WATER AND WASTEWATER
Year:2008 | Volume:18 | Issue:4 (64)|Papers Count:11

Application of attached growth systems (AGS) is associated with special limitations in wastewater treatment. One such limitation is the unavailability of cheap and appropriate media in Iran. The main objective of this study was to evaluate the feasibility of Luffa sponge as a natural media in treating synthetic wastewater. Luffa cylinders were used as the fixed media required for an aerated submerged fixed-film reactor (ASFFR) and the performance of the reactor in organic removal was studied. A Plexiglas column having a capacity of 8 liters was used as a reactor. The natural medium was coated by lacquer to protect it against biodegradation. Glucose was used as the carbon source for microorganisms. Organic loading rates of 0.6, 1.2, 1.8, and 2.4 kgCOD/m3.d were applied to obtain COD removal efficiencies of 82.8, 93.4, 89.5, and 81.3%, respectively. Results showed that Luffa sponge cylinders could be used as supporting media within ASFFR under low organic loading rates and limited time conditions. The maximum efficiency of COD removal (93.4%) was obtained for 1.2 kg COD/m3.d. Also, it was revealed that ASFFR with Luffa sponge medium was capable of withstanding organic loading shocks.

This study aims to conduct an experimental investigation of treating effluents using the electrochemical method. Removal of COD from effluents was investigated at different electric currents, different electrodes (Al, Fe and Stainless steel), and various electrolysis times. The experimental results show that removal efficiency depends on electrolysis time, type of electrode, and the current applied. From the experiments carried out at 30V, it was found that the efficiency of COD removal over an electrolysis time of 60 minutes was 74% for Al and Fe and 53% for Stainlss steel.

This study was performed to evaluate the corrosion and leakage potentials of some important heavy metals (Pb, Cd, Zn, Cu, Fe and Mn) using the USEPA standard procedure. For the purposes of this study, 76 sampling points were selected across the study area including raw water intakes, treatment effluents, and tap waters in Ahvaz distribution network. After a minimum retention period of 6 hours in the distribution network, the first samples were taken according to the standard method, repeating the sampling procedure on a monthly basis for six months. Sample preparation and digestion were accomplished using the spectrophotometric atomic absorption technique to determine the concentration levels of the above-mentioned heavy metals. The results obtained were compared with USEPA standard indices and the corrosion potential was evaluated on the basis of heavy metals leakage measurements using SPSS software version 11.5. The results from six rounds of tests indicated values of 8.48, 0.97, 3180, 168, 257 and 30.6 micrograms per liter as the mean heavy metal concentration levels for Pb, Cd, Zn, Cu, Fe, and Mn respectively. Furthermore, the data indicated the high corrosion potential in Ahvaz drinking water distribution network and the leakage of heavy metals into the network closely associated with the corrosion phenomenon. Based on our findings, the USEPA standard method for corrosion evaluation in drinking water distribution networks is simple, accurate, and reliable.

The Zayanderoud basin is located in the central plateau of Iran. As a result of population increase and agricultural and industrial developments, water demand on this basin has increased extensively. Given the importance of reservoir operation in water resource and management studies, the performance of fuzzy inference system (FIS) for Zayanderoud reservoir operation is investigated in this paper. The model of operation consists of two parts. In the first part, the seasonal river stream-flow is forecasted using the fuzzy rule-based system. The southern oscillated index, rain, snow, and discharge are inputs of the model and the seasonal river stream-flow its output. In the second part, the operation model is constructed. The amount of releases is first optimized by a nonlinear optimization model and then the rule curves are extracted using the fuzzy inference system. This model operates on an "if-then" principle, where the "if" is a vector of fuzzy permits and "then" is the fuzzy result. The reservoir storage capacity, inflow, demand, and year condition factor are used as permits. Monthly Zayanderoud basin is investigated as a case study. Different performance indices such as reliability, resiliency, and vulnerability are calculated. According to results, FIS works more effectively than the traditional reservoir operation methods such as standard operation policy (SOP) or linear regression.

In recent years, much attention has been paid to the optimal design of pipeline systems. In this study, the problem of pipeline system optimal design has been solved through genetic algorithm and mathematical optimization. Pipe diameters and their thicknesses are considered as decision variables to be designed in a manner that water column separation and excessive pressures are avoided in the event of pump failure. Capabilities of the genetic algorithm and the mathematical programming method are compared for the problem under consideration. For simulation of transient streams, explicit characteristic method is used in which devices such as pumps are defined as boundary conditions of the equations defining the hydraulic behavior of pipe segments. The problem of optimal design of pipeline systems is a constrained problem which is converted to an unconstrained optimization problem using an external penalty function approach. The efficiency of the proposed approaches is verified in one example and the results are presented.

The Zayanderoud River stretches over 350 Km along a roughly west-east direction, originates in the Zagros Mountains on the west of Isfahan, and discharges into the Gavkhoni Swamp on the east of Isfahan. The Zayanderoud River supplies for the irrigation, domestic, and industrial water demands in Isfahan Province. In this paper, some water quality parameters of this river including EC, TDS, pH, HCO3, and Cl were simulated at different stations using artificial neural networks. The results showed an ascending trend for EC and TDS along the river. The trend in simulated HCO3 was found to be similar to that over the past few years and was equal to the long-term average. The trend for Cl was ascending at upstream stations and also similar to the long-term average at downstream stations. In general, the simulations of water quality parameters EC, TDS, pH, and HCO3 were evaluated to be highly satisfactory and the one for Cl satisfactory.

Flood forecasting and the study of the factors involved in flood events form important issues of concern in water resources management. In recent years, the influence of large-scale global climate phenomena on flood peaks has attracted more attention. In this paper, the effect of El Nino-Southern Oscillation (ENSO) is investigated on annual maximum flood (AMF) in Iran’s southwestern basins. The basins are located upstream of Dez and Karun-I dams. ENSO effects on probability, magnitude, and intensity (probability times magnitude) of AMF in the Esfand-Farvardin (March-April) period are examined. The results indicate that following El Nino, the probability of an AMF occurrence larger than the AMF corresponding to neutral ENSO conditions is higher in the study period. The opposite is true for La Nina conditions. It is also seen that El Nino effects are more intense than those of La Nina period.

"Schmutzdecke" is developed by particle deposition of a few centimeters deep on the top of the sand layer in slow sand filters. It plays an important role in removal mechanisms and is responsible for the significant increase of head loss during operation. After several weeks of filter operation, the surface area of the bed becomes clogged due to deposition of suspended solids. Cleaning of the bed top is required when the final head loss occurs. Since the operation costs of slow sand filters depend on cleaning intervals, the operation cost decreases by increasing the time of filtration run. The objective of this study was to evaluate the effect of bed top layer mixing on filter performance. Two experimental pilots (one test and one control) were built from 240 mm PVC pipe 170 cm high. The sand media depth in each filter was 60 cm with a uniformity coefficient of 2.3 and effective size of 0.2 mm. During the 149 days, 30 cm of the top layer of the test filter bed was mixed every other day and filter performance was evaluated and compared with the unmixed control filter. This research indicated that the rate of head loss decreased with bed top layer mixing and that filtration run increased to more than two times the typical value without notable effects on effluent quality.

Hospital wastewater is a type of municipal wastewater which may contain pathogenic agents and different microorganisms. If properly treated, the effluent from hospital wastewater treatment facilities can be used for irrigation purposes. To investigate this, the effluent from Hamedan Atieh-Sazan General Hospital was studied. The existing treatment facility uses an extended aeration system with an average wastewater flow rate of approximately 150 m3/day. In addition to evaluating the performance of the wastewater facility at Atieh-Sazan General Hospital, quality parameters of the raw wastewater and the effluent were measured. The mean values obtained for pH, BOD, COD, MPN for total Coliform/100ml, and Nematode/lit in raw wastewater were about 7.1, 238 mg/l, 352 mg/l, 5.5´106, and 2340, respectively. The mean values obtained for pH, BOD, COD, Na%, MPN for total Coliform/100 ml, and Nematode/lit in the effluent were 7.1, 35 mg/L, 77 mg/L, 61, 1561, and 575, respectively. Based on these results, the efficiency of the existing system in removing BOD, COD, and MPN/100 ml were %85.3, %78.3, and %99.97, respectively. With respect to water quality standards available, the quality of the effluent was considered to be suitable for irrigation except for its Na%, MPN for total Coliform, and Nematodes values.