نشریه علوم و مهندسی آب و فاضلاب
سال پنجم شماره 3 (پاییز 1399)

Wastewater/runoff reuse is one of the strategies for sustainable water resource management which, based on the consumption type, requires supplementary treatment and standardization due to a wide range of environmental contaminations. Wastewater recycling not only reduces the pressure on fresh water resources but also is so frugal in comparison to the huge costs and the environmental and socioeconomic impacts of water transfer projects, especially between the basins. Nowadays, the application of bio-methods such as constructed wetlands has increased significantly due to the high cost of conventional wastewater treatment approaches. Constructed wetland systems have different design methods depending on the desired outlook (wastewater or runoff treatment). With regards to the flow patern, the system classifies into free water surface flow, and horizontal and vertical subsurface flow. Design configurations of the constructed wetlands depend on the kinematic description of biological reaction as well as the designer’s knowledge of the flow pattern. In this paper, the related literature is reviewed and the required supplementary treatment of secondary effluent of the treatment plant is presented. Then the performance of different types of constructed wetlands in removal of pollutants is investigated. Finally the principles of constructed wetlands design with the aim of harvesting and treating runoff and wastewater have been thoroughly described. The design criteria are presented based on the observed obstacles for such evolution in the field of water recycling. The feasibility of constructed wetlands is then investigated, especially in arid and semi-arid regions. By presenting the justified plan for the system application, the required measures for site selection of such constructed wetland systems are expressed.

Given the environmental conditions governing it, its stakeholders' expectations and its organizational mission and in the context of supplying and distribution of water and safe disposal of wastewater, the water and wastewater sector needs to grow and develop in parallel to the changes in environmental conditions. For this reason identifying the development condition of the water and wastewater sector is a necessity in the context of targeting plans and strategies from the aspect of sectorial management and senior management. This research was undertaken to identify the level of development of the water and wastewater companies (35 companies) from the aspect of the different indicators specific to the water and wastewater industry in the context of clarifying the economic plans and to enhance and improve operational activities. In the course of the study, after identifying 18 indicators, the exploratory factor analysis was undertaken and the number of indicators was reduced to 5 significant factors. Then the combined indicator was calculated according to the weight of factors and the entire sector was classified. In continuation and by applying the hierarchal clustering method the development levels of water and wastewater companies were categorized on the basis of 5 factors in three homogenized groups of development. The study's results indicate an unbalanced and non-homogenous level of development in the sector, with some companies failing to achieve the desirable level of development and needing greater attention and planning to improve the developmental conditions.

Today, due to legal restrictions on the methods burying sewage sludge, environmentalists recommend using it as a fertilizer as a fertilizer in agriculture to get rid of the problems caused by sludge produced in treatment plants. Sewage sludge can be the best and cheapest organic fertilizer for agricultural lands due to its high content of organic compounds and nutrients required by the plant. But at the same time toxic factors such as heavy metals in sludge are the most important limiting factor for its use. The purpose of this study was to investigate the effect of sewage sludge application on some soil chemical properties and heavy soil metals. This study was carried out in the Aburaihan Campus Research Greenhouse of Tehran University with three levels of sewage sludge for anaerobic and dehydrated anaerobic wastewater treatment plant south of Tehran containing 0, 10 and 20 g/kg soil, in three replications in a completely randomized block design on Helianthus annuus. After finishing the growing season, the Soil of control and treated pots were sampled. After physical and chemical tests on soil samples, it was observed that application of sewage sludge in soil significantly increased Organic Matter (O.M), Cation Exchange Capacity (CEC), Salinity (EC), total nitrogen, potassium and Heavy metals Pb, Ni, Cd concentrations, and There was a significant decrease in pH in the treated soils compared to the control treatment. Also, treatment of 20 g of sewage sludge per kg soil had the best effect on soil chemical properties.

Leakage in water distribution networks will cause waste of water and reduced pressure. Different leak detection methods are used in the networks among which the Meta-search algorithms have received much attention in the recent years. WaterGEMS commercial software uses genetic algorithm for optimal design and calibrate water distribution networks and detect leakage. In this paper, the WaterGEMS V8i performance in leakage detection using Darwin Calibrator tool was investigated in two hypothetical networks (Poulakis and Aniton). In the Poulakis network where only the node's pressure was put into the software as observational data, the location of leakage was determined at or in the vicinity of the exact location. However, in the Aniton network, where the input discharge was also introduced to the program as observational data, the location and the amount of the leakage were calculated more accurately. These results were similar to the leakage resulted in using the Ant colony algorithm.WaterGEMS is therefore evaluated as a good tool for engineers for estimating the location and amount of leakage in water networks.

In water distribution systems, pressure is one of the most important factors affecting leakage. Accordingly pressure management is an integral part of the leak reduction strategy. The main purpose of pressure management is to minimize network leakage by providing minimal pressure on network nodes. Using the pressure control valves (PRV) in the water networks is one of the common methods to reduce water leakage. In this study, with the aim of determining the optimal pressure in the network, the water distribution network was analyzed using WaterGEMS and ArcGIS software and based on field data. The modeling results showed that the pressure distribution in the network is uneven and some network nodes are experiencing non-optimal pressure. Therefore, based on the topography of the area, three pressure optimization scenarios were implemented in the model, which reduced the average night network pressure by 32% to 53%. The results showed that the infrastructure network leakage index (ILI) was reduced by 23.18 to 13.96, which showed a decrease of 28% to 40%. Finally, the calculations showed that by applying these scenarios, network leakage can be reduced by 24.2% to 34.5%.

Water quality is presented by its physicochemical and biological specification. The aim of this study was to analyze the physicochemical characteristic of waters (river, drinking, hybrid and pure water) including total hardness, magnesium, nitrite and ammonia (mg/L) which were determined based on the standard protocols of the EPA (2010) using photometer, Palintest, 8000. Furthermore, dissolved oxygen (mg/L), temperature (ºC) and pH were determined by oxygen meter, calorimeter and pH meter, respectively, with 3 repeats and in the limnology laboratory of Birjand University. In river water, the concentration of nitrogen is higher compared to other water sources due to the physicochemical reactions (especially due to the disposal of ammonia into water). For the hybrid water, consisting of drinking water plus pure water, the chlorine concentration (0.4 mg/L) was greater than the average (0.15 mg/L). The total hardness of the same (125 mg/L) was however lower than the average (185 mg/L). Finally, it is recommended that biological indicators such as the presence of rotifers, tubular cross-sectional fish, and salmon (which normally live in clean water) be used to assess the qualitative characteristics of the water. This is due to the fact that there are normally more living creatures in waters which can hold salts.