Enhanced Biological Treatment of Spent Metalworking Fluids 1 by Prior Removal of a Polymer

11 12 The biological treatment of spent synthetic metalworking fluid (MWF) has been investigated in many studies, 13 with most reporting the presence of un-degraded components in the residual waste. In this study, we 14 investigated a hybrid approach to waste treatment of spent MWF, involving both physical treatment and 15 microbial degradation. The effect on biological degradation, of the removal of two synthetic polymers, was 16 investigated in a bioreactor system. Polymer removal was found to have little effect on degradation efficiency 17 of the remaining components, but resulted in a waste product with a 14 % lower chemical oxygen demand 18 (COD) resulting from the physical removal of the polymers. An additional benefit of this approach is that it 19 enables the possibility of recycling of the recovered components, with the aim of economising on future 20 product formulation and reducing waste discharge. 21 22 INTRODUCTION 23 24 Metalworking fluids (MWFs) are a vital and widespread component of the metal manufacturing industry. They 25 are required as both coolants and lubricants to prevent damage of metal parts in working processes and ensure 26 effective cutting and drilling. Microbial contamination of in-use MWF is a common problem, which typically 27 originate from machine workers, water (fluid diluent) and factory air. This contamination is undesirable as it 28 can lead to partial bio-deterioration of the MWF, whereby emulsifiers are degraded resulting in a reduction of 29