Feasibility of utilizing moving bed biofilm reactor to upgrade and retrofit municipal wastewater treatment plants

In this study, feasibility of upgrading and retrofitting municipal wastewater treatment plants was investigated at laboratory scale using Moving Bed Biofilm Reactor [MBBR] process. For this purpose, an aerobic pilot was operated for nearly one year in different conditions, in which a moving bed carrier with a specific biofilm surface area of 500 m[2]/m[3] and a filling rate of 60% was utilized. System efficiency in removal of BOD[5] and COD was examined at different hydraulic retention times [HRTs] of 1, 1.5, 2, 2.5, 3 and 4 h. The obtained results indicated high ability of the system to tolerate organic loading and to remain stable at a high food to microorganism [F/M] ratio. The system produced effluents with good quality at low HRTs and led to an average BOD[5] removal efficiency of nearly 88% during the operational period. The Organic Loading Rate [OLR] applied to the system had a range of 0.73-3.48 kgBOD[5]/m[3].day and 2.43-11.6 gBOD[5]/m[2].day, at which the reactor showed a good performance and stability. In general, it was concluded that [MBBR] can be an excellent alternative for upgrading and optimizing municipal wastewater treatment plants

[Evaluating the quantity and composition of solid waste generated in Kashan during 2009-10]

Solid waste management is considered to be one of the most immediate and serious environmental problems confronting urban governments in developing countries. Qualitative and quantitative variety of waste composition, uncontrolled urban development and the lack of appropriate waste management technology cause particular problems that solving them needs a careful study and the coordination of science and experience in the form of a proper management. This descriptive study was carried out on solid wastes generated in Kashan over a limited timeframe of 12 months during 2009-10. One sample was randomly taken per month according to the standard instruction and subsequently the physical analysis of it was performed. The average daily waste generation rate in Kashan is 185 tons, of which 75.5% are putrescible materials. The average daily waste generation is tantamount to 638 g/capita while the average density of the waste 194 kg/m[3] at transfer station. The most frequent metal measured in the leachate solid waste was iron. According to the results high percentages of solid wastes in Kashan were allocated to plastic and corruptible materials, and then the paper and cardboard. Considering that the prevention of adverse environmental effects of solid waste is a priority and applying proper management techniques can help to achieve this, public education for the waste separation at the source, waste reduction and subsequently reduction of the leachate volume as well as the proper manner of recycling, collection and disposal of the waste are recommended

[Determination of the design parameters for making urban wastewater plants in cold regions of Iran]

Indicating the quantities and qualitative characteristics of raw wastewater entering treatment plant is one of the basic fundamentals of correct1 designation of treatment plants. The purpose of this study was to determine the design parameters for making urban treatment plants in cold regions of Iran. This applicative research is based on empirical studies which have descriptively been done in a temporal manner. In this study, three wastewater plants were selected as pilot from cold regions of Chaharmahal va Bakhtiari province i.e. Shahrekord, Broujen and Farsan wastewater plants. The quantative and qualitative characteristics of waste water entering to these wastewater plants were analyzed in a one-year period. In this research as well as measuring the waste water flow entering the plant the temperature, PH in entrance, chemical oxygen demand [COD], 5-days Biochemical oxygen demand [BOD5], suspended Solids [TSS], volatile suspended solids [VSS], Kajaldal Nitrogen [TKN] and phosphate phosphorous [P] were measured in 24-hours compound samples proportional to the wastewater flow. Data were analyzed using t-test and ANOVA. The final results of the research parameters in cold weather regions for BOD5, COD, TSS, VSS, TKN and P has daily been 41, 60, 65, 47, 8.3, and 0.93gr per capita. Average production of wastewater was found 177 liter per capita per day. The obtained results from Max and Min wastewater flow coefficient were 1.76 and 0.29, respectively. No significant differences were found for BOD5, COD, TKN and P between three wastewater plants, but TSS, VSS were significantly higher in Shahrekord [P<0.05]. In the case of using design parameters based on different climates and real characteristics of waste waters, we can obtain higher efficiency in guidance of exploitation from wastewater plants. In order to design plants in cold weather regions like Shahrekord [and most cities in the west of Iran] it is recommended that the per capita production and other design parameters to be considered in the trust range of this research

Conceptual hydrosalinity model for prediction of salt load from wastewater flows into soil and ground water

Dynamic hydrosalinity models are available, but are not used extensively on a large scale soil which receives wastewater from industrial areas, partly because adequate database are expensive to be obtained. Thus, for this reason, there is an urgent need to assess the salt and other pollutant loads collected in wastewater flows into the soil and/ or ground water systems. A conceptual hydrosalinity model was used on two major underlying principals of mass balance and steady state. This model was initially tested on the 4,117 km[2] plains west of the Yazd-Ardakan district in the central part of Iran. This model was used at a time when the soil and ground water salinity problem was serious due to the high shortage of water. It was possible to calibrate the model with +/- 2% of the flow volume and total dissolved solids of the industrial wastewater discharge from over 2,000 factories. The verification results were 98% of the measured values. Moreover, this model was tested for the verification of the model data from the analysis of 36 wells' water in the area where industrial wastewater discharge was used. The results showed that most of the indices of total dissolved solids, total suspended solids, biological oxygen demand and chemical oxygen demand are above standard levels. The results of the model can be used for the management practice of the reduction of salt pollutant load in the area to achieve sustainable development for location of industries in the study area

Improring the performance of Pars oil refinery wastewater treatment system

This study aims to inspect the performance of the wastewater treatment system of the Pars Oil refinery. Quantity and quality of wastewater are determined through samplings and measurements. The performance of system is evaluated considering total suspended solids, total dissolved solids, phosphate, chemical oxygen demand, biochemical oxygen demand, ammonia nitrogen, furfural, oil and pH. For precise comparing the qualitative and quantitative parameters, the wastewater entering the refinery is sampled four times from different places like boilers and from their channels, oil wastewater channels, and solvent wastewater channels. Despite some reforms that has been applied to the treatment system in order to reach the environmental standards, the system cannot treat the wastewater to the discharge standards. From the results of this research the advanced Membrane Bioreactor system for complementary refining along with optimized oil elimination system from wastewater is suggested

Applying the heat integration in order to environmental pollutants minimization in distillation columns

Due to the close relationship between the energy and environmental problems, recovering technology and optimizing energy consumption have a major role in environment protection by minimization the atmospheric pollutants such as SO[x], CO[x], NO[x]. This minimization may decrease the greenhouse effect, and the ozone layer destruction. On the other hand, optimization of Energy consumption and its recovering may minimize the water and hot oil consumption at the heat exchangers [reboilers and condensers] in petroleum distillation columns, specially. The present research has been performed about the kerosene pre-fractionation unit of one of the country's oil refineries. This system includes two distillation columns with a simple arrangement. Considering that the distillation section consumes a great deal of energy in the chemical and petroleum industries, hence studying the ways in which we may decrease this consumption is of great importance. One of these retrofit solutions is the heat integration, which is going to be presented in this research with a different idea from the other previous methods. This method makes it possible to add a shell and tube heat exchanger for performing a part of condensation and evaporation operation which can decrease the heat duties of reboilers and one of the condensers. To this end, the distillation columns were studied in the process and then the proposed model of columns arrangement were simulated by heat integration with all input and output streams using the Aspen Plus software, version 11.1 and the Rad Frac model in this software. The result has showed itself as a save of 14.26%, 10.86% and 14.26% in energy, water and hot oil consumption, respectively. On the other hand this system will decrease emission of SO[2] and CO[2] to atmosphere, 28 kg/h and 837 kg/h, respectively

Modeling of thermal pollution in coastal area and its economical and environmental assessment

The Persian Gulf is one of the aquatic ecosystems which has recently faced with different pollutions. Cooling water discharges due to various industries such as power plants can cause important disorders on present ecosystem balance because of its high temperature. Obviously, due to thermal pollution, a great number of aquatic creatures face with a new situation that they can not tolerate. Thermal pollution leads to their migration, creates a potential for new coming species which in turn can thoroughly change the marine ecosystem feature. The other impacts of this phenomenon are: disorders in reproduction, nourishment and other biological habits. In this research, thermal pollution due to Bandar Abbas Thermal Power Plant [BATP] development plan was modeled using MIKE21 software. In order to avoid a decrease on the power plant efficiency in development plan, the distance between inlet and outlet was determined by comparing the results of different scenarios and economical aspects. After determining the distance between inlet and outlet, the water temperature in the coastal area was compared with standards of Iranian Department of the Environment [DOE]. The model results represent that the water temperature, in Bandar Abbas coastal area, exceeds than the permissible limit [3 oC] in a distance equal to 200 m. far from the discharging location, and in order to reduce its harmful impacts, some suggestions are made to reduce the associated thermal pollution