Identification of Archaeal population in the granular sludge of an UASB reactor treating sewage at low temperatures.

Effect of low temperature on up-flow anaerobic sludge bed (UASB) reactor performance treating raw sewage was investigated in terms of the variations in methanogenic diversity using the 16S rRNA based Fluorescence In-Situ Hybridization (FISH) technique. The diversity of microorganisms present in the anaerobic granular sludge and the structure of the granules operated at 13 degrees C have been investigated using FISH combined with CSLM (Confocal Scanning Laser Microscopy). According to FISH results, archaeal cells representing methanogens were found intensively dominant in the bottom sampling port of the UASB reactor and acetoclastic Methanosaeta was the abundant methanogen. Other methanogens such as Methanosarcina and Methanobacterium like species were also observed. The abundance of originally mesophilic Methanosaeta-related Archaea under low temperature at all sampling days revealed the microbial adaptation to psychrophilic conditions. This might be attributed to the enzymatic alterations in Methanosaeta cells originating from seed sludge, which were exposed to sub-mesophilic temperatures at start-up and then to psychrophilic conditions during gradual decreases of temperature. According to CSLM observation, even though the sludge retained in the reactor kept its granular form as a whole, the majority of the granules had a tendency to be partly broken and they lost their rigidity when raw sewage was fed following synthetic sewage. Besides, Methanosaeta related species prevailing in seed sludge have noticeably lost their long filamentous forms and deteriorated during raw sewage feeding. Members of the order Methanobacteriales constituted the major hydrogenothrophic methanogens present in the psychrophilic UASB reactor, whereas the other hydrogenothrophic methanogens--members of the order Methanococcales and Methanogenium relatives--were absent.

Current and future strategies for water and wastewater management of Istanbul City.

Istanbul has experienced rapid increases in population to more than 12 million people, which has created infrastructure problems of water supply and wastewater treatment and disposal. In this article, the achievements and approaches of the Istanbul Water and Sewerage Administration (ISKI) to solve the water shortage problem and to improve services are summarized. Istanbul had a very severe water shortage problem in 1994 because of ignorance of the implementation of the needed projects. After reviewing the reasons and causes of the problem, new priority criteria adopted after 1994 are given. Following the implementation of the projects determined according to the aforementioned criteria, water supplied has exceeded the water demand. The added capacity is equal to one to three times of the capacity built up to 1994 for water treatment, service reservoirs, pumping stations, transmission lines, and the water distribution network; water quality has been improved the meet local and international potable water standards. Unaccounted for water has been reduced from 60% to 27%. The percentage of treated wastewater has been increased from 10% to 90% in 8 years, resulting in drastic improvements and rehabilitation of the Golden Horn and coastal water quality. Through improved customer services, complaints were reduced from 33% in 1994 to 0.3%. Some of the main criteria and the approaches behind this success are summarized.