فهرست مطالب azar asadi

Nowadays, membranes are widely used in various industries due to their advantages such as high removal efficiency and the ease of operation. However, membrane clogging is an important limiting factor in this process which is related to the hydrophobicity of membrane materials. Although reverse osmosis and nanofiltration processes were used to purify water, the use of nanofiltration is more cost-effective as the nanofiltration process is conducted at a lower pressure and plays a major role in water treatment and desalination. Recently, many researches has reported the improvements in the ability of nanofiltration process to reject salts, dyes, and heavy metals and also to reduce the clogging of nanofiltration membranes. Membrane clogging is the largest and most challenging barrier to membrane processes, greatly reducing membrane performance and membrane life, and increasing operating cost. In this review article, different methods of nanofiltration membrane modification using nano-minerals, carbon as well as mineral / carbon composite materials has been investigated in order to improve the performance of nanofiltration membranes.

Nowadays, inadequate available freshwater resources, population growth and industrialization of communities have led to the development of various methods for water and wastewater treatment. Different technologies have been used for water and wastewater treatment, among which ultrafiltration membrane with high separation and removal of contaminants is considered as a promising option for water and wastewater treatment. However, membrane fouling is one of the main problems in membrane operation resulted in reduced performance and additional costs. Membrane fouling can be caused by various factors, depending on the type of fouling, different methods can be used to prevent fouling. One way to decrease membrane fouling is to add hydrophilic nanoparticles to the membrane through diverse modification methods. In this review article, we have tried aside from introducing the methods of preparation of anti-fouling membranes, the effects of adding different nanoparticles on the performance and fouling reduction of ultrafiltration membranes through some approaches such as inversion phase, electrospinning, bonding through ultraviolet rays and polymerizations have been discussed.

considered as a variable (0.5, 1, and 1.5 g/L of guanidine concentration). ATR-FTIR, SEM, AFM, and water contact angle were used to characterize the surface-modified membranes. Also, dry milk powder solution was considered as an organic foulant to assess antifouling features of the fabricated membranes. According to the obtained results, the surface modified membrane with 0.5 g/L of guanidine concentration was the optimal surface-modified membrane with pure water flux (PWF) and flux recovery ratio (FRR) of 11.6 kg/m2.h and 88.8%, respectively. Moreover, the capabilities of the optimal surface-modified membrane and the pristine membrane for rejecting AS5+ and Hg2+ in aqueous solution with concentrations of 20 ppm and 50 mg/L were compared. Based on the obtained results, the optimal surface-modified membrane rejected more than 98.5 % of AS5+ and Hg2+ solutions with 20 and 50 mg/L of metal ion concentrations.

One of the most pressing challenges confronting modern civilization is the lack of enough clean water supplies. Membrane technology has emerged as a key technology for water treatment, including fresh water, salt water, and municipal or industrial wastewater treatment, owing to its energy savings, high performance efficiency, and cost-effectiveness. However, membrane fouling, resulting from a non-specific interaction between the membrane surface and fouling agents, significantly hinders the efficient utilization of membrane technology. The fabrication of antifouling membranes is a fundamental approach to dealing with fouling issues caused by various types of fouling agents. Significant progress has been made in membrane preparation techniques and modification strategies, notably in microfiltration membranes, in recent years. While outlining the key strategies for modifying antifouling microfiltration membranes, the present review highlights recent achievements in the mentioned field, which provides more details related to the fabrication and preparation techniques and enhances performance parameters of these membranes. Microfiltration nanocomposite membranes modified by blending method can be considered an emerging technology capable of converting laboratory/pilot scale to a reliable commercial technology due to their high performance efficiency and good antifouling properties among all modification methods covered in this study. While using modification techniques (blending, surface modification, interfacial polymerization, sol-gel, and electrospinning) to better manage fouling in microfiltration membranes has certain benefits in terms of boosting performance, it also has drawbacks. Therefore, further optimization of modifying methods with the aim of commercializing modified microfiltration membranes is essential.

Due to the increased use of plastic materials in the daily lives of human all over the worlds and the concerns about the negative impacts of petroleum based plastics on aquatic and soil environments, the researchers have attempted to introduce biodegradable alternatives to such plastics. The non-biodegradability of petroleum based plastic is due to the large and long polymer molecules and the strong bonds between them, which ultimately makes it very difficult and even impossible for microorganisms to break down the molecules. The bioplastics are simply decomposed into their constituent units by the activity of living organisms and do not remain in the environment. Polyhydroxyalkonates (PHAs) are among the biodegradable polymers that have been received attention in the recent years. PHAs are polyester compounds that are produced by bacteria under special conditions. Feast/famine methodology is one of the methods for PHA production from bacteria. In this method, a sequencing batch recator (SBR) is used to supply feast and famine conditions, so that bacteria which are capable to produce PHA, compete with other microorganisms and obtain the maximum amount of PHA from the culture medium. In this review article, the method of feast/famine and the influential factors on producing PHA including feed type, feast/famine ratio, feed to microorganism (F/M) ratio, dissolved oxygen and nutrients concentration are investigated.

Considering the increasing rigor of environmental laws, the removal of carbon and nutrients from wastewater is a key aspect of research, and the simultaneous elimination of carbon and nutrients in a bioreactor has a significant impact on reducing reactor volume and energy consumption. The objective of this study was evaluating the performance of an aerobic sequencing batch reactor (SBR) with granulated sludge removing carbon and nutrient (N & P) from an industrial wastewater. Aerobic granules were obtained in a SBR and in the next step, the experiments were designed by a central composite design (CCD) with five levels of biomass concentration (2000-7000 mg/l) and aeration time (6-24 h).  Eight dependent parameters as the process responses were measured and calculated. The results showed that the maximum value of total COD (TCOD) removal was obtained to be 69.07% at mixed liquor volatile suspended solid (MLVSS) concentration of 5600 mg/L and the highest value of the aeration time (24 h). In addition, the low TN removal (47.5%) directed the study to reduce the oxygen level from 7 to 3 mg/L. A reduction in dissolved oxygen (DO) in extended aeration mode led to an increase in TN removal and a decrease in TCOD, nbCOD, and BOD removal. Overall, granular sludge showed an acceptable performance in terms of carbon removal, however, intermittent aeration could improve nutrients removal from wastewaters.

Process of climate change, particularly changes in temperature and precipitation; have raised the most discussion in the realm of environmental science. Human systems that are dependent on climatic elements such as agriculture and industry were designed based on stable climate.

In this study the output of general circulation models (GFCM21, HADCM3, INCM3, IPCM4 and NCCCSM) was used to simulate the climate parameters (minimum temperature, maximum temperature, precipitation and sunshine hours) in Hamadan station during 2046-2065. Three scenarios A1B, A2 and B1 were considered. Monthly changes of climate parameters were calculated by LARS-WG model.

The results showed that the most increasing in minimum temperature were seen under A1B scenario of GFCM21 model (2.5˚C). The least increasing was related to INCM3 under B1 scenario (1˚C). The highest and lowest increasing in maximum temperature were seen in GFCM21 model under A1B and B1 scenarios by 2.4 and 1.4˚C, respectively. B1 scenario of IPCM4 model showed the highest increase in precipitation by 15.8 percent and A1B scenario of GFCM21 model reported the highest decrease by 13 percent. Solar radiation project by HADCM3 model, A1B scenario showed the most increase about 24 percent and based on NCCCSMmodel, A2 scenario lowest increase (by 13 percent) was seen.

The results of this study indicated minimum and maximum temperatures will increase in period of 2046-2065. Both increases and decreases in precipitation were seen. Also variations sun hour is very little.

In this research, the possibility of polyhydroxyalkanoates (PHAs) production in a mixed microbial culture fed by industrial soft drink wastewater was assessed. To enrich the microbial culture, an uncoupled carbon and nitrogen feeding strategy were used in sequencing batch bioreactor (SBR). To evaluate the efficiency of the strategy, PHA, substrate, dissolved oxygen, biomass and nitrogen concentration profiles were reported in the 16th cycles of the SBR. From the obtained data, COD and nitrogen removal efficiencies were 89 % and 75.5 %, respectively at the cycle time of 12h. Also, the maximum poly-hydroxybutyric acid (PHB) content and specific PHA production rate (qp) were achieved as 13.8% (mg-PHB/mg-TSS) and 6.4×10-3 (mg COD-PHA/mg COD-X.h), respectively.