Resource recovery from used water

Abstract

Single cell protein (SCP) defines the dried cells of microorganisms that can be used as a protein supplement both in animal feed or human food. SCP could represent an effective alterna-tive to meet the high and growing demand of feed products. This work aimed to develop a simple and economically feasible process to obtain SCP by adding value to an industrial waste stream. Spent sulfite liquor (SSL), pure glycerol and crude glycerol and two different types of wood oils were selected. However, the wood oils were early discharged (after characterization) as possible substrates due to their low chemical oxygen de-mand (COD) content and an unpleasant and undesirable smell. Thus, only SSL and pure and crude glycerol were tested. Crude glycerol proved to be the most viable choice given the high COD content – - g O2/L – and the low price per ton of COD – 200 €/ton COD. In continuous mode it was possible to achieve biomass concentrations of - g CDW/L (- g CDW/g COD) while efficiently removing - % of the COD of the influent stream. When tested in batch mode, biomass concentration reached a maximum of - g CDW/L (- g CDW/g COD) after - days of operation. After - days of operation, CDW per liter started to decrease which could indicate some sort of inhibition by fermentation by-products or other toxic compounds. Considering a batch operation mode, it was possible to produce SCP (- %w/w of protein content) with a commercial price of - €/ton protein. Thus, SCP production was considered feasible since it was possible to obtain a product that can highly compete with other feed products, for example, fishmeal (market price: 1.940 €/ton protein).