نوع مقاله : مقالات پژوهشی
نویسندگان
دانشگاه کردستان
چکیده
این پژوهش ویژگی های فیزیکی و شیمیایی، پتانسیل کودی و میزان آلودگی فلزات سنگین در 2 نوع کمپوست با زمان فرآوری بین 4 تا 8 سال (نوع A) و بین 1 تا 4 سال (نوع B) حاصل از زباله های خانگی شهر سنندج را با هدف استفاده از آن به عنوان یک کود آلی را مورد بررسی قرار داد. در این پژوهش ویژگی های فیزیکی (شامل: ناخالصی های نامطلوب، میزان رطوبت اولیه، توزیع اندازه ذرات، جرم مخصوص حقیقی و ظاهری، حداکثر ظرفیت نگه داشت آب و تخلخل کل) و ویژگی های شیمیایی (شامل: کربن آلی، pH و شوری) و میزان کل عناصر N، P، Ca، Mg، K، Na، Mn، Fe، Cr، Zn، Pb، Ni و Cd با استفاده از روش های استاندارد اندازه گیری شدند. نتایج این پژوهش نشان داد که جرم مخصوص ظاهری، میزان خاکستر و میزان کل عناصر با افزایش زمان فرآوری در واحد وزن خشک کمپوست، افزایش یافت، درحالی‌که اندازه ذرات کمپوست کاهش نشان داد. همچنین نتایج نشان دادند، که هر 2 نوع کمپوست مورد مطالعه از نظر میزان خرده شیشه (به گونه میانگین 7/21 برابر بیش از حد مجاز)، میزان سنگریزه (به گونه میانگین 4/1 برابر بیش از حد مجاز)، میزان سرب (به گونه میانگین 6/1 برابر بیش از حد مجاز)، میزان شوری (به گونه میانگین 4/1 برابر بیش از حد مجاز)، علاوه بر این کمپوست نوع B همچنین از نظر رطوبت اولیه (4/1 بیش از حد مجاز) و جرم مخصوص ظاهری (gcm-32/0، کمتر از پایین ترین حد مجاز) داری محدویت استفاده برای اهداف کشاورزی بودند. بنابراین، بدون اصلاح مناسب این محدویت ها، کیفیت کمپوست های بررسی شده برای اهداف کشاورزی مناسب نمی باشد.
کلیدواژه‌ها
عنوان مقاله [English]
The Assessment of Municipal Solid Waste (MSW) Compost Properties Produced in Sanandaj City with a View of Improving the Soil Quality and Health
نویسندگان [English]
- Z. Sharifi
- Mohammad Taaher Hossaini
niversity of Kurdistan
چکیده [English]
Introduction: the use of municipal solid waste (MSW) compost in agriculture as a soil conditioner is increasing day by day because of its positive effects on biological, physical, and chemical soil properties. However, some of the composts because of contamination with heavy metals and other impurities can have deleterious effects on groundwater quality, agricultural environment, food chain, plant growth and activity of soil microorganisms. Therefore, this study was conducted to investigate the physical and chemical properties, fertilizing potential and heavy metal polluting potential of two types of municipal solid waste composts with processing time between 4 to 8 years (type A) and between1 to 4 years (type B) produced in Sanandaj city with the aim of using it as an organic fertilizer.
Materials and Methods: Sanadaj city, the center of Kurdistan province, with a population of about 335,000 is located in the west of Iran. The current solid waste generation from the city is about 320 t/day, which are not separated at source of generation. About 200 t of the total produced wastes are composted using an open windrows system at the Sanandaj MSW Composting Plant, which is located in 10 km of Sanadaj-Kamiaran road and the rest are disposed at the landfill site. The compost manufactured by the composting plant has been collected around it in two different locations. The first belonges to the product of 2004-2008 (type A) and the second belonges to the product of 2009-2013 (type B). Till now, due to lack of quality information associated with these products, they have remained unused. Therefore, in this study, we sampled 3 samples composed of six subsamples (each containing 2 kg) from the products in March 2013. The samples were analyzed to determine the physical properties (including undesirable impurities, initial moisture content, particle size distribution, particle density, bulk density (ρb), porosity, and maximum water holding capacity), and the chemical properties (including organic carbon, ash content, pH and salinity) and total amounts of N, P, Ca, Mg, K, Na, Mn, Fe, Cr, Zn, Pb, Ni and Cd using standard methods.
Results and Discussion: The results showed that bulk density, ash content, and the amounts of elements based on the dry weight of compost increased with composting time, however particle size decreased. It is well known that dry bulk density increased with composting time as ash content increased and particle size decreased by decomposition, turning and screening. The decreases of particle size with composting time cause an enrichment of metals based on the dry weight of compost. It is likely due to solubilization of metals in waste by organic acid produced during the microbial decomposition of organic matter and their subsequent adsorption on finer particles due to the higher surface area and the higher ion exchangeable capacity. The evaluation of the fertilizing potential of the surveyed composts by comparing their properties with different standard sets showed that the both composts under test in this study were failed to meet the standard permissible limits with regard to glass content (on average, 21.7 times over the permissible limit), gravel content (on average, 1.4 times over the permissible limit), lead content (on average, 1.6 times over the permissible limit), and salinity content (on average, 1.4 times over the permissible limit). Furthermore, compost type B also failed to meet the standard permissible limits with regard to initial moisture content (on average, 1.4 times over the permissible limit) and ρb (0.2 gcm-3, less than permissible limit) for agricultural purposes. The results showed that excessive amount of glass impurity bigger than 2 mm, salinity and lead contents are the major problems in the use of the composts for agricultural purposes. It should be noted that according to the maximum permissible limit of lead (150-300 mg kg-1) for compost C1 quality class described by Australian standard; both the composts can be used as fertilizers or soil amendments. In order to eliminate glass impurity, remediation approaches such as fine milling and pelleting is needed to disguise the residual glasses and render it as relatively harmless. A feasible approach to eliminate these problems is probably physical fractionation of the studied composts. It allows us to assess the distribution of nutrients and contaminants values in the different physical fractions of the composts, which is useful to detect and to eliminate of the particle sizes which are the responsible for these impurities.
Conclusion: The assessment of MSW-based compost for use in agricultural soil as fertilizer or conditioner is a sustainable recycling practice owing to its nutrient content and its positive effects on soil physico-chemical properties. Thus, we evaluated the fertilizing potential of two MSW composts produced in Sanandaj city for agricultural purposes. Altogether, the results of the study showed that excessive amount of glass impurity bigger than 2 mm and salinity were the major problems in the use of the composts for agricultural purpose. As a result, the quality of the surveyed composts was not suitable for agricultural purposes without appropriate remediation of these restrictions.
کلیدواژه‌ها [English]
- Agricultural use
- Chemical and physical properties
- Processing time
- Municipal solid waste
- Compost
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