Nicoleta Ungureanu

Nowadays, the destruction and pollution of our environment has produced a growing awareness worldwide of the need for more effective wastewater treatment. Sedimentation is the oldest and most widely used unit operation in water and wastewater treatments. Sedimentation is the process of removing solid particles heavier than water by gravity settling. The terms sedimentation, settling, and clarification are used interchangeably. The unit sedimentation basin may also be referred to as a sedimentation tank, clarifier, settling basin, or settling tank. In wastewater treatment, sedimentation is used to remove both inorganic and organic materials which are settleable in continuous-flow conditions. This paper presents the results obtained in some research focused on wastewater decanting processes using different constructive variants of settling tanks.

Compaction is the most difficult type of soil degradation and it can be regarded as a mechanical pollution arising as a consequence of poor management of agricultural practices. In mechanized agriculture, soil tillage is often carried out by heavy agricultural machinery, with repeated passes, most often on soils with high moisture content. These machines apply mechanical stresses to the soil, which are further transmitted to different depths, resulting in the artificial compaction of soil, a phenomenon that affects the capacity of plant development and hence the agricultural production. The paper presents a summary of results reported in the literature regarding the influence of the number of passes of agricultural machinery on the artificial compaction, under various conditions, in terms of the variation of cone index and of stresses transmitted into the soil.

As a result of growing concerns about groundwater contamination, decreasing availability of land for waste disposal, respectively public health and aesthetic issues related to landfills, incineration represents an alternative method for the treatment of municipal solid waste. The paper presents the theoretical aspects related to waste incineration and its residues, namely gas emissions into the atmosphere, fly ashes and bottom ashes. Also, there are presented some mass balances obtained at the incineration of municipal solid waste and current possibilities for the recovery of bottom ashes.

Heavy agricultural machinery is major cause of one of the processes of soil degradation, compaction, which became a problem of significant proportions, especially on soils with high moisture. Excessive traffic affects soil quality and crop production, and also causes environmental problems. The paper presents the results of research conducted to determine soil compaction on three experimental fields: plot of energy willow, plot of clover and cherry orchard, while different moisture contents represent subfactor. Maximum penetration resistances were recorded at 45 cm depth, where the soil is severely compacted: 3194.5 kPa on the soil cultivated with energy willow, 2984 kPa in the orchard, respectively 3069 kPa on the plot of clover.

Knowledge of soil behavior under compressive loads is important in order to prevent or minimize the impact of soil compaction on the environment and agricultural production. The aim of this study was to simulate the behavior of a clayey soil under wheel loads applied by an agricultural trailer. For known characteristics of the soil, wheel loads of 4.5 kN and 21 kN and tire inflation pressures of 180, 240 and 300 kPa, were obtained the models of stress distribution and soil displacement. For 300 kPa tire inflation pressure and 21 kN wheel load, were obtained: maximum stress of 175 kPa concentrated in the topsoil at about 140 mm depth, with smaller significant values distributed to 380 mm, and maximum soil displacement of 28.1 mm.

Nutrient-rich wastewater has become a valuable resource for farmers, but if used untreated, the wastewater can pose serious risks for human health. There is potential for wastewater reuse in Romanian agriculture, but different wastewater treatment for agricultural reuse is only tested experimentally. Wastewater samples collected from the lagoon of a cow farm in Romania were tested to determine the microbiological load, expressed as efficiency removal of pathogens at UV treatment with germicidal lamps. Duration of treatment were of 1, 5, 10, 15, 20 and 30 minutes, and highest efficiency was of 87%, showing that UV treatment can be used at large scale for the disinfection of dairy wastewater before its reuse as irrigation water.

Vibratory working tools are designed to maximize the results of the soil processing process. The paper presents the results of some theoretical researches on the use of the effect of vibrations for increasing the performance of working organs of agricultural cultivators. During the simulations, in which the calculation of the working parameters was made at different speeds of the cultivator, it was found that the maximum tensions, were recorded as expected in the upper part of the spring. The maximum displacements were observed near the area where the force is applied, with values within normal limits. REZUMAT Organele de lucru vibratoare sunt proiectate pentru a maximiza rezultatele procesului de prelucrare al solului. În lucrare sunt prezentate rezultatele unor cercetări teoretice privind utilizarea efectului vibrațiilor pentru creșterea performanțelor organelor de lucru ale cultivatoarelor agricole. În timpul simulărilor, în care calculul parametrilor de lucru s-a făcut la diferite viteze ale cultivatorului, a rezultat că tensiunile maxime s-au înregistrat după cum era de așteptat în partea superioară a arcului. Deplasările maxime s-au observat în dreptul zonei unde acționează forța, având valori în limite normale. INTRODUCTION The influence of vibrations is equivalent to the action of an additional T force applied to the working organ, which influences the traction and friction forces between the working organ and the ground [Cabrera et al., 2011]. Soil physical quality is the ability of a given soil to meet plant and ecosystem requirements for water, aeration and strength over time, and to resist and recover from processes that might diminish that ability. The soil physical quality is strongly affected by soil management including crops, fertilization, tillage, agricultural machinery traffic and drainage (Naderi-Boldajia and Keller, 2016). The use of working tools with constructive-functional characteristics correlated with the parameters of the periodic process reflected by the effect of the performed operation or work process can also lead to the improvement of the quality of the working process by emphasizing the parameters characteristic of the performed work.

Wastewater treatment technologies are designed to ensure the removal of pollutants that are partially removed by conventional treatment methods. In the last period, a special attention has been accorded to electrochemical methods due to the advantages presented: safety in operation, possibility of the process automation, environmental protection and modular structure. These methods are based, mainly, on electrochemical generation of some free radical species with high oxidation potential, such as hydroxyl radicals. Hydroxyl radicals (•OH) is a strong oxidant, that can destroy most organic and organometallic contaminants until their complete mineralization into CO2, water and inorganic ions. In the present paper are presented the most used electrochemical advanced oxidation processes in wastewater treatment, namely electrochemical oxidation and photocatalysis. REZUMAT Tehnologiile pentru epurarea avansată a apelor uzate sunt destinate să asigure îndepărtarea poluanţilor parţial eliminaţi prin metodele de epurare convenţionale. În ultima perioadă, o atenţie deosebită a fost acordată metodelor electrochimice datorită avantajelor prezentate: siguranţă în exploatare, posibilitatea automatizării procesului, protecţia mediului înconjurător, structura modulară. Aceste metode se bazează, în principal, pe generarea electrochimică a unor specii de radicali liberi cu un înalt potenţial de oxidare, cum sunt radicalii hidroxil. Radicalul hidroxil (•OH) este un oxidant puternic, care poate să distrugă majoritatea contaminanților organici și organometalici până la mineralizarea lor completă în CO2, apă și ioni anorganici. În lucrare sunt prezentate cele mai utilizate procese de oxidare avansată electrochimică în epurarea apelor uzate: electrooxidarea și fotocataliza.

Water pollution due to animals, human faeces or sewage systems is one of the most dangerous sources of contamination because they contain many pathogenic microorganisms. Disinfection is a necessary step to destroy or inactivate microorganisms and prevent the spread of dangerous diseases. The properties of ozone, especially the ability to oxidize, have led to its use in water treatment. Ozone is an "ideal" reagent because it does not introduce, in water or in the atmosphere, reaction products with unfavorable effects. In this paper are presented the most representative studies on the use of ozone in wastewater treatment. REZUMAT Poluarea apei, din cauza animalelor, materiilor fecale umane sau a sistemelor de canalizare, reprezintă una din cele mai periculoase surse de contaminare din cauza faptului că acestea conțin numeroase microorganisme patogene. Dezinfecția este o etapă necesară pentru a distruge sau a inactiva microorganismele și a preveni răspândirea unor boli periculoase. Proprietăţile ozonului, mai ales capacitatea de oxidare, au condus la utilizarea lui în tratarea apei. Ozonul este un reactiv "ideal" deoarece nu introduce, în apă sau în atmosferă, produşi de reacţie cu efecte nefavorabile. În această lucrare sunt redate cele mai reprezentative studii privind utilizarea ozonului în tratarea apei uzate.

In the past few decades, size and weight of agricultural machinery have increased significantly, and as a consequence, the severity and depth to which the stress is transmitted into agricultural soil have increased. The objective of experimental determinations was to study the influence of some factors characteristics to compaction: tire inflation pressure, wheel load and contact pressure on the contact area between tire and soil, as well as 2D and 3D mapping of pressure distribution in the footprint. The front tire of the U445 Romanian agricultural tractor was tested at five tire inflation pressures: 100, 150, 200, 250 and 300 kPa, obtaining contact areas between 0.0252-0.0349 m 2 and contact pressures between 98-136 kPa. REZUMAT În ultimele decenii, mărimea și greutatea mașinilor agricole au crescut în mod semnificativ și, în consecință, au crescut severitatea și adâncimea la care se propagă tensiunile în solul agricol. Obiectivul determinărilor experimentale îl constituie studiul influenței unor factori caracteristici ai compactării, precum: presiunea din pneu, încărcarea pe roată și presiunea de contact asupra ariei de contact dintre pneu și sol, precum și obținerea hărților 2D și 3D ale distribuției presiunilor în pata de contact. S-a testat pneul față al tractorului agricol romanesc U445, la cinci presiuni în pneu: 100, 150, 200, 250 și 300 kPa, obținându-se suprafete de contact între 0.0252-0.0349 m 2 si presiuni de contact intre 98-136 kPa.

Current farming practices using heavy machinery are associated with soil compaction. The paper presents the results of tests aiming to determine in field the contact area and pressure distribution in the contact area between MSL machinery (for the precise application of the phytosanitary treatments in orchards) and the agricultural soil, respectively the determination in laboratory, on Hidropuls, of pressure distribution at 0-45 cm deep into the soil under the wheel of the MSL machine. The tank of the machine was loaded with 750 litres of water (wheel load 9.81 kN) and tire inflation pressures were 100, 150 and 200 kN. REZUMAT Practicile agricole actuale care utilizează mașini grele sunt asociate cu compactarea solului. Lucrarea prezintă rezultatele unor teste care au constat în determinarea în câmp a ariei suprafeței de contact și distribuției presiunii în pata de contact dintre roata mașinii MSL (pentru aplicarea cu precizie ridicată a tratamentelor fitosanitare în plantații pomicole) și solul agricol, respectiv în determinarea în laborator, pe Hidropuls, a distribuției presiunii pe adâncimea 0-45 cm în sol, sub roata mașinii MSL. Rezervorul mașinii a fost încărcat cu 750 litri apă (încărcare pe roată 9.81 kN) iar presiunile în pneu au fost de 100, 150 și 200 kN.

Seeking to become more climate-friendly and less energy-consuming, the European Union has pledged to cut its greenhouse gas emissions and milestones to achieve this are set to 20 % by 2020, 40 % by 2030, 60 % by 2040 and 80 % by 2050. Due to its abundance, biomass is gaining more and more importance both for the production of thermal energy by direct combustion or gasification of vegetal materials, for electricity and for the production of biofuels. Direct combustion of biomass generates CO 2 , but the process is neutral in terms of greenhouse gas emissions, because the same amount of CO 2 was absorbed by plants from the air during their life cycle. Ecological solid fuels such as pellets have become rapidly a viable alternative to fossil fuels, due to their high energy content, which makes them suitable for use by both small households and industrial consumers. Pellets are obtained from a variety of raw materials such as: agricultural residues, energy crops, forestry and wood residues, used exclusively or mixed and having different physical-chemical properties. This paper presents a summary of literature on the effect of the moisture content on the properties of pellets obtained from various types of biomass. Moisture content of raw material is one of the most important factors that influence negatively the properties of pellets, such as bulk density or mechanical durability during storage and transportation. Energy consumption increases during pelletizing of high moisture biomass, as moisture is a lubricant that lowers friction in the die. Other studies found a positive correlation between pellets durability and optimal moisture (10 %), because water together with the die temperature, pressure and chemical composition of raw material acts like a binding agent that increases pellet quality. Pellets with 5 % moisture have low strength, become brittle, and large amounts of dust are produced during their storage and transportation. Moisture higher than 15 % damages pellets during storage.

Sedimentation is perhaps the oldest and most common water treatment process. On the surface, a sedimentation tank appears to be a simple phase separating device, but down under an intricate balance of forces is present. Many factors clearly affect the capacity and performance of a sedimentation tank: surface and solids loading rates, tank type, solids removal mechanism, inlet design, weir placement and loading rate. Sedimentation (settling) is the separation of suspended particles that are heavier than water. Sedimentation is widely used in wastewater treatment systems. This paper presents the results obtained in some research focused on wastewater decanting processes in settling tanks.

Human exposure to wastewater discharged into the environment has increased within the past 15 to 20 years with the rise in population and the greater demand for water resources for recreation and other purposes. The organisms of concern in domestic wastewater include enteric bacteria, viruses, and protozoan cysts. Disinfection is considered to be the primary mechanism for the inactivation/ destruction of pathogenic organisms to prevent the spread of waterborne diseases to downstream users and the environment. The aim of this paper is to present the main types of disinfection used for the treatment of wastewater containing microorganisms.

The problem of water resources is aggravating as a result of accelerated urbanization, population growth, industrial and agricultural development. In addition to these factors, climate changes represent a substantial risk because it affects considerably both water resources and crops. Globally, agriculture is the largest consumer of water, accounting for approximately 70% of all freshwater. Farmers in many arid and semiarid areas are forced to find solutions to irrigate their crops, so they often must use treated, untreated or undiluted wastewater which is cheaper than other water sources. Increasing water needs (for drinking, food and irrigation) make the use of effluents (treated wastewater) an effective solution to solve the problem of water scarcity, to save significant quantities of drinking water, to reduce the use of chemical fertilizers (nutrients in the wastewater can replace conventional fertilizers), thereby protecting the environment and improving crop yield.

Worldwide, areas affected by drought and water scarcity are increasing rapidly. Thus, nutrient-rich wastewater has become a valuable resource for farmers. Over 20 million hectares (10% of irrigated land) are irrigated with untreated, partially treated, diluted or treated wastewater. Over 200 million farmers in 44 countries recover daily over 15 million m 3 of treated wastewater for irrigation. High chemical oxygen demand (COD) and biochemical oxygen demand (BOD), heavy metals, nutrients, antibiotics and pathogenic bacteria pose risks for human health and the environment, and high suspended solids can affect the irrigation system. In Romania, large agricultural area is affected by drought and deficient irrigation systems. There is potential for wastewater reuse in agriculture, but different wastewater treatment for agricultural reuse is only tested experimentally. Wastewater samples collected from the lagoon of a cattle farm were tested to determine the microbiological load (total coliforms, faecal coliforms, faecal streptococci) and physico-chemical parameters (pH, turbidity, conductivity, COD, BOD, total N, total P) before and after applying advanced electrochemical treatment. The aim is to reduce wastewater load and to obtain an effluent that can be safely used for irrigation of energy crops in arid, semiarid and sub-humid-dry regions. Removal efficiencies were 59.8% for COD, 82% for BOD, 23.7% for total N and 46.9% for total P.

Wastewater from livestock (swine, bovine, and poultry) is an unconventional source of water for irrigation, being widely used in both developing countries and in semi-arid developed countries, to compensate for the high water shortage. These wastewaters are characterized by high biological oxygen demand (BOD), high chemical oxygen demand (COD), high nutrients content (nitrogen and phosphorus that can be potentially applied as nutrients for crops), suspended solids and pathogens. Depending on these characteristics and the degree of treatment that must be obtained in order for these wastewaters to be safely reused or discharged directly to rivers or natural water bodies, have been developed various configurations of treatment plants for livestock wastewater. According to regulations in each country, animal farms must have more or less developed in-situ wastewater treatment facilities. Otherwise, farmers must pay fees for the wastewaters generated at their farms to be collected and treated at the municipal treatment plants. This paper presents some structures of treatment plants used in animal farms in the world, from common plants consisting on mechanical-biological treatment, to advanced ones that combine the mechanical-biological treatment with extensive treatment using lagoons, ponds, and constructed wetlands.

Municipal, industrial, livestock and agricultural wastewater that contains many organic and inorganic compounds are a potential support for the growth of microalgae and algae biomass, which have high tolerance level against adverse environmental stresses. Microalgae biomass has effective removal abilities of wastewater pollutants such as nutrient compounds (they use inorganic nitrogen and phosphorus for their growth within very short periods of time, nutrients that otherwise would produce water eutrophication), suspended solids, coliform bacteria, heavy metals and other harmful chemicals, and decreases the value of chemical oxygen demand and biological oxygen demand. Rapid growth rate and the ability to thrive even in extreme conditions make the microalgae an attractive means for sustainable and low cost wastewater treatment, without secondary pollution. Algae were found to further improve the final effluent quality through natural disinfection. In addition, microalgae consortium cultivated in open ponds for livestock wastewater treatment or in photobioreactors is rich in carbohydrates, proteins and lipids, which make them an important feedstock for biofuel production. This paper presents some of the cultivation methods and the advances in phytoremediation of livestock wastewater using microalgae.

Waste treatment involves all chemical, physical and biological processes that have the role of modifying certain characteristics of the waste in order to reduce their volume and hazardousness, thus facilitating their recovery. Among the available technologies, composting is presented as one of the most promising options for recycling the organic fraction into a valuable organic fertilizer called compost. In the present paper are presented the main composting methods, namely: passive composting in piles, turned windrow composting, passive aerated windrows, aerated static pile and in-vessel composting.

Biogas is a product of anaerobic ferment of organic products. Among the fuels from vegetal biomass, biogas has a great importance and can successfully replace fossil fuels for obtaining electricity and heat; the use of biogas exists for a few years also in the field of transport. Biogas formed in the methane fermentation process contains about 50÷60% of methane. Other ingredients such as carbon dioxide, hydrogen sulfide, water, water vapour and small amounts of nitrogen and oxygen are compounds that lower the energy value of biogas. In this paper are presented the main methods of biogas purification.

Current farming practices using heavy machinery are associated with soil compaction. The paper presents the results of tests aiming to determine in field the contact area and pressure distribution in the contact area between MSL machinery (for the precise application of the phytosanitary treatments in orchards) and the agricultural soil, respectively the determination in laboratory, on Hidropuls, of pressure distribution at 0-45 cm deep into the soil under the wheel of the MSL machine. The tank of the machine was loaded with 750 litres of water (wheel load 9.81 kN) and tire inflation pressures were 100, 150 and 200 kN.

Water is one of the world's most valuable resources, yet it is under constant threat due to climate change and resulting drought, explosive population growth, and waste. We optimize processes to reduce the volume of water used, take all possible measures to prevent contamination and use highly effective methods – some of which we developed ourselves – to treat wastewater. Wastewater is water that has been used and must be treated before it is released into another body of water, so that it does not cause further pollution of water sources. The purpose of wastewater treatment is to improve water quality, so that it can be discharged into the environment without harming environmental factors. This paper presents the types of equipment used in settling wastewater (United States Environmental Protection Agency, 2007). REZUMAT Apa este una dintre cele mai valoroase resurse ale lumii, dar este constant sub pericol din cauza schimbărilor climatice rezultat al creşterii explosive a populaiei, şi a deşeurilor. Optimizam procesele pentru a reduce volumul de apă uzata, luam toate măsurile posibile pentru a preveni contaminarea şi utilizarea unor metode foarte eficiente-unele dintre care le-am dezvoltat noi înşine-pentru tratarea apei uzate. Apă uzată este apa care a fost utilizata şi trebuie tratata înainte de a fi evacuata in alta sursa de apă, astfel încât să nu producă poluarea suplimentară a surselor de apă. Scopul tratării apelor uzate este de a îmbunătăi calitatea apei, astfel încât să poată fi deversata în mediul înconjurător, fără a afecta factorii de mediu. Această lucrare prezintă tipurile de echipamente folosite în decantarea apelor uzate (United States Environmental Protection Agency, 2007).

The paper presents the experimental results regarding the influence of solid-liquid mixture concentration and stirrer type on mechanical power consumption, aiming to determine the optimal mixing system for biomass in anaerobic digesters. As feedstock were used heterogeneous solid-liquid mixtures, composed of water and dry energy plant Miscanthus x giganteus, and also water and green grass chopped to sizes between 1 and 3 cm. For each tested mixture were used two concentrations (8.3% and 16.6%). Various configurations of stirrers were testes: impeller turbine, paddle and propeller, all being combined with baffles, and also without baffles in the mixing vessel. The lowest power consumption was obtained for the propeller stirrer. REZUMAT În lucrare sunt prezentate rezultatele experimentale privind influena concentraiei amestecului solid-lichid şi a tipului de agitator asupra consumului de putere, în vederea stabilirii sistemului optim de amestecare a biomasei în digestoarele anaerobe. Ca materii prime s-au utilizat amestecuri eterogene solid-lichid, alcătuite din apă şi planta energetic Miscanthus x giganteus uscată, precum şi din apă şi iarbă verde tocată la dimensiuni cuprinse între 1 şi 3 cm. Pentru fiecare amestec testat s-au utilizat două concentraii (8.3% and 16.6%). S-au testat diferite configuraii de sisteme de amestecare: turbină impeller, palete şi elice, atât în combinaie cu şicane, cât şi fără şicane în vasul amestecătorului. Cel mai mic consum de putere s-a obinut pentru agitatorul cu elice.

Artificial compaction is one of the most dangerous forms of degradation of agricultural soil. Recognized as a phenomenon with multiple negative effects in terms of environment and agricultural production, soil compaction is strongly influenced by the size of external load, soil moisture, size and shape of footprint area, soil type and number of passes. Knowledge of soil behavior under compressive loads is important in order to prevent or minimize soil compaction. In this paper were developed, by means of the Finite Element Method, various models of soil behavior during the artificial compaction produced by the wheel of an agricultural trailer. Simulations were performed on two types of soil (cohesive and non-cohesive) with known characteristics. By applying two loads (4.5 kN and 21 kN) in footprints of different sizes, were obtained the models of the distributions of stresses occuring in the two types of soil. Simulation results showed that soil stresses increase with increasing wheel load and vary with soil type.

The use of biomass has become extremely important for the production of clean energy from renewable sources. This is due to the continuously increased need for energy, to the possible depletion of conventional fossil fuels in the near future, and also to the regulations of European Union on the need to reduce significantly the emissions of greenhouse gases. This paper presents a synthesis on the raw materials used for pellets production, some of the important characteristics of pellets (density, ash content and heating power), and also data on the status of pellets production and consumption in different countries. Latest reported data show that the European Union is the biggest wood pellets producer globally, with a production of 13.5 million tonnes in 2014. Romania's pellets production in 2014 was of 740000 tonnes, and estimations are that in 2020 it will exceed 1.2 million tonnes.

In a continuously developing world, where many activities are high consumers of natural resources, including water, it has become absolutely necessary to apply methods of wastewater treatment. The purpose of wastewater treatment is to improve water quality, in order to be discharged into the environment, without being harmful for different environmental factors. In this paper are presented the equipment used in the mechanical stage of a wastewater treatment plant, and also the status of wastewater treatment plants in Romania.

Waste treatment involves all chemical, physical and biological processes that have the role of modifying certain characteristics of the waste in order to reduce their volume and hazardousness, thus facilitating their recovery. Among the available technologies, composting is presented as one of the most promising options for recycling the organic fraction into a valuable organic fertilizer called compost. In the present paper are presented the main composting methods, namely: passive composting in piles, turned windrow composting, passive aerated windrows, aerated static pile and in – vessel composting. REZUMAT Tratarea deșeurilor implică totalitatea proceselor chimice, fizice și biologice care au rolul de a modifica anumite caracteristici ale deșeurilor, în scopul reducerii volumului acestora și caracterului periculos, facilitând astfel valorificarea acestora. Dintre tehnologiile disponibile, compostarea este prezentată ca fiind una dintre cele mai promițătoare opțiuni pentru reciclarea fracției organice într-un îngrășământ organic valoros numit compost. În lucrare sunt prezentate principalele metode de compostare, şi anume: compostarea pasivă în grămezi, compostarea în grămezi cu întoarcere și amestecare, compostarea în grămezi aerate pasiv, compostarea în grămezi statice aerate forțat şi compostarea în containere închise.

Biogas is a product of anaerobic ferment of organic products (Bejan M. et al., 2007). Among the fuels from vegetal biomass, biogas has a great importance and can successfully replace fossil fuels for obtaining electricity and heat; the use of biogas exists for a few years also in the field of transport. Biogas formed in the methane fermentation process contains about 50÷60% of methane. Other ingredients such as carbon dioxide, hydrogen sulfide, water, water vapor and small amounts of nitrogen and oxygen are compounds that lower the energy value of biogas (Krischan J. et al.,2011) In this paper are presented the main methods of biogas purification. REZUMAT Biogazul este un produs al fermentării anaerobe a produselor organice. Dintre combustibilii din biomasa vegetală, biogazul are o importanță deosebită și poate înlocui cu succes combustibilii fosili pentru obținerea energiei electrice și a căldurii; utilizarea biogazului există de câțiva ani și în domeniul transporturilor. Biogazul format în procesul de fermentare cu metan conține aproximativ 50 ÷ 60% din metan. Alte ingrediente, cum ar fi bioxidul de carbon, hidrogenul sulfurat, apa, vaporii de apă și cantități mici de azot și oxigenul sunt compușii care scad valoarea energetica a biogazului. În această lucrare sunt prezentate principalele metode de purificare ale biogazului. INTRODUCTION A major concern for most people these days is the use and availability of energy. Peoples spend a large portion of their earnings on gas, propane and oil. These fossil fuels are being continuously used to a large extent. Because these forms of energy are non-renewable, their availability will continue to decrease and costs will continue to go up. This has led to a search for new energy sources. One excellent source of energy is biogas. Biogas originates from bacteria in the process of bio-degradation of organic material under anaerobic (without air) conditions. The natural generation of biogas is an important part of the biogeochemical carbon cycle. Methanogens (methane producing bacteria) are the last link in a chain of microorganisms which degrade organic material and return the decomposition products to the environment. In this process biogas is generated, a source of renewable energy. Biogas is a mixture of gases that is composed chiefly of:-methane (CH4): 40-70 vol.%-carbon dioxide (CO2): 30-60 vol.%-other gases: 1-5 vol.% including-hydrogen (H2): 0-1 vol.%-hydrogen sulfide (H2S): 0-3 vol.%

Shape and size of the footprint, and thus the depth at which stresses are transmitted into the soil are influenced by wheel load and tire inflation pressure. A mesh-type sensor was used for measuring of contact pressure in the footprints corresponding to five tire inflation pressures and five wheel loads. For each test were obtained the 2D maps showing the shape of footprint and also the distribution of pressure at soil-tire interface. It was found that at minimum tire inflation pressure the shape of footprint tends to be rectangular, and by increasing tire inflation pressure to the maximum, the footprint has rather elliptical shape. REZUMAT Forma și mărimea petei de contact și, prin urmare, adâncimea la care tensiunile sunt transmise în sol sunt influențate de încărcarea pe roată și presiunea din pneu. În lucrare a fost utilizat un senzor de tip plasă pentru a măsura presiunea de contact în petele corespunzând a cinci presiuni în pneu și cinci încărcări pe roată. Pentru fiecare test s-au obținut hărți 2D ce prezintă forma petei de contact și distribuția presiunii la interfața pneu-sol. S-a constatat că la presiune minimă în pneu forma petei de contact tinde să fie dreptunghiulară, iar prin creșterea presiunii în pneu la maxim, pata de contact are o formă mai degrabă eliptică. INTRODUCTION With increasing world population, to cope with the demand for more food it became necessary to intensify the farming and cropping systems. Thus, heavier machines per soil area have become common worldwide, resulting in the artificial compaction of soil. Compaction is a form of physical degradation resulting in densification and distortion of the soil where biological activity, porosity and permeability are reduced, strength is increased and soil structure partially destroyed (Abdel Rahman et al., 2016). The artificial compaction is human induced and is mostly due to technological errors in agriculture, such as excessive traffic on wet soils during agricultural works. All farm machinery operations, starting with the seedbed preparation, fertilizer and chemical applications and finally harvesting increase the risk of degradation of agricultural soil through artificial compaction. Nowadays, the risk of soil compaction increased due to due to significant growth of agricultural machinery. In European agriculture, the weight of tractors increased from 3 tons (in 1940) to 7 tons (in 1998) and up to 20 tons (at present). Nevertheless, compaction is not a recent phenomenon, because it existed in the form of hardpans long before the advent of intense mechanized agriculture (Batey T., 2009). Hardpans (or plough-pans) are compacted layers of soil with low thickness (2.5-5 cm), formed beneath the arable layer, usually due to repeated tillage at the same depth. Human induced compaction is one of the twelve forms of soil degradation in the E.U. and is a serious threat to soil sustainability, with numerous environmental and agronomic negative effects (Figure 1). Important environmental effects of soil compaction are: reduced water and air infiltration, increased risk of surface runoff and floods, increased erosion and sediment transport, reduced pesticide decomposition and increased pesticide leaching into groundwater, accelerated pollution of surface water by organic waste and applied agrochemicals (Keller and Lamandé, 2010). Some of the agronomic effects of compaction are: increased soil strength and limited root penetration into the soil, which ultimately lead to poor development