WATER AND WASTEWATER
Year:2009 | Volume:20 | Issue:2 (70)|Papers Count:11

One of the most sensitive and cost-intensive systems in urban water and wastewater companies is accident systems. Lack of a modem, accurate, and reliable burst management system at the present time results in great damages to consumers and to urban water and wastewater companies. Given the shortage of water and real loses in urban water distribution networks, burst modeling and management forms a necessary research area for water and wastewater companies. Improved efficiency of urban water supply and distribution system is the only possible way which cuts across innovative sciences and technologies. One such technology is the geospatial information system (GIS) that generates useful geospatial information and is used to perform spatial and hydraulic analyses that play an important role in urban water distribution networks. The purpose of this research is to study the fundamental concepts of establishing an accident management and modeling system in the Iranian urban water and wastewater companies using GIS. Systematic data storage, use of burst repair data, decreasing repair period, and determining real water losses, number of bursts, and required costs are of the advantages of this model. In this paper, a methodology is presented to gather and evaluate the burst data using the available spatial GIS analysis functions. Selecting a pilot area in Hamedan, accident information was gathered over a 6- month period. Several spatial and hydraulic analyses were performed and a number of indices were developed. The results showed that this network had a high break rate (13.58) which indicates poor infrastructure and management of the system. Furthermore, the main reason for pipe bursts was found to be poor hydraulic situation. It was concluded that applying this model which has been used in a real urban water distribution network increases the efficiency of the system and decreases the related burst costs.

In the present study, adsorption of dissolved Cadmium (Cd) onto walnut and almond shell charcoal and the standard granular activated carbon (GAC) has been investigated and compared. The effect of pH value, initial concentration of dissolved Cadmium and amount of adsorbent on the adsorption of Cd by the mentioned adsorbents were investigated. Results showed that the adsorption process was highly dependent on pH. Maximum Cd removal was achieved when the final pH of the mixture fell within 6.5-7. Adsorption test results revealed that Cd adsorption on the studied adsorbents could be better described by Longmuir isotherm. Maximum Cd removal efficiencies were obtained by walnut shell charcoal (91%), almond shell charcoal (85%), and GAC (81%).

Coagulation and flocculation are the principal units in water treatment processes. In this study, the Jar test was used to investigate the effects of the pH and TOC on Fecl3 and PACI coagulants for further removal of turbidity, organic matter, aluminum, total organic carbon (TOC), dissolved organic carbon (DOC), organic Aadsorption at a wavelength of 254 nm (UV254nm), alkalinity, residual aluminum and ferric, total trihalomethans (TTHMs) in the Karaj River in the year 2007- 2008. These experiments were conducted through a bench scale study using conventional coagulation in the influent to Tehran Water Treatment Plant No.2 (TWTP2). With normal pH levels, PACl demonstrated more efficiency than Fecl3 in removing turbidity, TOC, UV254nm, and TTHMs. The lower coagulant consumption, high floc size, lower floc detention time, lower sludge production, lack of the need for pH adjustment in turbidity of 25 NTU and the lower alum consumption were the advantages of PACl application instead of Fecl3 as a coagulant. Also, PACl application was efficient at low turbidity (2 NTU), average turbidity (6 NTU), and high turbidity (100 NTU) in TOC, turbidity, UV254nm, and DOC removal. Thus, PACI is an economical alternative as a coagulant in TWTP2.

Subsurface flow wetlands are one of the natural treatment methods used for municipal and industrial wastewater treatment that are economical in terms of energy consumption and cost-effectiveness. Much research has been conducted on wetland operation with continuous flow but not enough information is available on batch flow. This study investigates wetland efficiency in batch flow. For the purposes ofthis research, two pretreatment units of the anaerobic pond type with digestion pits and two subsurface flow wetlands with a 2-day detention time were built on the pilot scale. The cells were charged with sand of 5 mm effective size, uniformity coefficient of 1.5, and a porosity of 35%. One wetland cell and one pretreatment unit were used as control. The municipal wastewater selected to be monitored for the one-year study period had a flow rate of 26 m3/day and average BOD5 of 250mg/l, TSS of 320mg/l, TKN of 35mg/l, TP of 12mg/l and TC of 2x108 MPN/100ml from Sabzevar Wastewater Treatment Plant. The average removal efficiencies of BOD5,TSS,TKN,TP,and TC in the continuous flow for the combined control pretreatment and wetland cell were 77.2%, 92%, 91%, 89%, 96.5% while the same values for the batch flow for the combined experimental pretreatment and wetland cell were 92%, 97%, 97.5%, 97%, and 99.75%, respectively. The removal efficiency in the subsurface flow wetlands in the batch flow was higher than that of the continuous flow. Thus, for wastewaters with a high pollution level, the batch flow can be used in cell operation in cases where there is not enough land for spreading the wetland cell.

Phenol is one of the most common compounds found in the effluents of many industries such as petroleum refining and petrochemicals, pharmaceuticals, pesticides, paint and dye industries, organic chemicals manufacturing, etc. Due to the high toxicity of phenol, the contaminations of bodies of water with this chemicalis a serious problem for the environment and human health. In this study, the sonochemical, photochemical, and photosonochemical degradation of phenol in an aqueous solution were investigated. The sonochemical and photochemical experiments were carried out using a bath sonicator (500 W) working at 35 and 130 kHz frequencies and a 400W medium pressure UV lamp. Experiments were performed at initial concentrations varying from 1 to 100 mg L-1.The effects of such parameters as pH, initial phenol concentration, and oxidation period have been determined. Results showed that the effects of ultrasound wave for phenol oxidation were mainly due to hydroxyl radical production during cavitation-induced water decomposition. However, low rates underwent degradation at a faster rate at 130 kHz than 35 kHz. Besides, it was shown that reaction rates involving hydroxyl radicals (hydrogen peroxide formation and phenol oxidation) had a maximum value at higher frequencies. The best yield was observed at 130 kHz for phenol degradation perhaps due to the greater availability of hydroxyl radical on the outer surface of cavitation bubbles. It was found that the rate of photochemical degradation of phenol was higher than sonochemical destruction. Also, the results showed that the combination of ultrasound wave and ultraviolet irradiation was considerably more effective than either ultrasound or ultraviolet light alone. Thus, based on the results of this study, the synergistic action of ultrasound and ultraviolet light is confirmed. This may be the result of three different oxidative processes: direct photochemical action, high frequency sonochemistry, and reaction with ozone (produced by UV irradiation of air). The results of the study showed that the degradation of phenol was increased by decreasing both pH value and phenol concentration in all the processes used.

In the first stage of this study, the compound effects of sludge dry solid content and residual bulking agent type (paper, saw dust, straw) mixed with activated sludge (10, 15, and 20% dry solids) on volatile solids (V.S.) reduction were investigated using Eisenia foetida in pilot scale experiments with batches of fifty earthworms in each of the 10 experimental treatments over a period of 10 weeks. The maximum V.S. reduction was attained in the mixture of sludge and paper, with a D.S. of 15% (0.42 ±0.03 % day-1) while the minimum V.S. reduction was achieved in the mixture of sludge and straw, with a D.S. of 10% (0.26±0.01 % day-1). In the second stage, the survival of Eisenia foetida in the anaerobic sewage sludge was investigated. In the unmixed raw anaerobic sludge, all the earthworms died during the first 9 weeks of the study period due to acute toxicity. From week 10, however, their survival rate improved so that by week 12 when toxicity reduced to 25.40%, they completely survived. This is while in the mixture of anaerobic sludge with paper (D.S. 15%), 100% of the earthworms survived from week 8 after the volatile solids reduced to 20.42% and 17.40%.

This study investigates the effects of organic load, pH, and EC variations of raw wastewater as well as the effect of weather condition on organic removal in Yazd wastewater Stabilization Ponds (2007). During the course of this study, composite samples were collected from the inlet and outlet of the anaerobic pond and the final effluent to measure such quality parameters as BOD5, COD, TSS, EC, and PH. BOD5, COD, TSS, and fecal coliform removal efficiencies in the final effluent were found to be 64.9%, 44.9%, 62.6%, and 99.96% respectively. No intestinal nematode egg was observed. Comparison of BODs and COD concentrations in the filtered and non-filtered samples showed that 52% of the BODs and 57% of the COD in the final effluent, respectively, were due to the presence of algal mass and organic suspended solids in the non-filtered samples. The results showed that variations in organic load, pH, EC as well as seasonal weather variations had no effects on organic removal and that the removal of BOD5 was almost constant. Effluent EC was higher than influent EC. This phenomenon can be related to the evaporation rate in wastewater stabilization ponds. The survey of algae in the final effluent showed that the major species of algae were Phytoconis, Chlorella, and Anabaena.

Two-phase gas-liquid flows occur in a wide variety of situations, e.g., in chemical processing, power generation, water supply systems, and petroleum industry. The study of two-phase fluid flows is of great importance in hydraulic engineering. This type of flow typically occurs in pressurized flow tunnels, culverts, siphons, and bends in which the gas trapped in water pipelines releases from the water as the pressure reduces. The relative discharge rate of fluids and the pipe slope produce a wide variety of flow patterns including stratified, wavy, and slug flows. In this paper, the unstable two-phase air-water flow is experimentally investigated. The image processing technique is applied for estimating the fluctuations of such parameters as void fraction and length, period and celerity of slug waves. It is shown that the pipe inclination and air flow rate have significant effects on flow characteristics. Also, the relative wave length (L/D, D is the pipe diameter) in a slug flow varies from 10 to 85, while air bubble length varies from 1/3 to 1/2 of wave length.

Population growth, rising living standards, and rapid urbanization give rise to increasing water demands. One of the important challenges that policymakers face is the integrated view of water resources management by giving priority to water demand. In this study, the water demand in Pardis City was estimated using the Stone-Geary Utility Function which was used to calculate price and income elasticity. Results showed that the range of price elasticity was 0.08 to 0.321 and that the income elasticity ranged from 0.165 to 0.289. Increasing water price had a greater effect on decreasing water consumption, particularly where water consumption was higher. Moreover, price elasticity in the summer was greater than in other seasons. Price elasticity was greater in higher consumption blocks than in lower consumption ones. Results also indicated that domestic price elasticity was twice the non-domestic and that price elasticity was less than 1 in all cases.

It is essential to evaluate the methods applied in the detection and enumeration of bacterial indices used in water quality management. The present study (descriptive and analytical in nature) aimed to determine the correlation and compatibility rates of the detection methods of multiple tube fermentation (both traditional and direct techniques) using EC Broth and plate count in special fecal coliform culture media. The objective was to identify the one method among these which is economical, effective, rapid, and easy to use under emergency conditions. Pour plate count using eosin-methylen blue (EMB) was evaluated in comparison with the traditional and direct multiple tub fermentation (MTF) as techniques used in enumerating thermo-tolerant bacteria and Escherichia coli in water resources.. 14 samples were required for the pilot study. However, 70 samples were analyzed to obtain a higher level of accuracy through three microbial laboratory methods. In evaluating raw water collected from wells, springs, and rivers as well as the effluent from wastewater treatment plants, a high Pearson correlation was found for enumerating thermo-tolerant bacteria. The results revealed that the majority of the samples contained thermo- tolerant coliforms. Based on the correlation coefficients calculated among the three methods, economic considerations, test duration, and time to yield results the plate count, the direct MTF, and the traditional MTF may be ranked in a descending priority order from the viewpoint of bacterial quality assessment of water resources for the emergency conditions and irrigation purposes.