WATER AND WASTEWATER
Year:2012 | Volume:23 | Issue:2 (82)|Papers Count:15

Polychlorinated Biphenyls are xenobiotic pollutants, commonly known as PCBs. PCBs could enter the food chain of biological organisms and accumulate in their fatty tissues. Thus, before the discharge of PCBs compounds in the environment, it is necessary to focus on processes and techniques for its removal at their sources. The objective of this research was to investigate the biodegradability of PCBs compounds by Sequencing Batch Biofilm Reactors (SBBR). Acetone and acetic acid were used as solvent in two separate reactors. Organic loading rates (OLRs) were from 0.04 to 0.75 g COD/l-d (maximum concentration of PCBs =0.7 mg/l). The SBBR was operated with four phases including fill, react (aeration), settle (sedimentation/clarification), and draw (decant) during different loading rates. The efficiency of COD and PCBs removal were evaluated. Maximum removal efficiencies of COD was 85% occurred in 0.2- 0.4 g /l-d in the reactor 1 (solvent acetone). Also, in reactor 2 (solvent acetic acid) maximum removal rates were recorded as% in OLR of 0.56g COD/ld. The maximum removal efficiency of PCBs was observed at 240 days after start-up of both reactors and was 99%. The results of this research showed that the concentration of priority organic pollutants can be decreased by using biological processes such as SBBR. This study can also indicated that biodegradation of high weight compounds by aerobic bioreactors is a time consuming processes.

Use of low-cost biological methods for ammonia removal as partial nitrification has been attracted by many environmental engineering researchers in recent years. In this study the removal of ammonia in high concentration sewage based on both complete and partial nitrification with the different sub-cycles has been investigated in pilot-scale and the results were compared. Ammonia concentration in synthetic wastewater was about 900 mg-N/L and fixed and variable volume of reactor was 3 and 6 liter respectively to create a suitable hydraulic retention time of 1.05-1.55 days in the different cases. The results of ammonia, nitrite and nitrate measurements by spectrophotometer have shown that it is possible to achieve partial nitrification by controlling temperature, pH, and dissolved oxygen and having more sub-cycles. Ammonia specific oxidation rate was about 13 to 16 percent more in complete nitrification compared to partial nitrification and in this condition the percent of nitrite accumulation was reduced from 91 to 51 in 3 sub-cycles and from 81 to 30 in 1 sub-cycle. Furthermore, increase of sub-cycles number from 1 to 3 had significant effect on increasing ammonia specific oxidation rate from 29 to 32 percent in partial and full nitrification, respectively. Results of this study showed that this method will be used for high ammonia removal in side stream process in addition to low nitrite oxidation rate in partial nitrification as compared to complete nitrification.

Antibiotics are considered among the major pollutants in water environments. In this study, removal of Clarithromycin antibiotic has been studied from synthetic wastewater by combined coagulation and advanced oxidation processes. This study was done in laboratory scale. Samples of synthetic wastewater were prepared from Clarithromycin antibiotic. Concentration of samples was 200 mg/l. COD index was selected as a parameter evaluated in this study. In the first stage, coagulation process was done on synthetic wastewater and the proper condition was achieved (proper coagulant, optimum pH, dosage of coagulant). After that, Fenton oxidation process was done, on the effluent of coagulation process. In Fenton process the influence of pH, Fe2+ and hydrogen peroxide were studied on the removal efficiency of Clarithromycin antibiotic and the optimum values for each parameter were determined. According to the results of this study, Poly Aluminum Chloride (PAC) is the proper coagulant. With pH equal to 7 and 100 mg/l PAC, 84.37% removal of Clarithromycin was achieved. For fen ton process, optimum parameters for the removal of Clarithromycin were determined. The optimum condition for fen ton process were, pH=7, Fe2+ equal to 0.45 mmol/ l, hydrogen proxide equal to 0.16 mmol/l, ratio of H2O2/Fe2+ equal to 0.4 and detention time of 1hour.With Applying of optimum conditions for combined coagulation and Fenton processes, 96.3% removal of Clarithromycin was obtained.

Shiraz plain is facing elevated groundwater level problem in its south and south-eastern regions due to increasing population, conversion of farmlands and gardens into residential areas, and destruction of old Qantas that used to drain the plain. To overcome this problem, construction of three drainage aqueducts in the plain started since 2003. So far, more than half of one main aqueduct, with a length of ~15 km, has been constructed at eastern Shiraz. In this study, performance of the drainage system in dropping groundwater level in the plain has been evaluated under different scenarios. First, the hydraulic behavior of Shiraz plain aquifer was modeled using PMWIN. Besides the main aqueducts, measured precipitation and evaporation, recharge and discharge from the aquifer by remaining old aqueducts, wells, and Khoshk and Chenar-Rahdar Rivers, and returned wastewater were all considered in the model. After model calibration and verification, the required parameters were determined and groundwater level in the plain was predicted for different scenarios at the end of aqueduct construction. Results reflect a good performance for aqueducts in all scenarios as evidenced by large volumes of drained water in comparison to other inflow and outflows of water in the aquifer. As expected, the lowest inflow, outflow, and drained water were observed in the plain during the drought (3rd scenario), and the highest flows during the wet years (4th scenario). Results indicate that in order for groundwater level to drop to the expected extent, lateral aqueducts should also be constructed otherwise the water drained by aqueducts will be less than half of the expected value.

In this research in order to forecast drought for the next coming year in Zahedan, using previous Standardized Precipitation Index (SPI) data and 19 other climate indices were used. For this purpose Adaptive Neuro-Fuzzy Inference System (ANFIS) was applied to build the predicting model and SPI drought index for drought quantity. At first calculating correlation approach for analysis between droughts and climate indices was used and the most suitable indices were selected. In the next stage drought prediction for period of 12 months was done. Different combinations among input variables in ANFIS models were entered. SPI drought index was the output of the model. The results showed that just using time series like the previous year drought SPI index in forecasting the 12 month drought was effective. However among all climate indices that were used, Nino4 showed the most suitable results.

Recently, cadmium (Cd) concentration has increased in croplands through sewage sludge and phosphorous fertilizers application. On the other hand, some special methods, like phytoremediation, were introduced in order to decrease soil contamination hazard. Calcium carbonate plays an important role in Cd solubility in highly calcareous soils. Sulfurs oxidation, by dissolving Cd carbonate fraction, may improve phytoremediation efficiency. An experiment was conducted to study the effects of S application (equivalent to 0, 2, 4 and 6 Mg S ha-1) on Diethylene Triamine Pentaacetic Acid (DTPA) extractable Cd and also on Cd uptake and extraction by spinach (Spinacea oleracea L.) in calcareous soils which were contaminated by 40mg Cd kg-1. To ensure biological S oxidation, all S-treated samples were inoculated by Thiobacillus spp. and incubated for 50 days. The soil pH, EC and soluble sulfate were affected by S application and it clearly showed that S oxidation process was occurred in Cd treated soils. The most significant change for pH and sulfate were observed at 4 Mg S ha-1 and for electrical conductivity (EC) of soil it occurred at 6 Mg S ha-1. Application of S had no effect on DTPA extractable Cd in soils whereas; its concentration increased 73.55% in average in plant tissue. Plant dry matter decreased significantly (about 63 percent) following Cd application. Although the highest rate of S oxidation was observed at 4 and 6 Mg S ha-1 the maximum Cd extraction (2.5mg Cd pot-1) was observed at 2 Mg S ha-1. This may be due to adverse effect of Cd toxicity and increase of soluble salt resulted by S oxidation in higher level of S application.

The aim of this research is to study the performance of microalgae Chlamydomonas in orthophosphate removal from municipal wastewater. In this research three treatments in three replications were applied. The treatments were free and immobilized cells of Chlamydomonas in alginate and blank (without microalgae). Three treatments were added into bioreactors with different rate of aeration (0, 1 and 2.5 Lmin-1), containing 1.5 litre of secondary effluent of Shiraz wastewater treatment plant. Orthophosphate removal from wastewater was examined for 14 days. The highest orthophosphate removal rate (10.33 percent per day) belonged to the immobilized microalgae treatment with 2.5 Lmin-1 aeration rate. Furthermore, for the immobilized microalgae treatments, removal efficiency decreased as a result of decrease in aeration rate. The results of free Chlamydomonas with 1 Lmin-1 aeration rate in orthophosphate removal were remarkable. Immobilization of microalgae with increasing aeration rate would improve algal- bacterial process and also would increase efficiency of orthophosphate removal.

Organic and mineral compounds generated as products of waste mineralization within biological processes and accompanying physical and chemical processes are washed out by percolating rainwater through the deposit of wastes in landfill and form leachate that has created many health and environmental concerns. This study intended to determine the efficiency of reducing COD, BOD5, TS and color of Hamadan landfill leachate by using carbon nanotubes. Experiments were performed in batch reactor and changing effective factors such as pH, time and concentration of iron nanoparticles. The efficiency of carbon nanotubes were investigated using a statistical test, One-Way ANOVA software SPSS-12. Highest removal efficiency was at concentrations of 2500 mg/ L NZVI, pH=2.5 and 10 minutes reaction time, 58.23%, 12.5%, 66.87%, 80% for COD, BOD, TS and color, respectively. The project results showed high potential for carbon nanotubes into absorbing organic use for treatment or pretreatment of Hamadan landfill leachate.

In various researches, implementation of meteorological parameters in drought prediction is studied. In the current work, meteorological drought classes based on Standardized Precipitation Index (SPI) for six seasonal scenarios (autumn, winter, spring, autumn +winter, winter +spring, and autumn +winter +spring) and meteorological predictors contained ground and sea surface temperature, weather temperature (at 300, 500, 700 and 850 mi bar) and geopotential height (at 300, 500, 700 and 850 mi bar) wide of North (0, 60) and East (0, 90) was applied in prediction models based on data from 1975 to 2005. In these models, temporal range of meteorological predictors is between Octobers to April month on the same predicted SPI. SPI was calculated based on mean precipitation at seasonal time scale in the main watershed of Tehran (Taleghan, Mamloo) by verse Weighted Distance method. The well-known statistical supervised machine learning method, support vector machine (SVM), is applied to predict SPI. Regarding to selected data points, the effective regions on Tehran precipitation are southern, southwestern and northwestern of Iran in spring, northern and northwestern in autumn and northwestern and western in winter. SVM depicted accurate results in prediction of SPI, spatially prediction of SPI in all scenarios, and it can be proposed as a very suitable statistical learning method in investigating of nonlinear behavior of meteorological phenomena with a short samples. The predicted SPI in spring and autumn are more accurate than the other scenarios. 

The presence of toxic heavy metals in industrial wastewaters and its discharge into the sewage system is one of the most environmental problems. In this research, electrocoagulation method was used to remove cadmium as a toxic heavy metal from aqueous phase. The important parameters wich affect the removal of cadmium from wastewater such as the electrode type, area of the electrode, distance between electrodes, voltage, intial concentration of cadmium and the pH were examined. Six electrodes with aluminum and iron types were employed with the areas of 2352, 3360, 4200 cm2. The distance between electrodes were chosen to be 1, 2, 3 cm, respectively. The experimental results indicated that optimum condition was obtained with high surface area of the electrodes of 4200, distance of 1cm, entrance power of 185, residence of time of 40 minutes and pH of influent of 10.25. Results showed that change in initial cadmium concentration reduced its removal.

Design parameters for sanitary sewer networks are imprecise and subject to high degree of uncertainty. In this research, a new method based on fuzzy logic, is proposed for uncertainty analysis of flow in sanitary sewer networks. The method is flexible enough for selecting design parameters and simple to use. It is applied to part of the sanitary sewer network of Mashhad, as a case study. The results indicate that such an uncertainty analysis can provide designers and maintainers with an appropriate perspective of flow and its associated parameters such as discharge, velocity and depth. This can be used in performance analysis of networks by including a wider spectrum of parameters in the analysis.

Different statistical, non-statistical and black-box methods have been used in forecasting processes. Among statistical methods, K-nearest neighbor non-parametric regression method (K-NN) due to its natural simplicity and mathematical base is one of the recommended methods for forecasting processes. In this study, K-NN method is explained completely. Besides, development and improvement approaches such as best neighbor estimation, data transformation functions, distance functions and proposed extrapolation method are described. K-NN method in company with its development approaches is used in stream flow forecasting of Zayandeh-Rud Dam upper basin. Comparing between final results of classic K-NN method and modified K-NN (number of neighbor 5, transformation function of Range Scaling, distance function of Mahanalobis and proposed extrapolation method) shows that modified K-NN in criteria of goodness of fit, root mean square error, percentage of volume of error and correlation has had performance improvement 45%, 59% and 17% respectively. These results approve necessity of applying mentioned approaches to derive more accurate forecasts.

The presence of phenol and its derivatives in water and wastewater are of major concern because of their toxicity and threat to human life and environment. In this study, ostrich feather has been used as a new adsorbent in removal of phenol in different doses of 0.2, 0.3, 0.5, 0.7, 1 and 1.5 g and the effects of changing contact time, pH, adsorbent dose and temperature has been determined. Then, the adsorption data were described with Langmuir and Freundlich adsorption isotherms and Excel software for analyzing the data was used. The results obtained revealed that by increasing the dosage of the sorbent from 0.2 to 0.7 g the adsorption increases. The adsorption of phenol decreases by the increase of the pH value of the solution. Also, it is observed that the contact time significantly affect the rate of phenol adsorption (70%) from solution. The adsorption equilibrium was well represented by the Freundlich and Langmuir adsorption isotherms. The results showed that the ostrich feathers, a solid waste produced in poultry processing plant, can be used as an effective bio sorbent for removal phenol in aaqueous solution.

The purpose of this research was to study the effect of the dosage of sawdust absorbent, on the equilibrium time, the efficiency of absorption in aqueous solution of Copper. Sawdust was prepared and those with particle size of 500 microns was selected. For this study, four absorbent sawdust concentration of 1 (SD1), 10 g/L (SD10), 20 g/L (SD20) and 50 g/L (SD50) were used. The most absorption rate was occurred at pH6. Increasing sorbent the time of absorption at equilibrium condition increases. The maximum balance time of absorbents (SD1, SD10, SD20, and SD50), were, 110, 105, 100 and 80 minutes respectively. Mathematical relationship between mass absorption efficiency absorbent solution and initial concentration showed that although increasing sorbent mass absorption efficiency increases, but if the initial concentration of a certain amount (the amount of crime absorbing capacity) toward to approach zero, the efficiency of all absorbent and rise toward 100% limited to. This concentration toward infinity that applies to e-mail. The calibration results showed that Avram model regression coefficient 0.988 and the error factor 0.037 data better absorption Lagergren models and Ho et al. described.