WATER AND WASTEWATER
Year:2006 | Volume:17 | Issue:1 (57)|Papers Count:11

Optimization of coagulation process for efficient removal of Natural Organic Matters (NOM) has gained a lot of focus over the last years to meet the requirements of enhanced coagulation. NOM comprises both particulate and soluble components which the latter usually comprises the main portion. Removal of soluble NOM from low turbidity waters by coagulation is not a successful process unless enough attention is paid to stages of formation and development of both micro and macro-floes. This study, which presents experimental results from pilot scale research studies aimed at optimizing coagulation process applied to synthetic raw waters supplemented by adding commercial humic acid with Low turbidity levels, explains how pH and turbidity can be controlled to maximize soluble NOM removal. The removal of NOM at various coagulant doses and coagulation pHs has been assessed through raw and treated (coagulated-settled) water measurements of total organic carbon (TOC). For low turbidity waters, essential floc nucleation sites can be provided by creating synthetic turbidities, for example by adding clay. Adjusting the initial pH at 5.5 or adding clay before coagulant addition allows the formation of micro-floes as well as formation of the insoluble flocs at low coagulant doses.

Aeromonas is one the gram - negative, non spor - formatting rod shaping, facultative anaerobic and opportunistic bactria that can cause systematic infections, leision and diarrhoea in human. Fairly high bacterial population in distribution system is not only of concern because of affecting consumer health but also it makes it difficult to enumerate coliform bacterium indicator. So, the relationships between aeromonas and heterotrophic bacteria growth with pH, temperature, turbidity, free residual cholornie and DO were determined in this study. ADA-V media was used in/resumptive stage to count aeromonas bacteria for the first time in Iran on the basis of 1605 EPA (2001) metho and used oxidase tests, trehalose fermentation and indol test in confirmative stage. R2A media was used to count HPC bacteria and other factors measured on the basis of standards. The results showed that positive cases of aeromonas bacteria and HPC increase in higher temperature and turbidity and lower pH. In contrast, positive cases of aeromonas bacteria and HPC decrease while free residual cholorine and DO increase. In addition, no positive case of aeromonas was observed in more than 0.2 mg/L concentration of free residual cholorine.

In recent decades, increasing pollution of water resources has caused higher rates of organic pollutants in water resources. Considering the surface water resources as one of the main water supplies in many regions of Iran and the application of chlorination for disinfecting drinking water has increased the rate of Disinfection by- Products (DBPs) formation. Trihalomethanes (THMs) as the main group of DBPs are categorized and considered to have the potentiality of increasing the rate of liver, kidney and CNS adverse effects. Air stripping and membrane technology can be used for the removal of THMs. In this research, two pilots were designed and set up: Air stripping packed- column and Nanofilter (NF) spiral-wound modules. The effects of changes in flow rate and chloroform concentrations were investigated III both treatment systems and the transmemberane pressure for membrane pilot as the basic variables affecting removal efficiencies. Gas Chromatography (GC) with Electron Capture Detector (ECD) was used for determination of chloroform concentration in water samples. The obtained data were analyzed by SPSS and non-parametric Kruskal-Wallis. The results showed a positive correlation between the flow rate and chloroform concentration, and removal efficiencies. In this study, chloroform removal efficiencies for air stripping pack-column were higher than NF 300, and 600 Da. Variation Orange of removal efficiencies for air stripping column, NF 300 Da and 600Da with deionized water samples has been 82.3% to 97.6 %, 60.5% to 87.2 % and 42.3% to 67.6%, respectively.

Textile wastewaters from dying and finishing processes in the textile industry have been a serious environmental problem for years. Electrocoagulation (EC) as an electrochemical method was developed to overcome the drawbacks of conventional textile wastewater treatment technologies. EC technique uses a direct current source between metal electrodes immersed in polluted water. The electrical current causes the dissolution of metal plates including iron or aluminum into wastewater. The metal ions can form wide ranges of coagulated species and metal hydroxides that destabilize and aggregate the suspended particles or precipitate and adsorb dissolved contaminants. This paper studies the treatment of wastewater at Nagshejahan textile factory in Tabriz containing basic dyes by electrocoagulation using iron electrode m batch electrochemical cell and the effect of operational parameters such as current density and time duration of electrolysis. In addition, electrical energy consumption and current efficiency were also studied. To evaluate the efficiency of this method for treating the mentioned wastewater, color and COD reduction were measured after each treatment. The results showed that applying optimum current densities of 80-100 Am-2 and electrolysis time of 8 minutes for 250 mL of the wastewater, the color and COD reduced around 94% and 82%, respectively. Also, in the above mentioned conditions, the electrical energy consumption and Current efficiency were figured about 1.2 kWh/m3 and 103%, respectively.  

In recent years, the growth in the industries of olive oil extraction has brought about a number of environmental problems. The waste water resulting from olive oil extraction can not be naturally degraded due to the presence of phenol, volatile fatty acids, catchin, and other recalcitrant. In recent years advanced oxidation processes based on hydroxyl radical are paid special attention by scientific, research and industrial centers to degrade the pollutants. In this study, a combination of acid cracking and advanced oxidation process in terms of Fenton process has been studied. Results showed that acid cracking can remove 97, 47, 30, 63 and 57 percent of Turbidity, COD, Total Phenols, Color and Aromaticity, respectively. Fenton process in pH=3 at optimal conditions can remove 57, 97, 18 and 32 percent of COD, Total Phenols, Color and Aromaticity, respectively. Necessary time of reaction was 4 hrs and optimum concentration of H202 and Fe 2+ ions was determined 0.5 M and 0.02 M, respectively. Increasing temperature in the range of 25-35° C and type of iron used (ferric or ferrous) has no considerable effect in the efficiency of the process.

In this research the effects of algae on reduction of organic loading of industrial wastewaters were evaluated using stabilization ponds. For this reason, the blue-green algae (Oscillatoria sp. and Anabaena sp.) and green algae (spirogyra sp.) were collected, purified, identified and then added to the wastewater samples collected from slaughterhouse, sugar plant and vegetable oil refinery. The wastewater parameters such as pH, BOD5 and COD were measured at four different intervals of 15, 20 and 55 days. The data were analyzed using ANOVA and the Duncan's multiple test range to compare the mean values. The results indicated that the effects of different treatments (wastewater, algae or retention time) and their interactions are not statistically significant on pH of the wastewaters; however, the BOD5 and COD were affected significantly by different treatments and their interactions. Although the BOD5 and COD of treated samples with algae have lower values with respect to BOD5 and COD's of the controls, the Anabanea sp. and Osilatoria sp. are more effective on reaucing BOD5 and COD of waste water compared to spirogyra sp.

System dynamics, a feedback - based object - oriented simulation approach, not only represents complex dynamic systemic systems in a realistic way but also allows the involvement of end users in model development to increase their confidence in modeling process. The increased speed of model development, the possibility of group model development, the effective communication of model results, and the trust developed in the model due to user participation are the main strengths of this approach. The ease of model modification in response to changes in the system and the ability to perform sensitivity analysis make this approach more attractive compared with systems analysis techniques for modeling water management systems. In this study, a system dynamics model was developed for the Zayandehrud basin in central Iran. This model contains river basin, dam reservoir, plains, irrigation systems, and groundwater. Current operation rule is conjunctive use of ground and surface water. Allocation factor for each irrigation system is computed based on the feedback from groundwater storage in its zone. Deficit water is extracted from groundwater. The results show that applying better rules can not only satisfy all demands such as Gaw khuni swamp environmental demand, but it can also prevent groundwater level drawdown in future.

Various experimental and mathematical methods have been developed to assess the soil erosion potential and sediment yield. Among theses methods, the PSIAC method is one of the well known parametric and index methods. The uncertainty about recognition and decision of erodibility is an ambiguous uncertainty or on the other hand is a fuzzy problem. Furthermore, in PSIAC pattern, the space between input variables is divided into explicit and fixed sets so that the PSIAC indices of the input variables are not continuous. Hence, any variation of input parameter in this space and its effect will not be appeared at the final output PSIAC index. Due to the foregoing matters, in this study a fuzzy recognition approach is presented on the basis of PSIAC parameters. This method has a continuous form and is sensitive to the parameters variation in the discretized schemes. From conceptual point of view, the mentioned variations can be considered in the model output by fuzzy method. As a case study, both PSIAC and fuzzy pattern recognition were utilized to find the erodibility potential of Daryanchai watershed. The obtained results show, although the main trend of the erodibility potential in both methods is similar, some differences can be seen between the results of the two methods. These differences can be related to the computation schemes of the methods and continuous computational space of fuzzy approach in comparison with the PSIAC method.

The determination of spatial distribution of drought attributes in Isfahan province is essential for the study and management of drought. In this study, using ten drought attributes based on severity, duration and frequency of standardized precipitation index in 45 stations in Isfahan province and cluster analysis of this attributes, 5 spatial groups were identified in Isfahan province. The spatial distribution of these groups shows that the change in severity and duration of drought is based on various longitudes and latitudes in Isfahan province.

The construction of a dam on a river causes sediments to settle behind the dam. It is important for dam designer to estimate the rate and distribution of sediments in the reservoir in order to decide the dam stability and fix the sill elevations of the outlets and penstock gates. In this study, the accuracy of area-reduction and area-increment methods in estimating sediment distribution in the reservoir of Zayandehrud dam is evaluated. Measurement of sediment at dam reservoir was done in 1988 and 2000. The distribution of sediments in different heights was performed through volume-height and initial height-area curves plus area-increment and area-reduction methods. Comparison of the sediment distribution in the reservoir with these models showed that Borland and Miller area-reduction method was the best and has the least error in this respect. Therefore, this method has been applied to predict the sediment distribution for the years of 2020, 2045 and 2070.