North West Water Authority owns and operates 21 rotating biological contactors and 7 package extended aeration plants. The rotating biological contactors have performed effectively, reliably and cheaply. Site visits are required up to three times a week for simple routine maintenance, whilst desludging is required periodically, typically 3 to 9 times a year. The prefabricated extended aeration plants generally perform well but typically with more demanding operational requirements and higher capital and electricity costs than rotating biological contactors. The Authority has concluded that the rotating biological contactor is the primary option for sewage treatment for small communities.

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