Team:UCL/Project/Manufacturing

In the textile industry, global annual production of dyestuff amounts over millions of tonnes. Azo dyes represent two thirds of this value, of which a majority find their way to wastewater effluent streams.

Our idea is to develop an integrated end-of-pipe method for detoxifying effluent streams of dye factories. Our goal is to achieve a two-stage regimen in sequence to ensure optimal conditions for the degradation of azo dyes within a batch bioreactor system. This would be an attractive and effective approach to dealing with azo dye contamination of the environment. As a financial incentive, we are also looking at maximise the profitability of various potential breakdown products. As a lucrative continuous-process alternative, we are investigating the application of microbial fuel cell technology to an aerobic bioreactor system, implementing simultaneous detoxification of azo dyes and generation of electricity.

Given the potential for scalability, this method would present various economic and environmental advantages for industries that generate large amounts of dyestuff. We envision that our novel approach could be taken further and represented as a modular bioprocess method for wastewater treatment for other toxic, normally recalcitrant chemicals.

Key Features of Our System

• -Fermentation stage- optimized growth conditions assured through mixing and oxygen supply. At the end of this stage, viable E. coli cells expressing the enzymes of interest will be present in a broth.
• -Tubular Bioreactor modules- see cross section of a single TBR system. Continuous flow system with flow rates and residence times based on mass transfer kinetics, specific to E. Coli.
• -Module 1 designed to capture the bulk of the azodyes, module 2 is a polishing step.
• -Both anaerobic and aerobic reactions take place at the same time in both the modules, design based on gas supply (nitrogen vs. oxygen).
• -Cleaning operation using biodegradable chemical at high flow rate (from holding tank 2).
• -Continuous recycle system for maximal active and diffusive uptake.
• -Filter modules- exploring the use of disposable low cost agricultural waste for filtration.
• -Further processing- based on the commercial value of the breakdown products, investments could be made into higher-tier technology such as chromatography columns to separate the breakdown products individually.

Microbial Fermentation

Small-scale bioreactors are often the workhorse of bioprocess development. We will be carrying out experiments to determine the optimal operating conditions at this scale in order to assess the financial implications of this process at an industrial scale.

We are using E. coli to cultivate the enzymes necessary for the biodegradation of azo dyes (azo reductase, laccase). By combining information on the production of azo dyes in textile factories and stoichiometric relations, we will design an optimised cell growth (fermentation) stage.

Some typical things we are thinking about at this stage can be seen in the diagram below: