علی اکبر عظیمی

In drinking water treatments, for coagulation and sedimentation of suspended particles, several coagulants are used such as Alum, PAC and ferric chloride. In spite of their positive effect on turbidity removal, these chemicals cause some problems like corrosion and harmful by-products which result in bad effects on human and environmental health. Therefore, finding and using better and more effective materials without such adverse effects is a necessity. The aim of this research was to study the effect of chemically synthetized sodium ferrate (S.F.) in liquid state for the turbidity removal from Zayandehrud River in two conditions: normal turbidity (less than 100 NTU) and high turbidity (more than 900NTU). This research was performed in four states of 30×60, 40×60, 60×60, and 30×40; in each state, one of the water independent variables effective on water turbidity was changed. These four states were S.F. dosing rate, gentile mixing speed, rapid mixing time and pH. For the experiment design, analysis and optimization of independent variables effective on turbidity removal were used. In addition, the surface response method (RSM-D-Optimal) plus Design Expert-v10 optimization software were used for this study. Finally, in this research, according to the standard methods, the residual total Fe (due to sodium ferrate) was checked in the research in order to ensure that its value was in the allowable range for drinking water. The results showed optimum conditions as: pH of 8.5 and gentle mixing oscillating speed of 60rpm for 7min, 50rpm for 7min and 40rpm for 6min, (instead of 40rpm constant speed for 20min) and rapid mixing time of 30s with 120rpm (instead of  60s, which was conventional in Esfahan water treatment plant). In addition, the results showed that by using only 1.54mg/L of S.F. in the above-mentioned optimum condition, the water turbidity removal efficiencies were 95.17% and 99.07% for normal and high turbidity states, respectively. A comparison was made in this research between using S.F. and poly aluminum chloride (PAC) for both normal and high turbidity. The results showed the better effect of S.F. than PAC. The results also showed that the residual total Fe was in the allowable range before and after the filter (because of the reactivity of ferrate with Fe). From the results of this research, it can be concluded that using S.F. has a positive effect, technically and economically, on water turbidity removal (better effect than conventional chemicals) in both normal and high turbidity. Moreover, the results showed that residual total Fe remains in the allowable range.

The aim of this study is to reduce p-nitrophenol from wastewater using an SBR reactor for biological treatment of sewage and to study the effect of concentration of p-nitrophenol in wastewater on reduction of biomass production and sludge volume index. For this study, two SBR reactors with a volume of 20 liters with on-line control system were used. Once the stable conditions in the reactors are met, sampling and testing of parameters such as COD, MLSS, MLVSS, PH, DO, SV1, SOUR, and p-nitotrophenol (PNP), as well as the rate of reduction in production of biological solids were performed during the 12 months of research. The results showed that for the inserted amount of more than 100 mg/l of PNP, the COD decreased from 772 to 193 mg/l while the COD removal efficiency decreased to 75% and the PNP concentration decreased to 36.7 mg/l. The biodegradable solids decreased by about 49.5% relative to the control reactor. On the other hand, in this dose of PNP, the amount of SOUR was 31 mg O2/h, and VSS and the SVI value was less than 48 ml/g.  For the PNP dose of 150 mg/l, no biosolids was produced in the reactor but COD and PNP levels increased in the effluent. The presence of toxic organic compounds such as p-nitrophenol in high concentrations in the wastewater while reducing the removal efficiency of the organic matter decreases the biological solids and thus reduces the amount of excess sludge.

The design and upgrade of sludge treatment systems generally depend on the decision made regarding the appropriate system from among the options available. The selection process has become increasingly important and complex due to recent technological developments that have led to increased diversity in the available options which offer a wide variety of capabilities. The multi-criteria decision making method is one of the techniques recently developed which takes into account all the criteria involved in the decision making process. The Ghods Town WWTP in the west of Tehran located in the vicinity of residential areas has given rise to claims by citizens due to the odors emitted by the sludge sand drying bed، which justifies the replacement of the present sludge dewatering system. For this purpose، the multi-criteria decision making method based on the fuzzy synthetic evaluation method was used to identify the optimal sludge dewatering system appropriate for the WWTP under consideration. Furthermore، weighting of the subjective (social، environmental، and administrative) criteria was accomplished using the analytical hierarchy process and the objective (i. e.، economic) criteria were weighted using the entropy concept. In this method، the triangular fuzzy membership function was also used to take into account the uncertainty associated with each of the decision making parameters. Based on the results obtained، the belt filter press dewatering system and the filter press were identified as the preferred solutions.

Heavy metals pollution is very important in Environment. Toxicity and accumulation characteristics of these metals are more noticeable for health aspects. Today, using bio-sorbent is more noticeable because these ways are ecofriendly and economic. In this survey, in addition to achieving Ni and Cd bio-sorption by bio-solid, the results of other relative surveys used for comparing the results and bio-sorption affinity discussion. Bio-solid powder produced from municipal excess sludge by drying, grinding and grainsizing. Ni and Cd solutions in 0.25 and 0.75 mille molar have been contacted which 0.5, 1, 2 and 4 grams of biosolid in pH 4, 200 rpm stirring, 24-260C temperature and two hours (continuous 5-420 min in kinetic study) time and samples have been analyzed with atomic absorption spectrophotometer to kinetic and isotherm modeling study and comparing the results. The maximum equilibrium adsorption of metals observed at two hours contact time and increasing of pH up to 4 increased the adsorption rate. The equilibrium data of both metals could be fitted by Langmuir isotherm equation and the maximum adsorption capacity (qmax) for cadmium and nickel are 0.38 and 0.195 mmol/gr dry bio-solid, respectively. The same as other biomasses studied for bio-sorption of heavy metals bio-sorption affinity of bio-solid for Cd is more than Ni. Generally, the bio-sorption affinity of algae and fungi for heavy metals bio-sorption is more than sludge and bacteria that is the result of cellular wall characteristics.

Trihalomethanes are a group of compounds that can form when the chlorine used to disinfect drinking water reacts with naturally occurring organic matter. Trihalomethanes have been proven to be carcinogenic. The purpose of this study was to determine Trihalomethanes in drinking water of Eastern part of Bandar abbas city and to evaluate the feasibility of removing chloroform by ultrasonic irradiation. Sampling was performed from three stations located in the Eastern part of Bandar Abbas city and in the winter of 1389 and in the spring of 1390 (February and may). The maximum concentration of THMs was observed in the spring (119.3µgr/l) and the minimum concentration in the winter (68.7µgr/l). The concentration of THMs was less than of maximum acceptable concentration (200 µgr/l) established by Institute of Standards & Industrial Research of Iran. Synthetic sample solutions containing chloroform were irradiated by ultrasound with intensity of 17.85 W/cm2.The results showed that the ultrasonic irradiation has the ability to remove Trihalomethans from aqueous solutions. After 8 minutes, 70% of chloroform was removed from sample solutions.

One of the most important components of community’s health is providing clean drinking water. The aim of this study is evaluation of the quality of inlet and outlet water from desalination plants in Qeshm obtained by reverse osmosis (RO) and Multistage flash (MSF) processes and to compare the outlet water quality with National and International standards of drinking water.

The cross-sectional descriptive study was carried out during 7 months from November 2011 to May 2012. Sampling was carried out once every two months from inlet and outlet water of desalination plants in Qeshm. Parameters studied included total hardness, electrical conductivity (EC), total dissolved solid (TDS), turbidity, temperature, pH, fluoride, nitrate, nitrite, chloride, sulfate and biological parameters (total coliform, fecal coliform). Finally, analytical analysis was performed by SPSS (version 16) using paired T- test.

The results of this study showed that total hardness and fluoride concentration in the effluent of the both of the processes (RO and MSF) were lower than desirable concentration and chloride concentration in RO process was higher than allowable concentration limit, the rest of parameters (chemical and physical) in both processes were in the acceptable range. No coliform contamination was observed in the effluent from both processes (RO and MSF).

The low fluoride and hardness concentration in the effluent of both processes (RO and MSF), should be compensated by adding fluoride and calcium or magnesium compounds. More importantly, both processes have high capability in providing safe drinking water. 

According to the fact that almost all forms of mechanical dewatering needs foreign specific technology, special efforts were concentrated to optimize the use of drying beds.The main disadvantage of sludge drying beds is their large land requirement. This will limit the use of conventional drying beds to areas where sufficient land is available. To optimize and facilitate the operation of sludge dewatering beds, some assumptions are considered in this study that their purpose is to compare the technical characteristics of effluent and the retention time of sludge cake on the bed with control pilot.In this study, the capability of natural substances in replacement of the sandy layer platforms by changing drainage layer's thickness has been investigated. Also, at second step with no change in the thickness of sandy drainage layer, the use of this material on the sludge drying bed has been studied. Natural substances must be used for applying research hypothesis. One of the basic conditions in creating the best habitat for microorganisms in the production of high quality compost is carbon to nitrogen ratio. Microorganisms need carbon resources to supply energy and new cells materials and also, nitrogen resources for protein production. Thus, paying attention to the ratio of carbon to nitrogen in the compost material and the process of preparation is necessary. Therefore, one of the most important parameters in compost preparation from swage sludge is the C/N ratio in the output unit of sludge dewatering. The use of materials with high carbon such as straw, wood chips and sawdust in sludge dewatering process can increase C/N ratio in the sludge cake. In this study, cross bed drying doesnt affect studies; thus, cylindrical pilot is used to simulate a drying bed. Important points in preparing pilots are recommended to be the height of bed and desirable gradated constituent materials. Three pilots were made for this research. One of the pilots was produced as a control pilot with regard to the characteristics of the conventional drying beds and the two others were prepared and established with changes in their structure based on the research assumptions.For simulation of test beds, sand and gravel features recommended in references were used. The properties of sand used for pilot preparation were approved with sieve analysis in soil mechanics laboratory.For easy access to the output of aerobic digester, the pilots were set beside the sludge drying beds in a treatment plant of Tehran city after preparation.Aerobic stabilized sludge was discharged in 20 cm height at pilots and sampling was done with special containers. The effluent sampling was carried out after 3 hours from the time of discharge of sludge on the platforms and tests were performed before 6 hours. Drying process was studied by sampling and moisture measurement of sludge cakes from control and test beds in the future days.

This study evaluated the efficiency of Electrical coagulation process in removal of COD, turbidity, detergent and phosphate from carwash effluent. An experimental study in laboratory scale was carried out and a glass tank with volume of 3 liters (effective volume of 2 liters) containing 4 electrode-page iron and aluminum (AL-AL, AL-Fe, Fe-Fe) were used. Electrodes were connected to a power supply with using bipolar method to convert alternative electricity to direct current. Daily samples were collected from different carwash effluents. Initial pH of samples were reported between 7 to 9.At first different tests were performed on primary samples. Percentage of removal was calculated in range pH and electrical potential of 11, 7, 3 and 30, 20, 10 volts respectively. Reaction times were set 90, 60, 30 minutes with middle intervals of 2 cm. The results showed the efficiency of COD removal in the optimum range of pH=3, voltage of 30 and retention time of 90 minutes with iron electrode was more 93% also the capacity of detergent removal for this process in optimum pH of 7, voltage of 30 retention time of 90 minutes with iron electrode was 94%. The highest phosphate and turbidity removal efficiency in pH of 7 after 90 minutes retention time, voltage of 30, with aluminum electrode reached more than 99%. According to the results obtained electrical energy consumption in aluminum electrodes was less than others. However aluminum is more expensive than iron and the difference in energy consumption between iron and aluminum can be ingnored. Apart from that COD and detergent removal efficiency of iron electrodes is higher than aluminum electrodes therefore, using iron as the electrode is more economical and recommended. Altogether it was found that this method can be use as a safe and convenient method for treating carwash effluent and according to the high removal efficiency of process, effluent can be discharged safely into the environment.

Many industrial & semi industrial countries manage to use SBR in order to industrial & municipal wastewater treatment. Simplicity, flexibility & being economical of this technical biological treatment, lead it to its significance in utilizing for treating of industrial & municipal wastewater.To study this procedure, two units of SBR reactor's cylinder made of poly glass with 20 liter volume are used. For seeding the reactors, artificial wastewater with COD of 600 mg/l & BOD of 600 mg/l is used. Reactors with different solid retention time (SRT) (5, 10, 15, 20 & 25 days) are operated.After providing the steady state in the reactors, during 8 months research, sampling and testing parameters such as COD, BOD, MLSS, MLVSS, MLNVSS, pH, DO, SVI, SOUR & F/M were done.The results show that SRT (5, 10, 15, 20 & 25 days) for 10 days duration is the best results for COD removal efficiency without existence of any bulking, pin point flocks and also foaming & dispersed growth difficulties. In this SRT duration, the amount of SVI has been up to 90 mg/l. This SRT system has been used in growth phase and the amount of F/M is 0.25. In the SRT less than 5 days, inorganic material removal & sludge volume index efficiency (SVI=215 mg/l) due to voluminous foaming generation & also fine coagulation generation resulted from lowness MLSS and dispersed growth occurrence respectively was low and it which shows that the system was operated in log growth phase & the amount of F/M has been1.8. Also in the SRT more than 25 days filamentous bulking phenomenon was aggravated and system efficiency due to bad sludge settle ability (SVI=215 mg/l) was low & because of over growth of filamentous bacteria, sludge can not be settled easily.With the increasing of SRT (more than 20 days), due to entrancing to declining phase and increase of inactive & old bacteria, the rate of oxygen consumption & SOUR reached to 7(mgo2/hr/grVSS), however in a low SRT (5 days), due to entrancing log growth phase & increase of active & young bacteria, the rate of oxygen consumption increased & SOUR reached up to 22 (mgo2/hr/grVSS).

Background and Subsurface flow wetlands are one of the successful treatment methods used for municipal and industrial wastewater treatment, and are economical in terms of energy consumption and workforce. Much research has been conducted on wetland operation output in wastewater treatment, but no enough information is available on their start-up and maintenance. The present study investigates the circumstance of starting up and implementing a wetland. Methods and Materials: In this experimental study, two subsurface flow wetlands with a two-day detention time and two pretreatment units were built. The former was similar to Primary Settling tank with a 4-hour detention time and the latter was similar to anaerobic pond equipped a with digestion pit with a two-day detention time in a pilot scale. The wastewater (BoD5 = 250 mg/l, Tss=320 mg.l and ph=7.2) from municipal network in Sabzevar, Iran was used for irrigation; the pilot implementation and maintenance took one year. Pilot operation indicated that the principal factors in implementing subsurface flow wetland were temperature, non-penetrateability of the bed, and wastewater ingredients. However, pretreatment and bed obstruction were the limiting parameters of the wetland maintenance. Pretreatment of the subsurface flow of wetlands does not yield a high output; and if anaerobic ponds equipped with digestion pits are used, the treatment output is significantly enhanced, and the wetland operation will face minimum barriers.

Sludge drying bed is preferred to mechanical methods due to the need for very simple technology. Due to restriction of natural dewatering, we tried to eliminate some of these limitations by the tests and studies of assumptions. In this study, the effect of hydrostatic suction and sludge chemical conditioning has been studied in the natural sludge dewatering optimization. At first, hydrostatic suction created by water entry and exit control, then by adding ferric chloride in the optimum dosage to the aerobic digested sludge, dewatering process was compared with the control bed. Retention time of the sludge cake and quality of effluent from the drainage layer were compared with control pilot. The retention time of sludge cake decreased from 5 days to 2 days and by using inorganic agent with the consistency of 440 mg/lit to the aerobic digested sludge conditioning, it's retention time (production of sludge with the dry solids consistency of 45 percent) decreased from 6 days to 3 days. The third stage of experiment was simultaneous use of chemical conditioning and hydrostatic suction in drying bed and its result was very satisfactory.Use of Hydrostatic suction can improve physical and chemical characteristics of effluent from the output of bed, such as turbidity, pH, TSS and VSS, while it increases COD and TDS. It should be mentioned that sludge chemical conditioning, increase effluent factors like TS and TDS.

The efficiency of particle settling in tube settlers can be improved by reducing tube diameter; however, this has limits due to the clogging at low diameters. In this study, effect of reduced tube diameters on enhanced efficiency of tube settlers was investigated. This improvement was achieved by staging of the operation and reducing tube diameter in the last stage of the multi-stage tube settlers. Theoretical analysis indicated that the efficiency of tube settlers would improve if tube settlers were used in different stages in series and that if their diameter was reduced in the last stage. The predictions from the theoretical analysis were tested in a pilot study. One- and two-stage tube settler pilot plants were used to remove water turbidity caused by clay in the first and second phases of tests with and without adding coagulant, respectively. The tube diameter in the one-stage tube settler were 5.0 cm, and those in those the first and second stages of the two-stage tube settler was 5.0 and 1.2 cm, respectively. The results of both phases showed that the two-stage tube settler was more efficient than the one-stage for turbidity removal with no clogging observed because the majority of the particles had been removed in the first stage.

The current approaches applied for removing nitrate from drinking water، commonly uses many chemical additives that may have undesirable or unknown effects on human health and in some cases caused many by products more dangerous than nitrate in drinking water. In present there are few appropriate and economic processes in this field and because of water scarcity in many areas development a suitable technology for treatment of nitrate contaminated drinking water for application in actual scales is crucial. In this research we develop an economic process with high selectivity for nitrate removal and minimum disturbance in other drinking water quality parameters that utilizes only hydrogen and carbon dioxide، produced in a methanol based electrochemical gas generator by applying a very low DC voltage (5-10 volt). We evaluate the ability of hydrogenotrophic denitrification for removal of nitrate in a bioreactor packed by light expanded clay aggregates known as LEACA. The results showed by proper coupling of electrochemical gas generator and denitrification bioreactor only by injection of tow clean and harmless gases، hydrogen and carbon dioxide and without any other chemicals addition for common concentrations of nitrate in natural waters by hydraulic retention time of 2-5 hr، removal efficiencies greater than 95% can be achieved. Also in comparison with other conventional methods such as ion exchange، reverse osmosis، electrodialysis، and biological heterotrophic with organic carbon source this system has several advantages such as: high selectivity for nitrate ion، low biomass yields، low electrical energy consumptions، without any problems resulted from organic carbon source addition (for example: taste and odor problem، carcinogenic THM production in disinfection process and rapid clogging of biofilter)، easy operation، and compatibility with health issues in drinking water treatment.

Sulfur utilizing autotrophic denitrification synthetic wastewater in up flow packed --bed reactor was evaluated under different concentrations of alkalinity and organic matter. The reactor was filled with granular elemental sulfur particles with diameters of 2.8-5.6 mm and porosity of 40%. The initial culture was prepared from sludge of Shahrak Ghods wastewater treatment plant. First, the stoichiometry ratios,? SO4/?NO3-N (sulfate produced to nitrogen nitrate removed) and? ALK. /?NO3-N (alkalinity consumed to nitrogen nitrate removed) were determined 7.05 and 2.92 mg/mg respectively by varying the influent nitrate concentration. Under sufficient alkalinity, complete nitrate removal occurred with 650 mg NO3-N/lit influent nitrate concentration and 0.792 Kg NO3-N/(m3-day) volumetric loading rate. As influent alkalinity decreased to values less than stoichiometry requirements, the nitrate removal efficiency decreased to a final percentage of 60.2% at 810 mg/lit alkalinity as CACO3. Under this condition, organic matter (methanol) was added to feed at concentrations of 247, 494 and 741 mg/lit, equivalent to 20%, 40% and 60% of stoichiometry requirements for heterotrophic denitrification. Results showed that by increasing the methanol concentration, the above stoichiometry ratios decreased to a final ratio of 2.66 and 0. 04 respectively and the overall nitrate efficiency increased up to 100%. Increasing effluent pH and turbidity (as an indirect determinant of effluent biological mass) and almost complete removal of influent methanol was also observed. All these changes imply the co-occurrence simultaneous sulfur based autotrophic and heterotrophic denitrification in bio reactor and show that the addition of controlled concentrations of organic matter to high nitrate wastewater with insufficient alkalinity not only compensates for the lack of alkalinity but also improves the performance of sulfur utilizing autotrophic denitrification

Recently, the use of biological absorbent in removal of hazardous pollutants such as heavy metals has increased because of the decrease in sludge problems, economical issues, high efficiency and compatibility with the environment. This study was done over the Biosorption of Nickel by Biosolids obtained from the municipal wastewater treatment in a batch reactor. The pretreatment of the Biosolids includes dewatering, grinding and grain sizing with meshes between 50 to 120. Nickel adsorption kinetics follows the pseudo second model and maximum equilibrium adsorption observed at two hours. The optimum stirring rate in this system is 150 to 250rpm. The increase in pH results in adsorption increase and there is a significant adsorption increase between 3 and 4. The results from adsorption modeling shows that the Nickel adsorption follows the Langmuir model and the maximum Nickel adsorption (qmax) by biosolids is 0.195 milimole per gram of dry biosolids (11.442 mg/g) and the Langmuir constant (kd) is 0.238 milimole per liter (13.96 mg/lit).

Background and Waste stabilization ponds as a natural treatment method have been found among successful methods in municipal wastewater treatment. They are very costeffective in energy and manpower. Low efficiency rates and vast area required are some of their drawbacks which are less attended to. Therefore this study intends to research the optimization methods in anaerobic ponds. Methods and Materials: In this experimental study, two anaerobic ponds were built in pilot scale with 48 hours detention time, 12 m2 area (6x2 m) and 4m depth. The control pond was a conventional pond; the optimized pond was built in two parts: a digestion pit and a detention time of 12 hours, and the anaerobic pond with 8 baffles with a detention time of 36 hours. The wastewater with BOD5=250 mg/l and TSS=320 mg/l from municipal network in Sabzevar, Iran was used; the pilot took one year from December 2006 to December 2007. The collected data were analyzed in Excel and Tsp7. Average removal efficiency for BOD5 and TSS in the conventional pond were 37% and 53% respectively; the figures for the optimized pond were 68% and 85% respectively. Using optimized anaerobic ponds enhances the removal efficiency rate.