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This system is a cost-effective and environmentally friendly method of treating sewage through small treatment works . For teaching and research , the choice of organisms and test systems is a critical and often frustrating task . Wet-pipe sprinkler systems are a reliable and safe extinguishing method and are relatively easy to maintain . Although many of my constituents are beginning to see the benefits of video competition , the construction of new cable systems is a time-consuming and capital intensive undertaking .