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At least 1,405 records · Page 78Linked to original sources
PubMed1998

Impact assessment of a wastewater treatment plant effluent using the fish biomarker ethoxyresorufin-O-deethylase: field and on-site experiments.

The impact of a wastewater treatment plant (WWTP) effluent was assessed with the fish biomarker ethoxyresorufin-O-deethylase (EROD) using field and on-site laboratory experiments. EROD activity was measured in chub (Leuciscus cephalus) and stone loach (Noemacheilus barbatulus) caught at three sites of the Chalaronne River (southeast France). Liver somatic index (LSI) and organochloride bioaccumulation in muscle were estimated for chub only. In September, EROD activity and LSI of chub increased significantly between the sites above and below the WWTP effluent discharge. EROD induction detected in chub was confirmed by on-site tank experiments. EROD levels were determined in juvenile rainbow trout (Oncorhynchus mykiss) and mirror carp (Cyprinus carpio) exposed to different concentrations of the WWTP effluent and river water for 16 days. After a 4-day exposure, EROD activities of the carp exposed to the effluent increased significantly compared with the control. The response was linked to the effluent concentration and was stable with exposure time. WWTP effluent induced EROD activity, whereas organic and metal analyses, performed on fish muscle and sediment, did not indicate any difference between upstream and downstream of the discharge.

Animals↗
PubMed2002

Adsorption of dyes onto carbonaceous materials produced from coffee grounds by microwave treatment.

Organic wastes have been burned for reclamation. However, they have to be recycled and reused for industrial sustainable development. Carbonaceous materials were produced from coffee grounds by microwave treatment. There are many phenolic hydroxyl and carboxyl groups on the surface of carbonaceous materials. The base consumption of the carbonaceous materials was larger than that of the commercially activated carbon. The carbonaceous materials produced from coffee grounds were applied to the adsorbates for the removal of basic dyes (methylene blue and gentian violet) in wastewater. This result indicated that the adsorption of dyes depended upon the surface polar groups on the carbonaceous materials. Moreover, the Freundlich constants of isotherms for the adsorption of methylene blue and gentian violet onto the carbonaceous materials produced from coffee grounds were greater than those for adsorption onto activated carbon or ceramic activated carbon. The interaction was greatest between the surface or porosity of the carbonaceous materials and methylene blue and gentian violet. The microwave treatment would be useful for the carbonization of organic wastes to save energy.

Adsorption↗
PubMed2002

Textural and chemical characterizations of adsorbent prepared from palm shell by potassium hydroxide impregnation at different stages.

Preparation and characterization of activated carbon from palm shell, a carbonaceous agricultural solid waste, by potassium hydroxide treatment at different stages were studied. The effects of activation temperature and chemical to sample ratio on the characteristics of the activated carbon were investigated. Fixed-bed adsorption of sulfur dioxide (SO(2)) gas was carried out to evaluate the adsorptive capacity of the samples. Desorption tests were conducted to verify the occurrence of chemisorption due to some surface functional groups or of chemical reaction between SO(2) and KOH. It was found that pre-impregnation of raw palm shell was involved in replacement of some hydrogen ions with potassium ions to form cross-linked complexes, which retarded the tar formation during carbonization, resulting in a relatively high yield. Moreover, these potassium ions accelerated the reaction as catalysts during gasification of chars by carbon dioxide. For chars with mid-impregnation, potassium hydroxide acted in two ways: (i) formation of metallic potassium by dehydration and (ii) conversion into potassium carbonate. Metallic potassium intercalated to the carbon matrix accounted for pore development and potassium carbonate layer prevented the sample from over burn-off. Post-impregnation of final products modified the textural characteristics of the sample as some pore entrances were blocked by chemicals. However, potassium hydroxide enhanced the amount of SO(2) uptaken via formation of potassium sulfite.

Adsorption↗
PubMed2001

Total waste-load control and allocation based on input-output analysis for Shenzhen, south China.

The general objective for this paper is to reveal the dynamic relationships between the rapid economic development, water pollution and the subsequent waste-load allocation in different economic sectors through a case-study in Shenzhen City, South China. Two-objective analysis model was employed based on the input-output table for Shenzhen with the full consideration of various constraints in local area. The improved Tchebycheff procedure was used for obtaining the solutions. The predictions were made on economic development and pollutants from wastewater in different sectors and different planning years. The present study allows for the consideration of the economic structural adjustment. It is found that the current situation of economic structure is generally good and is subject to further adjustment in Shenzhen, although it has undergone the rapid development in the past 18 years. When the maximum Gross Domestic Production and the minimum Chemical Oxygen Demand are chosen as the two objectives subject to other constraints, the harmonized results indicated a scheme that claims substantial reduction of polluting effluences in Shenzhen while closely keeping the economic growth rate as planned.

China↗
PubMed2000

Quantitative polymerase chain (QPCR) reaction using the MIMIC approach to estimate Cryptosporidium parvum oocysts, an intestinal pathogen, in municipal water treatment sludge samples.

An accurate estimation of the number of Cryptosporidium parvum oocysts in water treatment plant sludge was determined using the Quantitative Polymerase Chain Reaction (QPCR) method. Approximately 8x10(6)purified viable oocysts were spiked into raw water and treated by conventional water treatment methods. The settled sludge was collected and the DNA extracted. The QPCR Mimic produced two competing products that were 300 and 435 base pairs in size. The log ratio of the products were used in the standard curve to determine a final estimation of oocysts in the sludge sample. The final number of oocysts in the sludge sample was estimated at 258 oocyst per two litres of treated water. This is the first time sludge from a water treatment process has been tested for presence of C. parvum oocysts, which is a known contaminant of drinking water. The QPCR method can be used to test other sludge samples and help estimate the sanitary risks associated with using sludge to fertilize agricultural lands.

Animals↗
PubMed2002

Microbial sensors on a respiratory basis for wastewater monitoring.

In respect of their rapidity, their online capabilities, and their moderate costs, biosensing systems generally offer an attractive alternative to the existing methods of water analysis. Additionally, one particular advantage of microbial biosensors is the ability to measure direct effects on living cells, e.g., their respiratory activity and its alteration caused by environmental pollutants. It is true that microbial sensors, often do not provide the optimum solution for the determination of individual analytes when compared to established physico-chemical analysis methods. However, these biosensing devices are predestined for the summary determination of environmentally relevant compounds and their complex effects, respectively. For this reason, microbial sensors allow an integral evaluation of the degree of environmental pollution including the interaction of various compounds. Moreover, in some cases specific metabolic pathways in microorganisms are used, resulting in the development of microbial sensors for the more selective analysis for those compounds or pollutants, which cannot be measured by simple enzyme reactions, e.g., the determination of aromatic compounds and heavy metals. This chapter gives an overview of microbiological biosensors on respiratory basis for the measurement of the following environmentally relevant compounds: inorganic N-compounds, heavy metals, organic xenobiotics and the estimation of sum parameters or so-called complex parameters such as BOD, ADOC, N-BOD, and the inhibition of nitrification.

Bacteria↗
PubMed2000

Biochemical engineering aspects of solid state bioprocessing.

Despite centuries of use and renewed interest over the last 20 years in solid-state fermentation (SSF) technology, and despite its good potential for a range of products, there are currently relatively few large-scale commercial applications. This situation can be attributed to the complexity of the system: Macroscale and microscale heat and mass transfer limitations are intrinsic to the system, and it is only over the last decade or so that we have begun to understand them. This review presents the current state of understanding of biochemical engineering aspects of SSF processing, including not only the fermentation itself, but also the auxiliary steps of substrate and inoculum preparation and downstream processing and waste disposal. The fermentation step has received most research attention. Significant advances have been made over the last decade in understanding how the performance of SSF bioreactors can be controlled either by the intraparticle processes of enzyme and oxygen diffusion or by the macroscale heat transfer processes of conduction, convection, and evaporation. Mathematical modeling has played an important role in suggesting how SSF bioreactors should be designed and operated. However, these models have been developed on the basis of laboratory-scale data and there is an urgent need to test these models with data obtained in large-scale bioreactors.

Animals↗
PubMed2003

Potential for anaerobic conversion of xenobiotics.

This review covers the latest research on the anaerobic biodegradation of aromatic xenobiotic compounds, with emphasis on surfactants, polycyclic aromatic hydrocarbons, phthalate esters, polychlorinated biphenyls, halogenated phenols, and pesticides. The versatility of anaerobic reactor systems regarding the treatment of xenobiotics is shown with the focus on the UASB reactor, but the applicability of other reactor designs for treatment of hazardous waste is also included. Bioaugmentation has proved to be a viable technique to enhance a specific activity in anaerobic reactors and recent research on reactor and in situ bioaugmentation is reported.

Anaerobiosis↗
PubMed2003

Monitoring and control of anaerobic reactors.

The current status in monitoring and control of anaerobic reactors is reviewed. The influence of reactor design and waste composition on the possible monitoring and control schemes is examined. After defining the overall control structure, and possible control objectives, the possible process measurements are reviewed in detail. In the sequel, possible manipulated variables, such as the hydraulic retention time, the organic loading rate, the sludge retention time, temperature, pH and alkalinity are evaluated with respect to the two main reactor types: high-rate and low-rate. Finally, the different control approaches that have been used are comprehensively described. These include simple and adaptive controllers, as well as more recent developments such as fuzzy controllers, knowledge-based controllers and controllers based on neural networks.

Anaerobiosis↗
PubMed2003

Kinetics and modeling of anaerobic digestion process.

Anaerobic digestion modeling started in the early 1970s when the need for design and efficient operation of anaerobic systems became evident. At that time not only was the knowledge about the complex process of anaerobic digestion inadequate but also there were computational limitations. Thus, the first models were very simple and consisted of a limited number of equations. During the past thirty years much research has been conducted on the peculiarities of the process and on the factors that influence it on the one hand while an enormous progress took place in computer science on the other. The combination of both parameters resulted in the development of more and more concise and complex models. In this chapter the most important models found in the literature are described starting from the simplest and oldest to the more recent and complex ones.

Acetates↗
PubMed1998

Cadmium contamination of vegetable crops, farmlands, and irrigation waters.

Cadmium, a highly toxic element that can accumulate in living tissues, is a potential threat to the environment and to human health. The main sources of Cd contamination of vegetable crops via farm soils and irrigation waters are reviewed, as are the influence of residual sludges used as fertilizers and the indiscriminate use of pesticides. The principal sources of exposure and toxicological characteristics of Cd are described, together with its effects on human health. Current European technical and health regulations aimed at controlling Cd levels are noted, and the most common analytical techniques for measuring Cd content are summarized.

Biological Availability↗
PubMed1995

Heavy metal toxicity testing in environmental samples.

The toxicity of heavy metals in the environment depends on a number of physicochemical and biological factors. The complexity of these relationships has encouraged the use of bioassays for direct measurement of the [table: see text] impact of toxic metals on selected test species. Fish and daphnid bioassays are well accepted by the scientific and regulatory communities, but their length (48 h or more) and the considerable time and effort needed to culture the test organisms make their application to sample screening problematical. Microbial and biochemical assays based on the inhibition of bioluminescence, enzyme activity, enzyme biosynthesis, growth, respiration, and heat production are typically faster and less expensive than the traditional and fish bioassays. Some of these tests approach or equal the sensitivity of daphnids to heavy metals. Since the soil acts as a sink for airborne and waste-applied metals, the uptake of metals by plants and the associated toxic impacts are important. Growth inhibition, enzyme induction, and production of stress proteins have been considered as toxicity end points. Enzymatic tests have been developed that are specific for heavy metal toxicity. Such tests can facilitate toxicity reduction evaluations. Detection of individual metals in the environment may eventually be possible using biosensors consisting of genetically engineered microorganisms. Direct solid-phase tests for soil, sediment, or sludge toxicity, using bacterial bioluminescence or enzyme activity as end points, have been developed. Such tests may complement traditional solid-phase toxicity tests using nematodes or earthworms as indicator organisms. Based on the work reviewed, we draw the following conclusions: 1. The Microtox assay is sensitive to mercury but would fail to detect the toxicity of certain metals, such as cadmium. Among all the microbial assays reviewed, the bioassay based on growth inhibition of the alga Selenastrum capricornutum appears to give the lowest EC50s, similar to those seen for daphnid bioassays. 2. Biosensors, using genetically engineered microorganisms, offer an elegant means of detecting the presence of specific heavy metals in environmental samples. However, at the present time, they are not designed for assessing heavy metal toxicity. 3. The use of bioassays specific for heavy metal toxicity can be useful for directly assessing the bioavailability of these toxicants in environmental samples, thus avoiding the need for fractionation.+4

Animals↗
PubMed2004

Production of lactic acid from paper sludge by simultaneous saccharification and fermentation.

Production of lactic acid from paper sludge has been performed by simultaneous saccharification and fermentation (SSF). The SSF process design was based on experimental data obtained from cellulose hydrolysis and fermentation. The SSF process was employed to avoid an excessively dense solution when the sludge content of the feed was higher than 15%; this is one of several benefits of SSF. The enzyme system used for hydrolysis of paper sludge for production of glucose was optimized. CMCase and beta-glucosidase with activities of 2.5 and 10 U mL(-1), respectively, were found to be optimum for hydrolyzing 5% sludge. In batch SSF 16 g L(-1) lactic acid was produced from 5% paper sludge with an yield of 80%. Paper sludge which served as a feed seemed to have a buffering effect during SSF, probably because of the inorganic ash component in the sludge. The final product concentration by SSF was observed to be limited by the cellulose content of the system, which can probably be resolved by intermittent feeding of the paper sludge. SSF of paper sludge fed in batch mode, with intermittent feeding, produced lactic acid at 162 g L(-1), with a yield of 74% and a productivity of 1.4 g L(-1) h(-1). The lactic acid production performance of the modified bioreactor improved after removal of indigestible solid materials from the upper compartment, which enabled the feed of paper sludge to be increased. A mathematical model is described which predicts glucose and subsequent lactic acid production on the basis of the rate expressions of each step of the SSF process. Saccharification kinetics were determined by experiments on enzymatic cellulose hydrolysis, by use of a Michaelis-Menten equation; growth kinetics of L. rhamnosus were determined by use of a Monod expression which incorporated lactic acid inhibition. The kinetic model is expected to predict the performance of the SSF process. For further use of the lactic acid, i.e. polylactic acid, it must be recovered and purified. Results from application of the simulated moving-bed (SMB) process for separation of lactic acid and acetic acid are given, as are several methods of lactic acid purification.

Bioreactors↗
PubMed1996

Modelling for waste water treatment by Rhodopseudomonas palustris Y6 immobilized on fibre in a columnar bioreactor.

A kinetic model of continuous treatment of waste water by Rhodopseudomonas palustris Y6 immobilized on soft fibre in a columnar bioreaction system was established. Good agreement was found between the model prediction and the experimental data from continuous operation [initial chemical oxygen demand (COD) concentration = 29.700 g/l] of the system. The optimum operational conditions for the maximum COD reduction capacity were investigated from the model prediction and the experimental data. The waste water treatment process may significantly increase the waste reduction capacity because a large amount of active biomass for COD reduction is immobilized in the system, resulting in operation stability. The results presented here provide a useful basis for further scaling up and efficient operation of waste water treatment processes.

Rhodopseudomonas↗