One of the environmental issues in most regions of Iran is the large number of bottles made from poly-ethylene terephthalate (PET) deposited in domestic wastes and landfills. Due to the high volume of these bottles, more than 1 million m3 landfill space is needed for disposal every year. The purpose of this experimental study was to investigate the possibility of using PET waste in asphalt concrete mixes as aggregate replacement (Plastiphalt) to reduce the environmental effects of PET disposal. For this purpose the mechanical properties of plastiphalt mixes were compared with control samples. This study focused on the parameters of Marshall stability, flow, Marshall quotient (stability-to-flow ratio) and density. The waste PET used in this study was in the form of granules of about 3 mm diameter which would replace (by volume) a portion of the mineral coarse aggregates of an equal size (2.36-4.75 mm). In all prepared mixes the determined 6.6% optimum bitumen content was used. In this investigation, five different percentages of coarse aggregate replacement were used. The results showed that the aggregate replacement of 20% by volume with PET granules would result in a reduction of 2.8% in bulk compacted mix density. The value of flow in the plastiphalt mix was lower than that of the control samples. The results also showed that when PET was used as partial aggregate replacement, the corresponding Marshall stability and Marshall quotient were almost the same as for the control samples. According to most of specification requirement, these results introduce an asphalt mix that has properties that makes it suitable for practical use and furthermore, the recycling of PET for asphalt concrete roads helps alleviate an environmental problem and saves energy.
ABSTRACT:The ability of native bacteria to utilize diesel fuel as the sole carbon and energy source was investigated in this research. Ten bacterial strains were isolated from the oil refinery field in Tehran, Iran. Two biodegradation experiments were performed in low and high (500 and 10000 ppm, respectively) concentration of diesel fuel for 15 days. Only two isolates were able to efficiently degrade the petroleum hydrocarbons in the first test and degraded 86.67 % and, 80.60 % of diesel fuel, respectively. The secondary experiment was performed to investigate the toxicity effect of diesel fuel at high concentration (10000 ppm). Only one strain was capable to degrade 85.20 % of diesel fuel at the same time (15 days). Phenotype and phylogeny analysis of this strain was characterized and identified as dieseldegrading bacteria, based on gram staining, biochemical tests, 16S rRNA gene sequence analysis. These results indicate that this new strain was Bacillus sp. and could be considered as Bacillus Cereus with 98 % 16 S rRNA gene sequence similarity. The results indicate that native strains have great potential for in situ remediation of diesel-contaminated soils in oil refinery sites.
The effects of synthetic polymer (HE, PEI, and PAM) and natural polymer (chitosan) and chemical (alum) coagulant on the removal of lignin (black liquor color, and TOC) from pulp and paper industrial wastewater were investigated. It was observed that the formation of flocs was rapidly taking place which was an indication of fast coagulation flocculation process. PAM which is a nonionic polymer had poor effect as compared to HE and PEI which are cationic polymers. Both HE and PEI resulted in good brown colored precipitate at pH of about 6. These coagulant resulted in removal of about 80% of color and 30% of TOC from alkaline (black liquor) wastewater by gravity settling in 30 minutes. alum resulted in good precipitate with less than 30 minutes settling time by gravity. The percent color removed by alum was the same as the one removed by HE or PEI, but the TOC removed was higher by this chemical coagulant (about 40%). The natural coagulant, chitosan, resulted in the highest removal in both color and TOC as compared to both synthetic polymers and chemical coagulant. Up to 90% of color and 70% of TOC were observed to be removed by chitosan.
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