WATER AND WASTEWATER
Year:2015 | Volume:26 | Issue:4 (98)|Papers Count:15

Advanced oxidation processes produce hyperactive hydroxyl radicals that have a high potential for the oxidation of organic compounds. One of these processes is the Fenton process in which iron ion as a catalyst reacts with oxidants in an acid environment to generate the hydroxyl radical. This is an oxidation-reduction reaction in which the metal ion transfers an electron. The efficiency of this method is influenced by such different factors as pH, iron and hydrogen peroxide concentrations, initial concentration of the contaminant, and reaction time. This study was conducted to investigate the removal of humic compounds in concentrations above 10 mg/L via an advanced oxidation process with Fenton technology. For this purpose, samples of synthetic humic acids were prepared and the effects of pH, different considerations of ferrous sulfate and peroxide hydrogen, different reaction times on the removal and filterability of humic acids from aqueous solutions were examined. The optimal ratio was determined based on the impact level of hydrogen peroxide to iron ratio. Results showed that the highest removal efficiency of 80% was achieved under the optimal conditions with pH 5, a molar hydrogen peroxide/iron ratio of 3.3:1, an oxidation time of 40 min, an initial concentration of 10 mg/L humic acid, and a UV254 absorbance level of 0.04/cm. In general, the results indicate that the Fenton process is capable of significantly reducing the humic acid present in aqueous environments.

The colors present in the effluent from dyeing and textile plants are one of the most dangerous sources of environmental pollution due to their toxicity and carcinogenesis. Dye removal is, therefore, necessary to prevent their discharge into the environment. A number of methods are available for dye removal from industrial effluents, among which Fenton/Ultrasonic oxidation process is an effective one due to its high efficiency in color removal. The objective of this pilot-scale experimental study was to investigate the operational parameters involved in the removal of Reactive Red 2 dye (RR2) using the Fenton/Ultrasonic process and its efficiency. The effects of pH, H2O2, and Fe2+ were evaluated using an ultrasonic reactor at 40 KHz with a power of 100W. Once the parameters had been optimized, the effects of temperature, mixing speed, and different dye concentrations on the Fenton/Ultrasonic process efficiency were measured. The optimal parameters of pH, hydrogen peroxide, and ferrous ion concentration in the were determined to be 3, 2, and 0.2 mmole, respectively, in 45 minutes so that a removal efficiency of 98.91% was obtained for an optimum hydrogen peroxide to ferrous ion ratio of 10. The results indicated that the Fenton process has a good performance in the removal of Reactive Red 2.

In this article, the degradation efficiencies of UV/TiO2, UV/H2O2, and UV/O3 processes are compared in the removal of Acid Red 14 which is the most commonly used dye in the textile industry. Results show UV/TiO2 recorded a degradation efficiency of above 90% in 30 minutes (pH=3, [Dye]=40mg/L, [TiO2]=400mg/L), UV/H2O2 degraded 75mg/L of dye (a degradation efficiency of more than 90%) in 160 minutes, and the efficiency of UV/O3 was above 95% in only 15 minutes using an ozone concentration of 0.9gr/h ([Dye]=250mg/L, pH=9). Judging on their high efficiencies, the use of these processes is recommended for the treatment of textile effluents. It may be noted, however, that the two processes of UV/H2O2 and UV/O3 are effective in both dye degradation and COD removal, but UV/O3 is costly and needs especial equipment. UV/TiO2 is not effective in COD removal and requires the post-treatment separation of nano-particles (using a centrifuge or sedimentation process). Thus, the UV/H2O2 process seems to be the easiest and most effective process in the treatment of textile effluent due to its simplicity and effective COD removal in a short time.

Lobster shells from Konarak Port were collected in October 2002, purified, and dried for the purposes of the present study. Chitin was extracted from the shellsusing the common chemical processes of demineralization, proteinzation, and decolonization, beforepurificationwith 1% CH3COOH and 1% NaCl to obatin an extract containing 12% (w/w) chitin. Chitin composition was determined using FT-IR, X-Ray powder diffraction, BET, and C.H.N.S analysis. The FT-IR spectrum of the extracted chitin was corresponded well to the Merck standard one, indicating that it is a linear polymer of N-acetyl-D- glucosamine on which metal ions can be adsorbed. Kinetic study of chitin’s reaction with Zn+2 at pH=6.75 and an ionic strength of 0.02 M indicated that adsorption equilibrium was reached within six hours of mixing. Adsorption Langmuir isotherms for a solution of Zn+2, Cd+2, and Pb+2 ions at an initial concentration of 2×10-3 M were determined for an ionic strenght of 0.02 M, different pH levels, and at ambient temparature using the discontinued in-pot method. The maximum amounts of metal ions adsorbed on chitin at pH=6.75 were measured to be 0.119 mol/kg for Cd+2, 0.714 mol/kg for Zn+2, and 1.630 mol/Kg for Pb+2. The overdyeing graphs, Cs= f (pH), show that the adsorption capacity of chitin is influenced by such factors as pH, reaction time, metal ion concantration, and adsorbent particle size. Thus, chitin as a non-toxic natural polymer may be highly recommended for water detoxification from heavy metal ions.

The Caspian Sea has recently experienced great damages due to intense pressure from human activities, petroleum contaminant discharges from oil extraction and refining activities, and domestic and industrial wastewaters discharged into the environment. The aim of this study was to determine the sources and levels of one of the most dangerous oil pollutants -polycyclic aromatic hydrocarbons- in the southern shores of the Caspian Sea (Anzali City). The data would be compared with standard PAHs concentrations in order to derive the information required for designing appropriate management measures. For the purposes of this study, nine surface sediment samples were collected from the experimental field and gas chromatography with mass spectrometry (GC-MS) was used to analyze the samples for their contaminants. The total PAHs concentrations ranged from 736 to 9009 ng g-1d.w with an increasing trend along the east-west direction. Also, multiple indexes were used to detect the petrogenic origin of these compounds. Compared with sediment quality guidelines (SQGs) of Florida (TELs/PELs), the levels for half the PAH compounds exceeded TELs. Moreover, naphthalene, fluorine, and phenanthrene concentrations exceeded the PELs in some stations, indicating likely acute toxic effects. However, comparison with sediment quality guidelines (SQGs) of the United States (TELs/PELs) revealed that most of the compounds at the stations investigated were lower than ERLs. It was concluded that the quality guidelines of the Florida State are more conservative for protecting the biotic organisms in the region.

Environmental conditions in sewer systems are such that the concrete in the sewer structures are attacked and heavy losses are inflicted. In this paper, the results of an in-situ study of the effects of environmental and service conditions on the surface strength of concrete are presented. In these investigations, different concrete mixes with different strengths were examined in the sewer system in the city of Malayer where the ambient pH (inside the sewage pipe and above the passing sewage line) ranged from 4 to 6. The in-situ, twist-off method was used for measuring the surface strength of concrete samples. Results indicate that concrete strength decreased with reducing pH level. Under neutral conditions, however, the strength of almost all the concrete specimens increased after 135 days. Finally, the concrete specimens with no additives exhibited reduced strength while those containing 10 percent micro-silica showed an increase in strength.

The effects of long-term irrigation with treated municipal wastewater on soil properties have been rarely ever studied. Soil water retention curve is an important tool in soil physics and it is essential for soil and water studies. The aim of this study was to evaluate the effects of long-term irrigation with the effluent from Shahrekord WTP on the shape and moisture curve coefficients in Taqank, Shahrekord. Soil moisture levels were determined at suctions of 20, 50, 100, 200, 300 (FC), 500, 1000, 5000, 8000, 10000, and 15000 cm (PWP) and the models van Genuchten (1980), Brooks-Corey (1964), Kasogi (1996), and Derner (1994) were fitted to the measured data. Based on the coefficients of determination obtained, the sum of squares, standard error, and Acaike information criteria, the van Genuchten model was selected as the best model subject to the condition 1-1/n. Effluent irrigation for 13 years was found to have increased the ps index by 8%, but no change was observed with long-term effluent irrigation. Although 13 years of irrigation with effluent did not change the coefficient a but longer irrigation was found to have decreased the value for this parameter from 0.03 to 0.014, indicating that an increase in air entry suction point from 30 to 70 centimeters. Although irrigation with WTP effluent tended to increase the value of the coefficient n, no significant increase was observed over the 23 years of irrigation with this effluent.

Wastewater collection network simulation in normal conditions dose not provide performance assessment in unusual circumstances. In this paper, a model has been developed for risk assessment of wastewater collection systems to manage their performance under natural or man-made critical conditions. In this model, certain criteria were defined, fuzzy MADM techniques were exploited, and a questionnaire was employed to measure such risk parameters as the probability of threats, the severity of their impacts, and the vulnerability of the network components. Based on the calculated magnitude of the risks, the threats and hazards were classified into groups ranging from low-risk to high-risk threats. The approaches adopted to combat the risks were also classified into the following three categories: "to deal with the risk", "risk shifting", and "risk taking". This process was implemented for the wastewater collection system in Shahrak-Gharb District in Tehran as a case study. ‘Introduction of chemical pollutants into the sewers’ and ‘drastic changes in wastewater quality’ were identified as the most threatening crises for the district and the ‘risk reduction strategy’ was proposed for combating the critical conditions in this district.

This paper proposes the application of a new version of the heuristic particle swarm optimization (PSO) method for designing water distribution networks (WDNs). The optimization problem of looped water distribution networks is recognized as an NP-hard combinatorial problem which cannot be easily solved using traditional mathematical optimization techniques. In this paper, the concept of dynamic swarm size is considered in an attempt to increase the convergence speed of the original PSO algorithm. In this strategy, the size of the swarm is dynamically changed according to the iteration number of the algorithm. Furthermore, a novel mutation approach is introduced to increase the diversification property of the PSO and to help the algorithm to avoid trapping in local optima. The new version of the PSO algorithm is called dynamic mutated particle swarm optimization (DMPSO). The proposed DMPSO is then applied to solve WDN design problems. Finally, two illustrative examples are used for comparison to verify the efficiency of the proposed DMPSO as compared to other intelligent algorithms.

In this study, a new numerical method based on Dual Reciprocity Boundary Element Method (DRBEM) is presented to interpolate scattered data. For this purpose, water samples were taken from 120 wells in Nuq region, Rafsanjan, for salinity measurements. The proposed estimator was compared with respect to its precision with the conventional ones, i.e., ordinary kriging and inverse distance weighting (IDW) while the spatial mapping of ground water salinity was performed in the study area. Besides, a more revealing measure of performance was obtained by computing the mean rank of each interpolation method. Results revealed the superiority of DRBEM over the kriging and IDW methods due to its lower root mean square error (RMSE) and relative root mean square error (RMSE%) as well as its higher goodness of prediction index (G). It was also found that DRBEM is the most accurate one when the mean rank and standard deviations of the ranks are used to avoid the outlier effects in assessing the prediction performance of the three methods. Nevertheless, further research is required before DRBEM could be properly combined with ancillary variables to improve the interpolation performance and to develop a user-friendly algorithm that can be implemented in a GIS package.

Water demand forecasting is an important tool in the design, operation, and management of urban water supply systems. The wide variety of factors affecting urban water demand and the variations in the impact levels of these factors due to changes in environmental conditions have undermined the efficiency of conventional mathematical forecasting models in forecasting water demand. Different methods have been so far employed for urban water demand forecasting, among which evolutionary algorithms are the most widely used. In this study, the gene expression programming model, which has a high convergence speed with high precision in calculation and simulation, is combined with the wavelet transform analysis to derive a hybrid model for forecasting daily water demand (consumption) in the city of Hamedan. Water consumption of previous days and climatic parameters constitute the factors affecting water demand in this model. In the first part of the present study, the efficiency of gene expression programming models in forecasting urban daily water demand is investigated to identify the best model (i.e., the best combination of inputs). The second part is dedicated to the evaluation of the effect of wavelet analysis on the results obtained. The results indicate that the best model for forecasting daily water demand is the one with water consumptions of 1, 2, and 3 previous days as well as those of the preceding week as its input. It is also found that the combined gene expression programming and wavelet transform analysis leads to a 10% improvement in forecasting results.

Biological treatment of wastewater depends on different factors including the nutrient and vitamin contents. In this study, the effects of different concentrations of folic acid (0.1 ppm, 0.2 ppm, and 0.4 ppm) together with different amounts of nitrogen (20 ppm, 30 ppm, and 40 ppm) and phosphorus (4 ppm, 6 ppm, and 10 ppm) were studied on the biological treatment of the industrial effluent from Tabriz Petrochemical Plant. The Taguchi method with an L9 orthogonal array was used to determine the optimum conditions for the growth of microorganisms. Turbidity, BOD5, TSS, and MLSS were measured as the main parameters of the treated effluent. The results showed that only N has a significant effect (78.4%) on BOD5 removal. Folic acid had the greatest effect (42.7%) on TSS reduction. This is while folic acid had a significant effect (90.1%) only on increasing MLSS. The optimum conditions for microorganism activity consisted of a folic acid concentration of 0.2 ppm, an N concentration of 30 ppm, and a P concentration of 4 ppm. Interactions between first level of folic acid×second level of P on turbidity reduction, second level of folic acid×second level of P on BOD5 reduction, second level of N×second level of P on TSS reduction, and first level of N×first level of P on increasing MLSS were highly significant. These results show that adding folic acid, N, and P to the effluent from Tabriz Petrochemical Plant not only enhances the growth of microorganisms but also leads to the improvement of the treated effluent for discharge into the environment

Given the importance of the microbial quality of drinking water and the fact that no comprehensive, analytical study of the microbial quality of drinking water in the Takab rural areas has been reported, this descriptive case study was conducted in the summer and fall 2012 to investigate the microbial quality of drinking water in the study area. The microbial parameters studied included total coliform (TC) and E. coli using the 9-tube fermentation technique and HPC. It was found that the drinking water sampled from 50% of the rural areas not served by the water supply network exhibited coliform and E. coli coliform contaminations while 11.9% of the samples collected from areas served by the water supply network showed coliform contamination and 9.5% exhibited E. coli contamination. The rural populations with access to clean, coliform-free water in areas both served and not served by the public water supply network were 88.4% and 27.5%, respectively, and 85% of the population in all the villages investigated had access to such clean water. Those having access to drinking water free from E.coli were 96.4%, 27.5%, and 91%, respectively, in the three groups mentioned above. Based on HPC test results from these areas, revealed that HPCV500 in all cases was zero. The latest WHO guidelines recognized 90% E. coli-free drinking water as excellent for communities with populations less than 5,000 provided sufficient samples are taken. Based on the results obtained from this study, the microbial quality of the drinking water in rural areas in TAKAB is desirable but lower than the Iranian standard.