Lab and pilot scale tests as tools for upgrading - Comparison with full scale results

Parameters such as hydraulic retention time, organic load, maximum COD removal, sludge characteristics and optimal nutrient dosage can be determined by simulation in small scale models of the chosen process. Laboratory tests are the natural first step when considering upgrading, or designing a new, biological treatment plant. The potential for a biological treatment can be examined at a low cost and within a minimum of time, often through parallel testing of different treatment methods. Once a suitable process configuration has been found, lab scale tests may well be used for optimizing the process and obtaining design data, thus minimizing the need for more expensive tests in larger scale. The principal reason for a pilot plant test is the possibility to investigate natural variations in wastewater composition and the effect this will have on process stability. The use of laboratory and pilot scale tests is here illustrated by the work carried out prior to the upgrading of the treatment plant at Nyboholm paper mill. A description of the upgraded full scale installation consisting of both chemical treatment and a suspended-carrier biofilm process is included and a comparison between results from lab, pilot and full scale treatment is made. (C) 1998 IAWQ. Published by Elsevier Science Ltd.