WATER AND WASTEWATER
Year:2010 | Volume:21 | Issue:3 (75)|Papers Count:15

This study was conducted to determine the efficiency of the up-flow anaerobic sludge blanket (UASB) process in treating the leachate from the municipal solid waste (MSW) in the city of Ahvaz, Iran, under tropical conditions. A pilot scale UASB reactor with a total volume of 30 L was seeded with anaerobic sludge from the sugarcane plant to which diluted municipal leachate was introduced as influent feed. The organic loading rate (OLR) of the reactor was increased from 0.58 to 15 g COD/L.d over a period of 230 days. A maximum COD removal efficiency of 87% was obtained for an organic loading rate of 12 g COD/L.d. The temperature of the reactor was maintained in the range 34-39oC during the study period. The maximum reactor temperature (39oC) highest reactor temperature (37-39oC) the results reveal that the UASB reactor is a feasible one for treating reached was due to the effect of ambient temperature. The highest COD removal efficiency was obtained at the MSW leachates as witnessed by its successful operation in the hot climate of Ahvaz (with an average temperature of 40oC over about 7-8 months of the year) and by its potential for receiving and treating high organic loading rates with a high COD removal efficiency (87%). However, an aerobic system must be used after the UASB reactor for the effluent to meet the standards defined for the proposed disposal method.

In this study, experiments have been conducted to evaluate the removal of nutrients from synthetic wastewater using a moving bed biofilm process. For this purpose, the process was applied in series with anaerobic, anoxic, and aerobic units in four separate reactors. Moving bed biofilm reactors were operated continuously at different loading rates of nitrogen and phosphorus and different hydraulic retention times. In addition, for kinetic analysis, first-order substrate removal, Grau, and Stover-Kincannon models were tested with the experimental data. Based on the results obtained, a close to complete nitrification with an average Total Kjeldahl Nitrogen (TKN) removal efficiency of 99.72% was obtained in the aerobic reactor under optimum conditions. In this reactor, the average specific nitrification rate was 1.92 g NOx-N/kg VSS.h. During the study, statistically significant correlation was observed between the aerobic phosphorus removal rate and the anaerobic phosphorus release rate. Under optimum conditions, the average total nitrogen and phosphorus removal efficiencies were 80.9% and 95.8%, respectively. Finally, based on the kinetic analysis and with regard to nitrogen and phosphorus removals, the Stover-Kincannon model was selected as suitable for analyzing the experimental data and modelling of the moving bed biofilm process.

Contamination of soil by crude oil can pose serious problems to ecosystems. Soil washing by solutions containing biosurfactants is one of the most efficient methods for the remediation of contaminated soil by crude oil because it removes not only the crude oil but also heavy metals. In this study, five soil samples were taken from fields exposed to oil compounds over the years in order to produce biosurfactants from microorganisms that were capable of degrading oil compounds._Sixteen such microorganisms were isolated. After cultivation, their emulsification strength was examined using E24 test. From among the experimental microorganisms, a gram-negative and rod-shape microorganism called A-12 showed the greatest value of the E24 test index (36%). For each liter of the culture medium containing 365 mg of microorganisms, 3 gr of the biosurfactant compound was produced and separated as dried powder. The purified biosurfactant was used in the soil washing process. Also, the insulated microorganisms were capable of degrading crude oil floating on wastewaters.

Wastewater sludge has relatively high amounts of organic matter and salts which favorably affect the physical and chemical characteristics of the receiving soil. Hence, it can be used as a cheap fertilizer if properly utilized. A number of studies have been reported in Iran on the effects of sludge on soil chemical properties but few studies have been conducted to investigate its effects on soil physical characteristics. In order to study the cumulative effects of sludge on hydraulic conductivity, bulk density, MWD, soil infiltration, EC, and soil pH, an experiment was conducted in a complete randomized design with 7 treatments (1x22.5, 2x 22.5, 3x 22.5, 1x45, 2x 45 and 3x 45 ton/ha wastewater sludge) in three replications over three years. The above mentioned traits were measured after the third year of the experiment period. Results showed that increasing amounts of sludge enhanced saturated hydraulic conductivity, soil infiltration, MWD, and EC but decreased bulk density. A significant correlation was observed between the amount of sludge and soil physical characteristics. Factor analysis showed that the amount of sludge and all soil physical characteristics were in first order (physical characteristic factor) which explained 71% of the total variance, indicating the high impact of sludge on soil physical characteristics. The second factor was pH (a chemical characteristic) that explained only 17% of the total variance. Finally, no relationship was found between pH and soil physical characteristics.

In order to study the effects of treated wastewater combined with manure and chemical fertilizers on the nutrients content and forage yield in corn, field experiments were conducted in 2007. The experiments were conducted in a split plot design with three replications. The treatments were comprised of two levels of irrigation water (W1=well water and W2=wastewater) in the main plot and five levels of fertilizer (F1=unfertilized, F2=100% manure, F3=50% manure, F4=100% fertilizer, and F5=50% fertilizer) in the subplot. Results showed that, compared to ordinary water, irrigation with treated wastewater significantly increased fresh and dry forage yield of corn. The treatment using treated wastewater also had a significant effect on N, P, and K contents in corn forage. However, wastewater had no significant effect on plant Fe, Mn, and Zn contents. Among the fertilizer treatments, the highest fresh and dry forage yields and the highest N, P and K contents belonged to the treatments using 100% fertilizer. The highest Fe, Mn, and Zn contents were observed in plants in the treatment with 100% manure.

This study examines the removal of lead from an aqueous medium using rice husk, sawdust, and sunflower stem. For this purpose, sieves No. 30 and 40 were used to obtain particles with a mean size of 500 microns from each of the absorbents. The Pb (II) solution was prepared with a concentration of 25 mg/liter before absorption tests were conducted. The results showed that the equilibrium time for rice husk was 90 min. while the same parameter for each of the other two absorbents was 120 min. An optimal absorption pH of 6 hours was obtained for each absorbent. The tests also showed that the absorption efficiency for each absorbent increased as the input lead concentration was reduced from 80 to 1mg/liter, so that the absorption efficiencies for different absorbents converged. Absorption efficiency also increased with mass. Isothermal absorption tests showed that the Tomkin model had a better fitness than the Langmuir and Freundlich models.

Nutrients and insecticides in runoff or drainage water from the agricultural lands have of long posed a great challenge to surface and ground water quality. In agricultural production, fertilizers supply the main source of nitrogen required for plant growth. Investigations have shown that part of the nitrogen fertilizers are excluded from the root zone and leached into the groundwater or rivers. Modern technologies employed cultivation, irrigation, and fertigation management s well as changes in the structure of fertilizers and insecticides could have positive effects on reducing the leaching of nitrogen. The objective of this research was to study the effect of clinoptilolite zeolite application on reduing urea leaching from soil. In this greenhouse experiment, four levels of zeolite (0, 5, 10, and 15% added to a silty clay loam soil), one level of leaching (25% of net irrigation depth), one level of fertilizer application (60 mg/L), two sizes of Mianeh zeolite (50 and 200 mesh), and one size of Mashhad zeolite (200 mesh) were used in four irrigation events. The results showed positive effects of zeolite on reducing urea leaching. The nitrogen concentration in the 0% zeolite treatment was reduced from 1337 mg/L (after the first irrigation) to 16 mg/L (after the fourth irrigation event). But, for 15% Mianeh zeolite (50 mesh). effective in adsorbing urea than Mianeh zeolite (both 200 mesh). Zeolite, in addition to reducing the urea potential for groundwater pollution, was able to decrease the rate of solute transport. It was found that zeolite size can have significant effects on the leaching of contaminants. Finer zeolite particles absorb and hold more urea.

Microbiological monitoring of surface waters designated for use as drinking water is essential by water utilities for the design and operation of drinking water treatment plants. Enzymatic assays have been applied as a rapid alternative approach to assess the microbiological quality of freshwater. In this study, the LMX broth (LMX) as an enzymatic assay was compared with the standard method of multiple tube fermentation technique (MTF) for the microbial monitoring of the Karoon River.Enumeration of total coli forms and E. coli averaged 9928 and 6684 MPN/ 100 ml by the LMX and 7564 and 6546 MPN/ 100 ml for the MTF, respectively. This difference was statistically significant for TC but the overall analysis revealed no difference between E. coli recoveries on LMX and MTF. In conclusion, LMX can be used for the enumeration of coliforms and E. coli in surface waters as it is less lobar-intensive, yields faster result, and simultaneously detects both total coliforms and E. coli.

Large-scale water resource development projects have been in many cases known to have  a multitude of complex environmental impacts. The proper assessment of these impacts not only requires novel approaches to deal with the multiple aspects of these impacts but also needs rather quantitative techniques to make more reliable and less uncertain synthesis of the overall consequences of the project activities on both the integrity and health of the surrounding environment. Analysis of the significance of the environmental impacts is a multi-criteria decision making problem and makes the core of the conventional environmental impact assessment methods. However, these conventional measures of significance analyses are proved to be inadequate for dealing with the imprecise, vague, and uncertain nature of the linguistic assessments of the ecological, social, and cultural impacts. A new numerical method called the fuzzy outranking sorting technique for ELECTRE TRI (ELimination Et Choix Traduisant la REalite) is proposed and applied in this research for the purpose of environmental impact significance assessment of the Ardebil Reservoir, Drainage and Irrigation Development Project in Northwestern Iran. The basic idea behind the research was to develop a methodological framework to assist the environmental impact analysts in reducing, as much as possible, the intrinsic imprecise and uncertain traits of the multi-expert judgment based methods currently used in the analysis of environmental impacts of the Compared to the compensatory MCDM techniques, ELECTRE TRI provides the advantage of using a fuzzy approach in the analysis of the vague and poorly determined set of judgment data and helps in more credible assignment of values to a set of predefined categories with respect to a set of impact criteria. Results of the Fuzzy ELECTRE TRI based analyses are compared with the weighted sum method, which is one of the current methods in environmental impact assessment process. It is argued that due to its multiple criteria and fuzzy characteristics, the ELECTRE TRI method is capable of producing more reliable inputs for the decision making process compared to the conventional additive techniques.

Conjunctive use of surface and ground-water resources, compared to disjunctive operation of these systems, increases system reliability and decreases water deficits and operational costs. In this study, the two alternatives of groundwater (GWOpt model) operation and conjunctive use of surface and groundwater resources (CONJ model) are considered for Abhar river basin in Iran. In both models, the objective function is minimization of mean groundwater drawdown. The vast amount of calculations needed for distributed parameter optimization models is a major limitation in real systems. However, the above two models are linear and the unit response matrix approach is utilized. The first step in this approach is to calculate the unit response matrices (as the behavior of the groundwater system) using a simulation model, such as MODFLOW. The next step involves incorporating these matrices into the optimization model. The results obtained from the solution of the optimization model indicate that the mean drawdown in the CONJ model is less than that in the GWOpt model. In addition, a decrease of only 6% decrease was observed in the mean drawdown when compared to the simulation model. A decision support system has also been developed that enables the model to be used in real situations.

The present study investigates water allocation of Kardeh Reservoir to domestic and agricultural users using an Interval Parameter, Multi-stage, Stochastic Programming (IMSLP) under uncertainty. The advantages of the method include its dynamics nature, use of a pre-defined policy in its optimization process, and the use of interval parameter and probability under uncertainty conditions. Additionally, it offers different decision-making alternatives for different scenarios of water shortage. The required data were collected from Khorasan Razavi Regional Water Organization and from the Water and Wastewater Co. for the period 1988-2007. Results showed that, under the worst conditions, the water deficits expected to occur for each of the next 3 years will be 1.9, 2.55, and 3.11 million cubic meters for the domestic use and 0.22, 0.32, 0.75 million cubic meters for irrigation. Approximate reductions of 0.5, 0.7, and 1 million cubic meters in the monthly consumption of the urban community and enhanced irrigation efficiencies of about 6, 11, and 20% in the agricultural sector are recommended as approaches for combating the water shortage over the next 3 years.

Accurate prediction of longitudinal dispersion coefficient (LDC) can be useful for the determination of pollutants concentration distribution in natural rivers. However, the uncertainty associated with the results obtained from forecasting models has a negative effect on pollutant management in water resources. In this research, appropriate models are first developed using ANN and ANFIS techniques to predict the LDC in natural streams. Then, an uncertainty analysis is performed for ANN and ANFIS models based on Monte-Carlo simulation. The input parameters of the models are related to hydraulic variables and stream geometry. Results indicate that ANN is a suitable model for predicting the LDC, but it is also associated with a high level of uncertainty. However, results of uncertainty analysis show that ANFIS model has less uncertainty; i.e. it is the best model for forecasting satisfactorily the LDC in natural streams.

High concentrations of heavy metals in soil are toxic to plants, animals, and human beings. The present study was performed in the region in the south of Tehran, which is exposed to pollutants and where the runoff from urban areas is being extensively used for irrigation. Soil samples were collected from 8 stations. The soil distillation method was used to extract heavy metals from the samples and their concentrations were determined using atomic absorption to decide whether the concentrations of such heavy metals as Pb, Cd, Zn, Cu, and Ni exceeded hazardous limits requiring protective measures to be taken. Results showed that the concentration gradients of all the parameters studied increased in the north-south and west-east directions. The average concentrations of Pb, Ca, Zn, Cu, and Ni were 61.12, 1.42, 61.07, 25.85 and 29.22 mg/kg, respectively, in the northern stations, and 76.40, 2.62, 172.05, 69.85 and 37.40 respectively, in the southern stations. Comparison of which might have been the cause for the wider distribution of heavy metal concentrations in this region. Moreover, the runoff passing through the deepest parts of the southern region and the extensive application of the flow for irrigation could have caused the higher accumulation of heavy metals in this region. Our findings also indicated that it is necessary to treat surface runoff and to avoid runoff application for irrigation as measures for preventing environmental pollution.