Evaluation of the substrate clogging processes at vertical flow constructed wetlands for wastewater treatment
Abstract
By far the biggest operational problem of constructed wetlands nowadays is the clogging of the filter surface of the vertical flow beds. The term "substrate clogging" summarises several processes which lead to a reduction of the infiltration capacity of the substrate surface. The substrate clogging leads to an extremely fast failure of the treatment performance of the system. The main reasons of clogging are accumulation of suspended solids and excess sludge production of the involved micro-organisms. Chemical precipitation and deposition in the pores, growth of rhizomes and roots which can block a part of the hydraulically active pore volume and the formation and accumulation of humic substances are also considered to play a role to a certain extent. The biggest problem is the quantification of the different factors. How much amounts each process to the clogging of the substrate? This of course is the basis of an optimisation of the clogging controlling factors like substrate selection, organic and suspended solids loading rates and filter feeding strategies. The project therefore is a detailed investigation on the clogging processes within the filter. The project focuses on measurements in the "black-box" itself using an innovative approach by combining methods of soil structure investigation (e.g. raster-electronic microscopy) with methods of microbiology (e.g. enzymatic tests) and methods of wastewater analysis. The investigations are made at 5 small scale constructed wetlands (1m¿ surface area). There are two categories of aims - on basic scientific research and on applied research. The basic scientific research is necessary to understand the processes within the black box "vertical flow constructed wetland". Only on this basis it is possible to establish and calibrate a model which describes the oxygen input and substrate clogging processes.
Project staff
Günter Langergraber
Priv.Doz.DI Dr.nat.techn. Günter Langergraber
guenter.langergraber@boku.ac.at
Tel: +43 1 47654-81111
Project Staff
01.05.2000 - 30.04.2002