جستجوی مقالات مرتبط با کلیدواژه « sawdust » در نشریات گروه « محیط زیست »

Large amounts of nitrate and nitrite in water cause different diseases in human and jeopardize plants and animals growth cycles. In this study in order to remove nitrate and nitrite ions from input of sample water, including high concentrations of nitrate by combining biological and physical methods a pilot was designed and tested. It should be noted that industrialization, cheap and availability of used materials in this pilot are benefits of this pilot.

The pilot was designed in the form of a cube with four drawers and a glass chamber at one end. The pilot drawers were filled with sawdust, wastewater (wastewater treatment plant in Islamic Azad University, Tehran) of treatment plant, including the best strain, handmade nitrate solution, the bentonite and twice washed sand. The experiments showed that the designed pilot in addition to the elimination of nitrate also removes the nitrite of the medium. The concentration of nitrate and nitrite was analysed by HACH/DR5000 spectophotometer.

In the case of the pilot performance of the continuous system and using the strains taken from the wastewater of the treatment plant after the aeration phase, the nitrate and nitrite removal efficiency of the input of sample water in 20 minutes retention time were measured 74.84% and 99.8% respectively. Additionally, in the case of the pilot performance in the continuous system and using the strains taken from the sludge of the treatment plant wastewater before the aeration phase and the yeast, the nitrate and nitrite removal efficiency in 20 minutes retention time were measured 72.63% and 56.33% respectively. 

Discussion and Conclusion:

During the experiments, the designed pilot had a promising role in the nitrate and nitrite removal. In the case of the pilot performance of the continuous system and using the strains taken from the wastewater of the treatment plant after the aeration phase, the maximum amount of nitrite and nitrate ions were removed. It should be noted that through the pilot performance in all cases, pH and temperature had an increasing and decreasing trend respectively.

Phenol presence and its derivatives in water and waste water on human health and the environment is one the major concerns. Because of the toxicity of phenol and also because of the presence of even low concentrations in natural resources, water disinfection and oxidation processes can lead to the formation of additional components. This material is one of the most common organic pollutants in water. In this research, adsorption of phenol from wastewater by sawdust was simulated using intelligent techniques. Intelligent techniques including multi-layer Perceptron, radial basis functions network and support vector regression were used. To design the network structure as well as the training and testing of 125 sets of experimental data is used. Performance evaluation criteria and stop network consists of % AARE and, which is used for all three models. All models compared results showed that the support vector regression with 0.5132 and 0.979, respectively, for %AARE and  is the best model. All models are better results than the quadratic polynomial model showed. Models showed good agreement with experimental data. The optimum conditions for the removal of phenol were 127.6 mg/l of initial phenol concentration, 0.84 g/l of adsorbent dose, natural pH value of 3.62 and 146.9 min of contact time, under these conditions the maximum removal efficiency was 91.23%.

Composting is one of the best methods for solid wastes disposal, therefore, some efforts seem to be essential for improving its process and its products quality. The aim of this study was to investigate the effect of sawdust admixture on composting process of municipal waste and some physicochemical parameters of compost such as temperature, pH, EC, heavy metals concentration and nutrient content.

4 piles were prepared and different amounts of sawdust were added (0, 16, 3 and 70%). Every day the temperature was measured within each pile; pH and EC were measured weekly; and heavy metals andnutrient content were measured in final products.

The pile without sawdust showed fluctuation in thermophilic temperature, and the gradual decrease in temperature was started on day 33, whereas this decrease was started on day 18 for 16 and 32% treatments. The pH value was shown to increase on day 21 and then slightly decreased to end of process. The pH value in final product was maximum in 0% treatment (8.1) and it was minimum in 70% treatment 7.73). The EC value showed a slight increase in all treatments during the composting process. Treatments with sawdust showed a low EC value in final products. 0% treatment gave a maximum amount (4.884) of EC and 32% treatment gave a minimum amount (4.235) of EC. The concentration of heavy metals and nutrients, except for Na and K, decreased with sawdust admixture. This was due to dilution effect of sawdust because of low metal content. Na concentration increased with sawdust admixture due to high content of Na in sawdust and used water.

Temperature fluctuation was controlled in composting piles and thermophilic temperature was preserved in active composting phase with sawdust admixture. Also compost quality was improved and heavy metals content decreased; therefore, the negative effects of compost on human health decreased with addition of sawdust

In Zahedan, about 0.8 ton sawdust generates in each day. This sawdust is landfilled despite their good effects on composting process. The aim of the present study was to reuse these serviceable wastes for improving C/N ratio, preventing nitrogen loss from the piles and investigating the effect of sawdust on moisture content of composting piles. Four composting piles were prepared with 0% (blank), 16%, 32% and 70% sawdust admixture. Once sampling was done in each week and samples were analyzed for the C/N ratio, moisture, nitrogen and carbon content. The percent of decrease in moisture content was 33% in blank treatment, whereas this decrease was 15, 15 and 10% for 16, 32 and 70% respectively. Loss of moisture was decreased with sawdust addition and this is very important for arid and hot area because of water sources shortage. The optimum C/N ratio was observed in 16% treatment and loss of nitrogen was decreased with sawdust addition. The percent of decrease in nitrogen content was 30, 7, 7 and 15% for blank, 16, 32 and 70% respectively. The maximum amount of nitrogen in final piles was observed in 16% treatment. Based on experimental data obtained, it can be concluded that sawdust caused water and nitrogen preservation in composting piles and it also improved undesirable and low initial C/N ratio. 16% treatment was shown more desirable effects on composting process and compost quality among other experimental treatments.