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[en] The effect of twelve weeks of composting on the mobility and bioavailability of cadmium in six composts containing sewage sludge, wood chips and grass was studied, along with the cadmium immobilization capacity of compost. Two different soils were used and Cd accumulation measured in above-ground oat biomass (Avena sativa L.). Increasing pH appears to be an important cause of the observed decreases in available cadmium through the composting process. A pot experiment was performed with two different amounts of compost (9.6 and 28.8 g per kg of soil) added into Fluvisol with total Cd 0.255 mg kg-1, and contaminated Cambisol with total Cd 6.16 mg kg-1. Decrease of extractable Cd (0.01 mol l-1 CaCl2) was found in both soils after compost application. The higher amount of compost immobilized an exchangeable portion of Cd (0.11 mol l-1 CH3COOH extractable) in contaminated Cambisol unlike in light Fluvisol. The addition of a low amount of compost decreased the content of Cd in associated above-ground oat biomass grown in both soils, while a high amount of compost decreased the Cd content in oats only in the Cambisol.
[en] Two composting processes were carried out; they lasted for about 165 days. In one of the processes the decomposition of the material was performed only by microorganisms only (direct composting) and in the other one, by microorganisms and earthworms -Eisenla foetida- (indirect composting). The first one was carried out in a composting system called camasand the indirect one was carried out in its initial phase in a system of panelas, then the wastes were transferred to a cama. The materials were treated in both processes with lime, ammonium nitrate and microorganisms. Periodical samples were taken from different places of the pile and a temperature control was made weekly. The following physicochemical parameters were analyzed in each sample: Humidity, color, pH soil : water in ratios of 1:5 and 1:10, ash, organic matter, CIC, contents of carbon and nitrogen and C/N ratio. In the aqueous extract, C/N ratio and percentage of hydro solubles were analyzed. It was also made a germination assay taking measurements of the percentage of garden cress seeds (Lepidium sativum) that germinated in the aqueous extract. The parameters variation in each process let us to establish that the greatest changes in the material happened in the initial phases of the process (thermophilic and mesophilic phases); the presence of microorganisms was the limiting factor in the dynamic of the process; on the other hand, the earthworm addition did not accelerate the mineralization of organic matter. The results let us to establish that the color determination is not an effective parameter in order to evaluate the degree of maturity of the compost. Other parameters such as temperature and germination percentage can be made as routine test to determine the process rate. Determination of CIC, ash and hydro solubles content are recommended to evaluate the optimal maturity degree in the material. It is proposed changes such as to reduce the composting time to a maximum of 100 days and to make the composting in a system of panelas
[en] Residues or wastes are a problem to the cities, owing to its collect and disposal produce many negative effects in public health and the environment as odors, microorganism (pathogens), vectors (flies, rodents and mosquitoes), and others. To solve this problem have been propose mainly two alternatives: 1. Sanitary landfills and 2. Recycling. To recover the residues as biodegradable as not-biodegradable, exist alternatives as composting (fermentation process or aerobic oxidation) and recycling - reuse, respectively. The composting process in aspects as the required conditions to that the organism acts efficiently as control of temperature (between 40-75 centigrade degrees), feed (carbon, nitrogen and other organic matter), aeration (by mixing or turning), control of moisture (between 50-60%), are present. Methodology aspects to composting also are described
[en] Heavy metal pollution has become a major environmental concern nowadays and the bioremediation of polluted habitats is an increasingly popular strategy due to both its efficiency and safety. A screening and selection protocol based on different composting processes was designed in order to isolate heavy metal-resistant microorganisms. A collection of 51 microorganisms was obtained and most of them showed the capability to tolerate heavy metals in multi-polluted aqueous systems (Cd(II), Cr(VI), Ni, Pb, Zn(II)), as well as to remove them. The highest detoxification ratios were observed for Pb. Some of the isolates detoxifying more than a 90% of this metal, while the other metals were removed in a range between 20% and 60%. The best isolates (Graphium putredinis, Fusarium solani, Fusarium sp. and Penicillium chrysogenum) were further assayed in order to determine the predominant removal mechanism and the potential use of their dead biomass as a biosorbent. Intracellular accumulation was the prevalent mechanism for most isolates and metals, with the exception of Ni. In this case, the proportion removed by extracellular adsorption was similar or even higher than that removed by intracellular accumulation. Thus, the efficiency of living cells was higher than that of dead biomass except in the case of Ni. - Highlights: ► Composting is a good reservoir for the isolation of HM-resistant microorganisms. ► Pb was the most removed heavy metal in multi-polluted aqueous systems. ► Intracellular accumulation was the predominant mechanism for heavy metal removal. ► Graphium putredinis, which detoxifies organic pollutants, was the most efficient isolate.
[en] Phosphate solubilizers are miroorganisms that able to solubilize insoluble inorganic phosphate compounds or hydrolyze organic phosphate to inorganic P. Therefore make the P to be available for plant and consequently enhance plant growth and yield. Recently, phosphate solubilizing microorganisms has been shown to play an important role in the biofertilizer industry. Fifty-one bacterial were isolated from eleven composts. Most of the phosphate solubilizers were isolated from natural farming composted compost and normal composting compost. This shows that both of these composts are more suitable to use for phosphate solubilizer isolation compare commercial composts. Fourteen of the isolates were found to be phosphate solubilizers. These isolates produced a clear zone on the phosphate agar plates, showing their potential as biofertilizer. AP3 was significantly produced the largest clear zone compared with other isolates. This indicates that isolate AP 3 could be a good phosphate solubilizer. Thus, their effectiveness in the greenhouse and field should be evaluated. (Author)
[en] The compostability of two different polyethylene (PE) products on the UK market under open-windrow composting conditions is explored within this paper. Chemical analysis of the PE bags has established their constituents in order to examine how the PE bags have an increased degradability depending on additives. Weight loss of the two different PE products within open-windrow composting conditions was recorded in order to establish the percentage weight loss as an indication of the degradability of the two products and their relative suitability for open-windrow composting. Scanning electron microscopy (SEM) of the PE products over the composting duration established the degradation processes for the PE products within the compost. These analyses concluded that one of the PE product mixes was more degradable than the other. However, neither product completed degraded within the timeframe of 12-14 weeks generally accepted for open-windrow composting in the UK
[en] Process of composting has been developed for recycling of organic fraction of municipal solid waste (MSW). The bioreactor design was modified to reduce the composting process time. The main goal of this investigation was to find the optimal value of time period for composting of MSW in thermophilic bioreactor under aerobic condition. The temperature profiles correlated well with experimental data obtained during the maturation process. During this period biological degraders are introduced in to the reactor to accelerate the composting process. The compost materials were analyzed at various stages and the environmental parameters were considered. The final composting materials contained large organic content with in a short duration of 40 days. The quantity of volume reduction of raw MSW was 78%. The test result shows that the final compost material from the thermophilic reactor provides good humus to build up soil characteristics and some basic plant nutrients
[en] The process of composting has been studied using five different types of reactors, each simulating a different condition for the formation of compost; one of which was designed as a dynamic complete-mix type household compost reactor. A lab-scale study was conducted first using the compost accelerators culture (Trichoderma viridae, Trichoderma harzianum, Trichorus spirallis, Aspergillus sp., Paecilomyces fusisporus, Chaetomium globosum) grown on jowar (Sorghum vulgare) grains as the inoculum mixed with cow-dung slurry, and then by using the mulch/compost formed in the respective reactors as the inoculum. The reactors were loaded with raw as well as cooked vegetable waste for a period of 4 weeks and then the mulch formed was allowed to maturate. The mulch was analysed at various stages for the compost and other environmental parameters. The compost from the designed aerobic reactor provides good humus to build up a poor physical soil and some basic plant nutrients. This proves to be an efficient, eco-friendly, cost-effective, and nuisance-free solution for the management of household solid wastes
[en] Composting of biowaste and diesel contaminated-soil is an efficient bioremediation method, with mature compost as a usable end product. - Soil spiked with diesel oil was mixed with biowaste (vegetable, fruit and garden waste) at a 1:10 ratio (fresh weight) and composted in a monitored composting bin system for 12 weeks. Pure biowaste was composted in parallel. In order to discern the temperature effect from the additional biowaste effect on diesel degradation, one recipient with contaminated soil was hold at room temperature, while another was kept at the actual composting temperature. Measurements of composting parameters together with enumerations and identifications of microorganisms demonstrate that the addition of the contaminated soil had a minor impact on the composting process. The first-order rate constant of diesel degradation in the biowaste mixture was four times higher than in the soil at room temperature, and 1.2 times higher than in the soil at composting temperature
[en] The aim of this work is to compare two different approaches for the evaluation of the respirometric index of dry biodegradable solid matter. The two used tools have been built in the University of Trent. The AIR-A respirometer (Open Respirometric Index Analyser) used in the experimentation is a pilot device made by a small steel reactor kept at steady temperature. The oxygen analyser and the temperature probe are directly connected to a PC through an acquisition device which allows to follow the evolution of the system. A balance between the amount of the volatile solids, the free volume and the decrease of the oxygen allows to assess the respiration rate. The AIR-C respirometer (Close Respirometric Index Analyser) is constituted by a reactor in which the trend of the internal temperature and the total pressure are constantly measured. A basic solution inside the reactor guarantees the absorption of CO2 allowing to associate an oxygen consumption to the measure of the total pressure. The reactor is built in order to allow a wide exchange surface between compost and atmosphere, limiting the thickness of the layer of compost in which oxygen must diffuse. A correct balance with the effect induced by the temperature allows to calculate the respirometric index, which is related to the microbic activity only in a portion of the total lasting of the test. The analysis of the generated data and the introduction of some technical modification have allowed to obtain with the two different approaches the same values for the respirometric index
[it]Il lavoro ha avuto l'obiettivo di mettere a confronto due differenti approcci utilizzabili per la valutazione dell'indice respirometrico di matrici solide biodegradabili. Le due apparecchiature utilizzate sono state messe a punto presso l'Universita' degli Studi di Trento. Il respirometro AIR-A (Analizzatore dell'Indice Respirometrico Aperto) usato nella sperimentazione e' un apparecchio pilota costituito da un piccolo reattore di acciaio di 17 litri mantenuto a temperatura costante. Al reattore e' collegato un circuito costituito da un compressore d'aria e una cella di misura dell'ossigeno presente. L' analizzatore dell'ossigeno ed una sonda di temperatura sono collegati direttamente ad un PC tramite una scheda di acquisizione che permette di seguire istantaneamente l'evoluzione del sistema. Un bilancio che coinvolge la quantita' di compost presente, la percentuale di solidi volatili, il volume libero ed il tracciato dell'ossigeno permette di definire il tasso di respirazione associato ai solidi volatili presenti. Il respirometro AIR-C (Analizzatore dell'Indice Respirometrico Chiuso) e' costituito da un reattore ermetico di 21 litri in cui viene misurato costantemente l'andamento della temperatura interna e della pressione totale. Una soluzione basica posta all'interno del reattore garantisce l'assorbimento della CO2 permettendo di associare direttamente un consumo di ossigeno alla musra della pressione totale. Il reattore e' costruito in modo tale da permettere comunque un'ampia superficie di scambio tra compost e atmosfera limitando nel contempo lo spessore in cui deve diffondere l'ossigeno. Un bilancio corretto con l'effetto indotto dalla temperatura permette di calcolare il tracciato respirometrico, che risulta essere indicativo dell'attivita' microbica solo in una porzione della durata totale della prova. L'analisi dei dati prodotti e l'introduzione di alcuni accorgimenti tecnici hanno permesso di evidenziare la congruita' dei valori di indice respirometrico ottenuti con i due diversi approcci