فهرست مطالب حسین نایب

Determining the wastewater quality index of municipal wastewater treatment plant for reuse or disposal purposes has always been an important issue. Therefore, developing a wastewater quality index facilitates the investigation and selection of the best option for wastewater reuse or disposal. Thus, determining the important quality parameters and the level of importance of each parameter in terms of the application of the wastewater are essential. In this study, after determining the important quality parameters by Delphi method, the weight of each factor was calculated using the multi-criteria decision making tools in order to develop the wastewater quality index. Then, the matrix for wastewater quality index was presented by defining the sub-indices for each parameter using the standards for wastewater reuse and disposal and by integration methods. Results indicated that the quality parameters including BOD, COD, TSS, TDS, Fecal Coliform, pH, NH4 PO4 are the most important parameters. Also, developing the wastewater quality index through different methods for reuse and disposal and application of various weights for each parameter was found to be a more accurate and reliable method. This method allows for fast and simple evaluation of wastewater in each treatment plant and comparison of different municipal wastewater treatment plants.

Currently, treated industrial wastewater is discharged to the environment in most industrial towns in Iran. It is, however, a potential water resource for produce industrial process water. For reach this reuse application, further treatment would be needed. Nowadays membrane separation processes are becoming quite popular in wastewater treatment and reclamation, since they combine process stability with an excellent effluent quality. One of this membrane processes for water reuse and reclamation is using reverse osmosis (RO) that is increasingly being used in all over the world. RO relies on pressure differential to force a solution (usually water) through a membrane that retains the solute on one side and allows the pure solvent to pass to the other side.
MBR is a process in which conventional biological system is coupled with the membrane process (microfiltration, MF or ultrafiltration, UF).
Due to the shortage of water resources in the Shokouhieh industrial town (located in Qom province, Iran) reclamation and reuse of industrial wastewater treatment plant effluent using RO modules were put on the agenda. Effluents of this WWTP were not being adequately treated by biological treatment and there are biodegradable organic matters in effluent of wastewater treatment plant. This research has focused on the evaluation of the pilot scale operation and monitor of an MBR system to advance treatment of an industrial wastewater in order to produce water with appreciate quality as RO feed water. In other words this study has discussed the feasibility of RO pretreatment for water reuse from industrial wastewater treatment effluent (before disinfection) with operation of a MBR pilot. The removal of certain pollution parameters such as chemical oxygen demand (COD) and suspended solids (SS) were monitored and Silt Density Index (SDI) analyses were performed on the MBR effluents to determine the fouling potential of MBR effluent as RO influent.
Actual wastewater used in this study was taken from an industrial wastewater treatment plant of Shokouhieh, Qom, Iran. This plant receives and treats the wastewater from different factories such as welding, dairy, beverage, metal finishing, … Due to poor design this existing treatment system is not effective in removing the all organic load of influent wastewater. So there is significant amount of biodegradable organic matters in effluent. The wastewater samples as MBR feed wastewater were collected from outlet of sand filters in plastic containers and were delivered to the laboratory where pilot is operated there.
Continuous operation of a pilot scale ultrafiltration membrane bioreactor system was carried out in this study. The bioreactor was made of Plexiglass with total volume of 32 liters. A flat sheet membrane ultrafilter was placed in the center of bioreactor.
Membrane operated at a constant flow rate of 4 L/hr using a prestaltic pump. Air blower was used to provide required sufficient air during operating the MBR. Also pilot was equipped with control instruments for measuring temperature, dissolved oxygen (DO), pH and wastewater level.
Membrane bioreactor was operated continuously, corresponding to an 8-hour hydraulic retention time (HRT) and the duration of operation was 30 days. Prior to use, membrane was washed with tap water until a steady pure water permeate flux was obtained. The MLSS temperature in the bioreactor was kept constant at 22–27 °C. Transmembrane pressure (TMP) was continuously recorded using an analogue pressure gage. Chemical cleaning of the membrane module was not carried out during the operation. No biomass was initially removed from the reactor to allow the biomass concentration build up in the system to about 2000 mg/L. After that Daily withdrawal of mixed liquor was conducted from the reactor in order to maintain the predetermined SRT (25 day) and to control an excessive increase of organic matter and solid concentrations in the bioreactor. Most analytical techniques used in this research followed the standard methods described by APHA. Data in this paper was averaged by at least 2 experiment results at each process
During this study, it was detected that the MBR had MLSS in the range of 1600–2300 mg/L. Because of the extend order of magnitudes of the concentration values, the concentration measurements are plotted on a logarithmic scale. Results shows excellent solids separation achieved by the UF membrane. Removal of SS reached greater than 98% resulting in the MBR permeate with SS levels below 3 mg/L.
Also as can be seen from results, the inlet COD varied from 178 to 320 with the average COD concentration of the influent 220 mg/L whereas COD concentration in Effluent varied between 41 and 51 and Average elimination rate was higher than 75%. It means MBR system produced excellent removal of organic constituents and it was capable of achieving a high removal of COD and can effectively decrease the COD. Some previous studies reported more than 90% of COD removal which is higher than results of this study. Lower COD removal in this study may relate to less organic material concentration in this bioreactor.
For investigation of membrane fouling, the change of TMP with time in the MBR was monitored. TMP increased and went up slowly in exponential manner due to the fouling of the UF membrane. TMP reached 58 kPa on the 13th day of operation which was the fastest fouled MBR. In this stage particle, colloidal, biological and organic matters rapidly accumulated onto the membrane, and formed a cake which was probably compressible, leading to a rapid increase in the TMP. Some of these foulants are easily removed through physical wash by water, thus called reversible fouling. There is another fouling that is not readily removable from the membrane surface and requires use of chemical cleaning. As was mentioned before, for remove fouling in this study membrane was soaked in a 250 mg/L NaOCl solution and afterwards with 4000 mg/L citric acid solution for at least 4 hours. Then membrane was cleaned with tap water. However, it still remains a bit clogging of the membrane pores that are not washed away and caused pore blocking. During operation of MBR and several cleaning of membrane, pore blocking increases. Thus, as was shown, the time interval between the membrane washing is reduced during operation and cleaning of membrane repeats in a shorter duration (10 and 7 days).
As mentioned before, if RO process feed directly with filtrate wastewater without any pre-treatment it will show a significant increase in process pressure. In this study, the permeate SDI was below 3 for most of the time, although there was a slight increase and fluctuation during the testing periods. The average measured value was 2.21, with the tendency to increase with increasing duration of operation.
In this study, we presented the possibility and applicability of MBR for RO pretreatment and reclaim effluent in an industrial wastewater treatment plant. The MBR pilot was evaluated in terms of effluent quality. In general, it can be concluded that MBR can produce high permeate quality and is capable to be a very efficient method for RO pretreatment. Product permeate from MBR with average SDI less than 3 indicate that by using MBR pretreatment for RO system, it can be anticipated that the rate of membrane fouling reduce and the life of RO membrane modules extend. Also effluent water from the MBR has a high quality according to SS and COD removal during operation.

Cadmium as one of the toxic heavy metal, because of harmful effects on health and the Environment, has attracted a lot of attention. The main sources of cadmium emissions are the environment, the waste of electroplating, melting, alloyed manufacturing, pigments, plastics, batteries, extraction and refining processes. This metal easily accumulates in different machines of people and has negative effects such as renal disorders, lung insufficiency, bone lesions, cancer, high blood pressure, on the healt. The adsorption process as an effective method for removing heavy metals from soil and water has spread. Various adsorbents such as clays, zeolites, the dry plants, waste pile of agricultural, biopolymers, metallic oxides, microorganisms, sewage sludge, ash and activated carbon for the removal of cadmium are used. Absorbed is known As an economic and efficient way with significant potential for removal, recovery and recycling metals of waste. In study of transmission and absorbed of minerals and compounds on the adsorbent, must exist Equations and relations between concentration and remaining of absorbed matter in constant temperatures, these equations are isotherms, Langmuir and Freundlich models are represent these equations. In this study, iron nanoparticles in size 8-18 nm and the effective level of 59-79 m2 / g was used, to prepare cadmium soluble was used of salt of cadmium chloride H2O(2/5) CdCl2.and for changes in PH was used NaOH hydroxide and HCl. Testing method.The experiments done as batch reactor and changing pH, change in the amount of nanoparticles, change in the initial concentration of soluble, change in the test time and Sedimentation time are investigated. The initial concentration of soluble is equal to 60, 30, 15, 5 mg / L, which is the value of 60 mg / L is included as the initial concentration of the soluble in other tests. in order to prepare 250 mm of 60 mg / L soluble, amount of 0.0035 gr of cadmium chloride salt is needed. At first 250 ml of the Concentration of cadmium is prepared and certain amounts of particles with 0.75, 0.5, 0.25 and 0.13 g weight, was poured into 100 ml test tube containing cadmium soluble, Then in order to uniform distribution of nanoparticles in soluble to increase the contact between pollutants and nanoparticles and to enhance the efficiency of adsorption, The Solubles were placed in an ultrasonic device. After washing with distilled water, magnet was poured into a test tube. And was adjusted onto a magnetic stirrer at high speed in a specified period of 60, 45, 30, 20 and 10 minute, And then was given Sedimentation time to the desired soluble. Also, in order to adjust the pH of concentrated nitric acid and were used normalized profits of 0.1. Assessing the effects of changes in pH on the removal efficiency of cadmium by iron nanoparticles.The results of the cadmium absorption in different pH at room temperature Was performed with an initial concentration of 60 milligrams per liter, 0.25 g of nanoparticles in 100 mg of soluble testing time 45 minutes. with increasing pH, Removal rates increased, And from pH= 5.8 to pH= 7.2 the removal efficiency increases about 60%, However, cadmium soluble in 8.4 = pH was tested under identical conditions without the presence of nanoparticles, became clear that without the presence of nanoparticles at this pH, there is also a 80% removal efficiency. but in pH=7.2 without the presence of nanoparticles, the removal efficiency was obtained 34%, indicating that In PH= 7.2 the presence of nanoparticles increases removal efficiency. Assessing changes in the amount of iron nanoparticles and its performance in the removal of cadmium.The results of the cadmium absorption was performed in varying amounts of iron nanoparticles at room temperature, with initial concentration of 60 milligrams per liter, a pH value of 7.2 with different values ​​of 0.13, 0.25, 0.5 and 0.75 g in 100 ml of nanoparticles and time-tested 45 minutes. Removal efficiency increases with increasing amount of nanoparticle and removal efficiency is increased with increasing amount of nanoparticle from 13/0 to 25 / 0 g by about 30%, While the the removal efficiency of cadmium with increasing amount of nano-particles from 5/0 to 75 / 0 g has increased only 3%. 0.75 g of nano has the best performance, but given the proximity the result with 0.5 g of nano, this value has been selected as optimal nano. because of the lack of affordable higher amount of nanoparticles. Assessing changes in testing time and the performance impact of nanoparticles in removal of cadmium.the results of Cadmium absorption was performed in varying amounts of testing time at room temperature, with an initial concentration of 60 milligrams per liter, a pH value of 7, 0.5 g nano-particles in 100 ml soluble at various times experiments, 60, 45, the 30, 20 and 10 minutes. of the Testing time 10 min to 20 min, the removal efficiency increased to 10% and from 20 minutes to 30 minutes, the removal efficiency increased only 3%. Assessing various amounts of Initial soluble concentration and the performance of nanoparticles in the removal of cadmium The results of the cadmium was performed absorption at different values ​​of the concentration of the initial soluble at room temperature, with initial concentrations of 60, 30, 15 and 5 mg l, pH value equal to 7.1, 0.5 grams of nanoparticles per 100 ml of soluble and time-tested 30 minutes. Whatever the soluble concentrations increases, the removal efficiency is reduced so that the maximum absorption of the soluble has happened at a concentration of 5 and 15 mg / L, which is equal to 98%. And in fact the removal efficiency for both samples was the same. As can be seen, the speed of absorption process for all four cases are very close. Assessing Change in settling time and the performance of particles in the removal of cadmium.The results of the cadmium absorption was performed at different times of sedimentation at room temperature, with an initial concentration of 60 milligrams per liter, pH value equal to 7, 0.5 grams of nanoparticles per 100 ml of soluble, test time of 30 minutes and the time of sedimentation 90, 60, 30 and 15 minutes. Eliminated by increasing the retention time increases if the maximum of percent absorption occurs at the retention time of 90 min, With increasing retention time from 15 to 30 minutes increases the percent absorption, but rate of increase is negligible, But in the retention time of 60 to 90 min, the removal efficiency increases to 20%. In this research, it was found that nano-zero valent iron particles are as an appropriate adsorbent for Cadmium reduction. Increasing amount of nano-materials, increases the absorption. Optimal obtained 0.5 gr per 100 ml of solution volume. In the study by Bahrami and his colleagues about removing of Cadmium from aquatic solution by nano-magnetic materials, it has been found that the removal efficiency increases with increasing amount of adsorbent. They concluded that by increasing the amount of adsorbent, the available adsorption sites for better adsorption of cadmium increases. By increasing of pH from 3 to 9, the removal efficiency increases but as it is clear on the diagram, the promotion rate of this efficiency in pH from 7 to 9 is insignificant and only 10% increased. Deposition has an important role in the removal of cadmium ions in the alkaline range. The likelihood of precipitation of metal hydroxides in the pore spaces around the particles is very low, because the adsorption process is faster than the precipitation process. Cadmium removal at pH lower than 7 is mainly controlled by adsorption process and this value at pH greater than 7 is significantly increased by cadmium hydroxide precipitation. In the study by L.V and his colleagues about Chrome removal by nano zero valent iron, it has been found that at pH greater than 7 removal efficiency decreases. At the time of testing, respectively, 20, 30, 45 and 60 min, the removal efficiency increases, but the rate of absorption reduces and the absorption rate is fixed at 30 and 45 minutes. So 30 minutes was considered as the optimal time. In the research by Alqudami and his colleagues about removal of Cadmium and Lead by nano-zero valent iron, it has been found that the best adsorption occurred in 20 minutes. This may be due to the rapid accumulation of nanoparticles which reduce the active surface and thus reduce the absorption capacity. Maximum adsorption by considering the all optimal situation occurred in a 5 mg/L solution. In the research by Bahrami and his colleagues about removing of Cadmium by nano-magnetic materials, it has been found that by increasing the concentration of the solution, removal efficiency decreases. At low concentrations of cadmium, specific surface areas and adsorption sites are more And cadmium ions can interaction by Surface of the adsorbent particles.So, The absorption efficiency increases.

With increasing development of urban communities and increase of population in towns, thus the need for water is also increased in the recent years. Production rate of municipal wastewater has also grown dramatically. On the other hand, increase of public awareness about the water pollution problems has followed the new and stricter environmental laws concerning wastewater discharge. Now producing of high volume of domestic wastewater and uncontrolled discharge into receptive water and underground resources, has faced the planners of the project with serious problems. Thus, that is anticipated until the year 1400 about 800 urban wastewater treatment plants arise in the country that enormous human and financial investment are included. Such investment must pay particular attention to the selected treatment process according to the economic and engineering criteria. In the recent years, many studies and optimization models is provided for finding the best options for wastewater treatment that most of them have only considered the cost of the investment and operation, while the best treating option is not always cheapest option. Selection of the optimization process of municipal wastewater treatment is an important and multidimensional issue. This is because of damages caused by failure of plan and waste of costs, Separate from satisfying Environmental standards and requirements, is requires to a systematic and completely scientific process for Selecting the process of optimal treating, To finally, has the minimal environmental impact with ability to perform in terms of technical and economical. In selecting the appropriate option of treating determine factors and decision criteria is important. And because of the complexity of communication between these criteria, and usually a criterion effect on the other criterion, making decision model and find the best options by using independent criteria is not easy. Therefore, the use of Multi-Criteria Decision-Making in this regard would be helpful. Since, several multi-criteria decisions methods such as weighted sum model, the TOPSIS method and Analytic Hierarchy Process (AHP) is presented. Analytic Hierarchy Process, is a useful method for working with multiple criteria and purposes in decisions, that Is able to evaluate the different objectives and determines difference between two options by priority vectors. The ultimate goal of this approach is identifying the best option and also determines rank of options by considering all decision criteria. This study is analytical- descriptive, that is conducted in the year 1392 in order to selecting the optimal municipal wastewater treatment and Evaluate matching the Frequency of wastewater treatment processes on the results of five different climates. The population of the study is consisted municipal wastewater treatment plants existing in the country (in operation and under construction) according to the latest figures released by the National Water and Wastewater Engineering Company in 1389. Climatic division of the country: In any studies plan, investigate the area and Understanding them is important.in other words, whatever the information about knowing the area be provided more complete and more precise, Principles of plan has been more appropriate would be face fewer problems. In this research, due to the unique diversity of climate of the country and in order to selecting the optimal process of wastewater treatment in different climates, According to the climatic classification of Publication No. 3-117 (revised in 1392), the country is divided five climate, mountain, Khazari, Mediterranean, semi-desert and desert. Treating Alternatives: According to available statistics and information, currently the most common methods municipal wastewater Treatment in the country are four processes: activated sludge, stabilization pond, aerated lagoon and Trickling Filter that Currently, more than 90 percent of the municipal wastewater treatment plants in the country take advantage from one of these four processes. It alone could cause choosing these four processes as appropriate treatment options in different operating area. In addition to usual of these methods, another reason that these processes have chosen as optimal treatment options is that facilities and most of the equipment needed to processes is made inside the country, and also access to technology of them is in the country. In present situation that the country is under different sanctions and lack of access to technology and equipment of a process, the process is virtually impossible to use, so different and new processes that are currently in developed countries are used as municipal wastewater treatment processes (such as membranous processes) were not in the list choosing the appropriate treatment process options. Decision criteria: Based on studies and summarized conducted, Criteria for selecting the appropriate treatment process for each basin in terms of three criteria, environmental, economical and technical were determined, Also, due to the extensive dimensions of each of the defined criteria, the following criteria were defined for each to achieve the best results. Data collection and Mode of scoring to the parameters In order to collect data and comments to resident experts in each climate, The five types of questionnaires were used that each of the questionnaire consisted of two parts, The first part using a pair comparison matrices, priorities of criteria and sub criteria has investigated in target climates and the second part, using a pair comparison matrix, the level of importance of treatment options relative to each criterion and sub-criterion are evaluated on the same climates. After collecting the opinions of experts, information obtained are reviewed and evaluated by a team of experts. In order to choose the optimal wastewater treatment process in the five state climates, In this study, four processes of urban wastewater treatment includes activated sludge, aerated lagoon, stabilization pond and trickling filter based on the environmental, economical and technical criteria and also related sub-criteria were evaluated by using AHP. In the mountainous climate of the country (type 1), activated sludge, aerated lagoons, stabilization ponds and trickling filter processes have obtained these weights: 0.347, 0.269, 0.209 and 0.174. Also in this climate, between the main criteria, environmental criteria with 0.558 weight has greater importance than other criteria and then technical criteria with 0.320 weight is in secondary importance. In the Khazari climate of the country (type 2), activated sludge, trickling filter, aerated lagoons and stabilization ponds processes have obtained these weights: 0.340, 0.273, 0.204 and 0.183. Also in this climate, between the main criteria, environmental criteria with 0.683 weight has greater importance than other criteria and then technical criteria with 0.200 weight is in secondary importance. In the Mediterranean climate of the country (type 3), activated sludge, aerated lagoons, trickling filter and stabilization ponds processes have obtained these weights: 0.334, 0.234, 0.231 and 0.201. Also in this climate, between the main criteria, environmental criteria with 0.540 weight has greater importance than other criteria and then technical criteria with 0.297 weight is in secondary importance. In the semi-desert climate of the country (type 4), stabilization ponds, activated sludge, trickling filter and aerated lagoons processes have obtained these weights: 0.276, 0.273, 0.270 and 0.181. Also in this climate, between the main criteria, environmental criteria with 0.493 weight has greater importance than other criteria and then technical criteria with 0.311 weight is in secondary importance. In the desert climate of the country (type 5), stabilization ponds, trickling filter, activated sludge and aerated lagoons processes have obtained these weights: 0.292, 0.266, 0.247 and 0.195. Also in this climate, between the main criteria, environmental criteria with 0.493 weight has greater importance than other criteria and then economical criteria with 0.311 weight is in secondary importance. According to the results of Analytical Hierarchy Process in order to selecting the optimal urban wastewater treatment in different climates, environmental criteria as the most important criterion is known in all climates and the highest it's weight is in the Khazari climate(0.683) and the lowest it's weight is in the desert and semi-desert climates(0.493). the high importance of ecological criteria in the Khazari climate due to natural conditions of mentioned region and factors such as tourism industry, high groundwater levels, have numerous rivers and other factors related to the environment of region, Would be justified. also, technical criteria in four climate: mountainous, Khazari, Mediterranean and semi-desert of country has been second in importance and the highest it's weight is in the mountainous climate(0.320) and the lowest it's weight is in the desert climate(0.196).that the high importance of ecological criteria in the mountainous climate Due to the sensitive environmental conditions and the poor performance of most wastewater treatment processes in cold weather would be justified. Based on the results in three climate mountainous, Khazari and Mediterranean activated sludge process Is introduced as the most appropriate treatment options. That the highest it's weight is in the mountainous climate (0.347) and the lowest it's weight is in the desert climate (0.247). Also, in two climate desert and semi-desert stabilization pond Is introduced as the most appropriate treatment options. That the highest it's weight is in the desert climate (0.292) and the lowest it's weight is in the khazari climate (0.183).finally, The highest and lowest weight of aerated lagoon process Is Respectively achieved in mountainous (0.269) and semi-desert (0.181) climates. And The highest and lowest weight of Trickling Filter process is respectively achieved in Khazari (0.273) and mountainous (0.174) climates.