Korišćenje drvene biomase u procesu kogeneracije / Usage of wood biomass in cogeneration / Использование древесной биомассы в процессе когенерации

Потенцијал биомасе у Републици Србији је велик и обухвата шумски и дрвно-индустријски остатак, огревно дрво, остатак из пољопривреде, биомасу прикупљену при одржавању путева и инфраструктурних објеката. Изградњом когенерацијских постројења на дрвну биомасу повећаће се удео коришћења обновљивих извора енергије, што ће вишеструко допринети испуњавању циљева енергетске политике Републике Србије. Реално је претпоставити да ће се за енергетске потребе повремено морати да користи и биомаса лошијег квалитета, што ће се неминовно одразити на погонске параметре когенерацијског постројења. У недостатку новијих домаћих искустава потребно је објективно и непристрасно анализирати податке о актуелном стању технологија, као и податке о погону когенерацијских постројења ложених дрвном биомасом. / The potential of biomass in Serbia is large and includes forestry and wood industry residue, firewood, residues from agriculture as well as biomass collected for maintenance of roads and infrastructure. The construction of cogeneration plants in wood biomass will increase the share of renewable energy sources, and will thus contribute to meeting the multiple objectives of the energy policy document. It is reasonable to assume that it will be occasionally necessary to use biomass of low quality which will inevitably affect the operational parameters of cogeneration plants. In the absence of recent domestic experience, it is necessary to objectively and impartially analyze the information on the current state of technology and information about the operation of cogeneration plants using wood biomass. / Республика Сербия обладает большими ресурсами биомассы лесов, излишних древесных отходов деревообрабатывающей промышленности, дров, сельскохозяйственных отходов, а также отходов от строительства и содержания дорог и придорожных сооружений. Строительство когенеративных установок на базе древесной биомассы увеличит объемы использования возобновляемых источников энергии, таким образом, во многом способствуя выполнению целей энергетической политики Республики Сербия. Имеются реальные опасения от использования некачественной биомассы, что может оказать негативное воздействие на производственные параметры когенеративной установки. За неимением отечественного опыта в данной области, необходимо провести беспристрастный объективный анализ актуальных данных о текущем состоянии внедрения новой технологии, а также анализ данных о работе когенеративных установок на древесной биомассе

Wastewater treatment

<p><em>Quality</em><em> of life on Earth in the future will largely depend on the amount of safe water. As the most fundamental source of life, water is relentlessly consumed and polluted. To halt this trend, many countries are taking extensive measures and investing substantial resources in order to stop the contamination of water and return at least tolerably good water quality to nature. The goal of water purification is to obtain clean water with the sewage sludge as a by-product. Clean water is returned to nature, and further treatment of sludge may be subject to other procedures. The conclusion of this paper is simple. The procedure with purified water is easily achievable, purified water is discharged into rivers, lakes and seas, but the problem of further treatment of sludge remains. This paper presents the basic methods of wastewater treatment and procedures for processing the products from contaminated water. The paper can serve as a basis for further elaboration.</em></p> <h1>Water Pollution</h1> <p>In order to ensure normal life of living creatures, the water in which they live or the water they use must have a natural chemical composition and natural features. When, as a result of human activities, the chemical composition of water and the ratio of its chemical elements significantly change, we say that water is polluted. When the pollutants come from industrial plants, we are talking about <em>industrial</em> wastewater, and when they come from households and urban areas, we are talking about <em>municipal</em> wastewater. Both contain a huge amount of pollutants that eventually end up in rivers. Then, thousands of defenseless birds, fish and other animals suffer, and environmental consequences become immeasurable. In addition, the waste fed to the water often ends up in the bodies of marine animals, so they can return to us as food. Thermal water pollution also has multiple effects on the changes in the wildlife composition of aquatic ecosystems. Polluted water can be purified by mechanical, chemical and biological agents. Mechanical methods are based on the effect of physical forces. Chemical agents are based on chemical processes. Biological measures are based on natural laws and activities of living beings. Water saving and its rational use are some of the most effective ways of saving water from pollution.</p> <p>Water treatment</p> <p>Water treatment is done in two ways: <em>by sedimentation and filtration</em>. Dirt falling on the bottom is called deposition. The passage of clean water through the material is called filtering. Water containing dissolved substances is purified by <em>distillation</em>. To improve the taste of distilled water, <em>aeration</em> should be performed. The sun’s ultraviolet rays destroy biological pollutants. Mechanical, biological and chemical methods are used for water purification.</p> <p>Mechanical methods</p> <p>Mechanical methods are based on the removal of physical impurities from water and the action of natural forces. For this purpose we use: grids and sieves, sedimentation, flotation, filtration, centrifugation, sand sedimentation tanks, grease traps, primary sedimentation tanks and flow equalization tanks. Wastewater aeration equipment is also used within these facilities.</p> <p><em>Grids and Sieves</em></p> <p>Larger, insoluble and floating substances in wastewater are removed with grids and sieves.</p> <p><em>Sedimentation</em></p> <p><em> </em></p> <p>The application of grids and sieves as well as sand sedimentation tanks and grease traps can be viewed as a process of deposition using certain infrastructure facilities intended for this type of separation of impurities. Infrastructure facilities are <em>sedimentation tanks</em>. There are vertical, horizontal and radial flow sedimentation tanks.</p> <p><em>Flotation</em></p> <p><em> </em></p> <p>Particle resurfacing with bubbles of air is called flotation. The best effect is achieved by aeration of bubbles of smaller diameters in a larger area.</p> <p><em>Filtration</em></p> <p><em> </em></p> <p>Filtration is a process used in water conditioning to remove insoluble substances. During filtration, water passes through a layer of granular material placed on a perforated surface. Some other processes can also take place during filtration.</p> <p><em>Centrifugation</em></p> <p><em> </em></p> <p>Centrifugation is a method of separating particles from a suspension due to the effect of the centrifugal force that is many times greater than the force of gravity. For larger water quantities, it is not realistic to apply centrifugation as a water purification technique.</p> <p><em>Sand sedimentation tanks</em></p> <p>Substances with specific gravity higher than water, such as sand, gravel, stone, earth, slag, mineral particles, etc., accumulate in the plants called sand traps.</p> <p><em>Grease traps</em></p> <p><em> </em></p> <p>Substances lighter than water: oil, grease, soap flakes, bits of wood, cork, etc., are removed by means of grease traps.</p> <p><em>Flow equalization tanks</em></p> <p><em> </em></p> <p>They provide conditions for the slow and steady movement of water and retain wastewater long enough to provide gravity sedimentation of suspended particles.</p> <p>Chemical methods</p> <p>Chemical purification methods are the processes in which the treatment is carried out by means of certain chemical reactions, or certain physical and chemical phenomena. Basic operations of the chemical wastewater treatment are the removal of suspended and colloidal substances: by <em>coagulation</em> and <em>flocculation</em>, and the removal of some dissolved substances: by chemical deposition, ion exchange, oxidation,   gas blowing and adsorption.</p> <p><em>Chemical deposition</em></p> <p><em> </em></p> <p>The process of chemical deposition is based on the conversion of dissolved substances in wastewater to insoluble compounds, using suitable reagents.</p> <p><em> </em></p> <p><em>Ion exchange</em></p> <p><em> </em></p> <p>Ion exchange is much more widely used as a water preparation process to remove water hardness than as a wastewater purification process.</p> <p><em> </em></p> <p><em>Oxidation</em></p> <p><em> </em></p> <p>Oxidation can convert some organic and inorganic substances in industrial wastewater into compounds that are far less polluting. The most often used oxidant is chlorine.</p> <p><em>Gas blowing</em></p> <p><em> </em></p> <p>Some dissolved substances can be removed from the wastewater by means of <em>blowing gas, ordinary air or steam</em>.</p> <p><em>Adsorption</em></p> <p>Adsorption is a process of accumulating fluid substances on the surface of the solid phase. A substance being adsorbed is  <em>adsorbate</em>, and the phase upon which the adsorption is carried out is called the <em>adsorbent</em>.</p> <p>Biological methods</p> <p>Biological purification processes are based on the activities of a complex microflora, which is in the course of their life cycle adopted by organic and parts of inorganic materials causing wastewater pollution, using them to maintain life activities and to create new cells. During a biological treatment, stabilized sludge is precipitated,and removed from the water in secondary sedimentation tanks. Biological purification processes can be <em>aerobic</em> and <em>anaerobic</em>, with the help of aerobic or anaerobic microorganisms. Aerobic processes with suspended microflora are divided into: the processes with activated sludge in bioaeration tanks, processes in aerated lagoons (biological lagoons) and processes in aerobic (shallow) lakes (biological artificial lakes).</p> <p><em>Activated sludge process</em></p> <p><em> </em></p> <p>This is an aerobic process of a biological wastewater treatment, as it occurs due to aerobic microbial population. Microorganisms are found in aeration basins, where, with the help of oxygen in the metabolic process, substrate degradation is provided. Microorganisms oxidize the dissolved substrate into carbon dioxide and water. A part of the organic material is synthesized into new cells or used for the growth of existing ones and the rest consists of waste and excess sludge. A part of sludge is returned into the process (activated sludge) where it has a role of an activator of the biological process. The rest of sludge is discharged into the sludge treatment device or disposed of in a proper way. Clear purified water (effluent) is discharged into the recipient, or, if necessary, taken to additional processing.</p> <p><em>Process in aerobic lagoons</em></p> <p>Lagoons and shallow basins, as an aerobic biological wastewater treatment method, provide a sufficient amount of oxygen through photosynthesis.</p> <p><em> </em></p> <p><em>Process in shallow lakes</em></p> <p><em> </em></p> <p>Aerobic lakes are large and shallow earthen basins in which wastewater treatment takes place with minimum regulation, practically as natural self-purification.</p> <p><em>Anaerobic processes</em></p> <p><em> </em></p> <p>The anaerobic treatment process is based on the <em>methane fermentation</em> of organic wastewater pollution, where organic material is converted into a mixture of gases. The use of microorganisms in the absence of oxygen is called <em>anaerobic digestion</em>.</p> <p>Processing products from the wastewater treatment process</p> <p>Waste materials from the wastewater treatment process should have a high proportion of isolated components and a small proportion of the remaining moisture. Sludge treatment methods may include: thickening, stabilization, conditioning, dewatering, drying or oxidation and disposal. In accordance with the applied technology, sludge treatment processes may be biological, technical and mechanical ones. Biological sludge treatment processes are performed for compost production, to improve sludge residue for disposal, for biological stabilization of sludge residue. Composting is the simplest way of processing biodegradable sludge (humus). Compost can be used in agriculture, to revitalize the soil laid bare by fire and to improve the quality of land next to roads. <em>Mechanical-biological</em> treatment of sludge is based on a process of mechanical treatment of sludge, where valuable components are separated from sludge. These components are metal, paper, plastic, nonmetal or harmful substances that cannot be disposed of in landfills. The thermal treatment of sludge is carried out using the following methods: combustion, pyrolysis and gasification.</p

Wastewater reuse

<p><em>Water scarcity and water pollution are some of the crucial issues that must be addressed within local and global perspectives. One of the ways to reduce the impact of water scarcity  and to minimizine water pollution is to expand water and wastewater reuse. The local conditions including regulations, institutions, financial mechanisms, availability of local technology and stakeholder participation have a great influence on the decisions for wastewater reuse.</em></p> <p><em>The increasing awareness of food safety and the influence of the countries which import food are influencing policy makers and agriculturists to improve the standards of wastewater reuse in agriculture. The environmental awareness of consumers has been putting pressure on the producers (industries) to opt for environmentally sound technologies including those which conserve water and reduce the level of pollution.</em></p> <p><em>It may be observed that we have to move forwards to implement strategies and plans for wastewater reuse. However, their success and sustainability will depend on political will, public awareness and active support from national and international agencies to create favorable    environment for the promotion of environmentally sustainable technologies.</em></p> <p><em>Wastewater treatment has a long history, especially in agriculture, but also in industry and households. Poor quality of wastewater can pose a significant risk to the health of farmers and users of agricultural products. The World Health Organization (WHO) is working on a project for the reuse of wastewater in agriculture.</em></p> <p><em> To reduce effects of human activities to the minimum, it is necessary to provide such technical and technological solutions that would on the one hand ensure complying with  the existing regulations and legislation, and on the other hand provide economically viable systems as seen through investments and operating costs.</em><em> </em></p> <p>The use of wastewater</p> <p>The practice of using wastewater varies from country to country. Its application and technology applied are ​​significantly dependent on socio-economic circumstances, industry structure, climate and politics.<br /> <br /> <em>Reuse of water for irrigation of agricultural crops</em><br /> <br /></p> <p>Fourty-one percent of the recycled water in Japan, 60% in California (USA), and 15% in Tunisia is used for irrigation of crops. In China, at least 1.33 million hectares of agricultural land is irrigated with untreated or partially treated wastewater (http://www.eolss.net). Agricultural irrigation is essential to improve the quality and quantity of production. By 2025, agriculture is expected to increase its water requirements by 1.2 times (http://www.unep.or.jp).<br /> If wastewater originatines from industrial sources, the presence of toxic chemicals, salts and heavy metals may limit its reuse. Such materials can change soil properties and may affect the growth of crops, so that appropriate treatment and supervision should be practiced.<br /> Recycled water that is important for agriculture must contain nitrogen, potassium, zinc, boron and sulfur. However, excess nitrogen can lead to overgrowth, delayed crop maturity and poor quality. Boron is an essential element for plant growth, and the excess boron becomes toxic.<br /> Tunisia is one of a few countries that have implemented a national policy for the reuse of wastewater. Since 1960., the wastewater in Tunisia has been used for irrigation of orchards. Since 1989, after a secondary treatment, the wastewater has been used for the cultivation of various crops (olives, fodder, cotton, etc.), except for growing vegetables.<br /> In countries such as Morocco, Jordan, Egypt, Malta, Cyprus and Spain, wastewater is either used or being considered for irrigation, while in Israel, the percentage of the use of wastewater for irrigation is the highest in the region, with 24.4% and should be increased to 36% in the future (<a href="http://www.eolss.net/">http://www.eolss.net</a>).</p> <p>Depending on the country, socio-economic conditions, may be different,  starting from the shortage of money for capital investments. Therefore, the EU funds are very important for the countries such as Greece anor Serbia.<br /> Egypt, Jordan, Tunisia, Palestine, Morocco and Syria irepresent a group of countries with a high need for the reuse of wastewater, but also with prevailing economic problems, limited experience, inadequate infrastructures, including sewers and wastewater treatment factories.</p> <p>Strict standards for the reuse of water such as the standards in California and other states in the U.S.A. (USEPA 1992),are not easy to achieve. The WHO directive is less severe, and it defines the treatment of wastewater for irrigation of crops, especially in developing countries.<br /> The countries that are the EU members, such as Greece, can expect to be provided with funding to improve health and to implement certain laws and regulations (Andreadakis A.. et al., 2001, 7th Conference on Environmental Science and Technology, Greece, September nd)</p> <p><em>Reuse of wastewater from households</em></p> <p>Gray water is water that comes from common household activities such as shaving, showering and washing machines. Since graywater represents 50-80% of common household water consumption, environmentalists believe that its discharge into drains is a waste and a missed opportunity to use such a resource. It can easily be captured, treated on site and reused in toilets and for landscaping, instead of  commonly used drinking water.</p> <p>Systems used for purification and disinfection depend on countries and requirements    that treated water must meet. In Australia, it is not allowed to treat water from the kitchen as gray water because of the presence of food, i.e. possible and therefore may be presen pathogenic organisms which make the purification process difficult. Some other states prohibit the reuse of gray water from washing machines- since cloth diapers can be washed in them clot, the water can be  contaminated with faeces despite no contact with the main sewage drains.</p> <p>In California, treated gray water has been used for garden irrigation for years, and studies have shown that its use does not cause health problems.</p> <p>Reuse of gray water means less energy consumption and less chemicals in wastewater treatment plants, which is good for the community, i.e. households will be spending significantly less money on water bills.</p> <p><em>Reuse of wastewater from industry</em></p> <p>In industry, water is used in refrigeration, industrial process and power boilers.</p> <p>In the  purification of industrial wastewater two approaches are generally distinguished: a pretreatment of wastewater that must be implemented to meet the criteria for its   discharge  into public sewers and a singular wastewater treatment (without interference from household waste) to meet the criteria for effluent to be discharged.</p> <p>More and more freguently companies release their waste into urban sewage,having previously partially refined it to the level where it is mixed with wastewater from households and then finally purified in the same installation. The composition of water for steam boilers is of very great importance, because the slightest disturbance in the steam boiler can cause a disturbance in the entire industrial process. The quality of water for steam boilers depends on the type of a plant, steam pressure and the purpose for which steam is used. Water should be of such quality that it does not leave residues and deposits and it should not have a corroding effect. The purity of produced steam should correspond to the purpose of the steam in question. Water should not contain substances that could cause foaming (fats, oils and other organic substances) and should be slightly alkaline (pH = 7 to 9.5).<br /> Industrial water, depending on the processes in the industry, can be purified up to a certain degree. When discharged into natural water systems, it must meet the principles underpinning the system of the limit  values of major wastewater parameters, developed by The Association for wastewater from the Federal Republic of Germany and presented in Table 6.</p> <p>Conclusion</p> <p>The date presented here, including quantities, methods of treatment, use of treated wastewater and different regulations, lead to a conclusion that in order to reach the standards of developed countries, the Republic of Serbia needs experts and a long time period to treat its wastewater to an adequate level for its reuse as well as for the sparing use of its water sources in general.</p><p> </p

Renewable electricity in Western Balkans: Support policies and current state

The use of renewable energy sources for electricity generation in the Western Balkan countries is analyzed in this review paper. Since those countries are part of EU or intend to be, data for Western Balkan are also compared with data for EU-28. The first part of the paper presents a brief overview of main promotion mechanism for electricity generation from renewable energy sources. As a dominant support policy, the feed-in tariff is more elaborated as an incentive measure and a de¬tailed overview of the amount of tariffs and quotas for dominant technologies in the Western Balkan countries is presented. Furthermore, the current state of installed capacities and annual productions of three particular renewable electricity technologies (small hydro power, wind power, and solar photovoltaic) are analyzed in detailes. Based on presented data, there is a discussion and consideration of the impact of incentive measures on the electricity market and power production from renewable sources. [Project of the Serbian Ministry of Education, Science and Technological Development, Grant no. III 42013

Energy auditing and energy saving measures in 'Zastava Automobili' factory

This paper deals with energy audit procedure implemented on only Serbian car manufacturer 'Zastava Automobili'. Based on the results of energy auditing and performed technological and economical feasibility studies several energy saving measures were proposed. The measures are related to different energy sources: steam, hot water, compressed air, electricity, and water. Such energy efficiency programs reduce energy costs and increase production profitability of the factory