Effect of nanomaterials on remediation of polycyclic aromatic hydrocarbons-contaminated soils: A review.

The remediation of toxic polycyclic aromatic hydrocarbons (PAHs) in the soil is always an important topic since exposure to contaminated soil with carcinogenic, mutagenic, and teratogenic potential can result in serious health effects. With respect to the remediation of PAHs contaminated soil, nanomaterials (NMs) have recently received a great deal of attention due to the special characteristics arising from their nanoscale sizes. However, the usefulness and potency of these NMs depend on their adaption to specific site conditions and soil properties. Since there is no comprehensive review of the applications of NMs, it is of great importance to analyze, discuss, and interpret the latest progress in the application of NMs for the remediation of contaminated soils containing PAHs. This overview essentially captures the novel advances made in nano zero valent-iron (nZVI), metal oxides, carbon-based NMs, and polymer-based materials. Each characteristic of NMs that contributes to the enhancement of the process is highlighted. Moreover, operational conditions in which the best-obtained results are achieved qualitatively summarize. This review is also given special attention to the type of soil and pollutant, which are major influential factors to affect the performance of the process. Furthermore, the potential implication of NMs and PAHs on soil properties is reviewed in terms of the changes in migration behavior of pollutants, plant phytotoxicity, and soil microbial community composition. Discussion on future perspectives is presented on the use and prospects for the application of NMs in contaminated soils.

Evaluating the efficiency of sediment metal pollution indices in interpreting the pollution of Haraz River sediments, southern Caspian Sea basin.

The Haraz River is one of the most significant rivers in the southern Caspian Sea basin. Towards the estuary, the river receives discharges of industrial, agricultural, and urban wastes. In the present investigation, bulk concentrations of Cu, Zn, As, Cd, Pb, Fe, Ni, Cr, Co, and Sr in Haraz River (Iran) bed sediments were measured from several sample locations. In addition, association of studied metals with various sedimentary phases was assessed to determine the proportions of metals in different forms. The intensity of sediment contamination was evaluated using an enrichment factor (EF), geo-accumulation index (I(geo)), and a newly developed pollution index (I(poll)). Both EF and I(geo) formulae compare present concentrations of metals to their background levels in crust and shale, respectively. In a specific area with its own geological background like Haraz River water basin where naturally high concentrations of metals may be found, such a comparison may lead to biased conclusions regarding levels of anthropogenic contamination. Accordingly, chemical partitioning results are substituted for the mean crust and shale levels in the new index (I(poll)). The Pearson correlation coefficient between the anthropogenic portion of metallic pollution in Haraz river-bed sediments with I(poll) showed much more value in comparison with those of geochemical accumulation index and enrichment factor. The order of metals introduced by anthropogenic activities are as follows: Sr > Pb > Co > Cd > Zn > Cu > Ni > As > Cr > Fe. The results showed relatively higher concentrations of Cd, As, Sr, and Pb in comparison with those of shale. However, based on the chemical partitioning of metals, it is found that Sr, Pb, Co, and Cd are the most mobile metals. In spite of the high As concentrations in sediments, it is not likely that this element is a major hazard for the aquatic environment since it is found mainly in the residual fraction. Also, Fe, Cr, and Ni are present in the greatest percentages in the residual fraction, which implies that these metals are strongly linked to the sediments.

Evaluating citizen attitudes and participation in solid waste management in Tehran, Iran.

Recently, increasing attention has been paid to the environmental impact of solid waste in Iran. Consequently, solid waste management has become a remarkably important issue. Solid waste comprises a wide range of materials and comes from a variety of sources. Having a population of about 10 million (about 1/7 of Iran's total population), Tehran is among the most populated capitals in the world. With 22 different districts, this city generates approximately 7,000 metric tons of municipal waste per day that culminates in a total of 2.5 million tons annually. If no reduction strategy on the waste stream is implemented, this huge amount of waste will be buried in Kahrizak (the exclusive landfill site of Tehran). Land and underground water resource degradation in the vicinity of the landfill site-as well as disease outbreaks in the area surrounding the site may be considered alarming warnings for further catastrophic consequences of uncontrolled waste dumping. In this study, the composition of Tehran's solid wastes is analyzed. In order to physically analyze waste generated, waste sampling was carried out by trained workers of the Tehran organization of waste recycling and compost in 2004 for 10 successive days in the middle of each of four seasons. As a result of the study, some practical recommendations are made to reduce the waste stream load directed toward the land. Furthermore, this study evaluated people's concern about the fate of the waste they generate. According to the data collected in a survey, citizens' participation is not remarkably high, but even the modest cooperation recorded may cause a great benefit if extrapolated to the whole city. By virtue of sharp decreases in the cost of total waste collection and transport, as well as the benefits of land and underground water resource preservation, separation of wastes at their source by individual households makes economic sense.

Role of water-saving devices in reducing urban water consumption in the mega-city of Tehran, case study: a residential complex.

Iran is one of 27 countries that are likely to face increasing water shortage crises between now and 2025 unless action is taken to reduce currently high-per-capita urban water consumption. Accordingly, consumption control in the mega-city of Tehran will be an invaluable achievement. A study of Tehran water consumers has determined that household consumers are responsible for 70 percent of the total consumption. Keeping that figure in mind, the authors set out to assess rates of consumption by water fixtures, with an emphasis on household users, and to examine the effects of installing subcounters and reducers. They selected an apartment complex in which it was possible to install water subcounters for each unit. The first step was to evaluate resident attitudes. Block 3, which had 10 units, was selected to cooperate with the project. The second step was to install counters for all 10 units to determine consumption by different fixtures. (The counters were installed in kitchens, in bathrooms, on toilets, on washing machines, and on flash tanks). In the next step, data entry forms for fixture consumption were completed for a period of 10 days. Then single-handle faucets and reducers were installed, and the outcomes were logged for a period of 10 days. Counter readings were performed by the volunteer residents or by educated personnel every 24 hours, and the total volume of inside consumption was compared with the consumption registered by a base counter placed outside each unit. In the course of the project, the consumption per capita was calculated every 24 hours to yield a real and unbiased model that is applicable to city of Tehran. The results showed a total reduction in water consumption of about 20 percent. Thus, with suitable planning and application of cultural and technical methods, it is possible to optimize consumption in Tehran in the near future.

Removal of manganese and zinc from Kahrizak landfill leachate using daily cover soil and lime.

The possibility of in situ removal of heavy metals found in leachate generated at municipal solid waste landfills was studied through amendment of daily cover soil. Kahrizak landfill, which receives the waste generated at Tehran, was selected as the source of leachate and soil samples. Manganese and zinc were selected in this study. The soil sample taken from the Kahrizak site contained about 17% clay, which was presumed to have significant capability for removing manganese and zinc. This capability was assumed to be enhanced further through the addition of lime and consequently to improve the potential for chemical precipitation of the selected metals. The in situ removal experiment was accomplished through a set of seven columns filled with the sampled soil with varying contents of lime (i.e., from 0% to 6% by dry weight). Fresh leachate of low pH was added to the columns on a daily basis. Concentrations of manganese and zinc were measured in the influent and effluent during 40 days when biological clogging resulted in a condition of almost no outflow in the columns. The results indicated a substantial increase in removal efficiency through the addition of lime to the daily cover soil. Desorption resulting from the low pH of fresh leachate occurs at later stages compared to the column with no lime addition.

Municipal solid waste management on the south coastline of the Caspian Sea (Golestan, Mazandaran, and Guilan Provinces of Iran).

The Caspian region (including the Golestan, Mazandaran, and Guilan provinces of Iran) occupies 58,678 square kilometers (22,651 square miles) and has a population of 6,270,192, according to the census of 1996. This part of Iran is attractive to tourists because of its proximity to the Caspian Sea. In addition, the region boasts invaluable forests and grasslands, and is the exclusive producer in the country of key agricultural crops like rice and tea. The lack of systematic solid waste management has put this region on the edge of irreparable environmental damage. The large number and dispersion of open-dumping landfills, as well as the faded role of functional elements like waste minimization and processing, have sped up the environmental deterioration. This article evaluates the current status of solid waste management in the Caspian region and suggests practical alternatives. As a result of a field and desk study, the authors offer some instructions for separation of putrescibles, paper and cardboard, plastics, and so forth. Finally, after considering all aspects of the environmental impact assessments for different alternatives, the authors recommend the construction of two compost-producing facilities in Golestan province with a combined capacity of 500 metric tons per day and a total cost of $60,000, and four incineration sites in southern and southwestern parts of the region (Mazandaran and Guilan provinces) with a total capacity of 2,000 metric tons per day and total cost of $75 million.

A new flat sheet membrane bioreactor hybrid system for advanced treatment of effluent, reverse osmosis pretreatment and fouling mitigation.

This paper introduces a new hybrid electro membrane bioreactor (HEMBR) for reverse osmosis (RO) pretreatment and advanced treatment of effluent by simultaneously integrating electrical coagulation (EC) with a membrane bioreactor (MBR) and its performance was compared with conventional MBR. Experimental results and their statistical analysis showed removal efficiency for suspended solids (SS) of almost 100% for both reactors. HEMBR removal of chemical oxygen demand (COD) improved by 4% and membrane fouling was alleviated according to transmembrane pressure (TMP). The average silt density index (SDI) of HEMBR permeate samples was slightly better indicating less RO membrane fouling. Moreover, based on the SVI comparison of two reactor biomass samples, HEMBR showed better settling characteristics which improved the dewaterability and filterability of the sludge. Analysis the change of membrane surfaces and the cake layer formed over them through field emission scanning electron microscopy (FESEM) and X-ray fluorescence spectrometer (XRF) were also discussed.

Evaluation of membrane bioreactor for advanced treatment of industrial wastewater and reverse osmosis pretreatment.

The evaluation of a membrane bioreactor (MBR) for pretreatment of reverse osmosis (RO) in order to reuse and reclamation of industrial town wastewater treatment plant was investigated in this study. Performance of MBR effluent through water quality in term of parameters such as chemical oxygen demand (COD), total suspended solids (TSS), total nitrogen (TN) and total coliform (TC) were measured. Also Silt density index (SDI) was used as indicator for RO feed water. The results of this study demonstrated that MBR produce a high quality permeate water. Approximately 75%, 98%, 74% and 99.9% removal of COD, TSS, TN and TC were recorded, respectively. Also SDI of the permeate effluent from membrane was below 3 for most of the times. It means that pilot yield a high quality treated effluent from the membrane module which can be used as RO feed water.

The influence of deposit control additives on nitrogen oxides emissions from spark ignition engines (case study: Tehran).

In the present research, the influence of a deposit control additive on NOx emissions from two types of gasoline engine vehicles i.e., Peykan (base on Hillman) and Pride (South Korea Kia motors) was studied. Exhaust NOx emissions were measured in to stages, before decarbonization process and after that. Statistical analysis was conducted on the measurement results. Results showed that NOx emissions from Peykans increased 0.28% and NOx emissions from Pride automobiles decreased 6.18% on average, due to the elimination of engine deposits. The observed variations were not statistically and practically significant. The results indicated that making use of detergent additives is not an effective way to reduce the exhaust NOx emissions from gasoline engine vehicles.