wastes and spills. As part of a program initiated by the International Agency for Research on Cancer (IARC), three chemical methods readily available in the hospital environment, viz sodium hypochlorite (NaOCl, 5.25%), hydrogen peroxide (H2O2, < or = 30%) and Fenton reagent (FeCl2, 2H2O; 0.3 g in 10 ml H2O2, 30%), were tested for the degradation of three alkylating agents (cyclophosphamide, CP; ifosfamide, IF, and melphalan). Pharmaceutical preparations corresponding to the most highly concentrated administration solutions in either NaCl (0.9%) or dextrose (5%) were inactivated by oxidation volume/volume with each of the methods for at least 1 h. The efficiency of degradation was monitored by high-pressure liquid chromatography. The mutagenicity of the degradation residues was tested by means of the Ames test using tester strains of Salmonella typhimurium TA 97a, TA 98, TA 100 and TA 102 with and without an exogenous metabolic activation system. Complete disappearance of CP was observed after 1 h with all degradation methods. However, direct mutagens were generated by the Fenton oxidation technique in the presence of dextrose (5%). IF was completely degraded by the Fenton reagent and NaOCl methods. No mutagenic residues were detected after 1 h of treatment with the Fenton technique, and after 3 h with the NaOCl method. Direct-acting mutagens remained after the H2O2 treatment in the presence of dextrose (5%). Complete degradation of melphalan was achieved in 1 h by each of the three methods, and no mutagenic residues were produced by any of the treatments. The use of NaOCl (5.25%) proved the most efficient system for degradation of the three alkylating agents.

Animals↗

PubMed2006

Kinetics of nitrogen removal from sanitary landfill leachate.

Leachates from municipal landfill 'Lublinek' in Lodz city (Poland) were treated in two-sludge sequence batch reactor systems (type ND). The external carbon source--sodium acetate was used in denitrification. Two versions were tested--with and without supernatant recirculation from D-SBR to N-SBR. The 99% removal of inorganic nitrogen compounds was achieved in both versions. Due to recirculation, the buffering (by means of sodium bicarbonate) was not necessary. Kinetic models for nitrification and denitrification processes were proposed. Kinetic parameters of the models were estimated by the optimization method. The experimental results of both nitrification steps (oxidation of ammonia to nitrites and nitrites to nitrates) were best fitted with the interactive limitation model of nitrogen compounds and oxygen. The denitrification process was limited only by the concentration of nitrogen compounds.

Bioreactors↗

PubMed2005

Biological deinking of inkjet-printed paper using Vibrio alginolyticus and its enzymes.

Recycling of office waste paper (photocopy, inkjet, and laser prints) is a major problem due to difficulty in removal of nonimpact ink. Biological deinking of office waste paper is reported using several microorganisms and their enzymes. We report here deinking and decolorization of the dislodged ink particles from inkjet printed paper pulp by a marine bacterium, Vibrio alginolyticus isolate no. NIO/DI/32, obtained from marine sediments. Decolorization of this pulp was achieved within 72 h by growing the bacterium in the pulp of 3-6% consistency suspended in seawater. Immobilized bacterial cells in sodium alginate beads were also able to decolorize this pulp within 72 h. The cell-free culture supernatant of the bacterium grown in nutrient broth was not effective in deinking. However, when the culture was grown in nutrient broth supplemented with starch or Tween 80, the cell-free culture supernatant could effectively deink and decolorize inkjet-printed paper pulp within 72 h at 30 degrees C. The culture supernatant of V. alginolyticus grown in the presence of starch or Tween 80 showed 49 U ml(-1) and 33 U ml(-1) amylase and lipase activities, respectively. Dialysis of these culture supernatants through 10 kDa cut-off membrane resulted in a 35-40% reduction in their efficiency in decolorizing the pulp. It appears that amylase and lipase effectively help in dislodging the ink particles from the inkjet printed-paper pulp. We hypothesize that the bacterium might be inducing the formation of low molecular weight free radicals in the culture medium, which might be responsible for decolorization of the pulp.

Amylases↗

PubMed2005

Monitoring of microbial souring in chemically treated, produced-water biofilm systems using molecular techniques.

The identification of bacteria in oil production facilities has previously been based on culture techniques. However, cultivation of bacteria from these often-extreme environments can lead to errors in identifying the microbial community members. In this study, molecular techniques including fluorescence in situ hybridization, PCR, denaturing gradient gel electrophoresis, and sequencing were used to track changes in bacterial biofilm populations treated with nitrate, nitrite, or nitrate+molybdate as agents for the control of sulfide production. Results indicated that nitrite and nitrate+molybdate reduced sulfide production, while nitrate alone had no effect on sulfide generation. No long-term effect on sulfide production was observed. Initial sulfate-reducing bacterial numbers were not influenced by the chemical treatments, although a significant increase in sulfate-reducing bacteria was observed after termination of the treatments. Molecular analysis showed a diverse bacterial population, but no major shifts in the population due to treatment effects were observed.

Biofilms↗

PubMed2005

Application of image analysis techniques in activated sludge wastewater treatment processes.

Image analytical techniques have been extensively developed to evaluate complex microbial aggregates such as sludge flocs and biofilms. This review covers the latest contributions concerning the application of image analysis to the activated sludge systems with respect to the most frequently used morphological parameters and relations between them and traditional wastewater treatment parameters. Recent developments have indicated that image analysis can be successfully used for the quantification of flocs and filamentous bacteria in the operating wastewater treatment plants, which enables prediction of bulking events and pinpoint flocs formation.

Bacteria↗