عنوان مقاله [English]
The efficiency of Khoy WWTP located in the cold region in northwest of Iran has been studied from April 2002 to April 2004. The efficiency of WWTP in different seasons has been compared. It was found that facultative aerated lagoons efficiency in warm months was favorable but in cold months the level of pollutants was higher than discharge standards. In order to optimize the existing process, a model which takes into account the variability of air temperature and flow-rate at three types of aerated lagoons: facultative, aerobic and dual-powered has been developed to simulate the performance of various alternatives of aerated lagoons. Results show that both aerobic and dual-powered aerated lagoons can produce the effluent with higher quality than facultative aerated lagoons. Since the dual-powered process costs less and is more compatible with the existing lagoons, this process is proposed for upgrading the existing system to enhance its effluent quality and also WWTP's capacity.