Energy recovery from dairy waste-waters: impacts of biofilm support systems on anaerobic CST reactors

Anaerobic digestion is one of the major steps involved in the treatment of dairy industry waste-waters and many CSTRs (continuously-stirred tank react ors) are functioning for this purpose all over the world. In this paper, th e authors describe their attempts to upgrade a CSTR's performance by incorp orating a biofilm support system (BSS) within the existing reactor. The foc us of the work was to find an inexpensive and easy to install BSS which cou ld significantly enhance the rates of waste treatment and methane recovery. Rolls of nylon mesh (with similar to 1 mm openings), of 5 cm height and 2 cm dia, when incorporated in the CSTR at the biofilm surface (with a digest er volume ratio 0.3 cm(2)/cm(3)), enabled the CSTR to perform better with > 20% improvement in the methane yield. Such simple BSS devices can signific antly improve the performance of a CSTR anaerobic digester treating dairy w astes. The enhancement is due to the development of active biofilms which n ot only enhance the microorganism-waste contact but also reduce the microbi al washout. Such devices are inexpensive and very easy to incorporate-the g ains are thus achieved with very little cost and effort. (C) 1999 Published by Elsevier Science Ltd. All rights reserved.