This paper presents the results of the study of sludge aggregates produced during electrocoagulation of model wastewater of a composition corresponding to the effluents from the cellulose and paper industry. Wastewater was electrocoagulated statically using aluminium electrodes with a current density of 31.25 A m−2 and 62.50 A m−2. In subsequent stages of the treatment, sludge flocs were collected, their size was studied and their floc settling velocity (30–520 μm s−1) and fractal dimension (D) were determined. The values of D ranged from 1.53 to 1.95 and were directly proportional to the degree of wastewater treatment. Higher values of D were determined for sludge with lower water content (after 24 hours’ settling). Fractal dimension can therefore be used as an additional parameter of wastewater treatment control.
An Electrocoagulation/Flotation (ECF) reactor was built to treat wastewater with heavy metals. Cadmium chloride was the source of metallic ions. Solutions were prepared between 10 mg/L and 30 mg/L, pH values of 8.0, 9.5 and 10.5, using lime as the coagulant. The ECF reactor was able to achieve metal removal efficiencies between 90% and 99% for all the applied current levels, after 30 min. Summarised operational parameters for reactor are: applied current of three amperes, treatment time of 30 min, at a pH of 9.5....
Dewatered sludge cakes from bench scale anaerobic digesters operated at mesophilic temperatures and solids retention times (SRT) ranging from 10 days to 40 days were evaluated for their sulfur odor generation potential. Extracellular Polymeric Substances (EPS) extraction for digested sludge samples was also carried out. Static headspace sulfur gas analysis was successfully used to compare different sludge digestion SRTs for their odor potential. Higher volatile solids destruction was observed at higher SRTs and...
Abstract
The removal of pollutants from effluents by electrocoagulation has become an attractive method in recent years. This paper deals with the batch removal of the reactive textile dye Colored Index (C. I.). Acid yellow 36 from an aqueous medium by the electrocoagulation method using iron electrodes. The effects of electrolyte concentration, initial pH, current density, electrode area, interelectrode distance, dye concentration, and treatment time on the decolorization efficiency have been investigated....
The analysis of volatile compounds (b.p.
The analysis is performed using a purge and
trap device which separates the compounds of
interest from the sample matrix, based on
differences in volatility and water solubility.
The analytes are identified using very sensitive
photo ionization and halogen-specific detectors
which respond selectively to the compounds of
interest while showing little or no response to
other compounds in the sample. Because of the
selectivity of the detectors, expensive test
metho...
Because of the widespread use and history of
indiscriminate disposal practices of gasoline
and fuel oils, their analysis in environmental
samples is in high demand. Gasoline and diesel
are both complex mixtures containing up to 400
individual compounds. The BTEX group
(Benzene, Toluene, Ethylbenzene, and the
Xylenes) are naturally occurring constituents of
gasoline and diesel (although also present in
kerosenes and fuel oils), and their analysis
simplifies the identification of these sources.
The enhancing effect of aerobic thermophilic (AT) bacteria on the production of biogas from anaerobically digested sewage sludge (methanogenic sludge) was investigated. Sewage sludge (5%, w/w) was incubated at 65°C with shaking for a few months to prepare the AT seed sludge. AT sludge was prepared by incubation of the AT seed sludge (5%, v/v) and sewage sludge (5%, w/w) at 65°C with shaking. The addition of this AT sludge (1.2% ± 0.5% of total volatile solids) to methanogenic sludge enhanced the production of...
Toxicity, or more appropriately, inhibition, is a measure of the interference of a compound or compounds with biodegradation. Since inhibition usually is expressed as the interference with bioconversion of an oxygen-consuming reaction – or gas producing reaction in the case of anoxic or anaerobic reactions – it is essential that a biodegradable substrate be present when assessing toxicity of specific compounds. A dilution series is one of the most common respirometric approaches used to assess toxicity. The test...
Up to now, the recovery of precious metals used as catalysts in chemical processes has involved the use of incineration. Now, however, a British-Swedish joint venture has developed a process which uses supercritical water oxidation instead, which provides many economic and environmental advantages.
Precious metals are used extensively in catalysts in a wide range of industrial chemical processes. Sometimes they are used in a homogeneous form, but more often fixed to a solid support for ease of handling. In many...
The Kemwater Recycling Process – KREPRO for treatment of sewage sludge is based on a completely new separation technology, which uses existing knowledge in an innovative way. It reduces both the organic and inorganic content of the sludge. The organic content is re-duced by about 30% and the inorganic about 70% if digested sludge is treated. All metals and salts are dissolved; the remaining undissolved inorganics are mainly silicates like sand and grit.
In constast, most sludge treatment technologies used today...
In this work sugar refinery carbonatation sludge is treated in a pilot scale facility for two purposes: reuse in the carbonatation process, mixed with fresh calcium hydroxide, and flue gas desulphurisation. The sludge is first dried, and then calcinated in a batch kiln with a capacity of 100 kg, designed for the purpose. This process is potentially attractive for the sugar industry, since it can save both process water and calcium oxide, simultaneously reducing the amount of wastewater. This paper presents the...
Abstract
Restriction of available water observed in the last years in arid or semiarid areas forces the planners to consider any source of water for irrigation. The purpose of this paper was to investigate the suitability of wastewater produced by the treatment plant of the city of Larissa, Central Greece for irrigation of corn. With a three year`s field experiment it was shown that wastewater significantly increased corn yield and may substitute considerable quantities of mineral fertilizers. Increase in corn...
Abstract
Material flows of Finnish printing papers in 1994-2000 are studied using the JTP -technique. The environmental and economic implications of two scenarios are studied. The basic scenario is built on the assumption that no major changes will take place during the study period. Predictable changes in paper consumption, recycling rate etc. are taken into account. Scenario two presents an alternative policy option with two changes to the basic model: the landfill gas is collected and incinerated and all the...
Issue: As part of an increasing sentiment among European consumers that environmental protection is important, concern about the impact of landfill is growing. Sensor technology makes it possible to measure and control inputs to landfill sites and pollutants arising from them. However, the exploitation - or uptake - of such technology has been lower than expected in the waste management sector. Relevance: Coordinated European science and technology policies can help improve exploitation of sensor technology, and...
Biofilters are the odor control system of choice at composting facilities. Despite similar capital costs, the biofilters are generally less costly to operate than chemical scrubbers. The key to keeping operating costs in check, however, is to get the maximum use out of the biofilter media, thus avoiding the time and money needed to do media replacements.
Allen Boyette, senior engineer and manager of the Cary, North Carolina office of E&A Environmental Consultants, Inc., tackled the topic, “Building Longevity...
Abstract
Africa
The economic and social needs of Africa depends more on its environmental resources but these natural resources are seriously declining and that is really effecting the entire region. Sustainable development in this rapidly changing region has become an imperative, and must take place in the complex context of a diverse and changing ecosystem, political transition and evolution toward market economies.
The region is heading towards integrating environmental components into sectors like...
Abstract
Different parameters were investigated to evaluate their effect on the process removal efficiency of COD and color, including H2O2 concentration, UV power, multi-step addition of H2O2, and air bubbling. As a result, the color can be removed completely within 20 minutes, and the COD removal of approximately 90% can be achieved within 40 minutes of UV illumination. This process favors the H2O2 addition in one step rather than in four steps. Supply of oxygen does not enhance the process removal efficiency....
` Growing volumes of both industrial and municipal wastewater are being discharged to surface waters but the treatment provided frequently is inadequate to protect the desired uses of the receiving waters. With limited resources in terms of both institutional capacity and finance, governments face difficult choices in optimizing their investments in municipal systems and establishing practical requirements for industrial wastewater treatment. This note presents an approach to making coherent decisions on levels...
` Management of hazardous waste is a growing concern in many countries. The long-term impacts and costs of improper disposal can be very high and the emphasis must be on prevention. A comprehensive management system should include (i) policies, institutions and effective regulations and (ii) adequate and acceptable disposal facilities (either public or private). This note outlines the key elements of such a system.`
Problems
Improper disposal of hazardous waste is an increasing problem in many developing...
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