WATER AND WASTEWATER
Year:2010 | Volume:20 | Issue:4 (72)|Papers Count:15

Conjunctive use operation policies play a vital role in the sustainability of water resources and their optimal allocation. To be realistic conditions of real water resource system should be considered in simulation and derivation of operating rules of real-world water resource system. In this research, the combined fuzzy logic and direct search optimization technique is used to account for the uncertainty associated with parameters affecting groundwater table level fluctuations. These parameters include specific yields and inflow recharge and outflow discharge from the aquifer, which are typically uncertain. A membership function is determined for each parameter using hydrogeologic and piezometric data. For each membership value (a level cut), the corresponding intervals are determined. These intervals are considered as constraints on the membership value of the groundwater table level fluctuations in the optimization model. The process is repeated for other a level cuts to obtain the fuzzy number. For the uncertainty influencing the water demands, a conjunctive use model with water resources constraints is developed. Using this model, the priorities for the different zones and their optimal allocations are determined. The results show that the better the real conditions are reflected in the conjunctive use model, the better will the system be reliably capable of handling the water demands. The results of the proposed model also indicate that it present reliable allocations compared to the static conventional models and that it performs more desirably and practically in allocating supplies to water demands as it duly includes the opinions of the decision-makers involved.

Advanced oxidation processes are associated with the production of very active hydroxyle radicals with a high potential for oxidation of organic compounds. One such process is Fenton process which reacts with ferrous ions in acidic media to produce a hydroxyle radical. It is an oxidation-reduction reaction in which the metallic ion accepts the transfer of one electron. A variety of factors such as pH, temperature, reaction time, and ferrous and H2O2 concentrations may affect the efficiency of the method. In this study, synthetic solutions of anionic LAS and ABS both having wide household and industrial applications were obtained and used to evaluate the efficiency of Fenton process in the removal and treatability of different concentrations of ferrous and H2O2 for a variety of contact times. Experiments were performed with different concentrations of H2O2 and ferrous iron at a constant pH of 3 in a jar test apparatus adjusted at 200 rpm and for different contact times (20, 40, 60, and 80 minutes). Results showed that increase in catalyst and oxidant concentrations increased removal efficiency. At a H2O2 concentration of 750 mg/l and a ferrous ion concentration of 130mg/l, 86% of LAS and ABS was removed in 80 minutes. Under these conditions, Fenton oxidation reduced the COD content of the ABS sample from 470 mg/L to 187 mg/L. The BOD5/COD ratio improved by 0.225 for a concentration of 600 mg/L of H2O2 and 130 mg/L of ferrous ion in 60 minuets. Measurements after the reaction revealed that pH reduced from 3 to 2.6 as a result of acidic intermediaries produced; this can be interesting for reaction control investigations.

Most organic compounds are resistant to conventional chemical and biological treatments. For this reason, other methods are being studied as alternatives to the biological and classical physico-chemical processes. In this study, advanced photochemical oxidation (APO) processes (UV, UV/H2O2, UV/H2O2/Fe(II), and UV/H2O2/Fe(III)) were investigated in lab-scale experiments for the degradation of phenol in an aqueous solution. A mediumpressure 300 watt (UV-C) mercury ultraviolet lamp was used as the radiation source and H2O2 30% as the oxidant. Phenol (initial concentration=0.5 mmol/L) was selected as the model due to its high use and application. Some important parameters such as pH, H2O2 input concentration, iron catalyst concentration, the type of iron salt, and duration of UV radiation were studied based on the standard methods. The results showed that the Photo-Fenton process was the most effective treatment under acidic conditions producing a higher rate of phenol degradation over a very short radiation time. The process accelerated the oxidation rate by 4-5 times the rate of the UV/H2O2 process. The optimum conditions were obtained at a pH value of 3, with a molar ratio of 11.61 for H2O2/Phenol and molar ratios of 0.083 and 0.067for Iron/H2O2 in the UV/H2O2/Fe (II) and the UV/H2O2/Fe (III) systems, respectively.

Phenol, or Benzene hydroxyl, is a toxic aromatic hydrocarbon which finds its way into the environment and water resources as a serious environmental hazard in the effluent from a number of industrial processes. The objective of this investigation was to compare the efficiency of advanced oxidation methods with that of O3 and UV radiation in Phenol degradation. For this purpose, a reaction chamber with a capacity of 3 liters (laboratory scale) was used. A photolytic cell system with a 125W UV lamp was designed and manufactured. The ozone used in the reaction was produced at a rate of 1g/h in a COG-OM ozonizer before entering the reactor. A set of experiments was carried out at pH levels of 5, 7, 9, and 11 to investigate the effect of pH on phenol degradation rate. Samples were then collected for analysis by a spectrophotometer. Our findings show that phenol is degradable at a basic pH of 11 with ozone application and at an acidic pH of 5 with UV radiation. Using a 125 WUV- light source, phenol degradation after one hour was 32.4% while it reached 93.6% after the same period when using ozone. Due to their desirable health and environmental impacts as well as their high efficiency, advanced oxidation processes are expected to be a promising technology for the removal of phenol and other similar pollutants from water and wastewater.

Methyl Tertiary Butyl Ether has been used in the United State since 1979 as a gasoline additive. Increased use of this compound has caused pollution in both surface and groundwater. Conventional treatment methods are not successful. In this study, Fenton-reagent based degradation of a high concentration solution (1000Mg/L) of Methyl Tertiary Butyl Ether was investigated on the bench scale using Ferric Sulfate as the Fenton catalyst. Effects of pH, time of reaction, and reaction reagent (Hydrogen peroxide and iron catalysts) concentrations were investigated. Under optimum conditions, the degradation efficiency was 99.995 percent. The optimum concentrations of ferric sulfate and hydrogen peroxide for the complete removal of MTBE were 5.4 Mg/L and 550Mg/L, respectively. The optimum pH was 3, and the remaining concentration of MTBE in the solution under optimum conditions was lower than 50]g/L (Gas Chromatography detection limit). Rate of reaction decreased after a few minutes. Variations in pH over time were measured. It was found that increasing the hydrogen peroxide concentration decreased Methyl Tertiary Butyl Alcohol and Acetone in solution. Concentrations of these by-products increased at high pH levels. Acetone and Tertiary Butyl Alcohol concentrations were 30 and 120 Mg/L, respectively, at pH=3, while they were 150 and 250 Mg/L, respectively, at pH=7.

Contamination of water with petroleum compounds is a serious environmental problem in Iran. Old fuel storage tanks, gasoline stations, and oil refineries are the main sources of gasoline leakage into water resources. In this study, the batch adsorption technique was used to investigate adsorption of petroleum compounds (gasoline) on granular activated carbon. Experiments showed that the adsorption capacity of activated carbon is a function of pH, temperature, and H2O2 concentration in solution. Maximum adsorption of petroleum compounds was obtained at pH of 8. Adsorption of petroleum compounds was increased by decreasing temperature (due to decreasing van der Waals forces between the adsorbent and the adsorbate) and H2O2 concentration in solution (due to the decrease in the initial concentration of the adsorbate by oxidation). In this experiment, the maximum equilibrium capacity of granular activated carbon was 129.05 mg COD/g GAC at pH 8 and at an ambient temperature of 10oC. The experimental adsorption data were fitted to the Freundlich and Langmuir adsorption model. The correlation coefficients calculated indicate that the Freundlich model was best fitted. Also, the regression analysis was used with a correlation coefficient of 0.981 to develop a model for describing the relationship between absorption variation in equilibrium state, pH, temperature, and H2O2. On the whole, the correlation coefficient calculated by the proposed model was found to be higher than Freundlich’s.

Development of effective methods for the removal of such pollutants as heavy metals (e.g., mercury) from surface and ground water resources introduced by municipal and industrial wastewaters seems to be inevitable, especially in the face of the importance of water reuse in combating water shortages, limited availability of water resources, and imminent risks of a water crisis in Iran. A number of methods are already available for the removal of mercury from water resources. However, these techniques must be investigated for their practicability and economy, in addition to their not only effectiveness. In this research, granular activated carbon, natural zeolite, and anthracite packed-columns were investigated as cheap and effective adsorbents for the removal of mercury. Moreover, the effects of changes in pH (6-8), influent mercury concentrations (0.25, 0.5, 0.75, and 1 ppm), contact time (0.5, 1, 2, 3 hr) were investigated. Mercury concentration in the samples was determined using a ditizon indicator and spectrophotometry at 492 nm. Results showed that decreasing influent mercury concentration from 1 ppm to 0.25 ppm (under constant conditions) increased the removal efficiencies of anthracite, granular activated carbon, and zeolite columns from22%, 63%, and 55% to 28%, 72%, and 64%, respectively. Increasing contact time from 0.5 hr to 3 hr caused the removal efficiencies of these columns to increase from 22%, 56%, and 54% to 42%, 86%, and 82%, respectively. Also, increasing pH level led to increased removal efficiencies of the studied columns. It was found that contact time played a more effective role in enhancing mercury removal efficiency in the granular activated carbon column than in the other two columns. The ranges of mercury removal efficiency obtained for the granular activated carbon, natural zeolite, and anthracite columns under various conditions were (51%-92%), (42%-88%), and (16%-52%), respectively. Based on these results, granular activated carbon could be recommended as an effective and cheap adsorbent for the removal of mercury from drinking water resources.

Environmental pollution with heavy metals and their absorption by plants form a universal problem around the world. Numerous investigations have been conducted to put wastewaters containing heavy metals to agricultural reuse. Little is known, however, about the absorption of cadmium in the root zone and its accumulation in the different organs of crops, particularly in root crops. This study was carried out to investigate the influence of different levels of Cd concentration in the root zone on the accumulation rate in various parts of four different types of common root crops in karaj Iran. The experiment was performed in a factorial testing plan in random blocks and in four treatments with three replicates. The treatments included four levels of Cd concentration in soil (50 mg/kg, 100 mg/kg, 50 mg/kg, control without Cd addition and water with 0.5 molar of EDTA). The soil used in this study was prepared by passing through a sieve with a 2mm mesh and adding Nitrate Cadmium (Cd(NO3)2). Cylinder plastic vases 40 Cm in diameter and 60 cm high were employed to cultivate vegetables. Water demandwas estimated via the Penman-Mantith method, in which Kc was calculated by means of recorded data at Meshgin-Abad synoptic station in Karaj. At the end of the growing season, samples were taken from different organs of the plants to measure Cadmium accumulation. The SPSS software was used for the variance analysis of the collected data. The Dunkan test (at 0.01 and 0.05 levels) was then used to evaluate averages of the specifications in the factorial testing levels. The results indicate a direct relationship between Cd concentration in the root zone and Cd accumulation in plant organs. Adding 0.5 molar of EDTA to the irrigation water caused Cd accumulation in plant organs to exceed 60 percent. The results also show that Cd concentration, except for the control, was in excess of the limit for human consumption and that its accumulation levels in the different species tested were ranked as: Root: carrot>potato>radish>sugar beet; Leaf: potato>radish>carrot>sugar beet; Fruit: potato>carrot>sugar beet>radish; and Fruit peel: sugar beet>potato>radish>carrot.

A greenhouse experiment was conducted with a completely randomized design with four treatments and four replicates to investigate the efficiency of sand, soil (calcareous and non-calcareous), and organic matter (rice husk and leaf compost) for the removal of copper, nickel, zinc, and chromium from industrial wastewater by filtration. PVC tubes (columns) 66.5 cm high and 10 cm diameter were chosen and each was filled from bottom to top with coarse gravel, sand, soil, organic matter, and fine gravel, respectively. Then, plating wastewater was added at nine pore volumes to each column. When the filter’s surface was completely dried, a second round of wastewater addition was performed. At the end of the experiment, the columns were cut to collect the adsorptive materials which were then air-dried and transferred to the laboratory for measurement of heavy metal concentrations by atomic absorption spectroscopy. The results showed that putting calcareous and noncalcareous soils under the applied organic matter (rice husk and leaf compost) affected their capacity for adsorbing heavy metals to varying degrees. It was also found that low the cation exchange capacity of soil compared to organic matter did not lead to its reduced adsorption capacity. Analysis of the organic matter revealed that rice husk was the best adsorbent for Cr, while leaf compost was the best for Zn and Ni. In addition, applied sand in this experiment was a good adsorbent for heavy metals in wastewater. Generally, it seems that application of the studied adsorbents was effective and that they could be recommended for the removal of heavy metals from industrial wastewater.

Degradation of the organic part of landfill in along with rainwater percolation produces a polluted liquid named "leachate", which poses a considerable hazard to the environment because of its toxic and hazardous compounds. In this research, the treatability of leachate was investigated using combined anaerobic digesters. Each digester had an effective volume of 150 l, a flow rate of 10 l/d, and a HRT of 15 d working at a temperature of 31oC (mesophilic). The OLR applied to the system was gradually increased from 0.07 to 3.4 g/l.d in 5 steps. TCOD concentration was 48552-62150.4 mg/l and BOD5/COD ratio was more than 0.7 during the study period. At an OLR of 2.2 g/l.d, the total maximum COD removal efficiency achieved in both digesters was 93.59%. Not only did ammonia concentration not reduce in the anaerobic system but it increased. Ammonia concentrations at optimum OLR in the influent to the 1st and 2nd digesters were 721, 952, and 1054 mg/l, respectively. Maximum biogas production was 9.823 l/day in the 1st digester and 6.298 l/day in the 2nd digester, both of which occurred at an OLR of 3.4 g/l.d.

River bed profiles and depth-averaged velocities are used as basic data in empirical and analytical equations for estimating the longitudinal dispersion coefficient which has always been a topic of great interest for researchers. The simple model proposed by Maghrebi is capable of predicting the normalized isovel contours in the cross section of rivers and channels as well as the depth-averaged velocity profiles. The required data in Maghrebi’s model are bed profile, shear stress, and roughness distributions. Comparison of depth-averaged velocities and longitudinal dispersion coefficients observed in the field data and those predicted by Maghrebi’s model revealed that Maghrebi’s model had an acceptable accuracy in predicting depthnaveraged velocity.