Water and Wastewater
Year:2009 | Volume:19 | Issue:4 (68)|Papers Count:11

In this research, horseradish peroxidase for phenol removal was utilized. First, the process was studied at the laboratory scale using a synthetic phenol solution (1-10) mM. Results showed that horseradish peroxidase (HRP) could effectively remove phenolic compounds from wastewater and that the catalytic capability of the enzyme was maintained for a wide range of pH, temperature, and aromatic concentration levels. The performance conditions were optimized for at lease 95% and 100% removal of phenolic compounds for both actual and synthetic wastewaters under high and low phenol concentrations (1 and 10 mM). The phenolic wastewater used was an olive mill effluent with a phenol concentration of 1221 mg/L (13 mM) and a pH value of 3.5. At the end of the reaction, the phenolic compounds changed to insoluble polymers and precipitated. Each enzyme/wastewater system was optimized for the following chemical dosages: hydrogen peroxide, enzyme, polyethylene glycol (PEG), and buffer. Furthermore, the reaction time to achieve at least 95% phenol removal was determined. According to the results, COD and BOD reduced to 58% and 78%, respectively. Experimental results showed an increase in H2O2 concentration beyond the optimum dose resulting from enzyme inactivation, thus reducing the phenol removal efficiency. On the other hand, increasing the enzyme, PEG, and/or reaction time beyond the optimum values resulted in only a marginal increase in removal efficiency.

In this research, the capability of the moving bed biofilm reactor (MBBR) for the treatment of aniline wastewater has been investigated. This compound is found in effluents from chemical, dye, pigment, herbicide, pharmaceutical, plastic, and paint industries. The moving bed biofilm reactor was developed to adopt the best features of the activated sludge process as well as those of the biofilter processes. In this study, a cylindrical moving bed biofilm reactor with an approximate capacity of 5 liters was used. The effects of LECA (Light Expanded Clay Aggregate) filling ratio and retention times (RT) of 8, 24, 48, and 72 hr were investigated on removal efficiency for different influent COD values. The best removal efficiency of 91% was obtained for a COD level of 2000 mg/L after 72 hour. Other experiments were conducted to evaluate the removal efficiency of the reactor under a decreased carrier volume of 30% and under continuous loading. NMR test results confirmed the capability of the reactor in the biodegradation of aniline. The capability of the reactor was also evaluated by feeding an organic shock that resulted in satisfactory performance of MBBR. The results showed that Grau and Stover-Kincannon were the best models to describe the biological kinetic data in this study.

Natural organic matter (NOM) forms the group of principal precursors to organic disinfection byproducts (DBPS), which have been recognized to be human carcinogens. In fact, a high TOC concentration, used as an indicator of NOM, indicates a high potential for DBP formation. The aim of the present work was to investigate the effects of nanofiltration with and without preozonation on TOC removal. Nanofiltration alone at operating pressures of 4 and 8 bars could reduce TOC levels to slightly less than 2 mgL-1, which recorded a profile of success for all the experiments. This is while preozonation at a concentration of 2 mgL-1 recorded an effluent TOC level of 3.3 mgL-1, which is not an acceptable record. Preozonation at a concentration of 4 mgL-1 increased effluent TOC to 4.2 mgL-1, which indicates that preozonation could convert NOM from higher-to lower-MW fractions, thus increasing effluent TOC. It was also shown that preozonation-nanofiltration increased effluent TOC, as compared to nanofiltration alone.

Humic substances have been known as precursors to disinfection by-products. Because conventional treatment processes cannot meet disinfection by-product standards, novel methods have been increasingly applied for the removal of disinfection by-products precursors. The UV/TiO2 process is one of the advanced oxidation processes using the photocatalytic technology. The most important advantages of this process are its stability and high efficiency removal. The present study aims to investigate the effect of UV/TiO2 photo-catalytic technology on removal of humic substances. The study was conducted in a lab-scale batch photo-catalytic reactor using the interval experimental method. The UV irradiation source was a low pressure mercury vapor lamp 55w that was axially centered and was immersed in a humic acids solution within a stainless steel tubular 2.8 L reaction volume. Each of the samples taken from the UV/TiO2 process and other processes studied were analyzed for their dissolved organic carbon, UV absorbance at 254nm, and specific UV254 absorbance. The results indicated the high efficiency of the UV/TiO2 photo-catalytic process (TiO2=0.1 g/L and pH=5), compared to other processes, for humic substances removal from water sources. The process was also found to be capable of decreasing the initial dissolved organic carbon from 5 to 0.394 mg/L. The Specific UV254 Absorbance of 2.79 L/mg.m was attained after 1.5 hr. under photo-catalytic first order reaction (k=0.0267 min-1). It may be concluded that the UV/TiO2 process can provide desirable drinking water quality in terms of humic substance content.

The biosorption of cadmium (II) ions onto Saccharomyces cerevisiae biomass from aqueous solutions was investigated. The cells were treated with 70% ethanol solution in order to increase the biosorption capacity of S. cerevisiae. The effect of solution pH, initial metal concentration and biomass dosage on biosorption by ethanol treated yeast was studied. Optima conditions of initial solution pH, Cd (II) ion concentration and biomass dosage were at 5, 37.5 mgL-1 and 0.1 gL-1, respectively. The Freundlich equation was applied to the experimental data. The maximum metal uptake value (qmax) was found as 25 mgg-1.

Removal of particles by filter is a complex water treatment process. Several factors are involved that include shape and size of filter grains, particle concentration, filtration velocity, and filter depth. The objective of this study was to evaluate particle removal efficiency (h) by changing particle concentration and media grain size in a rapid sand filter. Five concentrations (100, 200, 300, 400, and 500 ppm) of Kaolin particles and three mean media sizes (0.51, 1, and 1.41 mm) were used. The filter depth and the filtration velocity were 25 cm and 0.086 cmsec-1, respectively. Silica sand was used as the filter medium in all the experiments. The results showed that for the filter medium with an average grain size of 0.51 mm, removal efficiency increased with increasing influent particle concentration during the initial hours of filtration. Generally, suspended solids removal efficiency was higher at low particle concentrations. No significant differences were observed in removal efficiency for the three media sizes and particle concentrations of up to 300 mg/L, but for concentrations above 300 mg/L, removal efficiency decreased, especially for filter media with an average grain size of 1.41 mm. Removal efficiency decreased in filter media with average grain sizes of 1 and 1.41 mm at high particle concentrations from the very initial hours of filtration. The highest removal efficiency was observed in the filter medium with an average grain size of 0.51 mm. Differences in removal efficiencies between the filter media with average grain sizes of 0.51 and 1 mm were much greater than those between filter media with average grain sizes of 1 and 1.41 mm. In other words, the critical grain size for the filter medium was 1 mm.

Simulation of flow phenomena in porous media occur in many areas of sciences and engineering. It has wide applications in a variety of disciplines including water resources engineering, environmental and chemical engineering, petroleum engineering, and groundwater hydrology. Both theoretical and experimental studies conducted to further our understanding of flow and transport phenomena in porous media are based on Darcy and Forchheimer constitutive equations. In recent years, a few investigators considered converting original porous media into a 2-D and/or 3-D networks to address challenging and complex issues in porous media. Such a network can be conceptualized as consisting of a series of pore bodies and throats. Pore body comprises the void between grains and throat represents the channel connecting two pore bodies. The basic question is how to choose throat’s length and size. In this study, two porous media of uniform size (i.e., spherical balls) but different diameters were constructed in the hydraulic laboratory of school of engineering, Shiraz University. A methodology is developed to convert each porous media into an equivalent network and the resulting network is subjected to rigorous computer simulation. Validity of such conversion is achieved via triggering and monitoring the two actual porous media in the laboratory. For this purpose, the equivalent network of first porous media is calibrated Preprint submitted to Journal of Water and Wastewater Engineering 5 May 2008 for pipe roughness using three different resistance equations. As both porous media have the same surface roughness characteristics, the equivalent network of second porous media is solved in a forward manner with different upstream heads using roughness coefficient obtained from the first porous media. Observed and simulated water surface profiles and outflow discharges from the second porous media are compared and contrasted to each other. Results show a good agreement between predicted values of the network model and experimental data obtained in the laboratory.

Water resources optimization problems are usually complex and hard to solve using the ordinary optimization methods, or they are at least not economically efficient. A great number of studies have been conducted in quest of suitable methods capable of handling such problems. In recent years, some new heuristic methods such as genetic and ant algorithms have been introduced in systems engineering. Preliminary applications of these methods in water resources problems have shown that some of them are powerful tools, capable of solving complex problems. In this paper, the application of such heuristic methods as Genetic Algorithm (GA) and Ant Colony Optimization (ACO) have been studied for optimizing reservoir operation. The Dez Dam reservoir in Iran was chosen for a case study. The methods were applied and compared using short-term (one year) and long-term models. Comparison of the results showed that GA outperforms both DP and ACO in finding true global optimum solutions and operating rules.

Lime stabilization is a chemical method used for wastewater sludge stabilization. It is capable of decreasing large quantities of pathogens and of preventing microbial degradation of sludge organic materials. The main objective of the present experimental research was to investigate stabilization of the sludge from west Ahwaz wastewater treatment plant by lime addition and to control if the microbial quality of this sludge conforms to the USEPA standards for sludge reuse and safe disposal. The study was carried out on a pilot scale in 5 stages over a period of 12 months (July 2005 to June 2006) at west Ahwaz wastewater treatment plant laboratory using raw sludge. For the purposes of this study, a 30-liter reactor was commissioned and loaded with sludge and appropriate quantities of hydrated lime were added based on the solid waste percent. The parameters used to determine stabilization efficiency were pH, Total Coliform, Fecal Coliform, and parasite eggs. The results showed that lime addition at a ratio of 265g Ca (OH)2/kg. ds was the optimum level for sludge stabilization in west Ahwaz wastewater treatment plant, which is acceptable from both economic and technical viewpoints. The method is capable of achieving class B but never satisfied class A of USEPA standards.

Barmejamal Spring is located in northeast of Ahwaz, Khuzestan Province, Iran. The catchment area of the spring consists of the northeast and southwest flanks of the Koh-e-Safid anticline, which is made up of karstic calcareous Asmari formations. There are sinkholes, caves, and other karst landforms in the catchment area. The existence of several faults has brecciaed Barmejamal spring karst aquifer that may have caused karstification to occur in parallel fracture systems. For the purposes of this study, pH and water temperature were measured on a weekly basis for a period of 12 months and water samples were analyzed for major anions and cations. Flow rate was measured on a daily basis during the recession, and weekly during the rest of the study period. Using the PHreeqc 2.6 computer model, the partial pressure of carbon dioxide and the saturation index of calcite and dolomite were also estimated. Three distinct periods belonging to three recession coefficients (\1, \2, \3) were observed in the hydrograph of the Barmejamal Spring. No considerable differences were observed between the first and second recession coefficients. Base flow for \1, \2 and \3 constituted 49%, 75.34%, and 100% of the total flow in the first and second recession periods and in the precipitation period, respectively. The variation of specific conductance, calcium and bicarbonate concentrations, and calcite saturation indices were not significant throughout the study period. The morphology and geology of the Barmejamal Spring catchment area and the data from hydrograph and chemographs show that the hydrologic system is of the diffuse-conduit flow type.