THE ADVANTAGES OF A CONSTRUCTED REED BED BASED STRATEGY FOR SMALL SEWAGE-TREATMENT WORKS

The advantages of the use by a major UK water utility serving 8 millio n people in central England of constructed subsurface flow reed beds f or secondary, tertiary and storm water treatment at small sewage treat ment works is placed in context with improved permit compliance to mor e stringent standards and a continuing downward pressure on operating costs. Capital and energy costs are compared with the competing tertia ry treatment process of recirculating sand filtration. Further economi c advantage is gained by combining tertiary treatment and stormwater t reatment. With over 160 sites in operation by mid 1997 the success of the strategy has given confidence to allow for the early or emergency installation of reed beds to improve or maintain effluent quality befo re replacement, or in one case the provision, of secondary treatment. Use of constructed reed beds is now being extended to larger facilitie s where only a proportion of the flow needs to be treated to achieve s tandards. For tertiary treatment reed beds there is an additional envi ronmental benefit with the typical removal of 10.7 mg/l of total nitro gen. (C) 1998 Published by Elsevier Science Ltd. All rights reserved.