نشریه علوم و مهندسی آب و فاضلاب
سال دوم شماره 3 (پاییز 1396)

High pressure in water distribution networks leads to various problems such as increased leakage, bursts and unexpected consumptions. Hence, pressure management plans are implemented using pressure reducing valves (PRVs), tanks and pump stations. In this study, PRVs are applied for pressure management in three different approaches; fixed outlet, time modulation and flow modulation. In fixed outlet PRVs, a steady set pressure is considered for each PRV during the day. A simulation-optimization model is developed to find the optimal set pressures for all PRVs. In time modulation approach, PRVs are able to apply different pressure settings at different hours of the day which results the better control of the hourly pressure fluctuations in the water network. In this approach, optimization of set pressures is carried out. In flow modulation PRVs, the set pressure is regulated according to the average pressure in the network. In addition, in this study a new reliability index is introduced considering the average pressure and hourly pressure fluctuations and their effects on consumer’s satisfaction. This index is considered as an optimization objective function. Finally, comparing the performance of the above approaches shows that flow modulation, time modulation and fixed outlet approach are the most reliable, respectively.

Simultaneous with the change in the sequence and track of diseases, referred to as the “epidemiological transmission of illnesses”, and for the aim of measuring early deaths and disabilities, the use of a common basis seems essential. Since the late 1940s, researchers have identified ‘time’ as a common criterion for measuring early deaths and disabilities, and based on that, the DALYs have been introduced. This index, which is used in economic assessments and calculation of health expenditures and functions, consists of two factors: “years of life that are lost due to premature death” and “years of life associated with a type of disability with specific intensity and duration”. The World Health Organization has used this index in developing its guidelines for the microbial, chemical and radioactivity quality of drinking water. In this paper, while presenting the basic concepts of DALY, how it is calculated correctly in an effective cost estimate is presented in the form of an applied example.

In this study, the photocatalyst of TiO2/Fe2O3 based on clinoptilolite natural zeolite was synthesized by co-precipitation method and its function in degradation of Bentazone, as one of the most widely used herbicides in agriculture, was evaluated. The effect of process parameters simultaneously including pollutant concentration (1-40 mg/l), pH (4-10) and hydrogen peroxide concentration (25-100 mg/l) on photocatalytic degradation efficiency of Bentazone was investigated using design of experiments in response surface methodology. Synthesized photocatalyst was characterized by XRD, XRF, FT-IR, FE-SEM and EDX analyses. The results of XRD, FT-IR, and EDX confirmed the presence of TiO2 and Fe2O3 nanoparticles on the surface of clinoptilolite. The FE-SEM results confirmed the deposition of TiO2/Fe2O3 on the surface of clinoptilolite zeolite and also the approximate particle size of TiO2/Fe2O3 was 52 nm. According to XRF results, the synthesized nanoparticles had Fe3ﴸ optimal molar ratio of 0.06. The results showed that Bentazone concentration, pH and hydrogen peroxide concentration were the most effective factors on photocatalytic degradation efficiency of Bentazone, respectively. According to the experimental data at optimal conditions (pH, pollutant concentration and hydrogen peroxide concentration are 10, 10 mg/l and 50 mg/l, respectively), degradation efficiency of Bentazone was obtained 97% and the degradation efficiency was 78% at maximum concentration of pollutant (40 mg/l). This study showed that the synthesized photocatalyst has acceptable efficiency for degradation of non-biodegradable pollutant and removal pesticides from contaminated water.

Recently, the use of hybrid techniques is taken into consideration in wastewater treatment to achieve a high efficiency and effective removal of contaminants especially for resistant contaminants. In this research, the process of a combination of chemical oxidation by ozone and biological oxidation by aerobic attached growth bioreactor in the different modes for treating of wastewater were studied. At first, the performance of aerobic biological reactor was alone studied. Synthetic wastewater (sodium acetate as carbon source and ammonium chloride as a source of nitrogen) with the initial COD of 300 mg/L and the ratio of carbon to nitrogen of 10 was used. The results showed that there is a complete nitrification in bioreactor and COD removal efficiency is 89%. When using ozone oxidation before biotreatment, it was seen that the efficiency of COD removal increased to 94.0% and TSS was achieved to 75 mg/L in output. In the next step, the ozonation was used after biotreatment and it was observed that COD removal efficiency increased to 97.0% and the amount of TSS also decreased to 35 mg/L in output. In the final step, ozonation was used simultaneously before and after biotreatment as pretreatment as well as final treatment. In this mode, the results showed that the efficiency of COD removal in the output of the system increased to 98.3% and the value of TSS was declined to 20 mg/L.

The maintenance of health and quality of drinking water is one of the major priorities in water supply systems. Formation of biofilm in water pipelines, tanks and domestic water purifiers is one of the important concerns in this regard. Viruses, bacteria and protozoa could easily transport with water flow among which, some certain bacteria have the ability to attach to the surfaces and form biofilms. Formation and growth of the biofilm could negatively affect the water flow, quality and health. Biofilm forming bacteria eject compounds which protect them against the damaging factors and through this process biofilm become resistant to degradation. Some of the biofilm creating bacteria also have pathogenic capabilities even in humans, which is crucially important in maintenance of the health of drinking water. Due to the importance of knowing the biofilm forming communities in urban drinking water supply, the present paper investigated the biofilm and its major bacterial agents and removal methods.

The physical, chemical and microbial properties of water are crucial criteria for its drinking suitablity. Unfavorable changes in these parameters may threat consumers’ health. The aim of this study was to give a clear view of physical, chemical and microbial quality of drinking water distribution network in Ahvaz compared to the national and WHO standards. This study was a cross-sectional survey conducted based on 48-week sampling program in Ahwaz water treatment plants No. 1, 2, 3, 4 and 5 as well as in six points in water distribution networks. Water analyses were implemented according to the standard methods. Nine tube of fermentation method was used to determine fecal and total coliform bacteria. The mean values of measured parameters were as follows: electrical conductivity 2282.5 μs/cm, turbidity 2.3 NTU, pH 7.8, alkalinity 144.8, hardness 535.5 mg/L as CaCO3, calcium 137.2, magnesium 46.3, chloride 473.2, sodium 311.2, residual chlorine 1, TDS 1382.7, fluoride 0.53, nitrate 6.7, sulphate 370.2 mg/L, total coliform (0) MPN/100 ml, and fecal coliform (0) MPN/100 ml. Accordingly, the quality of drinking water in Ahvaz was not problematical from the health point of view and except the EC, hardness, sodium, and sulphate, all cited results met the national and WHO standards.

In this paper which is written as an experience acquired from one of the experts in water and wastewater industry, interaction between qanats and municipal water network has been investigated. The recorded problems seen in Naser-Khosrow experience is about during year 1997. After representing street in Tehran the experience and reviewing the case, major difficulties of current qanats located in urban areas together with suggestions to reduce occurrence or effects of this problem is presented. This article can be useful for experts and authorities in urban and rural water and wastewater companies, regional water companies and also consulting engineers and contractors.