Aerobic biological treatment systems are very suitable for removing contaminants of organic matter in the sewage. Accordingly, the continuity of the inlet flow to the treatment plant, in design and exploitation of these processes, is necessary to consider. One of the differences between industrial and low population areas wastewater, such as military garrisons, and the Municipal sewage, is their volumetric fluctuations. These fluctuations may have a negative effect on the activated sludge process,thus the efficiency of using balancing pool in activated sludge systems has been analyzed in this research. Wastewater treatment process is based on biologically activated sludge method and extensive aeration. In this method, the raw wastewater is directed to the pumping station gravitationally. Results illustrated that, the inlet flow rate to the treatment plant, has high fluctuations from 0 to 40 (m3/hour) at different hours of the day due to the low population. Based on the samplings, it has been determined that the efficiency of activated sludge process in removing the parameters of BOD5, COD, TSS and ammonia during one week is averagely 61, 61, 68 and 24%, respectively. According to the sewage standards, this treated sewage is not suitable for injection into water wells or surface water or for reuse in agriculture. Whilst, using the balancing pond and controlling the inlet flow to the aeration pond at a rate of 12 cubic meters per hour, the removal efficiency of BOD5, COD, TSS and ammonia escalates averagely 90, 90, 89. 19 and 81. 59%, respectively during a week.

Assembly Line production is one of the widely used basic principles in production system. The problem of Assembly Line Balancing deals with the distribution of activities among the workstations so that there will be maximum utilization of human resources and facilities without disturbing the work sequence. Research works reported in the literature mainly deals with minimization of idle time i.e. balancing, subject to precedence constraints. Lack of uniqueness in their optimum solutions has led to the present work where minimization of both balancing loss and system loss has been envisaged under the usual precedence constraints. The researchers suggest a generic approach for designing of an assembly line where, with a given number of workstations, one can efficiently arrive at the desired solution under different methods of search like simulation, heuristic etc. Thus, the main aim of this paper is to redefine the objective of the Assembly Line Balancing Problem and sequentially handle Balancing Loss and System Loss. A numerical example has been added to demonstrate the generic nature of the researcher's approach and improvement in the solution set when compared with different standard line balancing methods available so far in the literature.

The main goal of this paper is to develop a new generalization of balancing and Lucas-balancing sequences namely balancing and Lucas-balancing p-numbers and derive several identities related to them. Some combinatorial forms of these numbers are also presented.

Background: Waste stabilization ponds are simplest systems applied by human to treat the biological degradable materials. Today, computerized tools and special mathematical modeling is used to manage environmental systems problems. System Dynamics is a system for problems analys is when time is a significant factor. It includes the way action and reaction of system is encountered by external thistles.Methods: After sampling and testing, phosphorus was modeled by using mathematical relationships and system Dynamics method. After making the initial model and its testing, the model was calibrated using three months data from facultative pond in Yazd city in Iran.Results: Algal growth rate, phosphorus settling rate and losses due to algal respiration and excretion were from important agents. Respiration rate of herbivorous zooplankton, non living carbon hydrolysis rate and phosphorous to chlorophyll ratio were from low important agents.Respiration rate of carnivorous zooplankton and phosphorous to carbon ratio were from unimportant agents.Conclusion: In comparison with other models, our System Dynamics Model needs low data. This is also a cheap model and we perceived good operation of it. In sensitive analysis, algal growth rate and phosphorus settling rate were important in phosphorus removal. So, we can manage facultative pond better with increasing retention time in pond. Phosphorous to chlorophyll ratio had low important role in this model. Thus, system can tolerate phosphorous variations in inlet wastewater with sufficient algal growth. Respiration rate of carnivorous zooplankton and phosphorous to carbon ratio do not limit system equilibrium. Ability of the model increases with sufficient retention time and further data. System Dynamics ecological models give useful information for facultative ponds. It is recommended this model be used for management affairs and overall assessment of facultative ponds. For more precise assessment, it is apposite to use two or three dimensions models substitute zero dimensions models.

Rainwater storage is very important as a sustainable and practical solution for managing water resources, especially in places with dry and semi-arid conditions such as Iran. This method has been considered as a strategic solution in response to environmental challenges and agricultural and drinking needs. There are various structures for collecting and storing rainwater, the most important of which is the reservoir in Hormozgan. The possibility of using the rainwater stored in this pond to irrigate urban greenery has been the focus and goal of this research. For this purpose, Bibi Pond in Qeshm Island was chosen. For this purpose, the volume of water stored in this pond was calculated. Next, other parks and green spaces around the pond were investigated and their area and details were estimated. The results showed that there are 73 trees and shrubs and about 3400 m2 of green space (grass) in this park and its surrounding area. Estimates showed that the main reservoir of the covered pond and the open side pond are able to store about 400 and 1000 m3 of water, respectively, and this volume of water can supply the water needed for irrigating the green space of the park and the adjacent area in the major part of the year or at least in the stressful time (warm season). This issue will show the unique capacity of such structures for non-drinking purposes in urban environments and therefore should be considered in the planning and management of urban runoff.

In this study, a comprehensive mathematical model is developed to study the water evaporation process and brine concentration in a solar pond to recover the valuable salts in Bandar Imam Petrochemical Company. In this model, the energy source is just solar irradiation. The solar irradiation depends on the geographic characteristics of the location. The present model accounts for heat losses from (the surface of) the pond such as convection, conduction, radiation, and evaporation losses. Also, the wind effect and the variation of the brine physical properties with salinity are considered in the model. The mathematical results are also compared with experimental data. The results show that there are good agreement between the mathematical predictions and experimental data and the developed model can predict the variation of concentration and salt recovery accurately. Finally, by considering all important parameters, the developed model was applied to determine the optimum size of solar evaporation pond based on the concentration and initial volume of brine.

The turtles of Emydidae family in the northern Iran includes two species, Emys orbicularis and Mauremys caspica. In the present research, 200 specimens were collected from 25 different stations in Golestan and Mazandaran provinces during 1999-2001 and were biologically studied in terms of morphology, parasitology, feeding, reproduction and behaviour. Emys orbicularis coloration is dark olive with yellow spots, the bridges between carapace and plastron are cartilagenous and the interabdominal suture is shorter than interanal suture. It lays about 7 eggs every year, on average. Mauremys caspica coloration is dark olive with yellow parallel stripes, the bridges between carapace and plastron are bony, the anal plate is pointed and the interabdominal suture is longer than interanal suture. It lays about 4 or 5 eggs every year, on average. Both species are carnivorous and the males are more aggresive. Turtle leech, Haementeria costata, belonging to the order Rhynchobdellida was observed in some specimens of Emys orbicularis. Comparison of TL1 and TL2 in studied samples shows that anus position is different in males and females. In Emys orbicularis, 91% of males and females and in Mauremys caspica 77.5% of them are different in measured traits.