N. Abbasi, M. Mahdieh, M. H. Davoudi,
Volume 16, Issue 62 (Winte - 2013 2013)
Abstract
Stabilization of the silty sand soils which cover large areas of Iran and world is inevitable as their geotechnical properties are weak. In this research, the effects of different contents of lime and pozzolan admixtures on compressive strength of silty sand soil were investigated. To do this, different treatments were prepared by adding five levels of lime including 0, 1, 3, 5 and 7 percent by weight of silty sand soil, and four levels of pozzolan including 0, 5, 10, and 15 percent. Then, different specimens with 3 replications were remolded and cured for 7, 14 and 28 days and tested for determination of their unconfined compressive strength. Statistical analysis was made using SPSS software and the results showed that addition of lime and pozzolan increases optimum moisture content and decreases maximum dry density of the soil. Moreover, it was found that the addition of lime and pozzolan to the soil increases compressive strength considerably Compared with when applied individually. In this way, the compressive strength of the samples can be increased up to 16 times more than the natural soil strength. Based on the overall results of laboratory tests and statistical analysis, the combination of 3 percent lime and 15 percent pozzolan was determined as the optimum mixture for stabilization of silty sand soils
S. Jalinousi, E. Joudaki, A. Moghadassi, M. Mahdieh,
Volume 27, Issue 4 (Winter 2023)
Abstract
This research presents the application of phytoremediation to remove ammonia from effluent possessing high ammonium content and alkalinity in one of the most complex refineries in Iran. The objective of this research was to find new methods to protect and preserve water resources. At first, the algae distribution was investigated. After purifying the samples, Chlorella Vulgaris was selected as resistant algae in the areas that experienced ammonia shocks. A 10-liter container and an airlift photobioreactor with similar laboratory conditions were developed to control biomass production. Experiments were conducted over 20 days and maximum biomass production occurred in the first 16-17 days. Cell density was expressed as dry cell weight in ammonia concentration from 10 mg/L to 500 mg/L. It was also observed that when the Nitrogen content of the culture medium was less than 50 mg/L, ammonia was completely removed in both methods. At a concentration of 10 mg/L, total ammonia in both methods was removed in the first week. At 50 mg/L to 100 mg/L concentrations, about 94% of ammonia was removed in the glass container and about 95% in the bioreactor. In these concentrations, with high ammonia content, the final cell density, and absorption power were significantly low and this was evident at 500 mg/L. Prevention of water evaporation and biomass settling, better control of some vital parameters including pH, temperature, light, and energy intensity, effective mass and heat transfer, and carbon dioxide concentration led to better efficiency of the airlift photobioreactor. A noteworthy point in this result was the extraordinary performance of Chlorella Vulgaris in removing toxic pollutants such as ammonia and possibly using it in the biological systems of sanitary, refineries, and petrochemicals.
