Survey of Performance and Optimizing Methods of Aerated Lagoons of Bandargaz Wastewater Treatment Plants

As aerated lagoons method is a new method of wastewater treatment in our country and being used in Bandargaz wastewater plant and as there was no such study in this area, it was necessary to study the performance of Bandargaz wastewater plants. The treatment was started in 1996 with a capacity of treating 3100 m3/d wastewater per day, but now, after 14 years, it's efficacy has been decreased because of the factors such as, population growth, increasion of water consumption. So, the aim of this study was to determine the performance of aerated logoons and presenting methods for optimizing them with minimum costs. In this analytical study, carried out in 13 months and terminated in February 2009 current status of plants with qualitative and quantitative parameters was assessed. Moreover, alternative options and also prioritizing them with the matrix method was carried out, according to the standard methods of water and wastewater, in Bandargaz waste water plants. The results showed that present output for removing BOD, COD5 TSS, total coliform and fecal coliform were (76.82.2), (792.9), (762.6), (99.313.4), (99.1610.6), respectively so not being acceptable.But in terms of microbial quality, if is something acceptable on the basis of WMO. The output status is favorable in winter but not in other seasons (a). In this study q different alternatives were proposeal four of which were chosen for optimization of the system: with assessment of effective parameters. extrimely score earned by 4 alternatives are:1) introduction of new clarifier and converting the last clarifier to fl4. 2) addition of new module with a change in the replacement of clarifier 3) converting facultative lagoon no1&2 to complete mixed lagoon,4) changing the process of the system to extended aeration with an increase in MLSS in lagoon CML and storing sludge in Fli. Analysis of the data indicates that despite positive effect of temperature on wastewater treatment, seepage water is the main cause for this process which is more effective in winter. There fore the following alternatives are important respectively. alternative5›alternative1› alternative2› alternative3