Assessment of effective specific surface area for free water surface constructed wetlands

Biofilm bacteria attached to submerged surfaces play a major role in organi c matter degradation in free-water-surface(FWS) constructed wetlands used f or wastewater treatment. Effective specific surface area (a(s)) available f or the biofilm bacteria is an important parameter in organic matter degrada tion and in describing the biofilm kinetic models used in the design and op eration of constructed wetlands. In this study, kinetic models based on two possible biofilm geometries were developed for the determination of a(s) a nd its non-dimensionalised value or area factor (delta). The a(s) and delta values were estimated for a laboratory FWS constructed wetland treating do mestic wastewater based on the chemical oxygen demand (COD) removal perform ance and other kinetic parameters. With the assumption of slab geometry for the biofilm, the values of a(s) and delta were found as 3.15 m(2)/m(3) and 2.2 for the lab unit having 80% mass COD removal, whereas by considering t he cylindrical geometry for the biofilm attached on the lateral roots highe r values of a(s) and delta were obtained. (C) 1999 IAWQ Published by Elsevi er Science Ltd. All rights reserved.